Scipedia: Documents published in 2024

Estimation of the Soil Unit Weight of Mining Tailings through the Application of Machine Learning Techniques

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:29:32 +0200

There are several correlations in the literature that allow an estimate of the soil unit weight for natural soils, but when dealing with materials whose actual specific gravity of solids is outside the range of natural soils for which the correlations were developed, doubts arise, as occurs in the interpretation of tests on mining tailings. Therefore, the present paper aims to evaluate the application of a previously developed approach supported by machine learning techniques for estimating soil specific weights for mining tailings. This approach was developed considering a more comprehensive range of the specific gravity of solids. So, this work relies on a database with results of CPTu tests carried out in different mining tailings deposits from Brazil to estimate specific weights. The values of the specific weights obtained from the machine learning model were compared with literature data, presenting a suitable fit. The research demonstrates that artificial intelligence can contribute positively to the estimation of reliable design parameters and add security to the development of designs of mining tailings containment structures.

Enhanced, statistically-controlled integrated model of geo-data based on CPTu

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:28:27 +0200

The paper presents the possibilities of geostatistical analysis of geotechnical data using cluster analysis. As a result of the analysis, geological data from boreholes were replaced by digital data corresponding to parameters measured during CPTU static sounding. A unified database with a depth resolution of 2 cm was obtained, allowing it to be used to build geostatistical geotechnical models, e.g. using kriging. Techniques providing statistical control of the homogeneity of geotechnical separations, based only on measured data and not on interpolated or correlated data, were used to create the model. The technique used makes it possible to create an integrated geo-engineering model of the subsoil even for small sites with limited data.

Susceptibility mapping for shallow landslides in Tierras Altas, Chiriqui, Panama : An integration of geophysical measurements

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:27:48 +0200

The Tierras Altas region in Chiriqui, Panama presents a high agricultural activity susceptible to extreme climatic events, especially precipitation and surface runoff due to its high moisture retention capacity soils. A mountainous region with heavy winter rainfall and dry summers, part of the Chiriqui volcanic arc, and the point of triple convergence of the Coco, Nazca, and Panama microplate, also makes it a seismic threat zone. Historically, the Tierras Altas district has been susceptible to landslides, floods, and erosion-related phenomena. Through site characterization and the survey of ground dynamics, the research aims to build the input data of geological parameters and analyze dynamic properties through geophysical measurements of surface accelerations, allowing the characterization of the region and the coupling of the soil with climatic and seismic triggers. The results focus on geospatial maps and georeferenced datasets. The preliminary results were obtained through a GIS-based methodology that mapped the physical and dynamic properties of soils, identified high susceptibility zones, and analyzed how the measured dynamic data adjusted the Vs30 model.

The Pseudo-N Values: Proposal and Practice

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:27:30 +0200

The N-value by the standard penetration test (SPT) is commonly used for site characterisation in geotechnical engineering. S-wave velocity, typically estimated by borehole measurement or seismic survey, is also indicative of the strength of the ground. Many researchers attempted to find precise relationships between these parameters. However, N-values estimated from S-wave velocity using these formulae are subject to substantial errors, and the errors are inevitable due to the different nature of the parameters. The formula for pseudo-N value was first proposed in 2011 as (Suto, 2011). This is a simplified formula derived from the formulae found by the previous authors. By using this simple formula as a common practice, with understanding of existence of error, the results can be compared from site to site. This presentation first compares the N-value and S-wave velocity in their natures, methods, practice and cost. Then it examines the previously published formulae and proposed formula of pseudo-N value. Some examples of use of the pseudo-N values are also presented at the end.

Critical Shear-Wave Velocity Case Histories for Liquefaction Triggering Curves in Gravel

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:27:11 +0200

In 2022, a new set of probabilistic shear wave velocity (ðð) based liquefaction triggering curves was developed for gravelly soil by Rollins et al., using a dataset of 96 liquefaction and 78 no liquefaction case histories from 17 earthquakes in seven countries. Although these curves provide liquefaction assessment based on direct field performance, they suffer from the fact that there are relatively few case histories for high ð¶ðð and high ðð values to define the shape of the upper branch of the triggering curves. Thus, we made shear wave velocity measurements at three sites in Valdez, Alaska where liquefaction did not occur in the Mw 9.2 1964 Great Alaska earthquake. The Multi-channel Analysis of Surface Wave (MASW) technique was used to develop several median Vs profiles at each site that account for uncertainty in the experimental dispersion data and inversion parameterizations. ðð-based liquefaction evaluations were then made at each site, using the ðð profiles derived from each solution. Results from previous Dynamic Cone Penetrometer (DPT) tests were then used in selecting the most reasonable velocity interpretation. Based on this VS profile, the layer most likely to liquefy was selected and used to define ðð1 and ð¶ðð7.5 at the middle of this critical layer, obtaining three points of no liquefaction, that could change the shape of the upper branch of the existing VS-based liquefaction triggering curves. These preliminary results suggest that it might be necessary to shift the triggering curves to the left or steepen their slope to provide better agreement with observed performance.

Cone Penetration Test Data Interpretation for Layered Tailings Storage Impoundments with Perched Phreatic Surfaces

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:26:51 +0200

Cone penetration testing (CPT) is a widely used technique for soil characterisation. The introduction of the Global Industry Standard for Tailings Management (GISTM) in 2019 increased the necessity for understanding tailings properties (particularly shear strength), requiring better risk management and monitoring of tailings storage facilities (TSFs) to achieve zero fatalities. The complexity of tailings materials, influenced by ore processing, slurry deposition and water management techniques, causes greatly different geotechnical characteristics compared to other soils, requiring specialised monitoring equipment and in-depth investigation. One main aspect in interpretation of tailings properties is understanding the pore water pressure (PWP) within the deposited tailings layers which has often been overlooked in engineering studies. For example, in cases of interbedded layers of silt and sand, the downward drainage due to underdrain systems and lateral flow due to differences in lateral and vertical hydraulic conductivities can lead to the formation of distinct ‘perched’ phreatic surfaces in-between layers due to dissimilarity in material permeabilities. The use of commonly assumed linear PWP profiles in such cases can result in misinterpretations, hence, overestimation of tailings’ effective strengths. In these instances, instruments like vibrating wire piezometers (VWPs) have been widely used. However, VWPs provide limited data for understanding the true PWP profile. CPT with PWP measurements (CPTu) has therefore become a practicable technique for identifying internal PWP and distinguishing deposited layers. As such, a detailed approach to CPT data interpretation is required for interlayered tailings facilities with perched phreatic surfaces. This paper presents how CPTu techniques, combined with graphical interpretation, and VWP data can be used to understand complex internal profiles of interlayered TSFs.

Vulnerability of levees impacted by seepage near the Kettős-Kőrös River in Hungary

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:26:31 +0200

Due to climate change over the last decades, flood events in Hungary and other European countries have become increasingly frequent, with greater intensity and duration. These changes have impacted flood protection levees. A longduration flood allows water to seep into the levees, saturating them and maximizing the potential for damage. Seepage through earthen levees is often observed during floods and can lead to levee failure if combined with internal erosion. This study assesses the levee vulnerability relative to seepage by considering the characteristic time scales of the seepage phenomena and the main factors driving them. The procedure is applied to the Körös sub-basin (Hungary), a site that has shown a continuous trend of increased water levels in recent years. Along the critical section of the levee, a comprehensive site investigation was carried out. The analysis has shown that hydraulic conductivity is the most significant parameter when considering seepage for levees along the Kettős-Körös River. The investigated dyke geometry shows higher vulnerability to lower water levels associated with a longer duration of flood water levels.

Basic study for propagation characteristics of elastic wave around subsurface cavities

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:26:13 +0200

This study examines the detection of subsurface cavities using seismic wave propagation. Both vertical and horizontal excitation methods were employed to measure the reflection characteristics of artificially constructed cavities in a test field. The study was conducted at the Le Petau golf course in the town of Abira, Hokkaido, Japan. In this study, a new horizontal excitation technique was introduced along with conventional vertical excitation to compare its effectiveness in identifying wave reflections caused by cavities. An artificial cavity was created using rubber balloons reinforced with cardboard to simulate subsurface anomalies. The measurement used 24 geophones connected to an automatic data logger, and the acquired data underwent extensive analysis with bandpass filtering, amplitude normalization, and deconvolution to elucidate the interaction between the elastic waves and the subsurface structures. The results showed that horizontal excitation provided a clearer view of the cavity due to reflected waves. This is because only SH waves are excited and observed in the horizontal excitation mode. However, this study also recognized that it is difficult to distinguish the boundary between direct and reflected waves at shallow cavity depths, suggesting the need for excitation methods capable of generating shorter wavelengths to improve resolution. This study highlights the potential of integrating vertical and horizontal excitation methods in seismic surveys to enhance subsurface cavity exploration, and highlights future research issues, such as improving waveform analysis techniques and searching for alternative excitation sources, to advance the field of subsurface exploration.

Effect of Hammer Energy and Corrections on the Correlation between SPT N-Value and Shear Wave Velocity

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:25:58 +0200

The pressuremeter measures both the pressuremeter modulus and the limit pressure, which are used to estimate the bearing capacity of the foundation according to different standards. The results of the pressuremeter test include the pLM limit pressure and the EM pressuremeter modulus. These quantities cannot be directly input as data for geotechnical calculations using Finite Elements or Finite Differences in the study of civil engineering structures such as retaining walls, tunnels, embankments, and excavations. These modern calculation methods require, at a minimum, knowledge of the mechanical characteristics of the soil, including elasticity (with Young’s modulus (E) and the Poisson ratio ()) and resistance (with cohesion (c’) and the angle of friction (’)). This study is devoted to the interpretation of the pressuremeter test so that it is possible to use it for the determination of the mechanical characteristics of the soil. When the pressuremeter test is carried out into clay, it appears pore pressure during the test when only shearing is applied. In summary, understanding pore pressure and interpreting measurements to determine the effective shear modulus are crucial for geotechnical engineering and subsurface exploration. Effective shear modulus can differ significantly from the value determined solely based on total pressure. This study provides the theoretical value of the Skempton coefficient B. Additionally, it proposes an interpretation theory for the pressuremeter test in clay. Finally, the theory is validated through a comparison with tests performed in London clay at a depth of 20.6 meters

Peak Deviator Stress and Strain Uncertainty of Isotropically Consolidated Triaxial Compression Tests on Saturated Non-Cohesive Soils

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:25:44 +0200

This paper presents the methodology for calculating the peak deviator stress and strain at peak deviator stress uncertainty of triaxial compression tests on water saturated, non-cohesive soils consolidated under isotropic conditions. A silicious sand sample is prepared in the same way to produce identical cylindrical specimens. These are then tested under the same conditions. Type A and type B uncertainty are calculated separately and used to yield the combined and expanded uncertainty of the main results, peak deviator stress and strain at peak deviator stress. For both measurands, type A uncertainty is significantly higher that type B and it is the factor mainly affecting the overall uncertainty of the results

The Role and Performance of Instrumentation and Monitoring in Managing Risk During Deep Shaft Excavation in the Mercia Mudstone

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:12:28 +0200

The HS2 Bromford Tunnel intermediate shaft has an external diameter of 21.9m and a depth to formation of 47.1m below ground surface. The shaft is formed with a 63.1m deep 1.5m thick diaphragm wall primary lining, with a cast in situ secondary lining. The shaft works started in spring 2022, and formation level was reached in late 2023. Situated at the base of the Tame valley, the shaft excavation is predominately in the Mercia Mudstone, and is understood to be the largest and deepest excavation of its type in the Birmingham area. Instrumentation and monitoring played a vital role in managing ground risks during the diaphragm wall installation and bulk excavation. The paper covers: An overview of the shaft works and the subsequent tunnelling in the area; The geotechnical risks and parameters to be monitored; The specification, installation and performance aspects of the instrumentation, including the embedded SAAs and Vibrating Wire Piezometers; The design and performance of the specialists’ subcontractors dewatering system and excavation groundwater pressure behaviour during construction; Ground movements and third-party asset monitoring during diaphragm wall installation and excavation; diaphragm wall deflections during excavation - a comparison between design model calculations and actual monitored movement. As the shaft was constructed largely in advance of the main tunnelling works, some of the potential benefits from the experience and field observations made during the shaft works have been realised during the tunnelling.

Dark Fibre Optic Cables for Shallow Ground Charactrization alongside Railroads

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:11:31 +0200

We evaluated the feasibility of existing fibre optic telecommunication cable as a Distributed Acoustic Sensors (DAS) for shallow ground characterization alongside railways and using the running trains as seismic source. We utilized 5 km of fibre optic cable alongside a railway segment localized in the Hanzelijn corridor in the Netherlands. For almost a week, we recorded strain generated by passing trains that was utilized to retrieve coherent and multimodal Rayleigh waves at various soil conditions. The data was recorded in a continuous mode, using a channel spacing of 1.0 m and a sampling frequency of 1,250 Hz. The DAS interrogator was set to a gauge length of 2.0 m to reach the highest possible spatial resolution. We captured at least 60 train passages (running alongside the fibre optic cable) per day. We extracted Rayleigh waves by utilizing seismic interferometry method. The seismic interferometry processing provided virtual broad-band shot-gathers with coherent and clear surface waves trends. The computed phase velocity spectrum at frequencies as high as 30 Hz and wavelength as short as 6 m. The retrieved dispersion curves allowed us to determine S-wave velocity profile at a minimum depth of exploration of 2.0 m. The measured Rayleigh waves and calculated S-wave velocities are comparable to reference values measured with standard Geophone and geotechnical data available at the test segment.

Monitoring of Tunnels in Urban Environments Complementing InSAR with in-situ Ground Instrumentation

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:10:33 +0200

One of the challenges in urban tunnelling projects is to guarantee that the infrastructure assets crossing or adjacent to the tunnel alignment and other new build elements are not affected by the construction activity. Radar Satellite Interferometry (InSAR) is a non-invasive surveying technique which provides millimetric deformation measurements of terrain structures over wide areas without any need to access site. This technique allows a comprehensive and periodic vision, with the same accuracy as manual levelling in cities for a fraction of the cost of traditional systems. ATLAS is the Sixense’s InSAR processing chain, aimed to monitor the different tunnelling activities phases: access shaft excavation, tunnel construction and settlement. This study focuses on real data obtained by Sixense during the monitoring of urban tunnel construction work in three major projects in London (UK) and Porto (Portugal), using a combination of technologies: InSAR for remote monitoring and two topographic instrumentation methods: Topographic Control Prisms through measurements with Robotic Total Station and Topographic Levelling. The methodology employed integrated InSAR to obtain surface deformation data across the tunnel influence zone and on-site instrumentation for detailed and precise measurements. Its implementation enabled continuous monitoring, revealing accurate and real-time deformation patterns near the tunnels. The results demonstrated a significant correlation between InSAR data and on-site measurements, validating the effectiveness of this combination.

