Scipedia: Documents published in 2024

Numerical studies of compression failure in triply periodic minimal surface-based ceramic foams

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:52:23 +0200

Microstructures with minimal surfaces can be often found in natural porous architectures, where the surface tension minimizes the area. The triply periodic minimal surfaces (TPMS) [1] are an example of such microstructures. Compared with other porous structures, TPMS have three significant features: firstly, their geometries can be completely expressed via analytical functions; secondly, TPMS are periodic in three independent directions and thirdly, the mean curvature of TPMS is zero [2]. Transforming the TPMS-based unit cell into a lattice structure has particular usage in aerospace, nuclear energy, and biomedical applications where light weight, high stiffness, and temperature resistance are of critical importance. In the presented studies, the failure behavior of four typical TPMS structures (Primitive, Gyroid, Neovius, and IWP) under compression was studied using finite element analysis. Numerical modeling of the damage propagation and strength prediction was performed by removing the finite elements in which the appropriate damage criterion is reached. Utilizing the equations of the generated TPMS structures, the wall thickness of unit cell was considered the main parameter that defined the ceramics volume fraction and should be taken into consideration. Therefore, various unit cell models for different wall thicknesses were generated and used to investigate the impact of the cell geometry on the damage initiation, propagation, and overall compression strength. The results of compression strength and damage development were compared with those of other TPMS structures for the same wall thickness and volume fraction. Finally, the grade TPMS porous structure was provided to verify the effect of wall thickness variation on damage evolution on the macroscale.

Penetration resistance of graphene coated ceramic materials under projectile impacts

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:52:05 +0200

Extreme conditions including impact can result in material degradation, permanent damages, and occasionally property/life loss. Therefore, investigation of materials and structures under projectile impact has been a canonical field of research over the past decades. Such studies have led to the development of hybrid materials with high performance and durability under the aforementioned loading. As an emerging hybrid material, graphene oxide (GO) - silicon carbide (SiC) provides promising thermo-chemo-mechanical properties with various applications in defense, energy, and aerospace engineering. Nevertheless, penetration resistance of such composites under impact received less attention due to experimental and computational difficulties. Here, ReaxFF molecular dynamics is leveraged to address the aforesaid problem around room temperature. In that regard, the response of 4H-SiC thin films coated by GO samples under indentation and high-velocity projectile impact is studied. It is observed that (a) ceramic substrates coated by GO samples with higher functional groups concentration (oxidation degree) demonstrate softer behavior under indentation, and (b) fracture and penetration resistance under high-velocity impact are altered based on the oxidation degree of the coating layers. In essence, impact-induced complete perforation becomes more localized to the impacted region by increasing the oxidation content of the coating layers. The influence of oxygen functional groups on the adhesion energy between GO and SiC layers is also investigated. It is observed that adhesion energy between SiC and the coating can be ameliorated by the oxidation degree of the graphene samples. Eventually, the above-mentioned findings provide some insights into the bottom-up design pathways for developing ceramic-based protective barriers in which GO is used as a coating layer or reinforcement

A primal hybrid finite element method to solve general compressible, quasi-incompressible and incompressible elasticity using stable H(div)-L2 spaces

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:09:12 +0200

Hybrid methods are usually derived from an extended variational principle, in which the interelement continuity of the functions subspace is removed and weakly enforced by means of a Lagrange multiplier. In this context, a new primal hybrid finite element formulation is presented, which uses H(div) conforming displacement functions and discontinuos L2 approximation for pressure together with shear traction functions to weakly enforce tangential displacement. This combination allows the simulation of compressible, quasi-incompressible and fully incompressible elastic solids, with convergence rates independent of its bulk modulus. The proposed approach benefits from the property that the divergence of the H(div) displacement functions is De Rham compatible with the (dual) pressure functions. The hybridization of the tangential displacements is weakly enforced through a lower order shear stress space. This leads to a saddle-point problem that is stable over the full range of poisson coefficient (large compressibility up to incompressible). Moreover, a boundary stress (normal and shear) can be recovered that satisfies elementwise equilibrium. Hybridizing the tangent stresses and condensing the internal degrees of freedom, a positive-definite matrix with improved spectral properties can be recovered. The stability, consistency and local conservation features are discussed in details. The formulation is tested and verified for different test cases.

Complete variable kinematic cuf-based multilayered shell elements

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:08:57 +0200

The paper presents a methodology for formulating multi-layered composite shell theories with arbitrary kinematic fields. Each displacement variable is examined through an independent expansion function, allowing integration of equivalent single layer and layer-wise approaches within the Carrera Unified Formulation. Finite element method discretizes the structure in the reference plane of the plate using Lagrange-based elements. Governing equations are derived using the principle of virtual displacements. The study considers multilayered structures with different radius-to-thickness ratios and compares results with analytical solutions from the literature. Findings suggest the most appropriate model selection depends strongly on specific problem parameters

Band gap evolution in nonlinear dynamics of metamaterials made structures via gradually-changing mechanical properties

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:08:44 +0200

This paper explores the dynamic behavior of metamaterial-like structures by investigating the evolution of their band gap under the influence of geometrical nonlinearities in the large displacement/rotations field. The study employs a unified framework based on the Carrera Unified Formulation (CUF) and a total Lagrangian approach to develop higher-order onedimensional beam theories that account for geometric nonlinearities. The axis discretization is achieved through a finite element approximation. The equations of motion are solved around nonlinear static equilibrium states, which are determined using a Newton–Raphson algorithm combined with a path-following method of arc-length type. The CUF approach introduces two key innovations that are highly suitable for the evolution of the band gap: 1) Thin-walled structures can be effectively represented using a single one-dimensional beam model, overcoming the common limitations of standard finite elements. This is crucial as three-dimensional solid elements would result in significant computational costs, and twodimensional elements pose limitations for this type of investigation. Finally, employing onedimensional finite elements usually requires a combination of elements, leading to additional mathematical complexities in their connections and lacking geometric precision. 2) CUF enables the use of the full Green-Lagrange strain tensor without the need for assumptions, as is the case with von Karm´ an nonlinearities. ´ The paper specifically compares results obtained with linear and nonlinear stiffness matrices, highlighting the differences. Numerical investigations are conducted on thin-walled structures composed of repeatable cells, assessing mode changes under traction and compression loading. The findings emphasize that the band gap is an inherent property of the equilibrium state, underscoring the necessity of a proper nonlinear analysis for accurately evaluating frequency transitions

A compact sixth order finite difference scheme for the 3D Poisson equation

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:08:33 +0200

Discretization error estimation for flow simulations using general hybrid grids

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:08:19 +0200

A primary area of the author’s work with his students is outlined in the present article. It regards the estimation of the discretization error with mixed-element and adaptive meshes. Use of general hybrid meshes for computational flow simulations is of importance due to the complexity of both the geometry and the fields. The meshes can consist of a mix of hexahedra, prisms and tetrahedra with pyramids being transitional elements. The discretization error is a primary component of the numerical error in flow simulations. Primary factors affecting it are the local density of the mesh, as well as its “distortions”, namely the variation in local size and orientation (stretching, skewness), the shape of the individual elements (shear, twist), and the local change in their type (grid interfaces). Two distinct approaches have been followed in order to estimate and control the discretization error. The grid-based (“a priori”) approach assesses mesh quality from the analytic expression of the truncation error. The solution-based (“a posteriori”) approach monitors approximations of the variation of flow quantities (“sensors”). Those are then applied to guide adaptation of the grid to the simulated flow field

3D-ACA for the time domain boundary element method: Comparison of FMM and H-matrix based approaches

Jesús Sánchez Pinedo — Fri, 28 Jun 2024 11:08:07 +0200

The time domain Boundary Element Method (BEM) for the homogeneous wave equation with vanishing initial conditions is considered. The generalized convolution quadrature method (gCQ) developed by Lopez-Fernandez and Sauter is used for the temporal discretisation. The spatial discretisation is done classically using low order shape functions. A collocation approach is applied. Essentially, the gCQ requires to establish boundary element matrices of the corresponding elliptic problem in Laplace domain at several complex frequencies. Consequently, an array of system matrices is obtained. This array of system matrices can be interpreted as a threedimensional array of data which should be approximated by a data-sparse representation. The generalised Adaptive Cross Approximation (3D-ACA) can be applied to get a data sparse representation of these three-dimensional data arrays. Adaptively, the rank of the three-dimensional data array is increased until a prescribed accuracy is obtained. On a pure algebraic level it is decided whether a low-rank approximation of the three-dimensional data array is close enough to the original matrix. Within the data slices corresponding to the BEM calculations at each frequency either the standard H-matrices approach with ACA or a fast multipole (FMM) approach can be used. The third dimension of the data array represents the complex frequencies. Hence, the algorithm makes not only a data sparse approximation in the two spatial dimensions but detects adaptively how much frequencies are necessary for which matrix block. Numerical studies show the performance of these methods

Les energies renovables i el seu desenvolupament: Situació, impacte i objectius.

Genèric Congrés2025 — Thu, 27 Jun 2024 16:25:03 +0200

L’AIGUA REGENERADA PER ASSEGURAR LA RESILIÈNCIA ECONÒMICA, SOCIAL I AMBIENTAL DE CATALUNYA

Genèric Congrés2025 — Thu, 27 Jun 2024 16:21:03 +0200

SEGUIR EL CAMÍ DE L’AIGUA PER A L’ADAPTACIÓ AL CANVI CLIMÀTIC

Genèric Congrés2025 — Thu, 27 Jun 2024 16:18:03 +0200

Random Dense Packing of Continuous Distributions of Spherical Particles - Use of Particle Packing Model and Discrete-Particle-Method to predict Particle Spacing Factors

Jesús Sánchez Pinedo — Wed, 26 Jun 2024 15:04:21 +0200

Portland Cement (PC) is responsible for about 8% of global CO2 emissions and is mainly used as a binder in concrete, which is a basic material for all types of load-bearing structures. Due to its versatile usage (precast or ready-mix concrete) and availability almost all over the world, concrete is used in a wide range of applications. When looking at possible pathways to reduce the carbon footprint four measures emerge: 1. 2. 3. 4. Use of renewable energy for PC production (mainly clinker burning process) CO2 capture during PC production. Use of supplementary cementitious materials to reduce the amount of PC. Optimization of PC efficiency within the concrete to reduce the amount of PC needed. To optimize the efficiency of PC, particle packing methods can be used, see e.g. [1], [2]. A well-established geometrical particle packing model is the compressible packing model (CPM) [3], which was extended to the compressible interaction packing model (CIPM) to account for colloidal interactions [4]. Based on the CIPM a so-called cement-spacing-factor (CSF) is calculated [2], [4] by dividing the PC volume in concrete by the maximum packing density (PD). CSF is then used to optimize PC efficiency, i.e., strength of PC based materials. However, CSF calculated based on PD is only an auxiliary parameter (i.e., particle saturation on a volume base), which at best qualitatively describes PC spacing in a particle arrangement and does not take the spread of the PC spacing into account. In this paper, a DEM-based enriched particle packing algorithm is developed that accounts for particle type (i.e., inert particles or PC) and distribution of PC particle distance. The results are compared to strength tests on PC-based pastes and the correlation to the calculated distribution of PC particle distance is shown. Based on PD calculations and the enriched DEM particle packing algorithm an optimization of PC efficiency in concrete can be performed.

