Documents published in Scipedia

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

  J. Wierzbicki, K. Stefaniak

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  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 [...]

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

  C. Caballero, P. Castillo, J. Castrellon, S. Rodriguez, J. Gallardo

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  The Tierras Altas region in Chiriqui, Panama presents a high agricultural activity susceptible to extreme climatic events, especially precipitation and surface runoff due [...]

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• The Pseudo-N Values: Proposal and Practice

  K. Suto*

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  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 [...]

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

  K. Rollins, N. Salvatore*, B. Cox, T. Jackson

  ISC2024.

  
  

  Abstract

  In 2022, a new set of probabilistic shear wave velocity (𝑉𝑆) 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 𝐶𝑆𝑅 and high 𝑉𝑆 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. 𝑉𝑆-based liquefaction evaluations were then made at each site, using the 𝑉𝑆 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 𝑉𝑆1 and 𝐶𝑆𝑅7.5 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.

  Abstract
  In 2022, a new set of probabilistic shear wave velocity (𝑉𝑆) based liquefaction triggering curves was developed for gravelly soil by Rollins et al., using a [...]

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

  A. Schteinman, H. William*, S. Nazem

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  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 [...]

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

  E. Koch*, M. Mayassah, R. Ray

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  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 [...]

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• Basic study for propagation characteristics of elastic wave around subsurface cavities

  Y. Hara*, R. Kuwano

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  This study examines the detection of subsurface cavities using seismic wave propagation. Both vertical and horizontal excitation methods were employed to measure the reflection [...]

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

  M. Yadhunandan, P. Anbazhagan

  ISC2024.

  
  

  Abstract

  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 

  Abstract
  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 [...]

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

  A. Miliopoulou*

  ISC2024.

  
  

  Abstract

  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

  Abstract
  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, [...]

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

  J. Birks*, I. Papadatos, M. Rufo

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  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 [...]

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