Delivery added value using field measurements through the application of the Observational Method

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:09:28 +0200

High Speed Two (HS2) is the new high-speed railway line in the UK currently being constructed between London and Birmingham. The designs of many HS2 retaining structures, as can be the case for some projects in the UK, were progressed concurrently with ground investigation. In this situation, to manage uncertainties in the ground, a cautious assessment of ground parameters was usually adopted. The purpose of field monitoring varies depending on the responsible or interested party. For designers, the primary aim is usually for design verification of their permanent works design. This paper describes how field observations, particularly quality instrumentation and monitoring data, were used at HS2 Bromford Tunnel East Portal to improve the existing design as construction progressed to create savings. To improve the efficiency in data processing, DAARWIN, a machine learning-based technology was used. The design and construction of the eastern end of the Bromford Tunnel East Portal were modified by eliminating the requirements of temporary support using measured field data, site observations and a carefully controlled construction through the application of the Observational Method. The portal construction programme was shortened by at least two weeks despite only three of the remaining temporary steel props being omitted. The findings revealed opportunities to extend the application of the Observational Method on adjacent structures including Bromford Tunnel West Portal and Washwood Heath Retained Cut. Given the great length of retained excavations of the two structures, the potential efficiency gains in cost, time and carbon emissions are significant whilst enhancing safety.

Crossing a Landslide Area by a Motorway

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:08:31 +0200

A 1.5 km long stretch of a motorway built at midheigt of a valley eroded by an intermittent river, was almost completed in 2009. Budgetary restrictions led to a halt in construction. In the period 2009-2018, the motorway experienced severe damage, concentrated in three tributary shallow valleys, where the motorway was supported by compacted soil embankments. The “valleys” were, in fact, ancient landslides reactivated by the weight embankment of the embankment. The damaged embankments were substituted by bridges supported by pile foundations designed to resist the thrust of the active landslides. The bridges were completed by pile walls to improve the stability of the landslides. The construction of the wide roadway platform (40 m) required excavations at the mountainside, embankments at the riverside, additional stabilizing measures by anchored resisting walls, and systematic drainage. The miocene substratum is an irregular and heterogeneous set of conglomerate, sandstone, and claystone layers dipping 15-25º towards the river. The bedrock is covered by discontinuous quaternary clay and gravel formations. The paper describes: a) The singular sheared surfaces with very low friction, located in claystones, which were responsible for the instabilities observed; they played a key role in designing the stabilizing measures; b) The complex water pressure distribution and its variability in time, a consequence of the geological structure of substratum and the procedure designed to reduce pore water pressures and c) The difficulties encountered to install permanent high capacity anchors and the evolution of anchoring loads.

Preliminary tests on the UAV-enabled installation of wireless sensors for monitoring inaccessible slopes

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:07:31 +0200

Although remote sensing techniques (TLS, DPS) are useful for monitoring wide areas with diffuse hazard, the deployment of sensors in contact with the ground (slopes, cliffs, rock blocks) is mandatory when a focused mechanism is underway. So far, most of the so-called ‘geotechnical sensors’ (tiltmeters, jointmeters, stress sensors), and some surveying systems or accessories (like prisms, targets, GNSS receivers), must be installed manually on the landslide body. Furthermore, in some cases cables for the power supply and data collection are needed. Besides the technical difficulties, in some scenarios this installation phase may imply a high risk for the operators. To overcome this issue, in the contribution we present some test carried out with wireless sensors installed by means of Uncrewed Aerial Vehicle (UAV). Concretely, we deployed several wireless precision tiltmeters, able to acquire several measures per minute, and with LOng-RAnge communication capability. The experiments were developed in the frame of a risk mitigation project leaded by the ICGC in the Montserrat massif (near Barcelona, Spain), an area of paramount geomechanical and societal interest. There, the targeted instability mechanisms are medium and large rockfalls. The preliminary tests show that the installation of sensors with UAV can be of great help in the aforementioned situations. The UAV-enabled deployment method should be considered to speed up the availability of real time monitoring data.

Using Combined Geotechnical and Geophysical Methods for Site Characterization of Ultra-Shallow Submerged Sites

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:06:28 +0200

Ultra-shallow underwater environments (average water depth ≲ 1 meters) in rivers, estuaries, and coastal zones represent the transition between water bodies and landmasses relevant for many engineering applications including utilities and transportation, habitat monitoring and restoration, and resilience to extreme flood and coastal storm events. With climatic shifts and an increased occurrence of extreme events, ultra-shallow underwater environments and inundation zones receive increasing attention. However, the increasing need for data revealed current limitations in safe accessibility and survey methodologies suitable for those conditions. Adaptation of geotechnical testing methods such as cone penetrometer testing and free fall penetrometer testing enable updated geotechnical testing capabilities, but these methods still require physical access to the measuring site which may be compromised by significant flow conditions, unknown debris and bottom conditions, limitations in access points and time, and combinations thereof. Remote sensing using optic sensors from unmanned aerial vehicles as well as from satellites offer strategies of soil classification in a rapid manner and without need for physical access if water conditions are clear. Advances in geoacoustic surveying, particularly regarding the use of sonars in ultra-shallow environments offers seabed surveying even in murky waters. Fusing geoacoustic and/or optic data with geotechnical point measurements enables the optimization of data collection in ultrashallow underwater environments or inundation zones in a safe and efficient manner, contributing also to available data from these environments to advance our understanding of soil mechanics in inundation zones and ultra-shallow waters. Here, an overview of available methods and recent advances in methodologies is presented supported by case studies including riverine and coastal environments.

Ambient Seismic Noise Imaging for Tailings Storage Facilities Monitoring: a Benchmark between Accelerometers and DAS

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:05:36 +0200

Recent examples of tailings dam failure remind us how the monitoring of such sites is important. One major factor affecting the stability of tailings storage facilities (TSFs) is the presence and movement of water within the facility. Dam failures are often caused by seepage or the presence of weak layers within the tailings dam or the foundation soil. Thus, monitoring for the presence or movement of water within TSFs is becoming increasingly important, and solutions for permanent, non-intrusive and cost-effective monitoring of dams are a major challenge. One such solution is represented by geophysical imaging techniques such as ambient seismic noise interferometry. Through a research project, a nodal network system of accelerometer sensors was installed in a dense and random array on a TSF embankment wall at an Australian mine. Simultaneously, a fiber optic cable was deployed in a trench at the top of the TSF. Ambient seismic noise was recorded over a few weeks using the nodal network and with the fiber optic cable over several months using Distributed Acoustic Sensing (DAS) technology. Following data acquisition, benchmarking passive seismic imaging from the accelerometer network and the DAS system was conducted to evaluate the DAS capabilities for long-term TSF monitoring.

Combining Remote Sensing Techniques to Optimize Digital Surface Models for Change Detection – A Case Study at a Pit Wall in the Canadian Cordillera

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:04:28 +0200

Slope monitoring is vital for open pit mines during operations and nearing closure where pit wall instabilities are present. Change detection using terrestrial laser scanning (TLS) has become part of the state of practice for collecting accurate measurements with extensive spatial coverage. The approach can detect displacements associated with global slope movement, as well as surficial occurrences such as rockfalls and sloughs. However, TLS acquisition quality is vulnerable to atmospheric interference and reflectivity of the target materials. In this regard, the high-density surface information obtained from TLS could be complemented with other, less detailed, remote sensing information in order to construct a complete surface model. Such an approach, however, requires a systematic workflow and a means to calculate surface model reliability. The subject of this study is an unstable pit wall at an open pit coal mine transitioning to closure. The site is located in the Canadian Cordillera, in a setting with intermittent fog and cloud cover, wildfire haze, and seepage within the slope face and toe. Insufficient TLS data can be obtained in local areas of the slope impacted by these conditions, as well as in shadowed areas on the benches above the TLS base elevation. Aerial photogrammetry was undertaken using UAV and combined with the TLS scan to generate a representative surface model. This paper presents a methodology for registration improvement between the TLS and UAV photogrammetry clouds, and evaluation of the combined surface using concepts of Limit of Detection (LOD) adopted from change detection techniques.

Piezometers: a very important instrument to which we need to pay more attention

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:03:26 +0200

Piezometers are instruments that can produce high-quality information if suitable and effective installation and monitoring procedures are followed. In order to minimise errors and optimise quality of the obtained information, we must pay attention when prescribing the type of piezometer and its installation, as highlighted in the ISO/EN18674 standards. The use of piezometers as a geotechnical instrument is a commodity. This paper aims to exemplify how the use of piezometers can be optimised and how the most common errors can be avoided.

Revealing Structures below Vegetation using UAV-BASED LIDAR

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:02:27 +0200

LiDAR has been used for the last decade to create digital terrain models using Airborne Laser Scans (ALS) with about 10 points per square metre, mainly depending on flight altitude and speed. The data is used to produce elevation maps or digital surface models, calculate volumes and analyse the Earth's surface or objects above it. However, the resolution and elevation accuracy of about ± 0.3 m means that calculations are only estimates and ground features may not be identified. Unmanned aerial vehicle based LiDAR systems have some advantages over ALS data. Their lower altitude and speed allow the scanner to generate more points per square metre than an ALS. The more laser beams the scanner emits into the same area, the more beams pass through the vegetation and generate more points on the ground or other objects. This increases the level of detail in the digital terrain model. Reference points are another way of increasing the accuracy of the LiDAR scan. These points are placed within the survey area and have known coordinates and elevations to control and fit the result of the LiDAR scan to the coordinate system of the reference points. This data can be used for higher accuracy volume calculations and changes in the terrain structure (e.g. geological changes). Because the terrain is mapped at a high level of detail, it can also be used in explosive ordnance disposal to reveal hidden features such as trenches or bomb craters that may cause a problem for the project.

Event detection system for monitoring the cliff retreat and undermining of Castellfollit de la Roca village

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:01:29 +0200

Castellfollit de la Roca village (Catalonia, NE of Spain) stands on top of a basaltic cliff affected by rockfalls that are causing the retreat of the slope and the risk of undermining the buildings. So far, remote sensing techniques have been applied. They have detected centimetric precursory movements of toppling in basaltic columns, and unnoticed rockfalls of tiny volume as well. However, rockfalls of remarkable magnitude caused by other mechanisms have occurred at the foundation level of some houses, without any precursor movement detected by remote sensing techniques. In order to gather information from these events, a priority sector has been instrumented with a geotechnical network of crackmeters, tiltmeters and thermistors to monitor the thermo-mechanical behavior of the rock mass. Readings from the sensors have been automated through a wireless network based on Loadsensing nodes and gateway connected by LoRa technology. Tiltmeters are all-in-one devices of sensor and logger operating in dynamic mode. This system enables the detection of events and sending alert messages in real time. To receive reliable alerts for risk management, suitable thresholds have to be defined, based on the knowledge of the studied phenomena at the particular scenario. This paper presents the system set up and the threshold analysis through the observation of the cliff behavior on the daily and seasonal cycles registered during the first year of operation.

In-situ Characterization of Strength and Small-strain Stiffness in a Weathered Mudstone Profile

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:00:46 +0200

The weathering profile in mudstone outcrops can range from weathered clay to unweathered mudstone. The strength and small-strain stiffness of these materials, and of stiff clays and weak rocks in general, is critical to the design of geotechnical structures. Monitoring data and ground investigation data were gathered during the construction of a trial embankment founded on weathered, Jurassic-aged mudstone, for the HS2 high-speed railway project (UK). These data included outputs from in-situ downhole geophysical tests and extensometers at the embankment location. These were compared to ground investigation data from the wider mudstone outcrop over an 18.2 km stretch of the route. The installation of extensometers prior to loading by the embankment construction enabled the measurement of in-situ strains for a range of small and medium strains. It was therefore possible to characterise the stress-strain behaviour of the individual layers within the ground profile. The results showed that stiff clays derived from weathered mudstone at shallow depth (15 mbgl) showed higher strength (>300 kPa) and higher maximum stiffness than the overlying clay. Both the strength and stiffness profiles showed a transition zone between the weathered clay and the unweathered mudstone. This zone included a partially weathered mudstone that had the visual appearance and index properties of a mudstone, but the strength of a stiff clay (i.e. τu

Installation of Load Cells in Ground Anchors

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:00:23 +0200

Load cells are used to measure tension (kN, tonne-force) in ground anchors and tendons in pre- or post-tensioned structures. Before installing and commissioning, it is strictly necessary to know the characteristics of the anchors to control as well as the installation and service scenery. Although it may look a simple assignment, there are several issues before supplying and installing a load cell: geometry of the anchor head, measurement range, expected precision, type of output signal and data transmission, temperature variations in the structure, and foreseen service life. The sort of tensioning jack and load steps are additional, unavoidable points to consider. By installing a load cell on a tieback, this is transformed into a measurement element, helping to understand the performance of the anchor as well as that of the surrounding area, medium- and long-term. To ensure load cells’ values are correct, we must take extra care with installation. Otherwise, the outcome will be flawed, and it will lead to erroneous conclusions and actions, with the subsequent increase in risk and money loss. In this paper, we share our experience regarding design, installation, and follow-up of load cells as elements to monitor the behaviour of anchored and post-tensioned structures and their area of influence

A Soil Base Model of Adjacent Various Story Structures

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 13:00:05 +0200

The paper proposes an improved soil base model in the form of a continuous layer of finite distribution capability to simulate and calculate adjacent multistory structures in the base - foundations - structures system using powerful calculation packages such as SOFiSTiK, ABAQUS, PLAXIS, SCAD, Lira and others. The improved model considers the parameters of the stress-strain properties of the soils of the bases, the geometric profile taking account of the distribution capability of the base and different boundary conditions, but differs from the existing models in that it has a stepped geometric profile at the lower boundary of the model because of different compressible layer depths under each foundation of the structures. The use of this model improves the accuracy of simulating a soil base for large-sized foundations of adjacent structures to obtain reliable results of the stress-strain state of the base - foundations - structures system. An example demonstrates how to simulate and calculate raft foundations of a two-section multistory building in the base - foundations - structures system that interacts with an improved soil base model (linear strains of soils under loads are considered here) with reference to different numbers of stories of the sections. The numerical study results show on a specific calculation example that considering different compressible layers depths in the model under differently loaded foundations results in an increase in moment forces of up to 65% as compared with simulating the whole compressible layer, which may lead to the disruption of large-sized raft foundations.