Particle- based Simulation of Crack Propagation in Structural Connections Produced with Direct Energy Deposition 3D- Printing

Jesús Sánchez Pinedo — Wed, 26 Jun 2024 15:03:53 +0200

This paper explores how Force Flux Peridynamics (FFPD) can support the design of lightweight metal components in building structures produced with Direct Energy Deposition (DED) Additive Manufacturing (AM). DED is a relatively new technology that deposit metal layer-by-layer to create three-dimensional structures without the need for support structures. This process has the potential to significantly reduce the embodied carbon in building structures by reducing the weight of the structural connections and hence the weight of all other structural components [4]. However, the process applied in AM for metals can make the printed objects susceptible to defects which may compromise their structural integrity and may even lead to fracture [5]. In this paper we describe a design process for the creation of lightweight structural components while including modelling of anisotropy, yielding and brittle fracture. The central core of the process is the application of a particle method called Force Flux Peridynamics (FFPD) which is used to predict yielding and fracture. The paper thus builds upon strategies developed and defined in other publications including; the derivation of the FFPD particle method [2], a strategy for calibration of materials in paper [1], a motivation to apply this concept in the context of nodal connections for spatial structures as described in paper [3]. The specific nodal connection that is analysed in this paper is designed for rotational DED printing which creates a component with radial anisotropic mechanical properties. The node is analysed using an axial tensile and an axial compression load case where the load is applied by imposing incremental translations to the attachments where the structural members would be connected. The susceptibility to fracture in relation to the anisotropy of the printed metal is discussed.

Numerical Investigation of the Installation of Suction Caisson in Sand Using Material Point Method

Jesús Sánchez Pinedo — Wed, 26 Jun 2024 15:03:02 +0200

Suction caisson has gained interest in recent years as an alternative foundation for offshore wind turbines due to its cost-effectiveness and easy installation compared to conventional foundations such as monopile. After initial penetration due to its self-weight, suction is applied until the caisson reaches the desired depth. Applying suction provides additional driving force due to the pressure difference between inside and outside the caisson and induces seepage that degrades friction and tip resistance, which further facilitates the installation. The seepage plays a vital role in installing suction caisson in sand; however, it might change the soil state which affects the ultimate bearing capacity of the caisson. Several research works have been conducted to study the suction caisson installation in sand. However, the complexities of the problem including large deformation, solid-fluid and soil-structure interaction, inhibited these studies from fully understanding the installation mechanism. This paper proposes a large deformation modeling framework by using the material point method (MPM). MPM is a hybrid Lagrangian-Eulerian particle-based method that uses material points over a fixed computational mesh where governing equations are solved. During the convection of the particles, the background mesh is kept fixed, making it suitable for large deformation problems. The model considers soil-structure interaction by adopting a Coulomb contact algorithm between the caisson and surrounding soil. In this paper, the stability of the contact algorithm is ensured by correcting material point velocities in the vicinity of the caisson interface using a limiting velocity based on the element size and time step. The framework is validated by comparing a simulation of caisson installation under constant velocity with results published in the literature. Our proposed framework’s results agree with previous published results, demonstrating that the simplified stabilization procedure does not affect the simulation results. This is a promising result that will enable the incorporation of fully coupled analysis to better understand the effects of induced seepage on the installation mechanism of suction caissons.

NONLINEAR ANALYSIS OF SOLAR FLARES OF X CLASS

Leila Shakaraliyeva — Sat, 22 Jun 2024 01:04:40 +0200

The study of solar flares is definitely very important for our planet, because they have a direct impact on it. We have always wondered how solar flares, seemingly so far away from us, can affect the Earth. They are known for their effect on the ionosphere and magnetic field of our planet, thereby causing negative effects in addition to the fascinating aurora borealis. Thus, every flare that occurs on our main luminary can cause geomagnetic storms, bringing massive power outages, malfunctioning GPS systems, radio and telecommunications. In studying this issue, we decided to understand their patterns.

Thus, we studied methods of processing large volumes and presenting them in the form of graphs using MATLAB and Python programs, while using the relationship between the characteristics of the radio signal and its topology, developed by our scientist Zhanabaev Z.Ch. The uniqueness of our project is the use of only two coefficients (two-dimensional shape coefficient and information-entropy) characterizing solar flares to determine their patterns.

In conclusion, having set the goal of the project is to find the most efficient method to predict solar flare based only on the value of second flux and soft X-ray emission. We were able to make progress and discover a new to science concept of self-organization of solar flares.

REFORMA DE L’ADMINISTRACIÓ I QUALITAT INSTITUCIONAL

Genèric Congrés2025 — Thu, 20 Jun 2024 15:06:02 +0200

La relació proveïdor-finançador com a element determinant de la sostenibilitat del sistema sanitari públic

Genèric Congrés2025 — Thu, 20 Jun 2024 15:04:02 +0200

Catalunya Media City: a key infrastructure for the catalan and European audiovisual industry

Jaume Pujol — Wed, 19 Jun 2024 15:03:00 +0200

• The Catalunya Media City project aims to create an Audiovisual, Digital and Video Game Hub, a global reference in training, research, creation and innovation.
• The project is conceived as a Hub open to citizens and in dialogue with the environment, located both in the Tres Xemeneies area, specifically in the Nau Turbines, in the Tres Xemeneies buildings and adjacent spaces, as well as in Terrassa , in the Audiovisual Park.

• The infrastructure must become a strategic asset for the development of local industry, the attraction of talent and Investments.
• The Besòs project, together with the Terrassa Audiovisual Park, will make Catalonia a country of reference in the field of cultural industries related to digital, audiovisual and video games.
• Work is currently underway on the preparation of the functional plan, which will serve to define and propose the occupation and distribution of the different spaces of the future Catalunya Media City, and contacts are being maintained with the sector to establish synergies and possible col· works

The Future Challenge of Quantum Communications: The Barcelona Node

Ismael Pacheco — Tue, 18 Jun 2024 10:46:26 +0200

Ensuring confidentiality in the transmission of digital data is a globally significant challenge. When necessary, data can be transmitted securely using cryptographic keys based on algorithms such as the RSA schemes. Even supercomputers lack the computational power to decrypt these keys. However, there is no guarantee that vulnerabilities won’t emerge. In fact, one vulnerability is already known: a sufficiently powerful quantum computer, when available, will render all RSA-based encryption systems vulnerable, affecting data transmitted worldwide.

Quantum and post-quantum communications represent the next steps in securing data. Quantum Key Distribution (QKD) is a technology that offers absolute security by leveraging the fundamental properties of quantum physics. Post-quantum techniques rely on sophisticated algorithms beyond RSA, even resistant to future quantum computers.

While the timing of cryptographic vulnerabilities remains uncertain, it’s certain that unprepared systems will become vulnerable overnight. Recognizing this challenge, Europe is constructing the “European Quantum Communication Infrastructure.” This ambitious project aims to design, develop, and deploy a QKD network to protect critical European infrastructure (government institutions, data centers, hospitals, energy grids, etc.) as a first step toward a complete European Quantum Internet. Catalonia has the opportunity to pioneer this field, starting with a quantum network in the Barcelona metropolitan area. This initiative will create a positive economic and business impact, making it an innovative and competitive reference within the Catalan, Spanish, and European ecosystems.The project, named Qollserola, has support from the Generalitat de Catalunya, the Spanish government, the Barcelona City Council, and the European Commission. It will contribute to fostering a national quantum ecosystem and is led by ICFO and Cellnex.

An Innovative Technique to Measure Lateral Pressure of Self-Compacting Concrete Using Fiber Bragg Grating Sensor

John Chen — Tue, 18 Jun 2024 10:23:03 +0200

Self-compacting concrete (SCC) is the mostﬂowable concrete type that exerts high pressure on formwork. SCC is the most commonly used concrete globally for construction applications due to its cost-effectiveness. However, to make a formwork resist the exerted lateral pressure of SCC, it is required to have a suitable design for formwork. This paper presents a novel approach on how could create and prepare the Fiber Bragg Grating (FBG) optics using as a sensor to measure lateral pressure and temperature of SCC. To ensure the FBG sensor works properly a validated methodology is conducted. In theﬁrst stage, FBG sensors are calibrated with temperature sensitivity and then are calibrated with water pressure. The latter calibration is used to verify lateral pressure with SCC. However, this is not the only sensor used to record the result, a genuine sensor such as a transducer sensor has been positioned close to the FBG sensor to validate the results of the FBG sensor. The created FBG sensor demonstrates highly promising results, effectively validating the outcomes of the transducer sensor, while also reducing costs and enhancing usability for construction applications.

Multi-scale procedure for the mechanical analysis of composite laminate structures considering mixed boundary conditions

Fermin Otero — Sat, 15 Jun 2024 08:51:02 +0200

This paper presents a multi-scale procedure for the study of flat composite structures with discontinuities. In this procedure, the structure is solved using shell elements while the laminate performance and the structural discontinuities (e.g. connections or change in the laminate thickness) are analysed with a subscale model made with solid 3D elements. The kinematics of both models are coupled following the Kirchhoff–Love theory. This coupling is used during the homogenization procedure where the characteristic behaviour of the different micro-models is obtained. Periodical boundary conditions are used for the laminates whereas a combination between periodical and linear boundary conditions are used for the discontinuities. The proposed procedure allows to reproduce accurately the structure elastic behaviour, as well as the stress and strain states in regions with discontinuities, which until now could only be accurately simulated by means of expensive numerical models using volumetric solid elements.

La influencia del modelo de gestión en el consumo doméstico de agua en Catalunya

Miguel Iglesias — Thu, 13 Jun 2024 20:54:03 +0200

Multiscale modeling of prismatic heterogeneous structures based on a localized hyperreduced-order method

Julio García-Espinosa — Thu, 13 Jun 2024 16:49:03 +0200

This work aims at deriving special types of one-dimensional Finite Elements (1D FE) for efficiently modeling heterogeneous prismatic structures, in the small strains regime, by means of reduced-order modeling (ROM) and domain decomposition techniques. The employed partitioning framework introduces “fictitious” interfaces between contiguous subdomains, leading to a formulation with both subdomain and interface fields. We propose a low-dimensional parameterization at both subdomain and interface levels by using reduced-order bases precomputed in an offline stage by applying the Singular Value Decomposition (SVD) on solution snapshots. In this parameterization, the amplitude of the fictitious interfaces play the role of coarse-scale displacement unknowns. We demonstrate that, with this partitioned framework, it is possible to arrive at a solution strategy that avoids solving the typical nested local/global problem of other similar methods (such as the FE2method). Rather, in our approach, the coarse-grid cells can be regarded as special types of finite elements, whose nodes coincides with the centroids of the interfaces, and whose kinematics are dictated by the modes of the “fictitious” interfaces. This means that the kinematics of our coarse-scale FE are not pre-defined by the user, but extracted from the set of “training” computational experiments. Likewise, we demonstrate that the coarse-scale and fine-scale displacements are related by inter-scale operators that can be precomputed in the offline stage. Lastly, a hyperreduced scheme is considered for the evaluation of the internal forces, allowing us to deal with possible material nonlinearities.

Final open-door industrial day

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:45:24 +0200

The final open-door industrial day forms the final milestone of the project (MS 20) and thus the project completion. The event will take place again at one of the partners sites.
During the meeting the project results are presented comprehensively. The prototypes should also be shown again. In terms of content, the following points are in the foreground: Results of life cycle assessment and waste management, global business plan, standardization recommendations, final conclusions. (D7.12)

First open-door industrial day

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:45:05 +0200

The focus of the First open-door industrial day is on the presentation of the real scale demonstrators. Accordingly, the meeting should take place at one of the partners who is working on the demonstrators or where they are being produced. Among other things, the materials used (materials' catalogue), guidelines, the construction process, structural health monitoring (SHM system), tests and prototypes (D7.8) should be presented.

The aim of this meeting is, among other things, addressing various stakeholders and bringing the project results further into the public eye. Accordingly, the aim is to also invite external project representatives to the open-door industrial day, if possible. The agenda should be limited to one day in order to make a visit as uncomplicated as possible, even without an overnight stay. In addition, the ongoing project progress is discussed if necessary.

Second information day

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:44:49 +0200

The second information day will be held after 18 months. As the first information day, it is planned as a presence event. The agenda will be planed for 1 to 1 ½ days. The event will take place again at one of the project partners.
Focus of the agenda will be the project progress and presentation of further activities. A special focus will be on the market analysis and the OWTP concept. A workshop with the Standard Committee (D7.6) will complete the project meeting.

First information day

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:44:33 +0200

After 6 months, the first information day will be the first joint meeting of the entire project consortium. A presence event is currently assumed. Should the situation (Covid-Pandemic) make it necessary for the event to be held virtually, the agenda will be adjusted if necessary. 1 to 1 1/2 days are estimated for this information day. The meeting will take place at one of the project partners. It starts at noon on the first day. The first day ends with a consortium-dinner. The meeting will continue on the second day.
In terms of content, the focus will be on the following points: Presentation of the project objectives of the project progress and the expected results. During the meeting, the first results of the ongoing and possibly completed WPs should be presented. There is also a workshop with the Standardization Committee (D7.3) planned. In addition to the purely professional exchange, the meeting also allows you to get to know the project partners personally.

Measurements report

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:39:52 +0200

The measurement report will include the testing methodology and the results of the ocean sea trials of the 1:6 W2Power steel-based prototype with the FRP-based towers installed to hold the wind turbine generators.

Considering that the trials will last 3-5 months, sets of data will be collected and analyzed to assess the metocean effects on the platform, ensure the technical feasibility of the towers in composites and validate the different monitoring systems developed in FIBREGY.

In overview, the following industrial and technological achievements will be explained in the measurements report: 1st) guidelines for the installation of the FRP towers in the existing steel-based W2 Power prototype, 2nd) Installation of a SHM system based on accelerometers, strain gauges, and fiber optics in the FRP towers, 3rd) analysis of the results derived from the SHM system installed in the offshore platforms, 4th) conclusions regarding how useful are the obtained data for the digital twin model developed in WP3 to assess the structural integrity of the platforms, and 5th) analysis and conclusions of the influence of the metocean conditions in the structural integrity of the FRP-based towers installed on scaled W2Power prototype.

Development of the CAE models

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:38:46 +0200

The report will summarize the work to be carried out in subtask 6.3.1, related to the generation of two complete 3D CAE models of the structure of the W2Power platform and TIDETEC turbine housing, based on the hydro-elasticity and degradation model developed in WP3. These models will be used in WP4 to perform a final strength and degradation assessment of the structure.

Construction of the W2Power real-scale demonstrator

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:37:47 +0200

Deliverable 6.4 is a full scale demonstrator made up of 2 main connection part of a floating windturbine platform. The parts will be made of GRP with an estimated height of 9.2m.
This demonstrator should be built by month 30.

Construction of the turbine housing demonstrator

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:36:46 +0200

This deliverable will include the Tidetec’s turnable turbine housing large demonstrator and
a related detailed report in which the design process of the respective tooling (mandrels) and filament winding process simulation and manufacturing will be described

Construction of the W2Power tower demonstrator

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:35:44 +0200

Deliverable 6.2 is a demonstrator of the tower of the W2Power floating windturbine at scale of 1/6. The demonstrator made of GRP will have a estimated dimension of 10m with a diameter of 1.5m. This demonstrator should be built by month 24. This deliverable will be public.

Middle scale test on dry coatings and connections

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:34:44 +0200

The report of deliverable 6.1 will be split into 2 parts:
The first part will present the results of the performance tests on dry coating in realistic offshore conditions and on larger samples.
After the coupon level evaluations performed un WP2, several larger scale tests will be conduct. The configurations to be tested will be selected according to the WP2 outputs. Samples with and without integrated sensors will be compared as well. Recommendations for improvement of the process for both adhesive paint film and in-mold paint film will be done in accordance with the results.

For emerged composite parts, a natural outdoor exposure site will be used. This consists in an exposition in open air or under shelters in a tempered marine atmosphere site. Various exposure angles can be chosen (45° south, 5° south, 90° north) and all the conditions are properly monitored.

For immersed composite parts, tests in natural seawater will be conduct. The water can be regulated in temperature, oxygen and biological content. This test is performed on land and is able to give representative data on the durability and biofouling behavior of the products.

The second part of the deliverable will presents the results from the static and dynamic tests performed for selected adhesive connections. Then, the reduction factors, used for a complete fatigue calculation, will be determined and presented. And finally, in the case of reversible structural adhesive, results going from the comparison with traditional adhesives until the capacity to recycle them, evaluating the heat energy and the time needed to separate the bonded joint, will be presented.

Guidance notes for the production of large FPR OWTP

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:34:23 +0200

Description of the technologies and processes developed in the project for the production of the targeted OWTP platforms as well as manufacturing strategies for modular production. Furthermore, it will also contain a brief summary of the two open-door days
and workshops, which will be organized

Report on recommendations for predictive maintenance of FRP-based OWTP platforms (T4.4)

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:34:01 +0200

This report will gather recommendations and procedures to be considered in the analysis of predictive maintenance in OWT platforms built in FRP materials, considering the different SHM strategies, instrumentation and a digital twin models developed in the context of FIBREGY.

It should be noted that the diagnosis of the marine offshore structures will be based on the variations of various key performance indicators (KPIs), which will provide real-time information about the damage state and structural condition of the offshore platforms, including KPIs related to the onboard equipment and systems if needed.

Special attention will be also paid to the optimum number and location of the sensors to be embedded in the offshore platforms.

Project guidelines and recommendations for using FRP in large OWTPs

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:33:44 +0200

The project guidelines will define the methodology for the design assessment, the performance criteria to be applied and recommendations for the construction of OWTP in FRP.
The report will also identify possible gaps and deviation for the certification

Critical review of applicable standards and gaps identification in FRP offshore structures (T4.3.1)

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:32:58 +0200

The conclusions of an extensive review of the regulations and standards related to the use of conventional (steel and concrete) and unconventional materials (FRP materials and others) on marine structures will be included in this report, as well as the gaps that need to be filled in in the future by regulatory bodies to enable the rolling out of OWTP platforms in FRP materials.

A two-tier strategy will be performed with the fundamental objective to carry out the critical review. Firstly, it will be carried out an analysis of the potential standards for the application of FRP materials in the design of offshore structures. Secondly, it will be identified the existing gaps for the application of FRP materials in the design of the W2Power and the TIDETEC’s turntable tidal turbine developed in FIBREGY.

The findings of this report will be used as the background of the deliverable 4.7 focused on the development of project design guidelines and recommendations for using FRP in large OWTPs.

Multifunctional materials for SHM diagnosis and structural performance assessment

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:31:56 +0200

This report will evaluate the structural health monitoring (SHM) methodology developed in the framework of FIBREGY to obtain the damage state of the fibre-based structural elements used in offshore platforms.

The non-destructive vibration-based methodology deals with the variations of the key performance indicators (KPIs, e.g. overall vibration energy, damping, etc.) which are influenced by the presence of damage in the FRP materials.

To assess the damage state of the multifunctional materials, a set of sensors and/or optical fibers will be interleaved in the interlaminar regions of the FRP-based materials used in the marine structures.

Initially, the main scope of this report is to explore the selection of the most suitable sensors to manufacture the multifunctional materials. Subsequently, the mechanical performance of the multifunctional materials will be analyzed with the paramount purpose to evaluate the possible weakness of the material induced by the embedding of the sensor. Last, it will be considered the testing of different specimens of multifunctional materials and the preparation of the best strategy for the validation of the monitoring system in a real-case through one of the WP6 demonstrators (FRP-based towers).

Connections in offshore structures

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:30:58 +0200

Report containing a benchmark of the connection technologies in OWTP structures, their respective evaluation and selection. The report will also include the re-design and
optimization of the most promising connections, supported by a detailed description of the experimental testing campaign.

Environmental protection of composites

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:30:30 +0200

The report of deliverable D2.3 includes all the results of the durability tests performed during the extensive experimental campaign. The most relevant laboratory tests to evaluate the environmental performance of the various solutions are listed below:
- Alternate and continuous immersion in salt solution (ISO 11130, ISO 2812)
- High Humidity Test (ISO 6270) - 500 hours at 40 °C and 98 % HR
- QUV accelerated weathering test (ISO 11507) - 1000 hours with cycles of 4 hours UV light / 4 hours of high humidity
- Climatic chamber with thermal cycles (-20°C / + 80°C)
- Adhesion tests: Cross Cut (ISO 2409) and Pull Off (ISO 4624) before and after each ageing test
- Gloss (ISO 2813) and Colorimetry (ISO 7724) measurements before and after each ageing test
- Observation of visual defects before and after each ageing test
- The effect on the texture on biofouling will be evaluated at coupon level in natural sea water basin

A dedicated Design of Experiments (DOE) will be built to optimize the number of samples to be tested. The durability will be evaluated for the following configurations:
- At least 2 paint references (from 2 suppliers or 2 different chemistries)
- At least 2 composite substrates (1 thermoset and 1 thermoplastic)
- Three types of application: adhesive paint film, in-mold application of paint film and stand ard liquid paint application
- Three surfaces textures: flat surface and two fouling release textures
- Unprotected composite samples as a comparison

Fatigue performance of composites

Jesús Sánchez Pinedo — Thu, 13 Jun 2024 16:30:03 +0200

The deliverable will present the results and conclusions of the different fatigue tests to be performed.
An interim report will be delivered by month M24 describing the regular fatigue tests (O° and 90° lay-ups) and results. This data is the only one required by the numerical models for material calibration.
The report will be completed by M29, including the advanced fatigue characterization performed on oblique (45°) lay-ups and also the connections.