Reliability-based Assessment of Deep Cement Mixing Column Based on Core Strength

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:59:51 +0200

In the quality assurance procedure of the deep cement mixing method, the statistical parameters of the unconfined compressive strength of core samples, core strength, are adopted to assess the quality of the cement-treated soil ground. Since the statistical parameters of the core strength are the sample statistical parameters, the statistical uncertainty emerges when estimating the population parameters. Moreover, the spatial correlation of the core strength should be considered on the evaluation of the overall strength of cement-treated soil ground. The paper presents a reliability-based assessment for the deep cement mixing soil column based on the core strength. The analysis method in which the statistical uncertainty included in the core strength and the spatial variability of the strength are considered simultaneously is adopted to calculate the overall failure probability of the cement-treated soil column. The statistical uncertainty is estimated using a Bayesian inference method and the random fields of the strength are generated with the statistical parameters involving the statistical uncertainty. The random finite element method with the generated random fields is performed to simulate the compression failure behaviour of a cement-treated soil column. The analysis result provides the cumulative distribution function of the overall strength of the cement-treated soil column. The reliability-based assessment is performed on the basis of the cumulative distribution function of the overall strength.

Towards the development of a standard for the PS suspension logger

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:59:27 +0200

The PS logger is a well-established seismic tool for measuring P and S wave velocities in a single borehole, using low frequency indirect excitation originating from a dipole source. Because of its low operating frequency, it is capable of generating seismic waves in slow, unconsolidated materials such as those found in offshore environments where S wave velocity is often used to estimate the small strain stiffness, Gmax (of particular interest to offshore construction). Despite its widespread use, there is no current standard for the use of the PS logger, even though other methods operating on similar principles have well-established reference methodologies and guidelines. As such, PS logger methodology is largely dictated by user manuals written by manufacturers, which likely introduces inconsistencies in operation guidelines, and may impede consistency in data obtained by different users. In this paper, the authors conduct a literature review of existing standards for relevant methods including CPT, SPT, SCPT and downhole and crosshole seismic testing, as well as relevant ground investigation standards, identifying the need for standardisation of the PS logging method. Examination of the current state of standardisation concludes that although existing seismic testing standards could possibly be expanded to include the PS logging method, the differing constraints and operational requirements are such that the development of a specific PS logger testing standard is highly recommended. An initial framework is presented for a PS logger standard, identifying the required components, in terms of borehole requirements, testing procedure, data interpretation and best practice.

Development of international standard on the use of geotechnical instrumentation under the ISO umbrella

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:59:08 +0200

International standards for monitoring under ISO have been under development since 2010 and the intentions were presented during the 8th International Symposium on Field Monitoring in Geomechanics (FMGM 2011) in Berlin. Progress on this project was reported at FMGM 2015 in Sydney and ISFMG 2022 in London. The base standard on general rules was published in 2015, part 2, the standard on extensometers, in 2016 and in 2017 the third part on inclinometers. Part 4 on piezometers was published in 2020, Part 5 on pressure cells in 2019 and Part 8 on load cells in 2023. These standards have been published as ISO Standards in English and French worldwide. In Europe the standards have been published under EN ISO 18674 member countries of CEN have to publish these standards in their country. The standards on settlement measurements by hydraulic systems (part 6), geodetic measurements (part 9) and strain measurement (part 7) are under development and will be submitted to enquiry in the next few months.

Impact of Damping Boundaries on the Quality of the Output Signal in Bender Element Experiments

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:31:32 +0200

Bender elements are a popular experimental device for the measurement of the small strain shear modulus of geomaterials. Bender elements are easy to use, can be easily installed in most geotechnical devices (e.g., triaxial apparatus, oedometers, and Rowe cells), and yield shear modulus readings that compare well with those obtained from resonant column tests. Typically, bender element tests involve inducing a shear wave at one end of a sample (the input signal) and reading its arrival at the other end (the output signal). However, the wave propagation induced by bender elements is complex, hindering the interpretation of the output signal and inducing considerable uncertainty in the shear modulus readings. Indeed, besides the desirable shear wave, the vibration of the transmitter also generates laterally propagating compression waves, which reflect from the lateral envelope back into the sample and pollute the output signal. This study analyses the effect of lateral boundaries especially conceived to dampen the incoming compression waves on the quality of the output signal. In this context, damping moulds are designed based on computational simulations of the transient dynamics of the wave propagation, to promote an output signal that presents a clearly identifiable arrival of the shear wave, without it being concealed by compression wave pollution. Prototypes of a few promising designs are produced using 3D printing and tested in the laboratory using a benchmark material (Toyoura sand) and a range of input frequencies. The results are compared with those obtained in a conventional setup with no damping moulds.

Use of Elastic Full Waveform Inversion for Monitoring of Dams and Levees

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:30:28 +0200

Understanding subsurface conditions is critical to creating and maintaining resilient infrastructure systems, such as dams and levees. Seismic geophysical tools can be very effective for site characterization of these structures as they directly measure the elastic moduli and can provide insight into both the soil properties and groundwater conditions. Full waveform inversion (FWI) is one processing option for seismic geophysics that seeks to overcome some of the limitations in the traditional approaches by using the full time-domain recording of the wavefield to develop 2D or 3D profiles of shear wave velocity. In addition to providing characterization data, FWI can also potentially be used as a monitoring tool for dams and levees to assess how elastic moduli are changing with time and to infer how these changes might relate to changes in the hydromechanical properties of the soil. This study seeks to explore the use of seismic FWI as both a characterization and monitoring tool through numerical simulations of seismic surveys on a hypothetical levee with a low velocity anomaly in the foundation. The simulations are used to assess both the spatial resolution and the ability of the simulations to detect changes in properties that might be related to softening of the foundation or development of internal erosion failure modes. The findings from the study will be used to highlight potential benefits and challenges to using seismic FWI for characterization and monitoring of dams and levees.

Impoundment characterisation for hydraulic mining of tailings

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:29:27 +0200

Reprocessing old tailings storage facilities (TSFs) has become increasingly common in the past ten years because of economic, environmental, and social reasons. Tailings deposited by spigots experience segregation and layering, creating deposits that are difficult to excavate due to the highly erratic geotechnical behaviour of the exposed faces. Both in-situ and laboratory testing are necessary to understand how steep, temporary tailings slopes might behave, ensuring stability through engineering analysis. This paper describes a detailed geotechnical characterization of an old TSF impoundment by in situ and laboratory testing, including sonic drilling, SCPTu soundings, geophysical field testing, and oedometric, monotonic and cyclic triaxial lab testing. Two different areas were surveyed: tailings near the dam, where coarser material is expected, and in the centre of the impoundment for the characterization of finer materials. We focused on the critical state behaviour of tailings and estimations of the state parameter, required to calibrate the numerical models employed in the analyses.

Determination of the S-wave propagation velocity of ballast by Spectral Analysis of Surface Waves

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:28:47 +0200

The Laboratorio de Geotecnia-CEDEX uses some software and tools for studying different phenomena and performance of track sections. For this purpose, it is usually necessary to determine the S-wave (shear elastic wave) velocity of the different layers in the track section which typically are, from bottom to top: natural ground, embankment, form layer, subballast and ballast. The Laboratorio de Geotecnia-CEDEX has experimental S-wave propagation velocity (Vs) values of embankments, form layers and sub-ballast layers, obtained from several campaigns where the Spectral Analysis of Surface Waves (SASW) was applied on the different layers during the construction of several track sections. To complete the studies and to obtain Vs values for the ballast layer, two campaigns were carried out in the CEDEX Track Box (CTB), a railway testing facility where it is possible to test complete railway sections on a 1:1 scale; and a field measurement campaign on an in-service railway track. Due to the discontinuous nature of the ballast layer carrying out tests to obtain Vs presents serious problems. To avoid these problems, a new procedure was developed to obtain these values using the SASW method by installing sensors on top of the sleepers. Through the interpretation of measurements taken with the SASW technique on the ballast, the dispersion curve is obtained, and from it, the values of Vs are calculated. The results are presented in this article and are also compared with values found through a literature review obtained or estimated by other authors.

Dynamic Response of Marginal Soil using SPT, DCPT & Cyclic Simple Shear Tests

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:28:26 +0200

Coarse-grained soils are preferably used in geotechnical infrastructure projects such as retaining walls and highway embankments due to their superior drainage and frictional properties. However, such materials are not always available on or near the construction site. Given the limited availability, high cost, and transportation issues associated with coarsegrained fill, using the locally available marginal soil for the various infrastructure projects becomes essential. Marginal soils are soils with a high percentage of fines that can be cohesive or non-cohesive. The primary concern with marginal soil is its low permeability, which causes excess positive-pore water pressure evolution during load application. As a consequence, the soil loses shear strength over time. Previous researchers have provided some information on the dynamic behaviour of marginal soils in terms of cyclic strength and pore pressure development. However, more research is needed to understand the dynamic response of compacted marginal soils in terms of cyclic resistance ratio (CRR) using field and lab data. Therefore, an attempt has been made in this study to evaluate the cyclic resistance of compacted marginal soil (clayey sand) by performing stress-controlled cyclic simple shear (CSS) tests in the laboratory and Standard Penetration Test (SPT) and Dynamic Cone Penetration Test (DCPT) in the field. The cyclic strength of marginal soil has been determined as Cyclic Resistance Ratio (CRR) by using laboratory (CSS) and field (SPT, DCPT) test data.

Improved Modeling and Inversion of Surface Wave Method

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:28:04 +0200

The multi-channel analysis of surface waves (MASW) is a widely employed surface wave method. The fundamental mode inversion is the usual scheme in MASW, because separating the fundamental mode from other high modes is feasible with an adequately long array. However, the extracted fundamental mode represents only part of the dynamic characteristics, it may deviate from the theoretical fundamental mode due to truncation effect, and part of it may correspond to another higher mode or leaky mode, resulting in mode misidentification. Conversely, the spectral analysis of surface waves (SASW) method features a more rigorous inversion scheme by matching the effective mode, but it may suffer from the tricky phase-unwrapping in the dispersion data reduction. This study introduces an improved dynamic response solution for elastic-layered media subjected to vertical loads. The proposed dynamic response solution is fast and accurate, facilitating the full wavefield inversion in terms of the frequency-velocity spectrum. The MASW frequencyvelocity spectrum inversion considers testing configuration and comprehensively models all wave phenomena, including near-field effect, truncation effect, and leaky waves. The MASW frequency-velocity spectrum inversion merges the convenience of MASW dispersion analysis with the rigorous inversion scheme adopted by SASW. The new MASW frequency-velocity spectrum inversion is compared with the SASW effective mode inversion and MASW fundamental mode inversion. The results show that both SASW effective mode inversion and MASW frequency-velocity spectrum inversion produce better inverted results than the MASW fundamental mode inversion, while the process of MASW frequency-velocity spectrum inversion is more convenient and robust. Finally, a field example is used to demonstrate the applicability of frequency-velocity spectrum inversion.

The Next Generation of Testing with LWD to Assess the In-Situ Permanent Deformation of Geomaterials under Repeated Loading

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:27:45 +0200

This study focuses on evaluating in-situ permanent deformation in fine-grained soils through the application of a specially designed Repeated Light Weight Deflectometer (LWD) test. The primary objective is to investigate how water content and applied stress levels influence permanent deformations in the field. Additionally, the study aims to assess the utility of LWD-derived data in predicting permanent strains. Results indicate a significant correlation between permanent deformations and key parameters, such as the number of load cycles, applied stress levels, and water content. It is observed that permanent deformations increase proportionally with these variables, particularly in cases of elevated water content and higher stress levels. The soil demonstrates an increased susceptibility to accumulating permanent deformations, persisting even after numerous LWD load applications. In response to these findings, a predictive model is presented to estimate accumulated permanent strain, exhibiting a commendable fit to data for moisture contents up to 22%, corresponding to an average water content of 19%. Ultimately, this research underscores the pivotal role of water content and applied stress levels in determining permanent deformation characteristics in fine-grained subgrade soils. The study also provides a valuable predictive model derived from repeated in-situ LWD measurements, offering critical insights into the field permanent deformation behaviour of subgrade soil. This simple and time-saving test enhances engineering practices for pavement design and construction.

Model CPTs in Chalk

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:04:29 +0200

Cemented geomaterials exist in many parts of the world. Structure and bonding largely influence their strength, stiffness, permeability and other hydromechanical properties. Despite the CPT being the most widely used geotechnical engineering soil characterization tool, most existing correlations between penetration resistance and soil parameters apply only to uncemented granular deposits. Application of existing correlations to cemented geomaterials such as soft rocks can produce misleading interpretation making CPT application more challenging. In particular, CPT databases correlating tip resistance with yield stress of the intact material show a wide scatter prompting the need for a better understanding of the mechanics of cone penetration in soft bonded materials. In this work, 1g small-scale model CPTs are performed in a soft rock, whilst in-test X-ray techniques help to reveal mechanisms behind the penetration process. Thereafter, experimental results are compared to field scale results and those modelled using the Particle Finite Element method which is geared toward large deformation analyses. The combined interpretation of the experimental and numerical data is then used to discuss some of the unique attributes of CPT behaviour in soft rock.

Improving the reliability of sand-steel interface friction angle measurements based on the Ring Shear test

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:03:28 +0200

Understanding the shearing behaviour at soil-structure interfaces is crucial for the analysis and design of geotechnical structures. When significant relative displacements between soil and interface are involved during installation or operation, the ring shear interface testing method, which includes large pre-shearing, is considered reliable for assessing interface resistance. These tests are commonly applied in practical design approaches for driven piles. This research aimed to expand the unified database created by Imperial College London (ICL) and Norwegian Geotechnical Institute (NGI) by incorporating soil test data collected by Geo for North Sea sands with varying grain size distributions. We present an extended database that encompasses soil classification tests and Ring Shear (RS) tests conducted on soilsteel interfaces using Advanced Ring Shear apparatus (Bishop-apparatus-like). This paper introduces a database of interface shearing tests conducted on sandy silty soils with a low content of non-plastic fines. These results facilitate a comprehensive examination of the potential impacts of various factors, including physical soil properties (e.g. grain size distribution), interface characteristics (surface roughness), and testing conditions (normal effective stress). Trends identified within the datasets are synthesized with insights from prior studies to propose interface shear strength parameters suitable for preliminary design employing simple index tests for non-plastic sandy soils. Finally, the paper presents a newly advanced Ring Shear apparatus designed by Wille Geotechnik capable of accommodating static friction. This apparatus incorporates two novel test inserts that can rotate independently at varying radial speeds while being guided simultaneously. The two guided rings can be vertically adjusted, thereby mitigating static friction effects, even in cases of dilatancy.