FINANÇAMENT DE LES POLÍTIQUES D’ACCÉS A L’HABITATGE SOCIAL DE LLOGUER

Anton Gasol — Wed, 12 Jun 2024 19:23:02 +0200

Considerem que l’habitatge és un pilar clau de l’Estat de Benestar com ho són l’educació, les pensions, la sanitat, o els serveis socials. La gran política habitacional és la que planteja abastir la demanda de parcs d’habitatge públics i socials mitjançant un finançament adient a les seves característiques i necessitats.

La comunicació pretén posar l’èmfasi en el finançament de la promoció d’habitatge social de lloguer, pedra angular per tal de proveir a la societat d’un parc que pugui abastar les necessitats sorgides de la darrera crisi financera (2088-2012) que ha suposat un punt d’inflexió en el mercat de l’habitatge, amb un protagonisme molt més accentuat de les transaccions del lloguer. Un canvi estructural produït pel fort augment de la precarietat laboral en determinats col·lectius socials, com ara les rendes baixes, la població estrangera, i els joves. Som del parer que és fonamental blindar el dret a l’habitatge per damunt de la seva consideració com un bé de mercat.

La comunicació farà un repàs de les circumstàncies que han conduit a Espanya i a Catalunya a la manca d’un parc d’habitatge social suficient (tant en propietat com de lloguer).

Segons la projecció de la creació de noves llars que fa l’INE i el PTSH (Pla territorial sectorial d’habitatge) és necessita la promoció d’habitatge social amb suport de l’Administració Pública a una mitjana de 15.000 habitatges/any, durant els propers 15 anys, una xifra molt allunyada de la producció dels darrers 10 anys.

Per tal d’assegurar el finançament de la promoció d’habitatge social de lloguer cal:

Continuar comptant amb finançament regular per part del Banc de Desenvolupament del Consell d'Europa (BDCE, CEB), que té com a objectiu millorar les condicions de vida i la cohesió social a Europa mitjançant el finançament de projectes d’alt impacte social, mitjançant la concessió de préstecs i garanties. I també poder accedir al finançament de projectes a llarg termini per part del Banc Europeu d’Inversions (BEI). La provisió d’aquest finançament és bo vehicular-la a través de l’Agència financera tant de l’Estat (ICO) com de la Generalitat de Catalunya (ICF).
I, com a novedós, replicar el «Pla d’Inversions per a una Europa Sostenible. Pla d’Inversions del Pacte Verd Europeu» => amb el «Pla d’Inversions per a una Europa Inclusiva. Pla d’Inversions del Pacte d’Habitatge Social Europeu» que garanteixi una vida digna a tota la ciutadania: accedir a un habitatge en condicions assequibles. I així, igual que hi ha el «bo verd europeu» o «BVEu» hi hagi també el «bo d’habitatge europeu» o «BHEu». La pretensió de la Comunicació és que entre tots els agents implicats es pugui aconseguir durant el nou mandat del Parlament Europeu, juntament amb el Consell, adoptar un REGLAMENT (UE) que repliqui el del 2023/2631 de 30.11.2023 sobre els “bons verds europeus”, en aquest cas sobre els “bons d’habitatge social europeus”.

Com millorar la col·laboració publicoprivada en el finançament de les concessions de serveis públics

JOSEP MARTÍNEZ VILA — Wed, 12 Jun 2024 16:21:02 +0200

La Unió Europea tornarà a l’ortodòxia pressupostària dels seus estats, un cop finalitzada la fase post-Covid i amb ell s’acabaran els fons europeus Next Generation.

Els països, com l’espanyol, amb dèficits pressupostaris crònics i amb fortes pressions d’augment de la despesa social, tindran dificultats per poder complir les directrius europees i es veuran avocats a una dràstica reducció de la inversió i despesa públiques ja força limitada en els darrers anys.

Aquesta previsible menor inversió pública, especialment pel que fa a infraestructures de serveis, només pot ser compensada per part de la iniciativa privada.

La realitat actual de projectes d’inversió finançats amb iniciativa publicoprivada és molt minsa, tal com ho testifica l’últim informe de “OIReScon-Oficina Independiente de Regulación y Supervisión de la Contratación” a Espanya, i que està força per sota de la resta de països de la Unió Europea.

Les raons que poden justificar aquesta manca de proliferació de noves concessions són de caràcter polític, jurídic, financer i econòmic. Les causes de caràcter polític deriven d’un progressiu distanciament entre el món polític i empresarial, provocant que la capacitat d’inversió a llarg termini de la iniciativa privada s’estigui derivant cap a fora de les nostres fronteres. Cal que les dues bandes de l’equació tornin a apropar posicions i confiança, el més aviat possible, en favor de la nostra economia i la potenciació d’un sector de les infraestructures, generador d’ocupació de qualitat, que havia encapçalat el rànquing internacional sense afectar els pressupostos públics. (En el document desenvoluparé les raons de caràcter jurídic, financer i econòmic)

Davant d’aquesta situació, cal fer aportacions que redundin en el foment de la iniciativa privada per a nous projectes d’infraestructures i serveis, en la millora de la governança i en el posicionament polític i social de la col·laboració publicoprivada, en l’adequació dels processos de licitació pública a la realitat actual, en la facilitació de l’adaptabilitat de les concessions actuals a les condicions canviants i millora de la finançabilitat dels projectes, tant des de la perspectiva d’unes condicions atractives de rendibilitat com de la pròpia seguretat jurídica dels projectes.

Josep Martínez Vila

Conseller Delegat

SABA INFRAESTRUCTURAS, S.A.

Ongoing development of applications of the Cone Penetration Test in interpretation and design

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 13:04:04 +0200

This paper presents recent research on the application of the cone penetration test to site characterisation and foundation design. Aspects considered related to characterisation include the interpretation of relative density in granular soils, the derivation of the penetration-velocity characteristic, corrections for shallow penetration and scale effects in laboratory experiments and the influence of particle size on penetration resistance. In relation to foundation design, the paper outlines the nature of CPT-based correlations and describes the development of three types of such correlations for footings, axially loaded piles and laterally loaded piles.

The influence of soil structure on CPTu and SDMT results

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 13:03:46 +0200

The natural structure of clays has a significant influence on its mechanical behaviour and can be characterized using insitu and laboratory tests. It was reported by Robertson (2016) that soil structure leads to an increased tip resistance (qc) and shear wave velocity (Vs) when performing seismic cone penetration tests. However, only limited studies investigated changes in soil structure by means of in-situ tests. Sensitive, marine clays were investigated within the research project "VIBE – Sustainable Ground Improvement Solution for Oslo" at the Norwegian Geo-Test site Onsøy (Gundersen et al. 2019). Possibilities and limitations of the vibro replacement method were studied for very soft ground conditions based on a full-scale field test. The influence of soil structure on in-situ measurements of piezocone penetration tests (CPTu) and seismic flat dilatometer tests (SDMT) are further studied by intentionally disturbing the soil structure by a vibrator. Results of CPTu and Medusa SDMT, executed before and after treatment, are compared to characterize changes in soil structure. The results indicate that the vibration-induced destructuration led to a significant decrease of CPTu measurements, namely tip resistance (qc), sleeve friction (fs) and measured pore pressure (u2), within medium to high sensitive clays. As the decrease in fs is more significant compared to the decrease in qc, a significant decrease in friction ration (Rf) was observed. In analogy, SDMT resulted in a decrease in shear wave velocity (Vs), horizontal stress index (KD) and dilatometer modulus (ED) after the vibro treatment. It was further shown that the soil behaviour type chart according to Robertson (2016) leads to no sufficient characterization of soil structure in soft, marine clays.

BRIGHT SPARK LECTURE - A Machine Learning Paradigm for Subsurface Stratigraphy from Sparse Data

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 13:03:29 +0200

Subsurface stratigraphy is an indispensable component of geotechnical site characterization and primarily deals with the interpretation of geological interfaces from site-specific measurements, such as boreholes. Traditional geological profiling methods often rely on engineering judgement for manual drawing or entirely depend on parametric models for interpolation. Both approaches face challenges when dealing with limited geo-data. To effectively address the dilemma, a new machine learning paradigm is proposed in this study to combine valuable prior geological knowledge and sparse site-specific measurements for data-driven predictions of both two-dimensional geological cross-sections and threedimensional geological domains. The valuable prior knowledge is quantitatively represented as training images, which are compiled and stored in a training image database that is further enriched and augmented by employing deep generative models. Subsequently, the optimal training images that are compatible with the available site-specific data are adaptively selected for onward stochastic predictions under the framework of non-parametric Bayesian analysis. The method has been successfully applied to tackle geological profiling challenges in Hong Kong. The proposed framework is demonstrated to be capable of not only predicting the most probable geological patterns but also effectively quantifying associated stratigraphic uncertainty. The framework holds great potential of revolutionizing current engineering practices

Interpretation of Cone Penetration Tests in Gravelly Soil

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:56:22 +0200

Although gravelly soils have been observed to liquefy in 27 earthquakes in the past 120 years, many engineers believe that gravel cannot liquefy due to its high hydraulic conductivity. Gradations from gravel liquefaction case histories have shown these deposits typically contain 25 to 40% sand, reducing the hydraulic conductivity and enabling excess pore pressures to cause liquefaction. While cone penetrometers (CPT), typically used to evaluate liquefaction resistance in sand, may show increases in penetration resistance due to their small diameter relative to gravel particles, the CPT has successfully predicted gravel liquefaction for looser sandy gravels. Case histories in Wellington, New Zealand demonstrate the successful identification of gravel liquefaction hazards using CPT. Although some layers in the profile indicated high penetration resistance, most of the profile was correctly predicted to liquefy. The Soil Behavior Type (SBT) from the CPT did not consistently indicate a sandy gravel profile but was often classified as behaving like a sand or silty sand; likely influenced by higher sand percentages between gravel particles. To evaluate the ability of the CPT to characterize gravelly soils and their liquefaction potential, additional field case histories are desirable. This paper presents test results from two case histories, one in Wellington, New Zealand, and one in Petrinja, Croatia, where gravels have liquefied. In both cases, the CPT occasionally overestimated liquefaction resistance in gravel layers. The advantages of using a 74 mm diameter Dynamic Cone Penetrometer (DPT) are also highlighted with companion testing.

Quantitative Assessment of Tip Saturation for High Quality Piezocone Testing

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:55:17 +0200

The research compares 2 CPTU profiles obtained with a same piezocone setup but having a different degree of saturation associated with the pore pressure measuring system. In the reference test, saturation was performed injecting 20cS silicon oil in the conduit connecting the porous stone to the pressure sensor and applying vacuum while submerged in oil for 15 minutes. The piezocone tip was then assembled with a saturated porous stone while submerged in oil. In the other test, the degree of saturation was purposely lowered by introducing air in the same conduct, whereas all other saturation steps were unchanged. The degree of saturation was compared quantitatively by measuring an analogue of the Skempton’s coefficient B, which is routinely used in laboratory testing to assess specimen saturation in a triaxial cell. The value associated with the saturation condition was measured employing a tool specifically designed for this purpose. The saturation procedures adopted were selected based on preliminary experimental activity in the laboratory, which provided target values of the pore pressure parameter corresponding to full or partial saturation. The CPTUs were performed at a test site presenting 10m clay unit followed by sand. The profiles measured were compared in terms of pore-pressure profiles, as well as the influence this had on corrected tip resistance, Soil Behaviour Type classification and mechanical properties. Additionally, a dissipation was performed for each test to compare consolidation parameters.