Gassy Soils ofF the Llobregat Delta: Impact on Geomechanical Characterization

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:02:28 +0200

The presence of biogenic gas in the soft soils of the Delta del Llobregat at the Port of Barcelona has already been reported by various authors based on geophysical investigations and in-situ tests. As the impact of gas presence on soil behaviour remains uncertain, it is of interest to describe the behaviour of these gassy soils as they may affect future expansions of the Port of Barcelona. Recently, in new geotechnical investigations at the Port of Barcelona, gas emissions have been observed, in several locations in the vicinity of the South breakwater, while performing in situ tests (CPTu and SDMT) or during borehole drilling. Samples were extracted from those boreholes that were subsequently used for laboratory tests. Given the potential impact on geotechnical properties, the results of the investigation were utilized to increase the understanding of gassy soils. Essentially, the focus was on detecting anomalies in geotechnical parameters at the points where gas was detected. These anomalies were also correlated with observations of soil structure obtained from microCT scanning X-ray images of undisturbed samples from the zones where gas was present.

Application of Physics-Informed Machine Learning to Geotechnical and Geophysical Site Investigation Data To Define Centimetre-Scale Design Parameters for Offshore Wind

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:02:05 +0200

Offshore wind plays a pivotal role in enhancing Europe's energy security and achieving energy decarbonization goals. However, expediting offshore wind deployment necessitates efficient and economical site investigation surveys. To address this challenge, we introduce a novel approach utilising a deep neural network (DNN) to establish correlations between geotechnical cone penetrometer test (CPT) data and shear wave velocity (ð) from seismic CPT. Subsequently, porosity and P-wave velocity (ð) are derived using a ð to bulk density correlation and a dynamic poroelastic model. The DNN is trained and tested on a dataset comprising 5284 instances of public-domain geotechnical CPT test data, including depth, tip resistance, sleeve friction, and ð from seismic CPT. During testing, the DNN model demonstrates a mean absolute error of 55 m s-1 between predicted and measured ð values. The uncertainty in ð predictions is attributed to factors such as (i) limited training data for some soil types such as gravelly sands, (ii) intricate relationship between geotechnical CPT features and seismic properties influencing ð, (iii) the presence of CPT features and ð combinations that lie well outside the region from most combinations (i.e. outliers), and (iv) CPT features and ð measurements that are averaged over different depth ranges. The derived porosity and ð

Small Strain Shear Modulus Derived From Offshore Seismic Reflection Data

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:01:33 +0200

Small strain shear modulus ðº preferred reference method for ðº is an important parameter for design of foundations of fixed offshore structures. The is the seismic velocity test (SVT) performed as part of a seismic cone penetration test (SCPT). SVTs provide in-situ ðº values for discrete depth sections of SCPTs. This paper focusses on added value achieved by (1) generation of 15 million synthetic ðº (2) a ðº profiles to 50 m depth and zonation map for the IJmuiden Ver Wind Farm Sites Alpha and Beta (offshore Netherlands). The synthetic ðº profiles were derived from a data set of 51 SCPT profiles, 250 CPT profiles and 2D UHR seismic reflection traces along survey track lines spaced at about 70 m. The quality of the SCPT data and UHR seismic reflection data was stateof-the-art (as of 2021). The data process included the use of a (1) multi fidelity data fusion statistical framework and (2) machine learning by a convolutional neural network. The synthetic ðº data were the basis for the ðº zonation map used to enhance an integrated ground model for the wind farm sites. Particularly, the map can be used to quickly identify and constrain areas which are favourable and challenging for design of monopiles and other common foundation types typically considered for offshore wind turbines.

Linking multi-sensor core logger data with in-situ and laboratory testing: A North Sea case study

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 12:00:56 +0200

Driven by an increase in the scale of laboratory testing programs, the industry is looking for new methods of soil characterisation and ways to extract more benefit from existing data. In this paper, applications of Multi-Sensor Core Logging (MSCL) to site characterisation projects are discussed, highlighting the potential for providing a fast, quantitative assessment of recovered samples. Sensors of the MSCL include bulk density, P-wave velocity, natural gamma, electrical resistivity and magnetic susceptibility. Natural gamma is shown to be related to higher silt and clay content, acting as a useful parameter for soil classification and quantitative assessment of fines content. A comparison between MSCL and in-situ CPTu data reveals correlations between natural gamma and friction ratio, normalised soil behaviour index, Ic, and net pore pressure response. By collecting MSCL data on all samples at the beginning of a lab program, one can obtain a full overview of the material available for testing, leading to more strategic sample selection and a reduced overall volume of testing. Correlations with MSCL parameters and geotechnical properties can be used to predict continuous profiles, and be extended to in-situ measurements from borehole logging and CPT

"Development and Preliminary Testing of a New Robotic Tool for Direct Determination of ‘P-Y’ Soil Reaction Curves for Offshore Geotechnical Applications"

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:59:59 +0200

Monopiles are the most widespread foundation option for offshore wind turbine foundations and their design is largely governed by lateral stability and serviceability. The determination of lateral soil reaction ‘p-y’ curves is a crucial element for their design. At present, ‘p-y’ curves are typically determined through indirect methods, such as correlation from fundamental constitutive parameters, CPT data or extracted through numerical procedures. This paper presents the specification requirements, initial mechanical design, sensor calibration and preliminary testing in a small calibration chamber of a new robotic site investigation tool, the ROBOCONE ‘p-y’ module. This new device can be fitted behind a standard CPT cone. It features a cylindrical module that, after insertion in the ground, can move sideways to closely mimic the kinematic mechanism experienced by a laterally loaded pile element and provide direct “in-situ” characterisation of the ‘p-y’ soil reaction curves. The imposed horizontal translation is substantially different from those of the typical pressuremeter and dilatometer, and analogous to that of a small laterally loaded pile. Movements of the module can be programmed to apply simple monotonic lateral loading conditions and complex stress-controlled or deformation-controlled histories (i.e. cyclic loading, consolidation stages, maintained load). These provide data that can be scaled directly to support advanced cyclic and whole-life design procedures for the lateral ‘p-y’ response of piles.

Pleistocene and early Holocene palaeo-landscapes of the Dogger Bank South Wind Farm Sites

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:59:28 +0200

A preliminary ground model was prepared for the planned Dogger Bank South Wind Farm Sites in the UK sector of the North Sea. This ground model is based on a geological interpretation of 2D Ultra Ultra High Resolution Seismic (UUHRS) data and geotechnical data. The interpretation results include seismostratigraphic horizons which delineate major soil units. Mapping of these soil units is important for the planning and design of wind turbine locations and inter array cables. Additionally, these horizons reveal (1) multiple generations of buried palaeochannels and (2) evidence for shifting coastlines. The buried palaeochannels have tributaries and contain evidence for the local presence of marshlands (peat beds) beyond the channel margins. These landscapes formed during the Pleistocene and were subsequently flooded when sea level rose as a result of meltwater release from rapidly decaying ice sheets. Locally, thick sequences of early Holocene marine sand deposits show evidence of large-scale clinoforms, which indicate that palaeocoastlines prograded seaward over a distance of up to 20 km during the early Holocene. The top of these clinoforms contain erosion surfaces and gravel lags, indicating sub-aerial exposure of the delta top. This shows that while in general ‘Doggerland’ was rapidly flooded during the early Holocene, there were short periods when the land area expanded.

Preliminary insights from Foundations for Offshore Wind Turbines (FRONTIErS) Doctoral Network

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:58:58 +0200

The European offshore wind sector has grown rapidly, with significant advances in turbine technologies, in creased sizes, and construction locations further from the shore in deeper waters than ever before. A critical challenge has emerged relating to a growing lack of knowledge surrounding how to design foundations to support these new turbines, with the safety, life-span, cost, and environmental implications coming increasingly into question. To maintain Europe’s stance as a World-leader in offshore wind, Foundations for Offshore Wind Turbines (FRONTIErS) Doctoral Network has been designed to bring together research-intensive universities and major industry stakeholders to train the next generation of graduates with the appropriate skills to tackle the emerging issues presenting as a barrier to continued development of the sector. Eleven Doctoral Candidates have been recruited to tackle significant challenges related to foundation design and performance. Projects focus on topics such as: understanding soil variability, effect of cyclic loading on axial capacity, pile aging, dynamic modelling informed from in-situ testing, time and spatial variation in soil properties, driveability modelling, gravity-base scour effects, multi-directional loading effects, centrifuge testing of cyclic loading response, and dynamic features of wind turbine foundations. This paper presents a preliminary overview of the various PhD projects ongoing as part of this network, which are in the early stages, as well as a summary of training conducted to date.

The importance and influence of the interpretation of geological-geotechnical data on safety of earthen dams

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:40:32 +0200

The geological-geotechnical investigation campaign plays a fundamental role in dam safety by providing essential information for assessing and managing the risks associated with these structures. It also allows potential problems to be identified, such as the presence of geological faults or unstable soils. This information allows preventive actions to be taken to avoid catastrophic collapses, through additional containment measures or the revision of the dam's design.The aim of this article is therefore to present the interpretation of the geological-geotechnical data (geophysical tests, Vane Test, triaxial tests, CPTu and mixed borehole) obtained from a robust campaign to investigate the structure of a sediment containment earth dam, raised downstream, located in the state of Minas Gerais. The use of these results meant that the structure could be evaluated with the real conditions of the terrain in different situations such as seismic or hydrostatic overloads, guaranteeing the stability of the structure. In addition, it was possible to determine the soil's capacity to withstand the loads exerted by the dammed water and identify possible points of fragility.From the results obtained in the analysis and interpretation of the structure's sections, it was possible to measure the influence of the discretization of the earth dam massif through the structure's stability analysis, which also made it possible to make a comparison with the analysis sections before and after the geological-geotechnical campaign. In addition, it was possible to discuss the importance and demonstrate that it is essential to carry out comprehensive and up-to-date geological-geotechnical investigation campaigns to ensure that dams are built and operated safely.

Post-liquefaction analysis and shear wave assessment by means of instrumented DCP: application to Cephalonia island (Greece) and Petrinja region (Croatia)

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:39:38 +0200

This work presents both a summary of its implementation at two post-seismic sites: the island of Cephalonia (Greece), and the Petrinja (Croatia) along the Kupa river. In the first case, the main objective was to characterize the surface formations of the Koutavos plio-quaternary sedimentary basin to propose a 1D model of the surface soil column and assess the influence of the variability of these surface formations on the amplification of seismic motion. The second experimental campaign in Croatia was aimed at identifying the soil layers that had been liquefied following the events of 2020, as well as highlighting the different soil models obtained by geophysics or constructed from instrumented variableenergy DCP. For each investigated site, additional geophysical and geotechnical tests were carried out. The data collected with this new technology were compared with those obtained previously with other geophysical methods (MASW), in order to assess the shear wave velocity obtained in particular.

Geotechnical characterisation of tailing deposits with instrumented variable energy dynamic penetrometer: a state of art

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:38:33 +0200

Chile is the third country with most tailing dams worldwide (764, of which 15% active, 62% inactive, and 23% abandoned). Today, one of the main challenges of the mining industry is to ensure environmental sustainability. To achieve this, it is not only necessary to have regulations guaranteeing correct design, maintenance, closure stages, but also supervision and suitable technology enabling rapid, reliable, and cost-effective diagnosis of the overall tailings dam stability. For the last 20 years, French instrumented dynamic cone penetrometer, P.A.N.D.A®, has been used for in-depth quality control of tailings deposits, mainly due to its rapidity, portability, easy-to-use, cost-effective, and environmentally friendly testing which is based on standardized methods and able to produce immediate results. The last few years, different studies have been carried out to characterize tailings dams from a geotechnical perspective as well as to assess their spatial and temporal variability. This article presents a summary of the 20 years of Chilean experience in compaction quality control and geotechnical characterization of mine waste facilities using P.A.N.D.A® to assess the overall stability, slope analysis stability, liquefaction triggering, spatial variability of material properties and evaluation of some geotechnical parameters. Indeed, given the scale of the problem these structures represent for the community and the environment, it seemed necessary to bring together most of the work carried out in Chile to propose an innovative alternative to the rest of the mining community.

A review of 30 years French instrumented and variable energy dynamic cone penetrometer Panda

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:37:58 +0200

Dynamic penetrometer is a worldwide practice in geotechnical exploration and the French Panda (1) lightweight variable energy is the most developed device nowadays. Widely used in France and other countries, The Panda penetrometer is relatively unknown for characterizing surface soils domain and the possibilities it offers. In this article, the authors offer a brief review of the principle of measurement, its uses, advantages and disadvantages calibration, and interpretation, as well as the different relationships with other in-situ test (CPT, SPT…) and some geotechnical parameters. A summary of the works that can be found and that are based on this technology is also presented. The overall aim is to provide the reader with a basic historical document for a better understanding of the operation and analysis of the results obtained with this device, enabling it to be integrated, as a complement, into in situ investigation campaigns.

Ligthweigth and heavy-duty instrumented, servo assisted dynamic cone penetrometers for shallow soil characterisation

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:37:19 +0200

Based on the principle of the Panda® penetrometer, a third-generation of variable-energy dynamic cone penetrometer has been developed in France: the Panda 3(1). This is an instrumented dynamic penetrometer which, by measuring strain, acceleration, and displacement on the rods, close to the anvil, and then decoupling the deformation waves created by the impact and propagating within the rods during penetration, makes it possible to obtain for each blow, at the soil/cone interface, a dynamic load penetration curve, called DCLT curve. Several experimental and numerical studies have been carried out to develop different techniques for processing DCLT curves and dynamic signals to assess input energy, dynamic and pseudo static cone resistance, dynamic stiffness, elastic modulus, and compressional wave velocities of soil. This technique has been adapted to the DPSH cone penetrometer (ISO 22476-2), for which it was necessary to servoassisted the impact force as a function of the soil penetration obtained after each blow to improve then the quality of the signals and DCLT curves obtained. Recently, in France, a vast experimental program involving two universities and two geotechnical companies was carried out to develop this new technique. A large laboratory and in-situ test data base was performed. After a brief presentation of the theoretical and technological development of this new technique is presented.

Application of Swedish Weight Sounding Test for the Geotechnical Assessment of Solar Power Plant

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:36:50 +0200

As part of the global efforts to mitigate climate change and foster sustainable development, the construction of solar power plants has experienced significant growth in the Philippines over the past few years. This constitutes an increasing contribution to the renewable energy sector. This paper presents the applications of the Swedish Weight Sounding Test in the geotechnical assessment for solar power plant facilities. Utilizing SWST is a more portable and cost-effective way to evaluate the soil conditions crucial to establishing the solar panel arrays' foundation system and the project's overall feasibility. The penetration resistance data of SWST was employed to establish the soil stratification, soil strength, and consequently the foundation type and allowable bearing capacity. Moreover, the results were also used to assess the susceptibility of the project site to geohazards, such as liquefaction. Theoretical capacities of the helical and screw piles, the widely used foundation system for solar panels, can be derived and correlated with the results of the SWST. This paper shall present the utilization of SWST, as a supplement to SPT, primarily on the geohazard and foundation assessment for solar power plants. This study is expected to provide a reliable reference on the advantages of SWST and the selection of foundation type based on the results obtained from this cost-effective geotechnical investigation method.