Calibration Chamber Testing on Tailings for Interpretation of Partially Drained CPT

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:54:20 +0200

The Cone Penetration Test (CPT) is the primary site investigation tool in silt-rich tailings. The permeability and compressibility range of tailings often puts the standard CPT penetration rate in the partial drainage range where the tip resistance, pore water pressure, and sleeve friction become functions of not only the state, but also drainage conditions. This makes interpretation of the state parameter, which represents liquefaction susceptibility and residual strength of tailings particularly challenging. It is not clear whether existing CPT interpretation frameworks are capable of accounting for effects of partial drainage. Developing field correlations for interpreting partially drained CPT data in tailings is hampered by spatial variability and sampling disturbance. CPT tests were performed in a calibration chamber and in the field on a gold tailings material. Dissipation tests were performed, and the pore water pressures on the cone at the u2 position were monitored. The degree of partial drainage was estimated based on the coefficient of consolidation inferred from these dissipation tests. Similarities and differences of the calibration chamber and field CPTs were discussed.

Methodology for Determining Optimum Vibrating Wire Piezometer Pairing Relationships in VWP Monitoring Clusters

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:53:13 +0200

Current trends in the mining sector and specifically tailings storage facilities have seen a significant increase in monitoring frequency, instrumentation installed on site and field tests conducted. Monitoring methodologies are also shifting away from analog and towards digital electronic systems. These instruments are also being integrated with online dashboards. Owing to all these factors, the instrument that is now most commonly being installed to meet these requirements are VWP’s (Vibrating Wire Piezometers). However interpreting VWP results and deriving the phreatic surface from these are not as straight forward as initially assumed, it requires engineering judgement and a methodology to determine and verify optimum pairing of VWP clusters. Obtaining the correct phreatic surface from VWP’s is critical as this will have a direct impact on the trigger levels and TARP’s of the online dashboard. Inaccuracies in calculating the phreatic surface can lead to the triggering of incorrect levels, which may result in flawed assessments of stability. The primary approach relied on phreatic surface and hydraulic gradients from CPTu testing being compared to the phreatic surface and hydraulic gradient determined from various combinations of VWP’s in a cluster at the time of CPTu testing. In cases where no historical VWP data is available at the time of CPTu testing, a methodology was also investigated using standpipe piezometers only. Piezometric head was converted to pressure and linear regression used to determine the phreatic surface. Results from the primary approach showed that certain pairs of VWP’s yield phreatic surfaces and hydraulic gradients that match the CPTu findings. Standpipe interpretation provided a good starting point and correlates with primary identified pairs. This methodology provides a verification tool to provide confidence when selecting VWP combinations for dashboard reporting.

Restrictions of CPTu Based Interpretation Methods and Impact Thereof on Limit Equilibrium Modelling

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:52:55 +0200

There is a large reliance on piezometric cone penetration testing (CPTu) in the tailings industry to estimate strength parameters for assessing the stability of tailings storage facilities (TSFs). It is common practice to assess the post-liquefied stability of a TSF using a residual undrained shear strength ratio (USSR). In such an assessment the residual USSR is typically applied to all saturated tailings. The current methods available to analyse CPTu data, are largely based on correlations and assumptions, and therefore contain limitations. Due to the limitations of the methods, this could lead to either over- or un-conservative estimates of stability. In this study, three methods for determining liquefaction potential and residual undrained shear strength ratio (USSR) are compared, namely: Robertson (2022), Been and Jefferies (2016), and Olsen and Stark (2002). These methods differ in the way in which they apply cone resistance, sleeve friction, and dynamic pore pressure response to estimate residual USSR. Their limitations are highlighted and discussed. A hybrid method is proposed for applying the results to post-liquefaction stability analyses. The hybrid interpretation approach uses a combination of the methods to account for different ranges of effective overburden stress and to identify weaker and stronger layers in the tailings profile based on state parameter, residual USSR, and pore pressure response. This hybrid method was applied to a stability assessment of a decommissioned platinum tailings storage facility in South Africa. The results indicated that the hybrid interpretation resulted in a more realistic phreatic surface location and a more accurate failure plane than conventional interpretations.

Technical Note on Calibration for Cone Penetration Testing in Soft Soils

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:52:38 +0200

Even the most experienced geotechnical engineer is likely to assume that the results of cone penetration tests are unquestionably accurate, reliable and repeatable. There are, however, multiple factors, some that have nothing to do with the soil properties, that need to be carefully addressed prior to testing if the equipment is to return results that can be relied on for design purposes. In soils which are very soft or soft, cone penetration test results can be particularly sensitive to the method of calibration. A high degree of rigour to the calibration process is required, otherwise there is a risk that the results obtained could be inaccurate and adversely impact on the reliability of the interpretation of design soil strength profiles. In this technical note sources of error in cone calibration are discussed. Reference is made to ISO 22476-1 which was revised in 2022, with the addition of a defined approach to calibration. Examples are used to demonstrate the typical errors that could be introduced during calibration.

Portable Pressiocone System for Carrying Out CPTU+FDP (Full Displacement Pressumeter) Tests

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:52:20 +0200

Geotechnical investigations in the subsoil of existing buildings have always been challenging due to limited space and difficult access. URETEK has developed a portable integrated system for simultaneously carrying out a CPT and a pressumeter test with Full Displacement Pressuremeter (FDP). The 30 kN thrust penetrometer to be used is very small. The reaction is given by two “microanchors”. The cone is a standard 10 cm2 digital memory cone (no cable), capable of measuring qc, fs, u every centimetre. Above the cone there is the FDP equipment with a rubber sheath covered by steel plates and connected, by a tube filled with water, to a device for creating pressure to inflate the sheath and measure pressure-volume curves as in a standard pressumeter test. The pressure-volume device and the depth transducer are connected to a microcomputer that is programmed to carry out CPT+FDP tests in an easy-to-use/user-friendly way.

Finite element analysis of self-boring pressuremeter tests in clay

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:51:45 +0200

Self-boring pressuremeter (SBPM) tests are widely used in site investigations, due to their distinct advantage to measure the shear stress-strain-strength properties of the surounding soil with minimum disturbance. The measured pressuremeter curve can be interpreted using analytical solutions based on the long cylindrical cavity expansion theory with relatively simple constitutive models. However, SBPM tests are strongly affected by the soil behavior and details of installation procedure. In addition, the derived parameters for clays (e.g. undrained shear strength, and shear modulus) are affected by a number of state variables such as overconsolidation ratio, and stress level. In this paper, SBPM tests are investigated using finite element analysis and the MIT-S1 model, to consider complex soil behavior more realistically. SBPM tests in K0-consolidated Boston Blue Clay at different OCRs are simulated in axial symmetric and plain strain conditions, consistent with the assumptions used in analytical solutions. The derived undrained shear strength from both contraction and expansion curves are compared with theoretical values from stress-strain curves, to evaluate the reliability of the derived parameters from the SBPM tests.

Development of a Calibration Chamber System for Testing at High Confining Pressures

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:51:24 +0200

Cone penetration testing with pore pressure measurement (CPTu) represents a state of practice tool to assess the in situ state parameter, strength, and liquefaction susceptibility of sandy soils and mine tailings. Many techniques for the interpretation of CPTu data are based on the results of calibration chamber test programs on sand and, more recently, mine tailings. While these efforts have led to the current methods to interpret CPTu data, two factors relevant to CPTu interpretation require consideration: (i) the available calibration chamber data is dominated by tests with consolidated mean effective stresses

Does CPT Reference Value Drift Really Inform CPT Correctness?

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:51:05 +0200

The two authors’ company (IGS) is an in situ testing and sampling contractor. Approximately 40% of the company’s business is cone penetration testing (CPT). The CPT cones they use are good quality commercial units supplied by the Dutch company Geomil, with qc capacities ranging from 3MPa to 100MPa. Both compression-type and subtraction-type cones are used. IGS undertakes their own in-house calibrations on all cones, using externally calibrated load cells, and a combination of dead weights and hydraulic load application. Calibration and adjustment is undertaken on every cone on an unusually frequent basis, explained in the paper, far more frequently than current standards or manufacturer recommendations require. At each calibration, the reference readings (sometimes known as baseline readings) of each cone’s tip qc, sleeve fs, and pore pressure U sensors are noted. And the slope of the applied-load/pressure-vs-cone-readout for each of these sensors (ie accuracy) is measured and adjusted to give as close as reasonably possible 100% accurate output. All of this is recorded for each cone. Thus the authors have a database of reference reading drift that can be compared to slope adjustments (ie calibration adjustments) that have been needed to achieve the desired cone accuracy. This paper graphically reports the data for tip and sleeve of eight typical CPT cones of the day-to-day types used by the company.

Importance of Calibration Laboratories in In-situ Test Methods

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:50:43 +0200

Geotechnical in-situ test methods provide valuable data for asset development, operation, and decommissioning. For confidence in test results, industry typically requires calibration and verification of in-situ test sensors to be conducted in a calibration laboratory. A calibration laboratory typically operates according to ISO/IEC 17025 (2017) ‘general requirements for the competence of testing and calibration laboratories’, or similar standard. This paper summarises observations from practice, with focus on the following challenges (1) evaluation of measurement uncertainty of key parameter values for which no standardised methods or verification materials are available, (2) validation of test methods with no backup from a formal standard published by a standardisation organisation and (3) field test site and interlaboratory comparisons within a competitive industry setting. Specific examples are presented for the (1) estimation of calibration uncertainty for sleeve friction of a subtraction-type cone penetrometer and (2) method validation for thermal conductivity of soil derived from in-situ heat flow measurements.

Offshore shear wave velocity measurements for the assessment of soil sampling quality

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:43:05 +0200

Shear wave velocity Vs is a critical soil parameter for several geotechnical and geophysical engineering applications including seismic site response analysis, liquefaction risk assessment and design of shallow and deep foundations. Moreover, the comparison of shear wave velocity between laboratory and in situ measurements has become a standard acceptance criterion for the assessment of sampling quality. Offshore in situ shear wave velocity testing is considerably more challenging than onshore, due to the difficulties in the correct deployment of the instrumentation as well as of the wave source, in absence of direct visibility of the ground level below water. This paper describes the methodology employed for offshore shear wave velocities (Vs) measurements in the harbour of Barcelona in September 2022. Medusa SDMT tests were performed in sea depths ranging between 15-17 m from a jackup and employing a drill rig to penetrate the probe down to 40 m below the seafloor. The paper includes examples of recorded S-wave seismograms, analyses of Vs repeatability for the same depth measurements and Vs profiles with depth. In the same test locations, carefully prepared specimens of undisturbed samples were tested after reconsolidation to the estimated in situ stress states in stress path triaxial cells with bender elements transducers. The obtained lab shear wave velocities were compared with the in situ values obtained with the Medusa SDMT tests to assess sample quality.

Influence of hydrogeological conditions on estimation of undrained shear strength by CPTu tests: case study in a tropical soil

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:42:25 +0200

CPTu tests have gained prominence in the geotechnical characterization of materials, registering a significant increase in their application in the Brazilian context, especially due to requirements to consider undrained resistance in analyses guided by more recent regulations. However, the interpretation of these tests often lacks a detailed and personalized approach, as they disregard specific nuances of each location. In this study, the foundation of a dam made up of tropical soil with a specific hydrogeological condition, characterized by bottom drainage with deep percolation, previously identified in other research campaigns, was evaluated. The interpretation of the CPTu test aimed to estimate the undrained resistance of the material through two different approaches: considering the dissipation tests carried out to model the insitu pore pressure according to the elevation versus a hypothetical hydrostatic condition, which could be misinterpreted in places where there is a predominance of SPT tests and insufficient geological knowledge. Multiple methodologies were evaluated to interpret undrained shear strength, including approaches that use Bq directly and that exclusively considers the laboratory characterization of a sample and the overconsolidation ratio at that point. In this case analyzed, it was observed that the change in pore pressure conditions resulted in a considerable variation in the undrained shear strength ratio, over 10% when pore pressures are considered in the equations. The results highlight the relevance of considering local hydrogeological conditions when interpreting field tests, especially for foundations of large structures.

Engineering characterization of lacustrine soil deposits at the inner bay of Puno around Titicaca Lake

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:41:24 +0200

The inner bay of the city of Puno has been the subject of various investigations that seek to recover and enable floodprone areas, through strategic urban development projects (urban infrastructure) and protection works. On the other hand, the characteristics of soft soil deposits, such as those in the inner bay of Puno, represent a risk of problems with excessive settlement of the infrastructure. This study presents an engineering characterization of the lacustrine soil deposits in the inner bay of the city of Puno, around Lake Titicaca. The site lies around the Pier of Puno city at Lake Titicaca, the highest navigable lake in the world, approximately a few hundred meters in front of the National University of the Altiplano of Puno (UNAP) and a few hundred meters to the southward of the Pier of Puno city. Physical, strength, and deformation properties were determined from standard laboratory tests. The material studied corresponds to the shallow layers of the study area, corresponding to sedimentary soils of the lacustrine units and fluvial-alluvial deposits of the inner bay of Puno. These lacustrine soils are classified as highly plastic silts and organic clays (MH and OH). The results show the significant influence of the quality of soil samples, due to the sampling method and storage time, on consolidation and resistance parameters. Finally, this study provides valuable insights into the influence of sample quality on consolidation parameters and shear strength of the lacustrine soils in the inner bay of Puno city around Titicaca Lake.

Assessing shear wave velocity profile uncertainty using multiple sCPT interpretation and processing methods

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:40:26 +0200

This paper quantifies the influence of seismic Cone Penetration Test (sCPT) interpretation and processing methods on shear wave velocity (VS) profile uncertainty using data from 20 sites in Christchurch, New Zealand. The near-surface soil profiles varied across the sites, both in terms of the soils that were present and the profile layering characteristics, reflecting the depositional environment that is influenced by alluvial and coastal processes. The same experimental setup was used at each site, consisting of a dual receiver sCPT cone and a hammer source method at a consistent horizontal offset distance. Three commonly used shear wave arrival time picking methods and the cross-correlation method were used to define arrival times and time intervals between testing depths for each site. The pseudo-interval, true-interval and slope-based processing methods were used with these arrival times and time intervals to develop 11 VS profiles for each site. Alongside this, a ray tracing inversion method provided an additional VS profile at each site. The uncertainty in the VS profiles that were developed at each site are presented, highlighting the variability resulting from different processing and picking methods. Results across sites are combined to provide a representation of the uncertainty across all methods and the differences in the uncertainty across the various processing methods.

Uniaxial Compressive Strength versus Shear Seismic Wave Velocity

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:40:03 +0200

Worldwide, geotechnical engineers frequently use the Uniaxial compression test for soils and rocks as a basis for determining the strength of the materials, despite the fact that test results are subject to a wide range of uncertainties (drilling technique, care during transport and stockage, sample preparation, and sample representativity of the soil or rock layer). The process of geophysical site research uses Refraction Seismic Survey and Passive Tomography to determine the shear and compression seismic wave velocities for various rock and soil layers under the surface. The study examines the correlation between the outcomes of the Uniaxial Compression Tests and the shear seismic wave velocity measured at a 400 ha location in the Atacama Desert (Chile), which was intended to host 84 km of linear solar panels. A robust survey of the axial compression value was determined at a vast site spanning 400 hectares by integrating Uniaxial compression tests, Brazilian test, Shear, and Compression seismic wave velocity.

Seismic P-, SH- and SV-Wave Cross-Hole Testing Using Direct-Push Technology for the Determination of Geotechnical Parameters

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:39:44 +0200

Seismic surveys are often carried out between two or more pre-installed boreholes to assess unknown geological situation in the subsurface with high resolution. However, the cost of installing boreholes is often a budgetary constraint. Therefore, the direct-push technology, where rods are pushed into the subsurface, seems to be a more suitable tool and by incorporating seismic sources and receivers into the push rods, geophysical methods can become more flexible and adaptable, especially for larger areas of investigation or sites in harsh environments. In this paper, we present field results using such a direct-push seismic system as a cost-effective alternative to standard borehole-based investigation techniques. For both techniques complete cross-hole datasets of P, SV and SH waves were acquired at two different test sites (1) between direct-push boreholes and (2) between PVC cased boreholes. The in-situ profiles of the paired shear wave velocity profiles (SH and SV) were used to evaluate the stress history of the soils by deriving the over-consolidation difference (OCD). Many geotechnical parameters are influenced by the soil stress history, such as deformation properties and soil stiffness, but in the calculation of geotechnical parameters, such as the lateral stress state (K0), consolidation coefficient and liquefaction response the OCR also plays an important role. The tests also showed that direct-push based techniques make even seismic methods more flexible as test positions can be easily adapted and changed according to the results, local conditions or client requirements.

Development of a framework for automatic quantification of uncertainty in seismic cone penetration testing

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:39:24 +0200

Accurate quantification of the shear wave velocity, Vs, of geo-materials is an important consideration in geotechnical design. Seismic Cone Penetration Testing (SCPT) measures shear wave travel times from a source to in situ receivers along assumed travel paths to calculate Vs. Despite complexities and uncertainties associated with obtaining Vs, results are often reported to designers as a single deterministic profile without an intuitive measure of uncertainty that can be incorporated into the design process. A rigorous workflow to rapidly obtain uncertainty-quantified profiles from SCPT using a Bayesian inversion approach is developed. While similar approaches have been documented, this inversion approach explicitly considers sources of measurement error which are generally neglected (i.e., assumed to be low) in order to deliver more realistic probability distributions of true Vs and improve robustness against imperfect data. Such errors can remain undetected when using traditional approaches, despite potentially leading to inaccuracy. Additionally, an outlier detection framework is incorporated into the workflow to improve accuracy. The workflow is demonstrated by application to a large database of SCPT data. The results show significant improvement over existing methods in terms of robustness and validity, and therefore that the workflow is a valuable tool for practical analyses. Further, they provide crucial insight into the prevalence and magnitude of key errors which are traditionally present but undetected.

Multi-method in situ geophysical testing in a high porosity chalk mass

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:39:06 +0200

Chalk is a silt-sized soft biomicrite rock often encountered as a low to medium density, high porosity, structured material within a fractured mass. In recent years, there has been increased interest in the behaviour of chalk and the development of new design procedures for pile foundation installation design, motivated by several large-scale onshore and offshore infrastructure projects. Recent modelling has demonstrated the importance of accurately characterising the operational stiffness of the chalk mass. While several methods exist to measure the chalk’s stiffness in situ, they are often subject to significant scatter, with no guidance available to the end user on interpretation or on which method should be used as a baseline. A new programme of multi-method in situ geophysical testing in chalk at a well-characterised onshore test site in Southern England is described that forms part of a wider research project. The chalk deposit is shown to be relatively uniform with depth which provides a unique opportunity to apply multiple methods and interpretations without the influence of significant layering. The experimental programme is described and the interpretation and selected results of downhole geophysical tests at depths up to 40m are presented. The chalk’s remarkably high shear stiffnesses are shown to be highly repeatable and consistent when rigorous test execution and analysis is applied

A case study addressing the development of a novel marine seismic cone penetration testing system.

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:38:26 +0200

Within the offshore wind sector, following the conclusions of the Pile Soil Analysis (PISA) Project increased emphasis has been placed on the acquisition of in-situ ðºðºðððððð data, to corroborate laboratory-based measurements, to allow for foundation weight optimization. This requirement for higher fidelity data at all wind turbine locations is coupled with the increased requirement to acquire data in shorter periods to meet ambitious development schedules for offshore wind farms. The development of a deep push seabed SCPT which can be deployed fully autonomously is considered to address this challenge facing the offshore wind industry. Recognising that within the current standards there is a shortfall on what is considered as accurate and reliable data with regards to having confidence in the shear wave velocity (ð£ð£ð ð ) measurements obtained offshore, there is a requirement for discussion within the industry; clients, designers and contractors, on how to provide improved set-ups, acquisition and interpretation methods in order to increase the confidence in the ð£ð£ð ð data acquired. The case study described within this paper, initiated by such dialog, presents the specification, construction, testing and utilisation of a dual array non-drilling mode seismic cone penetration test (SCPT) device and seismic source to provide demonstrable reliability and accuracy in acquisition and interpretation of in-situ ð£ð£ð ð measurements. Within this context, the paper describes; the engineering considerations and optimisation of a novel device intended for deployment from a new generation of robotic vessel; application and limitations of the set-up during trials and offshore operations; commentary on the in-situ data including challenges encountered during interpretation and comparison with existing data acquired at the same location, established correlations and site-specific correlations.

Evaluation of the Liquefaction Resistance of Sandy Soil for Shaking Table Tests

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:37:27 +0200

Seismic liquefaction of loose saturated cohesionless soils is one of the most dangerous and catastrophic phenomena that involves a temporary loss of soil shear strength and stiffness as a consequence of increase pore pressure and reduced effective stress. Therefore, the evaluation of the excess pore pressure induced by shaking is important to predict the liquefaction behaviour of soils at a large scale. In this regard, the study provides the static and dynamic characterisation of a liquefiable sand. For this purpose, a laboratory testing programme, which included the execution of cyclic direct simple shear (CDSS) tests, was performed. The CDSS tests were carried out by means of the CDSS device at the Soil Dynamics and Geotechnical Engineering Laboratory of the University “Kore” of Enna (Italy). The device is designed to allow the soil specimen to be consolidated one-dimensionally and then sheared under constant volume conditions, which replicates the undrained shear condition of the soil specimen. The CDSS tests were conducted to evaluate the liquefaction resistance of the sand under several test conditions, i.e. initial relative density, vertical effective stress or cyclic stress ratios. Results of this study provide useful information for the geotechnical characterisation of the liquefiable sand to be used in shaking table tests at the Laboratory of Earthquake Engineering and Dynamic Analysis (L.E.D.A.) of the University “Kore” of Enna. The laboratory is equipped with a large biaxial laminar shear box for reduced-scale model tests developed to monitor liquefaction under two-dimensional shaking.