Vibro-Penetration Tests for The Evaluation of Blasting Compaction in very loose Sandy dumps

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:36:24 +0200

During the so‐called vibro‐penetration test (VPT), a vertical harmonic excitation force drives a rod with a conical tip into the ground. For the evaluation of the VPT resistance, an energy‐corrected number of vibration cycles Nz10 for 0.10 m penetration is used. In order to determine Nz10, the dynamic penetration resistance, the tip and shaft resistance, the tip acceleration, and the depth of the penetrometer tip are continuously recorded and processed according to a mechanical vibro-penetration model. Calibration chamber tests, field tests, and Finite Element Analyses, which were carried out to validate the assumed penetration mechanism and to investigate the influence of the state variables (density and effective stresses) and the machine parameters (static moment, frequency, and static load) on the penetration resistance. As the force and displacement of the penetrometer are determined at the tip, an equivalent spring stiffness, which is correlated with the soil stiffness, can be calculated over the driving depth. Since vibro‐penetration resistance is closely related to the soil behavior under cyclic shearing, the VPT should be more appropriate than monotonic tests to characterize the ground response to repeated dynamic and alternating loading, e.g. pile drivability, ground compaction, and soil liquefaction susceptibility. Compared with the cone-penetration test (CPT), the VPT equipment is much lighter, the execution time is shorter, and in‐situ investigations of medium-dense to dense cohesionless soils at large depths are feasible. In this contribution, VPT and CPT are used to investigate the effect of blasting compaction in very loose dumps from opencast mines in Lusatia, Brandenburg, Germany. It is concluded that the VPT results are reproducible. In addition, Nz10 shows a clear correlation with the state variables and the VPT records before and after blasting compares well with the results of CPT.

Dynamic modulus E_kd evaluation by dynamic penetration test

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:35:53 +0200

Dynamic penetration tests DPT have been routinely employed in the geotechnical characterization of the subsoil in different types of engineering projects. The evaluation of the results of these tests has been performed considering a limited number of parameters obtained in the field, so the definition of new parameters allows a more accurate evaluation of soil characteristics. The purpose of this paper is to present a methodology for the evaluation of the dynamic modulus (Ekd) based on the analysis of the dynamic force and velocity signals recorded in each hammer impact. Variable energy DPT tests were performed on Fontainebleau NE34 sand specimens in a K0 calibration chamber. For each hammer impact on the penetrometer, a decoupling and wave reconstruction method was applied to obtain the force and velocity signals at the cone-soil interface, which are analyzed in the frequency spectrum to obtain the Ekd modulus. The results show that it is possible to evaluate the dynamic modulus at different vertical loading conditions and independent of the impact energy level of the hammer on the penetrometer.

Evaluation of Cone Resistance Results from Dutch Formula

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:35:19 +0200

The Dynamic Penetration Test (DPT) is widely applied for soil field characterization. The technique is usually appreciated as a simple and cost-effective means of determine soil resistance which can be obtained either from Newtonian or from wave equation methods. While wave equation analysis has demonstrated numerous advantages in recent decades, its adoption is constrained by the need for specific instrumentation and more complex analysis. Consequently, the simpler Newtonian analysis, and particularly the Dutch Formula specified by ISO 22476-2, remains the more commonly used approach for routine geotechnical applications. To ensure its accuracy comparing to wave equation-based methods, a field campaigns were conducted on experimental sites with various soil types. The campaigns included Cone Penetration Test (CPT), which is used as a reference tool in this study, and instrumented DPTs allowing easy application of wave equation methods. Results revealed that Dutch Formula resistance values were comparable to both CPT results and those derived from wave equation methods in most cases. In addition, DF variation formula applying energy measurement seemed to underestimate cone resistance in all case examined. The study highlights the importance of applying good practice rules to enhance DPT results

Investigation and monitoring to model the interaction between the Scrovegni’s Chapel in Padova (Italy) and the underlying foundation soil

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:34:15 +0200

In Padova's historic centre lies the renowned Scrovegni’s Chapel, painted by Giotto in 1303. The local subsoil primarily consists of silty sand with some layers of silt. The crypt beneath acts as a buffer against soil moisture, preventing damage to the frescoes. However, during heavy rain, groundwater rises flowing across the floor and lateral walls, therefore flooding the pavement. A pumping system is eventually activated to mitigate the pavement inundation. Several investigations including geophysical surveys, piezocone tests, and boreholes with soil sampling have been conducted to provide the subsoil geotechnical model and understand the local hydrogeological behaviour. Monitoring systems, such as piezometers, deep extensometers and optical fiber cables, track groundwater levels and long-term soil displacements. The paper aims to characterize the subsoil's stratigraphy, mechanical properties and permeabilities to model how the environmental conditions affect the ancient Chapel and ensure its long-term stability.

In-situ experimental tests for shallow foundation design using dynamic penetration testing method

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:33:16 +0200

To develop an advanced and innovative method for shallow foundations design with the aid of dynamic penetration testing technique, several in-situ tests are realized on various experimental sites to enrich the available database and to valid the computed results. This communication presents the field tests consisting of the Foundation Loading Tests and the Dynamic Cone Penetration Tests (DCPT): their performance, operation principles, equipment and results obtained. A direct method for bearing capacity prediction based on the measured data is also proposed, then compared to other approaches already standardized. Therefore, this study contributes to the improvement of the shallow foundations design method by providing full-scale experimental results and discussing their findings.

Responses of Dynamic Penetrometers according to Hammer Weight and Drop Height

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:32:16 +0200

This study characterizes the dynamic responses of hammer weight and drop height in dynamic penetration tests. The tests were conducted using an instrumented dynamic cone penetrometer (IDCP) to obtain the dynamic responses during penetration. Various hammer weight and drop height types were used at a fixed potential energy of 45.1 N∙m. The measured compression stresses and transferred energies into the rod head and cone tip were analyzed for hammer weight and drop height. The compression stress at the rod head varied with the hammer weight and drop height, whereas the compression stress at the cone tip is irrelevant to the hammer weight or drop height. In addition, the transferred energies into the rod head and cone tip increased as the hammer weight increased but decreased as the drop height increased. This study demonstrates that hammer weight and drop height should be considered when the characteristic of subsurface is profiled using dynamic penetrometer.

Applicability of CPTU to characterize diatomaceous fine-grained soils: a case study in Euganean Hills (Italy)

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:31:46 +0200

Diatomaceous soils, composed of diatom fossils and clay minerals typically formed in volcanic environments, exhibit characteristics such as low unit weight, high plasticity and liquid limit, significant compressibility, and high friction angles. Despite their presence in various locations globally, knowledge about their geotechnical behavior is limited and primarily based on laboratory tests conducted on artificial samples. This paper presents data obtained from undisturbed samples of natural diatomaceous soils and discusses the interpretation of Cone Penetration Test with Pore Pressure (CPTU) data to classify these complex non-textbook soils and estimate their mechanical properties. The study area is situated in the Po Plain near the thermal anomaly region of the Euganean Hills in Northeast Italy. Three CPTUs and one borehole with the collection of four Osterberg undisturbed samples were conducted. Laboratory tests on the undisturbed samples provided values for Atterberg Limits, soil unit weight, in-situ void ratio, compressibility, and permeability, which were compared with estimations derived from CPTU data analysis. Moreover, Scanning Electron Microscope images provided insight into the distinctive microstructure of diatom microfossils embedded in a clayey matrix. Based on these comparisons, CPTU proves to be effective in estimating relevant parameters of diatomaceous soils, particularly the Soil Behavior Type (SBT) and consolidation coefficient from dissipation tests. However, the agreement in estimating the oedometric modulus is less satisfactory. Therefore, for a precise definition of the geotechnical model, it is recommended to conduct additional laboratory tests, particularly those focused on defining compressibility parameters, given the unique behavior of natural diatomaceous soils.

Soil Characterisation Using a Dynamic Penetrometer

Jesús Sánchez Pinedo — Fri, 07 Jun 2024 11:31:19 +0200

In offshore engineering, a geotechnical site investigation is an important step in analysis and design to ensure the integrity and serviceability of infrastructure. The Cone Penetration Test (CPT) stands as the prevailing technology for offshore soil characterisation. However, this test method requires a substantial allocation of resources for equipment transportation and operation personnel. This proves inefficient and costly for conducting comprehensive surveys over ocean beds. Alternatively, free-falling penetrometers (FFP) have attracted attention as a CPT replacement for soil characterisation. Nevertheless, these devices can penetrate only to shallow depths within soils, limiting their applicability for offshore site investigation purposes. A new device has been created to overcome this constraint, featuring a dynamic penetrometer launched by a speargun. Unlike conventional free-falling penetrometers, this apparatus can attain a greater penetration ratio, exceeding 20 times its diameter. The process of experimental testing yielded notable enhancements, particularly in effectively addressing challenges associated with tilting when attempting low-penetration depths. By implementing rate corrections into the methodology, promising results were obtained for equivalent static penetration resistance. This approach not only represents the capacity to influence future penetrometer designs but elevates the overall efficiency of in-situ soil characterisation procedures.

Machine Learning-Based Modeling of Net Ecosystem Exchange Using Numerical Weather Data and Satellite Images

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:24:22 +0200

Recently, the increasing severity of climate change attributable to global warming has emphasized the imperative of carbon absorption to mitigate greenhouse gas emissions. The use of the carbon sink based on the carbon absorption and storage functions of forests is suggested as an effective alternative for domestic greenhouse gas reduction. Additionally, agricultural land cover comprises approximately 38% of the Earth's surface, underscoring the importance of comprehensively understanding the carbon cycle within not only forests but also agricultural landscapes. This significance arises from the fact that agricultural land locally amplifies seasonal variations in carbon dioxide by approximately 25% compared to vegetated areas. Consequently, a comprehensive understanding of both forest and agricultural land carbon cycles is imperative, necessitating quantitative analysis of carbon uptake in agricultural settings. Thus, this study aims to construct a machine learning-based model for estimating the net ecosystem exchange (NEE) of rice paddies in South Korea using ground flux data, meteorological variables, and satellite images. Through quantitative assessment, the NEE was determined, with a mean absolute error of 1.387, root mean square error of 2.203, and correlation coefficient of 0.872. Notably, observed NEE values demonstrating extremes in magnitude were associated with calculation errors, reflecting tendencies of both underestimation and overestimation. This phenomenon is likely attributed to the study's reliance on a limited dataset and the inherent challenges of training models across a broad spectrum of observations. To enhance calculation accuracy, future endeavors should focus on accumulating a more extensive repository of NEE flux observations and leveraging high-resolution satellite imagery and meteorological datasets for refining machine learningbased models.

AI Modeling for Characterization of Paddy Rice Yields under Extreme Weather Conditions Using Remote Sensing and Geospatial Data

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:24:04 +0200

Climate change, such as increase in CO2 levels and rising temperatures, can have a significant impact on paddy rice production and increase the uncertainty of yield forecasts. This study aims to employ AI modeling for forecasting paddy rice yield and present the findings of a quantitative analysis to determine its ability to generate stable forecasts under extreme weather conditions, such as heatwaves, low temperatures, and heavy rainfall. Vegetation growth indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite product were utilized. These indices include the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Leaf Area Index (LAI), Fraction of Absorbed Photosynthetically Active Radiation (FPAR), and Near-Infrared Reflectance of vegetation (NIRv). Meteorological variables such as downward solar radiation flux, daily temperature difference, precipitation, relative humidity, and temperature were also used. Over 23 years of experimentation (2000-2022), yields under extreme weather conditions did not exhibit a significant difference from the normal period, with a Mean Absolute Error (MAE) ranging from 0.30 to 0.33 ton/ha, representing a 4-5% error of the average yield. This study presents an AI modeling methodology that enables stable predictions of paddy rice yields, even under extreme weather conditions. Future work should focus on refining input data and optimizing the model by analyzing cases of extreme weather.

Taillings Characterization: Exploring Laser Granulometry with Machine Learning

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:23:46 +0200

The conventional particle size test has been a widely used method in the characterization of soils and tailings. Such information is particularly useful in the evaluation of materials deposited in tailing stacks or compacted landfills, which must follow reference particle size ranges. However, the method has limitations, the main one being the execution time, which usually lasts around three days. On the other hand, laser testing appears as a viable alternative. This innovative method obtains the grain size curve of the soil through the light dispersion pattern and lasts a few minutes, a significant improvement over the conventional method. Furthermore, this method can cover particle size ranges of up to 0.1 micrometers, while the conventional method is limited to 1 micrometer. Despite the benefits of using this equipment, the laser grain size test does not yet have specific standardization for use in the field of soil mechanics. In this context, this work proposes the use of machine learning techniques to demonstrate the existence of compatibility between both methods. To this end, tests were carried out using both methodologies on different samples of iron ore tailings and an algorithm was developed to predict the material classification. The evaluation of the results made it possible to verify the consistency and precision of the results between the two methods, reinforcing the reliability and viability of the laser test as an efficient alternative to the traditional method

Integrated geophysical methods in identifying preferential flow paths in an earth dam

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:23:23 +0200

The evaluation of safety conditions in dams is of utmost importance to ensure stability and often involves subsurface investigation methods. Geophysical methods have emerged as a modern and relevant alternative, often more practical than traditional direct methods. This study aims to integrate the application and interpretation of resistivity and selfpotential methods to identify preferential flow paths in a small earth dam. The investigation was conducted at a dam located on the Viçosa Campus of the Federal University of Viçosa (UFV), with three main soil layers: embankment, silty clay, and alluvium. Analysis of the results revealed potential conductive zones and negative spontaneous potential anomalies, suggesting the occurrence of piping and the presence of buried structures in the spillway area. Moreover, the geophysical investigation methodology proved effective in evaluating geotechnical characteristics and flow conditions of the dam, contributing to the foundation for future safety and stability analyses of the structure.

Data-driven Multi-stage Sampling Strategy for Machine Learning of Underground Digital Twins Consdiering Stratigraphic Uncertainty

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:22:20 +0200

A sound understanding of subsurface geological conditions is crucial for the digitalisation of underground infrastructure. The building and updating of underground digital twins heavily rely on sparse geotechnical measurements (e.g., boreholes) retrieved from the ground, and an efficient sampling strategy can facilitate the interpretation of subsurface heterogeneities. Geotechnical sampling design can be viewed as a constrained optimization process that aims to obtain as much geological information as possible from a limited number of sampling locations within a given site boundary. In this study, a data-driven intelligent sampling strategy is proposed to optimize borehole locations for a multi-stage site investigation of a three-dimensional (3D) geological domain. The initial sampling plan is determined using weighted centroidal Voronoi tessellation, which assigns uniform sampling densities to zones of different importance. Measurements obtained from the initial stage are combined with prior geological knowledge to build underground digital twins using an image-based stochastic modelling method. Multiple realizations of the geological domain can be developed under the framework of Monte Carlo simulation, and stratigraphic uncertainties associated with multiple random realizations can be quantified using information entropy. The location with the maximum entropy is adaptively selected as the next optimal sampling location. The proposed method is the first sampling strategy that can explicitly consider 3D subsurface stratigraphic variations. The performance of the proposed multi-stage sampling strategy is demonstrated using a simulation example. Results indicate that the proposed method can efficiently identify the optimal sampling locations while accounting for irregular site geometries and 3D subsurface stratigraphic uncertainties.

Predicting Soil Behavior Types Along the Danube: An AI-Driven Approach Using CPT Data in the Szigetköz Floodplain Area

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:21:18 +0200

The Szigetköz (Hungary) is a hotbed of sand boil formation, owing to the combination of a 100-250 m thick gravel layer beneath a relatively thin covering of poor soil with varying thickness. Soil behavior is critical for flood protection in this region. This work proposes a novel way to predict Soil Behaviour Types (SBT) based on detailed CPT data collected from 29 sites in the Szigetköz area using an artificial intelligence (AI) model. The study follows a methodically planned approach that includes data collecting, preprocessing, SBT categorization based on the SBT chart developed by Robertson et al. (1986), and AI model building. The CPT dataset contains critical metrics like cone resistance and friction ratio, which are essential in characterising soil behavior. The AI model, built with powerful machine learning algorithms, is intended to learn complicated associations within data to forecast SBT classifications. Extensive feature selection, hyperparameter tuning, and cross-validation are all necessary steps in model construction to ensure accuracy and generalizability. The results show that the model can accurately forecast SBT classifications for the Szigetköz area, shedding information on the soil's behavior near the Danube River. Spatial distribution visualizations emphasize the region's many SBT categories, giving valuable information for engineering projects, land use planning, and environmental conservation activities. The AI model's interpretability elucidates the major CPT parameters driving SBT forecasts, providing stakeholders with actionable information for decision-making. Furthermore, validation of the model with new, previously unseen CPT data confirms its applicability and robustness in real-world circumstances.

Artificial Intelligence in Dynamic Compaction for Geotechnical Site Characterization

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:20:18 +0200

We present a novel method using four artificial intelligence (AI) algorithms to anticipate the cumulative degree of soil compaction (CDSC) after dynamic compaction (DC). Four AI algorithms adopted in this study include support vector regression SVR, artificial neural network (ANN), random forest (RF), and gradient boosting machine (GBM). Input variables for AI algorithms involve the average SPT N-value before dynamic compaction, cumulative applied energy normalized with a cross-sectional area of tamper, and the number of the tamper drops. Apart from cross-validation with a testing set, additional in situ test data compiled from a different section within the studied site are used to estimate the generalized capacity of the AI models. In addition, we conduct out-of-distribution analyses for the four AI algorithms in view of parametric studies. The CDSC prediction performance for the four AI models results in high prediction metrics of accuracy with the r2 higher than 0.9 for the testing scenario while the r2 of the other AI models is more than 0.9 when out-of-sample data are considered except for the GBM. The ANN seems to be the best model as the parametric study considers out-of-distribution data and suggests a strong relationship between input variables and CDSC that is more coherent with engineering principles for DC. Finally, the ANN model can be utilized to develop a mathematical model for CDSC prediction.

Integrating laboratory and geophysical data considering measurement errors

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:19:17 +0200

Laboratory and geophysical tests are commonly used in site characterization. Combining these data sets based on empirical relationships can essentially enhance data interpretation. While in traditional approaches, the uncertainties in the relationship between these data sets are ignored. The Bayesian updating method is used to consider these uncertainties. Besides, the uncertainties due to measurement errors in the laboratory tests, particularly for preconsolidation pressure, are considered based on the kriging fitting method. The outcomes of kriging fitting are utilized to establish the prior distribution, and these outcomes are then compared against the baseline established by the trend fitting method. The Markov chain Monte Carlo (MCMC) algorithm is applied to incorporate the shear wave velocity measurements from a seismic dilatometer test to derive the posterior distribution. Bayesian updating of parameters considering measurement errors is able to get a more convincing design profile.

Application of handheld mobile terrestrial laser scanning for cultural heritage documentation.

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:18:15 +0200

The preservation and documentation of cultural heritage sites are fundamental to safeguarding our shared history and identity. This study explores the innovative application of the viDoc RTK rover for cultural heritage documentation, presenting a forward-looking approach to capturing high-precision spatial data in the preservation and analysis of Brari bridge located in Tirana, Albania. Handheld mobile terrestrial laser scanning (HMTLS) offers versatility and mobility, enabling rapid and non-invasive data acquisition in complex and challenging environments. The methodology encompasses equipment selection, data acquisition techniques, and data processing workflows tailored for HMTLS technology. The results demonstrate the potential of HMTLS to produce highly accurate 3D models, showcasing intricate architectural details and capturing fine surface textures with an accuracy of 3 cm. Furthermore, the portability of handheld devices allows for documentation in areas where traditional scanning methods may be impractical. This study underscores the transformative impact of HMTLS on cultural heritage preservation, offering a cost-effective, efficient, and accessible means of creating digital archives. The adoption of this technology contributes to the long-term conservation, research, and education associated with our cultural heritage, ensuring that these invaluable assets continue to inspire and inform future generations.

A combined approach to Automated Parameter Determination (APD)

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:17:14 +0200

The success of numerical analysis relies on several factors, with one crucial aspect being the accurate determination of constitutive model parameters. Extracting these parameters directly from in-situ tests has several advantages, such as costeffectiveness and minimal soil disturbance. However, obtaining soil parameters directly from in-situ tests is not feasible, as empirical correlations are used to interpret them. An ongoing research project aims to create an automated parameter determination (APD) framework using a graph-based approach to determine constitutive model parameters from in-situ tests. The process involves using two spreadsheets as input: the first defines the parameters, while the second specifies the correlations used to compute them. The system then generates connections between the parameters and computes values for each one. The paper discusses the validation of the correlations database used by the system, which includes over 100 correlations for deriving parameters for various soil types. The framework determines parameters based on cone penetration tests (CPT), dilatometer tests (DMT), and in-situ shear wave velocity measurements. The system's output is compared to values interpreted from laboratory tests. To collect data for this validation, a web-based application "Datamap" was employed, which stores and categorizes geotechnical data. The validation process utilized data from the Norwegian GeoTest Sites (NGTS), specifically the NGTS-silt project. The parameters were calculated based on CPT, DMT, and in-situ shear wave velocity measurements. Ongoing research aims to evaluate the accuracy of the derived parameters and expand the system's capabilities to include additional in-situ tests

The stratigraphic reconstruction of longitudinal tunnel based on improved coupled Markov chains

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:16:56 +0200

The distribution of natural strata is uncertain due to tectonic movements and sedimentation. Capturing geological uncertainty is a challenge for traditional deterministic models. In this study, an improved three-dimensional coupled Markov chains method for probabilistic stratigraphic reconstruction was developed. This method considers the correlation between the field borehole data. On this basis, an inversion analysis method for horizontal transition probability matrix estimation is proposed. This method makes the predictions more suitable for possible stratigraphic distributions. The accuracy of the method was further verified by different borehole schemes from the Mawan Tunnel in Shenzhen. The results show that the proposed method can still have high accuracy when the number of boreholes is sparse. This method can reflect the asymmetry, continuity and anisotropy of three-dimensional strata.

Digitization of subsurface geological stratigraphy using machine learning and neighborhood aggregation

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:16:36 +0200

In engineering geology and geotechnical engineering, subsurface soils and rocks are natural geomaterials and exhibit inherent variability in stratigraphy due to geological deposition process. Explicit knowledge of subsurface stratigraphy is a critical input for the analysis, design, and construction of geotechnical engineering systems. However, the accurate and reliable modelling of subsurface geological stratigraphy is challenging due to the limited number of available boreholes in practice and the complex nature of soil stratigraphy. This paper presents an innovative machine learning framework built upon the neighborhood aggregation technique for the prediction of digitized subsurface geological stratigraphy. To predict the stratigraphy at a given point of interest, neighborhood aggregation is first performed to intelligently consolidate the stratigraphy information from its neighboring boreholes, resulting in additional features associated with the target location. By combining the extra stratigraphy information with conventional location-specific features, the framework enhances the predictive capabilities of classical machine learning models at a finer scale. The proposed framework is implemented using common machine learning models and is validated using a simulated benchmark 3D example. The results of leave-one-out cross-validation demonstrate that the proposed framework can improve the performance of classical machine learning models, leading to more reasonable stratigraphy transition and associated uncertainty quantification.

Calibration and Test Bed Simulation of a 40 Cm2 Cptu Cone

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:16:20 +0200

In cone penetration testing (CPT) an electronic penetrometer is pushed at a constant rate into penetrable soils and cone bearing (qc), sleeve friction (fc) and dynamic pore pressure (u) are recorded with depth. The measured qc, fs and u values are utilized to estimate soil type and associated properties. Cone tips have areas which vary from 5cm2 to 40 cm2. The larger tips allow for the penetration of gravely soils while small cone tips are utilized for shallow soil investigations. The measured cone bearing and sleeve friction values are blurred or averaged. The measurements are also susceptible to anomalous peaks and troughs due to the relatively small diameter cone tip penetrating sandy, silty and gravelly soils. The cones with relatively smaller cone tips are significantly more susceptible to the anomalous peaks and troughs while the cones with larger cone tips are more susceptible to the smoothing of the cone tip and sleeve friction measurements. Baziw Consulting Engineers (BCE) has invested considerable resources in addressing the qc and fs measurements distortions. This paper outlines the techniques developed by BCE and integrates them so that optimal soil properties can be obtained from CPT data sets. Particular focus is put on relatively larger cone tips because they can penetrate soils with high resistance and are less susceptible to the additive measurement noise of anomalous peaks and troughs. The anomalous peaks and troughs are more challenging to remove or minimize than the qc and fs blurring effects. It is of paramount importance to first implement newly developed signal processing and optimal estimation algorithms on extensive test bed simulations prior to processing real data sets. This paper also outlines the results from processing a challenging test bed simulation of a 40 cm2 cone tip data set with BCE’s newly developed algorithms.

Cone Penetration Test-Based Correlations to Forecast Critical State Parameters

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:16:04 +0200

In critical state soil mechanics, the critical state refers to the combination of effective stress and void ratio (e) at which a soil continues to shear with no change in effective stress, shear stress, and e. The phenomena can be visualized using the critical state line (CSL). The CSL represents the locus of e at critical state with effective mean stress (σ′mean). To define the CSL, the CSL slope (λ), termed “compressibility,” and CSL y-axis intercept at 1 kPa (Γ), termed “altitude,” are required. The CSL in e – σ′mean space provides a simple model of complex soil behavior that allows engineers to construct constitutive models using the state parameter (ψ), which is the mathematical difference between the in-situ e of the soil and the e of the soil at critical state. Currently, Γ can be obtained only through laboratory testing, while λ and ψ can be obtained via laboratory testing or correlation. This paper presents forthcoming correlations based on the ΔQ soil behavior index (which is obtained via the cone penetration test, CPT) to forecast Γ, λ, and ψ, and compares the ΔQ-based correlations’ performance to other CPT-based correlations as well as to data obtained from literature. To compare the correlations, the authors used data from a site investigation performed in Fraser River sand as part of the Canadian Liquefaction Experiment.

Inferring Spatial Variation of Soil Classification Using Clustered Bayesian Analysis by Both CPT and Borehole Data

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:15:49 +0200

Soil boundary delineation is an important task in geotechnical site characterization. It can be achieved by either extracting borehole samples, conducting laboratory tests, and classifying them according to a soil classification system such as the Unified Soil Classification System (USCS) or utilizing multiple cone penetration test (CPT) soundings, and identifying soil boundaries at the soundings from the Ic (soil behavior type index) profiles. However, most soil-layer delineation methods can only take a single type of test result as the input. For instance, the well-known Markov random field (MRF) method can only take soil-type data such as sand, silt, or clay at boreholes as the input. Recognizing that soil classifications and soil properties are correlated, this paper proposes a novel coupled MRF-Bayesian framework to infer the spatial variation of USCS classifications (e.g., sand, silt, and clay) as well as soil properties by integrating both CPT and borehole data. This integrated approach leverages both CPT and borehole data to address some main challenges e.g., uncertainties and multivariate soil data input in underground stratification problems by simultaneous sampling of soil properties and soil types. The new unified framework can accommodate multivariate data, hence the new framework is compatible with the geotechnical engineering practice. The uncertainties for the spatial variation of USCS classification at sounding locations are quantified through a “layer-specific” Bayesian updating i.e., updating posterior cross-correlation behaviors for different layers (such as sand, silt, and clay), independently. In this Bayesian updating, soil-type data can provide some information about the soil properties according to the unified soil classification system. Further, the soil boundaries can be identified across the entire domain by the realization of conditional random fields of soil properties once the spatial variation of USCS classification is inferred at sounding locations, followed by a 3-dimensional Markov random field process.

Data-Driven Two-Dimensional Near-Surface Seismic Imaging

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 16:15:33 +0200

Non-invasive site characterization techniques have the potential to rapidly evaluate large subsurface volumes to guide subsequent invasive geotechnical site investigation. Among these methods, seismic full waveform inversion (FWI) stands out for its potential to recover detailed two-dimensional (2D) images of the subsurface. However, FWI’s need for substantial computational resources and sensitivity to the initial starting model has limited its utilization as a generalpurpose geotechnical site characterization tool. Addressing this, prior studies have shown data-driven methods can predict 2D subsurface structures composed of soil over rock. In the present study, we aim to generalize these findings to all nearsurface conditions. We propose a novel model generation framework that utilizes techniques from geostatistics to generate complex 2D subsurface models. The generated models include dipping soil and rock layers, soil lenses, boulders, and underground utilities; none of which have been considered previously. We use our model generation framework to simulate 100,000 2D subsurface models. We simulate field data acquisition along these 100,000 synthetic models, by numerically solving the elastic wave equation using an impulse source at the model’s center surrounded by 24 receivers (12 on either side). The data-driven predictive model, trained on 90% of the simulated data, achieved a mean absolute percent error on the testing set of 19%. Furthermore, these predictions are made within fractions of a second circumventing the computational and starting-model-related challenges associated with traditional 2D FWI. These results demonstrate that data-driven methods can predict complex images of the subsurface to enable rapid subsurface imaging for geotechnical applications.