Liquefaction Assessment at Gravel Sites in Croatia Based on Vs and DPT Blow count

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:36:24 +0200

Liquefaction of loose saturated soil poses a significant threat to civil infrastructure during major earthquake events. Although liquefaction is most common in loose saturated sands, numerous liquefaction events in gravelly soil profiles have been reported. Assessing liquefaction resistance in gravelly soils is challenging because large particle sizes can interfere with the standard penetration test (SPT) and the cone penetration test (CPT). To address this challenge, recent efforts have focused on developing liquefaction triggering curves based on a large diameter (74 mm) dynamic cone penetrometer (DPT) blow count and normalized shear wave velocity, Vs1, which are less affected by gravel-sized particles. While based on field case histories, the curves are poorly constrained in some areas; additional case histories continue to be highly desirable. This paper describes an investigation of six gravel sites that liquefied in the 2020 Mw6.4, Petrinja, Croatia earthquake. At each site, boreholes were completed to define the soil profile, accompanied by DPT soundings and shear wave velocity profiling using the Multi-channel Analysis of Surface Waves (MASW) approach. At some sites, the DPT blow count increased through a silty clay surface layer even though the CPT cone resistance remained constant in this layer. This increase was thus attributed to side friction on the drill rods during penetration. Subsequent DPT tests performed after casing through the silty clay eliminated the rod friction. The measured blow count and shear wave velocities in the critical layers at these sites correctly predicted liquefaction using recent probabilistic DPT- and Vs1-based triggering curves

Estimating the Small Strain Modulus G0 from DMT tests for loess subsoil as an example of the practical application of the non-seismic method

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:35:27 +0200

Seismic tests in geotechnics are used to determine the maximum shear modulus, which is a parameter characterising the subsoil in the range of very small strains. Maximum shear modulus is employed in deformation analyses, in particular when using advanced constitutive models describing the behaviour of the subsoil. Deriving parameters indirectly is a routine procedure in geotechnics. In the absence of seismic measurements or at an early stage of analysis, knowing the correlation between the shear modulus and other parameters measured in situ makes it possible to approximately estimate these parameters. The value of the shear modulus is closely related to, among others, the density of the medium and the shear wave velocity, which is significantly influenced by the in situ vertical effective stress. Therefore, the rule is that the shear modulus increases with depth. The article presents the results of research on loess subsoil. Based on the seismic dilatometer tests (SDMT), a formula was established that allows the shear modulus to be estimated from non-seismic dilatometer tests (DMT). The results were compared to those obtained in laboratory tests such as bender element test (BET) in an advanced triaxial testing apparatus. Formulas were derived to estimate the maximum shear modulus in the loess subsoil based on the vertical geostatic stress and the value of the constrained modulus MDMT. Moreover, the results were analysed with reference to the results for other soils in Poland and validated in additional field tests.

Upgrading a resonant column apparatus to reliably measure specimen void ratio

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:34:50 +0200

The small strain shear modulus of soils is an important design geotechnical parameter for a wide range of civil infrastructure applications. The small strain shear modulus can be determined by using elastic theory as a relationship between the soil density, which is expressed as a function of void ratio, and the measured shear wave velocity. Thus, the void ratio has a fundamental impact on the accuracy of the result. Laboratory testing involving resonant column apparatus allows for determining the changes in stiffness of soils with varying void ratios. Standard of-the-shelf resonant column apparatus works well for clayey soils but presents a number of limitations for coarse soils that makes accurate and reliable void ratio measurement difficult due to both pore fluid and (often) sample loss during removal from the equipment. This paper presents the development of a modular set-up which allows for complete specimen sealing at the end of shear wave velocity testing. The modular set-up along with the specimen can be removed from the resonant column apparatus and the void ratio can be determined by means of end-of-test-freezing similar to triaxial testing. From this, reliable small strain stiffness at well-determined void ratio can be computed. The void ratio measurements using the new modular set-up were compared to those from triaxial tests performed on identically prepared specimens. The difference in void ratio at any given isotropic confining stress was between 0.001 and 0.011.

Engineering surveys for construction based on the concept of sustainability resource to external influences and nature-based solutions

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:34:32 +0200

The resource of resistance to external influences (or sustainability resources) is understood as the ability of natural or natural-technogenic objects and systems to withstand negative impacts and at the same time preserve and maintain their basic functional properties within acceptable or specified limits. The use of the concept of sustainability resources (SR) to assess the risk of a system leaving an acceptable state necessitates a revision of some methodological issues in surveys for construction. Traditionally, the purpose of research is to obtain initial data for design decisions and calculations for various purposes. We emphasize that the existing approach corresponds to the strategy of protection from hazardous processes, and the use of the SR concept to external influences is more consistent with the strategy to prevent negative consequences. In addition, social and environmental factors, combined with global climate change, also increase the risks of hydrometeorological hazards and associated floods, activation of landslides, erosion, and karst-suffusion processes. Reducing these risks has traditionally been achieved by implementing protective engineering controls (or gray infrastructure), but nature-based solutions (green and blue infrastructure) are increasingly being explored. This approach, in our opinion, corresponds to the goals of ensuring rational and sustainable interaction with the geological environment during construction. The methodology is discussed and examples of the use of nature-based solutions are given.

Interface direct shear tests with novel binders

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:34:09 +0200

In the offshore/marine environment, foundation elements need to be particularly long or wide in diameter in order to reach a competent bearing stratum through weak, low-strength sediments. The seabed conditions in oil&gas and renewable energy projects can be difficult, and the skin friction produced during driving operations could be insufficient to support the service loads placed on the structures. In this study, low-pressure injections of an acrylate gel and a colloidal silica product were made into reference sand, and interface direct shear tests were conducted under constant stiffness conditions. Conventional ground improvement projects already employ these items. Oedometer tests on untreated sand were used to evaluate the stiffness properties of the sand, which provided the foundation for determining the stiffness in the DSTCNS system. At an initial low relative density (Dro) of 0.40, Holcim sand samples were generated. This value is thought to be representative of the top zone of normal sediment profiles under offshore settings. Shearing the sand over a steel plate has been done by direct shear experiments conducted under constant normal stiffness conditions. The effects of injection have been compared using pre- and post-grout interface shear tests. The new binders' activity is causing an increase in skin friction, according to the results.

Evaluation of the challenges present in the obtaining, processing and interpreting useful data from offshore seismic cone penetration testing

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:33:47 +0200

The Seismic Cone Penetration Test (SCPT) is an essential tool for establishing in-situ shear wave velocity (ð£ð ), which is then used to establish profiles of Small Strain Shear Modulus (ðºððð¥), a direct input parameter to the design of offshore wind turbine foundations. Performance of SCPT offshore presents greater challenges than on land and each offshore site investigation contractor uses their own different non-standard equipment to try to address these challenges. This contributes to the multiple areas of uncertainty in the assessment of wave arrival time and distance, which can result in less reliable data sets. Additionally, a variety of data processing and interpretation methods are used across the industry, the benefits and limitations of which must be understood if one is to specify, plan or undertake such testing. The authors provide a review of methods of acquiring data, the equipment required and the different processing and interpretation methods available, specifically comparing true interval straight ray analyses with pseudo interval true ray path analyses and the different processing steps which can be taken to increase reliability in datasets.

Development of a 3D Ground Model for an Offshore Wind Farm with Complex Interlayering of Silty Soils

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:29:35 +0200

Three-dimensional (3D) ground models enable the visualization of complex subsurface conditions in offshore wind farms, which aid engineers in understanding the spatial morphologies and interrelations of different soil layers. Due to the large areas of offshore wind farms, 3D ground models established solely based on limited geotechnical data (e.g., boreholes and cone penetration tests) might lack the required accuracy. Geophysical data, particularly seismic profile data, is capable of revealing stratigraphic information and can be obtained at a relatively low cost. This study presents a case study in which a 3D ground model for an offshore wind farm located off the Southern China coast is developed through the integration of geotechnical and geophysical data. The wind farm features complex interlayering of silty materials below the soft Holocene marine deposits due to repeated sea level changes during the Quaternary period. This created significant challenges for developing a reliable ground model. In this paper, the challenges that were faced and solutions that were applied in this project are presented and discussed.

Exploration for Wave Propagation Around Ground Loosening Using Discrete Element Method

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:29:11 +0200

Ground loosening and subsurface cavities potentially cause ground cave-ins, even if they are deep in the ground. Loosened soil and cavities, for example, formed by shield tunnel excavation or breakage of underground pipes occur frequently. Recently, ground-penetrating radar method has been utilized to detect subsurface cavities, and studies such as dynamic wave surveys have been considered. However, these methods assume that cavities several meters deep can be detected by surface-based surveys, and do not target loosened soil directly above a deep tunnel. This contribution is a fundamental study aimed at detecting loosening depth in the ground, with the goal of measuring dynamic waves from the inside of a tunnel. To understand wave propagation and particle-scale response around loosened sandy soil, this study adopts the discrete element method (DEM) using cohesionless spherical particles. A series of DEM simulations are performed to understand how dynamic waves propagate or reflect around loosened sandy soil in comparison with dense ground without loosening.

Statistical analysis between intensity measures at the bedrock and the seismic response of the site

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:28:45 +0200

This research work focuses on the seismic response of sites considering uncertainties. There are two main objectives. The first consists on assessing the effectiveness of intensity measures to predict properties of the expected wave motion at the surface. According to recent studies, special attention has been paid to predicting velocity-related ground motion parameters, which are highly correlated to the nonlinear dynamic response of civil infrastructures. The second objective is to analyse the evolution of the dynamic properties of the soil because of seismic waves. The main database of acceleration records in Colombia has been analysed, as well as three soil profiles that correspond to real building projects designed and built in the same country. From this information, a series of site seismic response analyses have been carried out using the equivalent linear method. Then, using statistical regression techniques, the correlation between input variables (parameters of the seismic records) and output results (intensity measures at the surface, maximum soil deformations, damping and shear wave velocity variations) have been evaluated. The paper shows that a series of highly correlated variables can be used to incorporate, in a simplified manner, site effects in the analysis of seismic risk at a regional scale.