Geological and geotechnical study of a construction site in Porto Romano area-Albania

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:50:28 +0200

Porto Romano port complex new facilities are part of the expansion plans of Durres port and its modernisation. However, the relocation site presented many significant spatial and geotechnical challenges to be considered and mitigated. Soil conditions and the country’s high seismic activity meant the project required extensive feasibility and technical studies to find a safe and sustainable approach. For a detailed geological and geotechnical investigation of the area, various geotechnical, geophysical tests were carried out such as: borings, SPT test, CPTU test, Seismic refraction, MASW, Downhole and HVSR allowing to obtain the fundamental resonance frequency of the ground. Field recordings per each layer were than compared and calibrated to the results and tests performed in the laboratory. The construction site displayed a variety of soils from soft to firm silty Clays, to loose to medium dense silty Sands and layers with high organic content. During execution of SPT tests, sandy layers gave more satisfactory results, meanwhile, for silty CLAY layers, the results of CPTU testing were considered in analysis. This detailed soil investigation and characterization served to properly design the new port facilities, identify, and protect from the liquefaction phenomena at this specific site.

Open-source implementation of the new unified CPT-based axial method in sands

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:49:36 +0200

This paper presents the implementation into the open-source finite element simulation framework OpenSees of the new Unified CPT-based method for driven piles in sands. The formulation incorporates the maximum skin friction and endbearing CPT values based on the new ISO-19901-4 under development, within the non-linear load-transfer curves calibrated against the measured responses from the static pile tests in the unified database. Special attention was paid to maintaining an open-source philosophy during the implementation. The important EURIPIDES research tests in highly dense sands are considered as a worked example to illustrate the application of the implemented method. The numerical benchmark shows good agreement between the model and full-scale measurements.

Comparison of Different Prediction Methods to Derive Synthetic CPT Profiles - An Offshore Wind Farm Case Study from the German North Sea

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:47:36 +0200

The further development of offshore windfarm areas in various countries plays a key role in the transition of energy production towards renewable sources. As offshore windfarm areas tend to expand and the amount of ground truth data is limited, the estimation of geotechnical parameters at unknown locations integrating other site investigation data becomes a necessary tool. This is especially relevant for cost efficient area wide site characterization. Here, the proper integration and correlation of geotechnical and geophysical data is a key factor for reliable ground model building. This study investigates different prediction methods, while presenting a modelling framework which incorporates geological, geotechnical, and geophysical information to derive synthetic Cone Penetration Testing (CPT) profiles using offshore windfarm site investigation data from the German North Sea. We combine geological interpretation, CPT data and 2D ultra high-resolution seismic reflection data. The geophysical and geological information are used to guide geotechnical parameter prediction. Additionally, seismic horizons constrain the prediction as structural information. For evaluation, we test and compare several prediction techniques, with different level of complexity, from geostatistical methods to machine learning. Seismic attributes are used as auxiliary information to improve CPT parameter prediction. To validate the results, CPT parameters are predicted onto a representative 2D seismic line and a leave-one-out cross-validation (blindtest) is performed. Though all methods struggle to replicate local extremes, results indicate a reduction of prediction uncertainty when implementing seismic attributes.

AI-Based Digitization of Legacy Ground Information

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:46:27 +0200

Geotechnical characterization of site materials is of paramount importance in the construction and mining industry. The analysis of large volumes of geotechnical information from multiple sources leads to data-driven decisions that help to minimize uncertainty. For this purpose, a unified digital information platform becomes handy to have a global perspective and improve the analysis of available ground information data. Access to historic ground investigation data from previous projects during the project planning stage might increase efficiency. However, accessing and processing legacy data from companies’ databases is time and resources consuming. In the recent years, software tools that are capable of extracting data in a digital format from images have become popular, but still require human-supervised interpretation. A novel tool combining Optical Character Recognition (OCR), digital data extraction technologies and AI-based data interpretation system is presented herein. The state-of-the-art OCR technology is capable of accurately recognizing and extracting text from various document types, such as scanned documents, images, and PDFs. It utilizes advanced machine learning algorithms to process text, even in challenging conditions, ensuring data is extracted accurately and reliably. Then, a data interpretation system has been trained to identify the type of site characterization data and its structure while retrieving all the content in a digital format. All components work seamlessly together to provide a comprehensive solution for automating the interpretation and extraction of site characterization data, streamlining data management and analysis processes. The capability of gathering data from multiple sources in a unique ground information system provides valuable information for planning and design stages while decreasing costs, time and uncertainties. In addition, all these data are then available within DAARWIN platform to feed the ground model workflow.

Direct-Push Profiling Technologies for Sustainable Investigation of Contaminated Sites

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:45:24 +0200

Most contaminated site investigations still rely on conventional characterisation approaches based on collecting a limited number of soil samples and installing long-screened wells. However, it is widely recognised that these methods cannot adequately capture the subsurface heterogeneity largely governing the fate and transport of contaminants. Following the example of cone penetration testing (CPT), multiple direct-push profiling tools have been developed over the years to investigate and manage contaminated sites in a more efficient and sustainable way. The objective of this work is to present well-established and emerging direct sensing technologies for contaminated site investigation and demonstrate how their application does not just result in a reduction of uncertainties but also in improved sustainability outcomes. The assessed technologies included the Hydraulic Profiling Tool (HPT), laser-induced fluorescence (LIF), Membrane-Interface Probe (MIP), and nuclear magnetic resonance (NMR). Direct-push profiling techniques were found to be valuable throughout the project lifecycle, from initial site screening phases to remedial design and closure. The high-density data collected helped to delineate contaminant source zones, preferential migration pathways and low-permeability zones. This information complemented the analysis of a reduced number of physical samples to optimise remedial designs and monitoring networks. Additional benefits related to sustainability concepts included the production of minimal investigation-derived waste, the need for less field campaigns and the little impact caused to site owners and their activities. High-resolution site characterisation approaches are paramount to conduct informed risk assessments and effectively achieve remediation goals.

Advances in the Characterisation of Sites Contaminated with Petroleum Hydrocarbons: Insights from a Collaborative Effort

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:44:26 +0200

Petroleum hydrocarbons (PHCs) such as gasoline and diesel are among the most common and widespread contaminants in urban and industrial environments. The authors were engaged by the imprint Springer to complete a book giving visibility to technologies overcoming limitations associated with conventional characterisation approaches, as well as pertinent concepts and methods that may still be underutilised by the industry internationally. The open access book entitled ‘Advances in the characterisation and remediation of sites contaminated with petroleum hydrocarbons’ was prepared as a contributed volume involving the participation of more than 100 global experts from academia, government agencies, and the private sector. An analysis of the book contents yielded general insights into the state of the art regarding the investigation of PHC-impacted sites. As highlighted in several chapters, fate and transport of fuel products are controlled by multiphase flow mechanics and constitutive relations intrinsically linked to biological phenomena and the spatial and temporal variability of multiple subsurface properties. Most site characterization methods presented in the book (from direct-push vertical profiling and biogeophysics to sequence stratigraphy or molecular biological tools) address aspects often overlooked in conventional site investigation projects, including: (i) the entrapment of fuel products due to capillary forces, (ii) the essential role played by microbial activity, and (iii) subsurface heterogeneity effects. Further research and adoption of up-to-date concepts and methods are encouraged to ensure best practices are implemented and PHC risks are managed sustainably and responsibly

Towards An Integrated And Automated Digital Workflow In Geotechnical Engineering

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:43:24 +0200

The use of soil data is essential in geotechnical design, but in a preliminary project phase such data are usually limited to that inferred from field tests, like CPT, SPT or DMT. In previous publications by the authors and co-workers, it was shown how such data can be automatically processed into soil profiles and parameter sets for geotechnical finite element analysis. Another publication demonstrated the automated processing and creation of geological models as an intermediate step to more advanced 3D geotechnical modelling in a BIM / Digital Twin environment, which facilitates the link with other disciplines and stakeholders in a project. The major challenge of connecting layers across multiple 1D boreholes to form 3D soil layers is overcome by using a Machine Learning clustering algorithm. As a next step, the previously introduced Automated Parameter Determination (APD) method (connecting correlations using Graph theory) is applied based on averaged CPT parameters from all contributing layer sections. The result is an automated system that creates a complete 2D or 3D finite element model, including constitutive model parameters, for geotechnical analysis purposes. An automated system may be very efficient when exploring different design alternatives in an early stage of a project. However, it is important to emphasize the role and responsibilities of the geotechnical engineer in the design process, which requires the system to be transparent, verifiable, and adaptable. This paper describes the state-of-the-art of this ongoing research project.

Data-driven site characterization - Focus on small-strain stiffness

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:42:25 +0200

Non-linear soil behaviour adds complexity in accurate parameter selection for numerical modelling. One of these parameters is the small-strain shear stiffness. This parameter depends strongly on the soil mass density and the shear wave velocity; the latter can be determined through in-situ tests or laboratory tests. The paper focuses on training various machine learning models to predict shear wave velocity estimates based on raw data from cone penetration test soundings. Three decision tree algorithms are considered for the analysis: XGBRegressor, HistGradientRegressor, and RandomForest. Various data preprocessing approaches are investigated, including noise removal and outlier identification, to assess their impact on the model performance. The results indicate that different data preprocessing approaches yield significant differences in the model performances. When applied to unseen raw data from a sand site of the Norwegian GeoTest Site, the model demonstrates promising predictive capabilities and is in a good agreement with well-known correlations. This study underlines the importance of data quality and preprocessing for reliable machine learning models. To enhance transparency and reproducibility, a GitHub repository with all the used files is made available online.

Effect of Precast Pile Driving on Liquefaction Potential Mitigation of Sandy Silts Based on CPTu

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:41:27 +0200

Precast concrete piles are adopted as a foundation solution in liquefiable silty sand and sandy silt layers of north of Oman Sea shorelines for large diameter liquid tanks. The ground water table is about 6 m deep, and a highly potential liquefiable layer is identified from 7 m and continues to about 12 m deep. This liquefiable layer not only reduces the pile shaft skin friction, but also could have caused damage to slender precast piles as a result of kinematic and inertia shear forces and bending moments, in particular at the intersection of liquefiable and non-liquefiable cohesive layers underneath. The main objective of the paper is to evaluate the effect of densification of sandy silt deposits attributed to pile installation and the possibility of liquefaction mitigation effects due to radial compaction of the soil. CPTu tests were carried out prior to and after the installation of piles. It is noticed that both qc and fs were increased depending on the center-to-center spacing of piles. Liquefaction analysis is carried out on CPTu results before and after piling installation and it is observed that the sandy silt layers are significantly strengthened against liquefaction and the safety factor notably rose above unity after the pile driving operation. The results are compared with triaxial cyclic tests on samples taken from a comparable depth for further investigation, indicating that the mitigation has occurred simply with a 10 percent increase in the relative density of the liquefiable sandy silt layer

Characterization of the Consolidation Coefficient Behavior from Piezocone and Piezoball Tests in a Brazilian Soft Soil

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:40:26 +0200

The present paper aims to validate the applicability of a piezoball test equipped with pressure transducers at the probe’s tip, middle, and equator faces to estimate the coefficient consolidation behavior of a soft soil deposit. The proposals of Mahmoodzadeh et al. (2015) and Liu et al. (2023), derived from numerical solutions, can be adopted to estimate horizontal coefficients of consolidation (ch) through the piezoball dissipation measurements. The dissipations tests were performed at depths of 4, 6, 8, and 10 m and were conducted up to at least about 70% of dissipation of the excess pressure generated during the penetration, except for the test at a depth of 4m, done at 85%. Results were directly compared with piezocone, and the estimated values for the consolidation coefficient were similar for all methodologies applied, both at the face and equator positions.

The Use Of Large-Scale 3D Numerical Modeling to Identify Areas of Increased Seismic Risk in Polish Underground Copper Mines.

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:39:25 +0200

Seismic activity and related rockbursts are currently one of the most dangerous threats negatively affecting work safety and continuity of operation in Polish underground copper mines. Taking into account the experience to date, it can be clearly stated that current technical and organizational tools do not make it possible to eliminate mining tremors, however, by taking appropriate actions, it is possible to minimize the threat and partially control it, e.g. by active de-stressing the rock mass. However, developing an appropriate schedule of preventive activities is still a burning issue. This is due to the random nature of mining-induced seismic phenomena which makes it impossible to accurately predict the place, energy and time of the seismic event. A breakthrough could be the use of stage-based large-scale numerical modelling based on which it would be possible to track stress changes with ongoing exploitation and locate areas of increased seismic risk. This study presents the results of large-scale three-dimensional FEM-based numerical modelling enabling tracking of changes in stress distribution with the progress of exploitation. Then stress distribution and areas identified as prone to instability occurrence were correlated with the areas of high-energy seismic tremors manifestation. Models were prepared at monthly intervals, and validated with the use of measurements obtained with underground geomechanical monitoring systems. As preliminary analyses show, well-validated numerical models can be the basis for estimating seismic risk and may be useful at the stage of designing methods for preventing active rockbursts and seismicity prevention.

A Data-Driven Approach to Predict Shear Wave Velocity from CPTu Measurements: An Update

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:38:32 +0200

This paper is an extension of our previous research investigating the potential of machine learning models to estimate shear wave velocity (Vs) from piezocone penetration test (CPTu) measurements. The aim of this update is to examine the effect of incorporating geographical information, namely latitude and longitude, as input parameters to the machine learning models. New models are developed by incorporating both CPTu parameters and spatial coordinates as input features and are compared to models developed with only CPTu parameters. Furthermore, SHAP (SHapley Additive exPlanations) analysis is employed to assess the importance of different features and variables in the developed machine learning models. The results show improvement in prediction performance when adding geographical data, indicating the influence of geological variations on Vs. The paper shows the potential of using geospatial information to improve the data-driven approach for estimating soil properties from CPTu tests when large worldwide datasets are available.

A Data Driven CPTu-PINNs Method to Predict Soil Settlement

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:38:16 +0200

Obtaining soil parameters through laboratory tests and solving the governing equations that describe soil settlement can be time-consuming, making immediate on-site predictions of soil settlement challenging. In-situ testing provides a more efficient approach to obtain soil parameters than laboratory tests. Data from the Piezocone penetration test (CPTu) can be used for on-the-spot interpretation of soil mechanical parameters, which can then be incorporated into the governing equations for soil settlement calculation. Physics Informed Neural Networks (PINNs) algorithm uses automatic differentiation method to directly embed partial differential equations (PDEs) into a deep learning neural network and provides solution for these PDEs in a cost-effective manner compared to traditional numerical methods. In this paper, a framework integrating data from CPTu and PINNs to predict soil settlement is proposed and evaluated through comparison with numerical simulations from Finite Element Methods (FEMs). Results show that the framework gave a reasonably good agreement with the FEMs benchmark while substantially reduced the computation time. This method allows for immediate on-site prediction of soil settlement during site investigations, thus better guiding surveying and construction activities.

Can Seabed Spatial Uncertainty Be Quantified Using Advanced Statistical Approaches?

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:37:55 +0200

Knowledge of seabed properties away from investigated locations is often required, for example, when geotechnical surveys are sparse or when the field layout changes between investigation and construction phases. In such cases, design lines that appropriately incorporate the uncertainty of the seabed properties must be defined to ensure reliable (yet not overly costly) design. This paper explores how two different approaches, traditional engineering judgement and advanced statistical methods, fare at quantifying the uncertainty of a real offshore site. This is achieved by ‘hiding’ different data and ‘scoring’ the predictive performance of the methods against a range of criteria. The work reveals that complex geological sites are significantly more challenging to represent than the stationary random fields often examined in research and suggests that more advanced approaches incorporating broader data sets are required to reduce uncertainty.

Soil Variability From High-Resolution S-Wave Full-Waveform Inversion: Deriving Reliable Cone-Tip Resistance From Vs for Geotechnical Evaluations

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:37:35 +0200

Capturing the spatial variability in soil is crucial for ground response analyses in the context of seismic hazard mitigation. The lateral variability in thickness and properties of the different soil layers is one of the main factors that determines the variability of the ground motion spectrum from one location to another. The absence of such lateral variability information in the subsoil in between the locations of Cone Penetration Tests (CPTs) may be compensated by the use of more densely sampled seismic data. In this research we aim to derive a shear-wave velocity field through seismic full-waveform inversion that yields a model resolution approaching that of high-resolution seismic CPT surveys. Following this, a datadriven correlation between geophysical and geotechnical information is attempted through the application of new machine-learning-based approaches.

Stress History and Effective Shear Strength Parameters Evaluation of a Dilative Stiff Clay

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:37:15 +0200

The Cone Penetration Test (CPTu) can be used to evaluate the soil behaviour and properties through correlations (empirical and/or analytical), and the results must be compared to laboratory tests to be validated. This paper presents the evaluation of the effective friction angle (φ’) of a stiff over-consolidated Brazilian clay based on CPTu data and laboratory tests characterization, such as index properties, and the comparison of the effective shear strength parameters obtained by triaxial tests. Based on CPTu data, the soil was classified using the Soil-Behaviour Type Classification System (SBTn) proposed by Robertson (2016), and properties such as over-consolidation ratio (OCR) and the effective friction angle were determined using well-known correlations such as Chen & Mayne (1996) and Ouyang & Mayne (2019). The shear response defined by CPTu was compared to the results of isotropic consolidated triaxial compression tests (CIUC). The results showed mainly a clay-like behaviour based on the CPTu data, in agreement with the laboratory characterization, which indicated high plasticity. Regarding the shear response, both the triaxial test and the CPTu data indicated dilative behaviour under shear. Furthermore, the effective friction angle obtained from the triaxial test and the CPTu data were similar depending on the OCR used in the equation, demonstrating the applicability of the adopted methodologies for the Brazilian stiff over-consolidated clay. Finally, based on CPTu data it is proposed a complement of the SBTn developed by Robertson (2016) with OCR isolines.

Numerical and experimental assessment of steering forces during horizontal penetration in sand – a validation of a bio-inspired optimal tip shape

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:30:12 +0200

The exploration, characterisation, and monitoring of the subsurface is relevant to a wide range of applications, from environmental monitoring and in-situ characterisation to infrastructure construction (e.g., directional drilling and tunnelling) and resource withdrawal. Bio-inspiration offers promising solutions to overcome two of the most important challenges in the development of autonomous subsurface exploration probes: exploration range (related to drag forces) and steerability (i.e., ability to control direction of movement). The work uses a previously proposed bio-inspired intruder shape to study the relationship between tip orientation and the resulting forces (lateral and vertical); and explores the idea that these forces can be used to steer the probe, i.e., control the direction of motion of the probe as it advances. Numerical results with the discrete element method and experimental results with a large-scale test bed show a direct relation between tip orientation and the steering (lift and lateral) forces – supporting the case for steering systems based on intruder tip rotation. In the results, lateral and vertical forces also show a strong relation with tip orientation, however, for the tip shape tested, the vertical forces are limited to the neutral to upwards range (i.e., towards the free surface). Experimental results evidence the significant effect of intruder deformation (bending) and/or path deviation in the penetration forces acting on the intruder.

Particle Crushing and Liquefaction Resistance of Crushable Aragonite Sands

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:29:51 +0200

The influence of soil crushability on the strength parameters of aragonite sand under cyclic undrained conditions is investigated in this study. The investigation used aragonite sand, which is known for being susceptible to crushing under normal loading conditions. A series of cyclic simple shear tests were carried out at different normal loads of 100kPa, 150kPa, 200kPa, and 250kPa under a constant confining pressure. To maintain consistency in particle crushing, sieving tests were used to assess the level of particle breaking, with testing stopping after a predetermined number of cycles. The results show that particle crushing increased the fines content of the soil, even when the effective stress was low during the undrained shear phase. The liquefaction resistance of aragonite sands increased as normal load increased. These findings show the major influence of soil crushability on the engineering behavior of aragonite sand, implying that conventional assumptions about the link between normal load and liquefaction resistance may not be true for crushable soils.

Hydraulic Profiling Tool for Groundwater Vulnerability Assessment at an MSW Landfill

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:29:31 +0200

Characterization of the unsaturated zone below an MSW landfill is critical to evaluate the groundwater pollution vulnerability assessment. The permeability of the soil in the unsaturated zone, the depth of the water table, and the quality of pore water in the soil can provide a reliable site-specific estimate of pollution vulnerability. To evaluate these factors, an attempt was made to use the hydraulic profiling tool (HPT) in the unsaturated zone below a non-engineered MSW landfill in Delhi. HPT was equipped with an injection logger capable of qualitatively measuring permeability at the cm scale and an electrical conductivity (EC) dipole that measures the bulk soil conductivity. HPT findings were compared with piezocone penetration tests (CPTu) and the electrical conductivity of extracted pore water from the soil cores. The results indicate that pressure from the injection logger works effectively for medium/fine sand and silt and has greater sensitivity to permeability changes for these soils than CPTu. Pore-water EC was found to have a good correlation with volumetric water content and EC from HPT. A groundwater vulnerability matrix was conceptualized using factors based on the time of leachate travel and maximum pore-water EC observed, both derived from HPT, and risk scores were assigned from 1-5, corresponding to the 9 zones of the matrix. The locations surveyed at the dumpsite received scores of 4 and 5, which depicts high vulnerability. The results indicate that HPT can be used for rapid site-specific groundwater vulnerability assessments.

Comparison Between Eggshell Lime and Commercial Lime as a Soil Stabilizing Agent

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:29:14 +0200

Reducing the extraction of natural resources is a current demand in the construction industry. Studies show that eggshells are rich in calcium carbonate and have the potential to replace limestone in lime production. In this context, the objective of this article is to use an eggshell lime produced in the laboratory to stabilize a residual clayey soil and compare the unconfined strength of the admixtures with others using commercial dolomitic lime. Different lime contents and porosities were evaluated and the porosity/lime ratio was studied to understand the unconfined strength behavior of admixtures. In addition to the soil and limes characterization tests, X-ray diffraction tests were carried out to analyze the chemical and mineralogical composition of the materials. The results showed that increasing lime content and decreasing porosity increased unconfined strength. Also, the unconfined strength achieved with the eggshell lime was greater than that achieved with dolomitic lime for the same lime content. The X-ray diffraction tests showed that the eggshell lime is composed almost entirely of calcium hydroxide, and microscopic images demonstrated much stronger bonds in the final product obtained from eggshell lime. The porosity/lime ratio was a good parameter for evaluating unconfined strength. A unique relationship was achieved linking unconfined compressive strength with the porosity/lime ratio for both the eggshell and the dolomitic lime mixtures.

Considerations on the site characterization of tropical soils by in situ tests

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:28:57 +0200

The fundamentals for predicting the mechanical behavior of soils by in situ tests have been developed for conventional soils (either clay or sand) based on the stress history. The behavior of unusual geomaterials, such as the tropical soils, is characterized by bonding and structure, anisotropy as well as by the unsaturated condition. The behavior of tropical soils cannot be correctly predicted by models and correlations developed by the Classical Soil Mechanics. This paper presents the fundamentals of the behavioral classifications used to interpret CPT and SDMT and discusses their applicability to tropical soils, especially those of pedogenetic evolution of sandstone. Laboratory and in situ tests (CPTu and SDMT) were carried out at two research sites in São Paulo state, Brazil, at different periods of the year to better understand the soil behavior and the seasonal effects. Classifications and correlations to estimate soil parameters from CPTu and SDMT are assessed. Interrelationships between elastic parameters of small (G0) and large to medium strain parameters (qc, ED, MDMT) determined by in situ tests are presented to identify the presence of microstructure and unusual soil behavior. Classification criteria based on these relationships to identify collapsible soils also is presented

Drainage Effects in a Dilatant Carbonate Silty Sand

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:28:40 +0200

This paper presents and discusses results from a series of cone, vane and footing tests in a carbonate silty sand, conducted in a geotechnical centrifuge, that investigate how drainage effects scale with the diameter of the device/foundation. The tests involved different penetration and rotational velocities to quantify how velocity influences the drainage response, and in turn, the magnitude of the deduced soil strength. Cone and foundation resistance, and the shear stress measured in the vane tests, were seen to increase with increasing penetration/rotational velocity, consistent with a dilatant shearing response. The collective dataset is interpreted within the ‘drainage backbone curve’ framework, with an attempt made to understand how drainage path length varies for the different devices and is affected by stress level.

Site characterisation, data management and data integration for submarine cable landing Projects

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:28:21 +0200

There is an increased need for submarine cable infrastructure across the world to serve the offshore wind power industry and the expansion of the submarine interconnectors and telecommunication networks. Cable landfall projects are complex as land, intertidal, nearshore, and offshore environments all coverage, creating an array of dynamic processes, constraints, hazards, and engineering challenges that an asset may face over its lifespan. Robust site characterisation and ground modelling is key for the success of these projects, to allow for the effective, safe, and economical site selection, design, installation, and operation of an asset. In order to accomplish this, the integration of engineering and geoscientific datasets, obtained through several data sources and survey techniques is required; as well as collaboration and integration between multiple technical disciplines. This paper lists the key stages, techniques, and sources available for obtaining the required data. We then consider how the data can be managed and integrated to obtain a holistic ground model for use in the design, construction, and operation of the asset. We discuss the value these models can provide throughout the lifecycle of landfall projects.

Nanotechnology Applied for Soil Stabilization - a Survey

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:28:03 +0200

The technical and constructive challenges inherent to the execution of engineering works on problematic soils require a continuous development or improvement of the techniques and methods used to investigate the soils’ behavior and to design and evaluate the performance of these works. Soil stabilization is one of the most used techniques to improve the mechanical behavior of the soil. In addition to classic soil stabilization methods, nanotechnology is increasingly being used for various purposes, such as introducing nanoparticles of different compounds into the soil mixture or in the field of geosynthetics for fiber treatment. Although they do not have cementing properties, nanoparticles improve mechanical properties, thermal stability, and physicochemical behavior. Studies carried out with different types of soil show that introducing nanoparticles into the soil-cement matrix reduces the space between particles and provides a more robust and rigid soil skeleton. Considering this, it improves the material's resistance properties and reduces cement consumption, contributing to sustainability. The literature review presents research that evaluates different nanoparticles applied to soil mixtures and their influence on the final product. This paper reviews the state of the art of several studies showing that nanotechnology is a successful solution that can be used in soil stabilization because of its capacity to improve, for example, shear strength, unconfined compression strength, and the elastic modulus of soil. The research gap and prospects for using nanotechnology for soil stabilization are also exposed.

Organic Soil Identification by CPTu

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:27:45 +0200

A soil behavior type (SBT) chart was developed to more reliably identify organic soil deposits at sites in the state of Michigan based on piezocone (CPTu) data. Organic soils are often highly compressible organic silts, clays, and peats. Many of these soils are fluvial with high void ratios and large compressibilities. These soils are typically removed prior to the construction of roadways and shallow bridge foundations due to the risk of excessive settlement. CPTu soundings were strategically performed alongside companion soil borings in which standard penetration testing (SPT) was performed and from which split-spoon and Shelby tube samples were recovered and tested. While many of the widely used SBT charts characterize the inorganic soils with reasonable agreement to the soil descriptions presented in the soil boring logs, the organic soils are often mischaracterized as inorganic clays. A hybrid SBT approach was therefore developed that yields more accurate characterization of the organic soils. The inorganic soils are reliably characterized by plotting the normalized tip resistance versus the normalized friction ratio. This SBT approach, however, ignores the valuable piezometric data provided by the CPTu. For organic soils, piezometric data helps to more reliably distinguish between inorganic clays and organic soils. As such, a screening tool was implemented to flag likely organic soils by plotting a parameter that accounts for both the tip resistance and pore pressure versus the normalized friction ratio before characterizing the likely-inorganic soils using existing approaches.

Challenges in Site Characterization and Work Verification of Compacted Crushable Sands

Jesús Sánchez Pinedo — Thu, 06 Jun 2024 15:27:27 +0200

During reclamation projects huge amounts of sands are dredged and placed to create artificial land. To increase the density and therefore to mitigate the potential risk of liquefaction as well as to increase the stiffness and internal friction angle of the sand, it is often necessary to compact the reclaimed sand. The performance targets for compaction are frequently verified by means of achieving a particular relative density that is generally correlated from Cone Penetration Tests (CPT). For many reclamation projects, due to the non-availability of local quartz or silica sands, crushable, carbonate or calcareous sands are used. In these crushable sands, due to the very high stress concertation below the CPT cone, the particles tend to crush. The well-known published correlations between the relative density and cone resistance are established for non-crushable silica sands and are thus not applicable to these crushable sands and can result in over treatment costing time and money. Usually, the crushing effect is quantified in a calibration chamber test and a project specific correction factor is introduced. Alternatively, to avoid this costly and time-consuming procedure the use of measuring the shear wave velocity with seismic CPTs (SCPT) is possible. The Cyclic Stress Ratio (CSR) for liquefaction analysis and other soil parameters required for the design verification can be correlated without being influenced by the crushing of particles due to the non-invasive procedure. This paper gives an overview of the common practice for work verification in crushable sand and shows an approach to determine the required compaction parameters using seismic CPTs.