Field Site Characterization of a Coastal Aeolian Sandy Subgrade for a Proposed Tank Farm Site in Peru

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:28:21 +0200

Analysis of shallow foundations, pavements, and slabs-on-grade requires adequate site characterization of the nearsurface soils. Key properties required for the above are the soil stiffness and its nonlinearity. In this paper, we present the results of field site characterization at a coastal aeolian sand site located in Villa El Salvador, Peru, where large storage tanks are being proposed to be supported on concrete slabs-on-grade and shallow ring foundations. The site characterization included standard penetration tests (SPT), dynamic cone penetrometer (DCP) tests, lightweight deflectometer (LWD) testing, and geophysical tests such as multichannel analysis of surface waves (MASW), seismic refraction, and electrical resistivity. The paper focuses on estimating elastic soil stiffness (Es) values on the main bearing layer of the tanks. The observed large variability of Es estimates was associated with inherent soil variability at the site, the in-situ test method, and the use of empirical correlations between Es and different in-situ tests. Good elastic soil stiffness estimates for the bearing layer (Upper SP sand) were required to make reliable estimates of absolute and differential settlements for the tanks. Due to soil nonlinearity, the elastic stiffness values from the different methods decreased with increasing levels of shear strains associated with each test. Accordingly, the highest elastic stiffness values were from the MASW, followed by the LWD, and the lowest from SPT-based correlations. The soil stiffness estimates using SPT-based correlations yielded the highest variability due to the high uncertainty and low confidence of the empirical correlations between Es and SPT field values.

Dynamic characterization of alluvial deposits through geophysical anda specialized test in Floridablanca santander

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:27:57 +0200

The Metropolitan Area of Bucaramanga is located within one of the three seismic nests in the world and therefore presents a high seismic and geotechnical threat (INGEOMINAS, 2001), therefore certain zones, especially those with alluvial and colluvial deposits, have limitations for the development of infrastructure projects, unless a threat assessment is carried out that indicates otherwise or, in its absence, it is reduced to low levels with stabilization works. The thicknesses of these deposits vary from a few meters to two hundred meters and their definition and dynamic behavior (damping coefficient and terrain degradation curves), would allow analysis with special non-linear constitutive models to better understand their response to a possible earthquake and to ensure the stability of the structures and even an optimization based on a possible lower spectrum. A new two-tower housing project of up to 36 stories high is a perfect scenario to carry out a local seismic response study and perhaps transform the way future projects are designed. It should be noted that, given the acceptable stiffness and granular composition of the soils, it is difficult to take unaltered samples and the Colombian NSR-10 standard does not require local behavior studies and therefore its study has not been properly established. It is sought through geophysical tests and laboratory tests such as triaxial, resonant column and bender element to perform such characterization and to perform soil modeling that allows the calculation engineer to have the appropriate inputs for their analysis.

Calculation of heights for local datum points of tide gauges in Albania referred to the average sea level and albageo program

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:27:34 +0200

The accurate measurement and monitoring of sea levels are of paramount importance, especially for coastal regions like Albania, where sea level changes can have significant impacts on various aspects of life, including coastal infrastructure, ecosystems, and human settlements. This abstract provides an in-depth overview of a study focused on the calculation of heights of local datum points at tide gauges in Albania with reference to the average sea level, using the ALBAGEO3 program. Tide gauges play a crucial role in understanding the dynamic nature of sea levels. These instruments measure the height of the sea surface relative to a reference point, which is typically known as the local datum. The calculation of heights of local datum points is crucial for several reasons. Firstly, it provides insights into the relative sea level changes at different locations in Albania. It allows for the identification of areas that may be more vulnerable to such events, enabling betterinformed decision-making in terms of coastal management and disaster preparedness. Furthermore, accurate knowledge of local datum heights is essential for navigation and maritime activities. It ensures that nautical charts are up to date and that ships can safely navigate Albanian waters without the risk of running aground or encountering obstacles related to sea level changes. In summary, the study on the calculation of heights of local datum points at tide gauges in Albania, utilizing the ALBAGEO3 program, plays a pivotal role in advancing our understanding of sea level variations in this coastal nation. The accurate and reliable data generated through this research benefits not only the scientific community but also provides actionable insights for policymakers, urban planners, and other stakeholders involved in the sustainable development and protection of Albania's coastal areas.

Spatio-Temporal Prediction Surface Displacement in Urban Underground Excavation: A Case Study in Seville"

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:27:05 +0200

One of the primary challenges in excavating underground in urban areas is controlling and mitigating ground surface displacement caused by Earth Pressure Balance (EPB) tunneling. It is crucial to avoid damaging historical monuments and buildings in these areas. This paper presents a new method for predicting the surface displacement caused by EPB in Seville. A spatiotemporal dataset was generated for this study using numerical simulation in FLAC3D. The simulation replicates the excavation process of the Seville metro line in real-time, and records the surface displacements at selected points in the dataset. The last 20-time steps of excavation are predicted, and the first 80-time steps are chosen for training and tuning hyperparameters, as the dataset is spatiotemporal. A recurrent neural network (RNN) is used to detect and predict patterns between surface displacement and input features at different time steps and locations of the excavation. After fine-tuning the RNN, the model achieved an accuracy of 0.91 for the evaluated R-squared (R2), indicating its practicality for real-time prediction of surface displacement in underground excavations in Seville. The model's performance can be further improved with a larger data range. By deploying it as a hazard detector, the model can issue a warning if the ground displacement exceeds the limit, thereby preventing potential hazards. This approach can help control and mitigate potential hazards in underground excavations in historical cities.

Geotechnical monitoring at the speed of light: New insights from distributed acoustic sensing

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:26:31 +0200

Recent advances in distributed fibre optic sensing enable new opportunities in geotechnical monitoring and characterization. Distributed acoustic sensing (DAS) is a distributed fibre optic sensing technology relying on Rayleigh backscattering of light to detect and locate disturbances in near real-time along tens of kilometres of fibre optic cable. The dynamic strain sensing capabilities of DAS have prompted numerous research initiatives from the seismology community over the past decade. Although research on DAS for seismic applications is well established, studies on DAS for geotechnical monitoring applications are less common. Here, we present a summary of two recent case studies involving DAS for geotechnical monitoring. The first study considers a slow-moving landslide where DAS data were acquired over a three-day period of rainfall. The DAS aseismic strain and strain-rate data support the interpretation of the triggering and retrogression failure mechanism of the landslide. The second study considers an active mine site in northern Canada. Data were acquired from a cable installed ~1m below a tailings dam crest. Passive seismic interferometry was applied to DAS data to infer changes in seismic velocities in the uppermost several meters of the subsurface. These findings represent a first step towards advancing continuous monitoring techniques with fiber optic sensing technologies. However, further research is needed to improve our understanding of DAS performance for geotechnical monitoring applications over longer-term periods.

Effects of storage time on sample quality in Ballina clay

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:25:25 +0200

This paper explores the effects of the storage time on the engineering properties of Ballina clay, an estuarine silty clay that represents the soft soil deposits encountered along the eastern and southern Australian coastlines, which serves as foundation material for most of the country’s transport and energy infrastructure. An experimental program was carried out to evaluate the variation in soil compressibility and soil shear strength for tube specimens retrieved with an open sampler (Shelby tube) as well as an Osterberg fixed-piston sampler. Mechanical parameters obtained from tests performed immediately after sampling are compared against those measured over a period of 1 year, to assess the influence of the storage time. Results indicate that long-term storage has small influence on the quality of Ballina clay specimens in comparison with the mechanical disturbance caused during tube penetration and extraction, which is controlled by the sampler type.

Relief well identification from satelite imagery using dual kernel filter unets

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:24:26 +0200

Precise identification of levee relief well locations from satellite imagery can be challenging and time-consuming. In this research, we propose a novel approach utilizing a U-Net architecture to identify relief wells along flood control levees, as a proof of concept of combining freely available imagery with machine learning techniques. The goal of this research is to develop techniques to make infrastructure asset management more efficient by automating the process. Our study highlights the crucial role of the convolution kernel size in the U-Net architecture, which significantly influences the accuracy of the results. Larger convolution kernel sizes excel in capturing extensive contextual information from the input image, potentially leading to superior outcomes. However, training with larger kernels is computationally intensive. Conversely, smaller convolution kernel sizes excel in capturing local features. To strike a balance these considerations, we introduce a Dual Kernel Filter U-Net, which combines two U-Nets with distinct convolution kernel sizes, 3x3 and 11x11. This innovative approach aims to harness the strengths of both convolution kernel sizes to improve accuracy and overall performance. The proposed Dual kernel filter U-Net was trained and evaluated on a real dataset of relief wells from Google Earth imagery. Our evaluation results demonstrate that this model achieves an accuracy rate of 99.76% with training dataset 2626 satellite images. Notably, this significant accuracy enhancement is achieved without substantially increasing computational time, making it a promising advancement in satellite image analysis for object location identification and asset, and disaster management

Prediction of Future Settlement of Backfill at an Aggregate Mining Quarry Site in Irwindale, CA Using Numerical Method and Settlement Monitoring Data

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:23:26 +0200

Future static settlement of a former aggregate mining quarry site in Irwindale, California is predicted based on the monitoring data and using numerical analyses that consider the total settlement of the deepest portion of the rockfill. The portion of quarry analyzed was backfilled with approximately 61 to 67 meters, has a volume of 2.6 million m3, and covers an area of 114,900 m2. The backfill material ranges from silty sand (SM) to silty gravel (GM) and was compacted to achieve an average relative compaction (RC) of 96%. The deepest fill area is currently being monitored with survey data to predict future 50-year settlement due to secondary compression. Settlement monument data from three different locations has been collected and made available starting from May 2009 up to now. A 3-dimensional model of the rockfill was used to determine an appropriate upper and lower bound of predicted future 50-year settlement from today in 13 stages and scenarios. The modified secondary compression index was estimated along with the modified compression index that was back calculated to match the field monitoring data. We could find good agreement between the field monitoring data and our numerical model when considering total settlement of the rockfill.

How to get a good match for consolidation coefficient

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:23:03 +0200

It is difficult to get accurate magnitudes when dealing with consolidation coefficient, decisive when clays and clayey silts, are compressing, especially if secondary consolidation is in play. This is a typical condition in harbours when new areas are to be reclaimed to get more and more loading/unloading areas. There are several approaches to assess consolidation rate. The oedometer cell is the main lab test used to get the compressibility parameters. It is accepted that 24 hours is a good time for each pressure. However, some soils consolidate slowly, and they need more time. Especially when slope is far from horizontal. On the other hand, “true” consolidation coefficient is obtained when surpassing the preconsolidation pressure. Thus, values obtained below preconsolidation pressure are usually discarded. Horizontal coefficient of consolidation can be assessed with dissipation tests from piezocones. If piezometers are installed within the consolidating layer, comparing with the theoretical isochrones we may derive the “true” consolidation coefficient. If settlements are measured, a comparison with theoretical ones can be informed on the predominant consolidation phenomenon. Much care is to be applied and not misunderstand the process in play. Dissipation tests give way to much higher consolidation values than laboratory tests. This could be due to anisotropic effects, but the main reason is that dissipation occurs in a reloading process, while oedometer tests are in primary consolidation, at least from the preconsolidation pressure and on. This paper shows some ideas to properly assess the process involving consolidation.

Site Characterization of a Restored Coastal Dune and Beach

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:22:08 +0200

Coastal beach and dune ecosystems are critically important for shoreline protection and significant resources have been allocated to their conservation. Dune vegetation is known to modify site response to wind, waves, and storms, but little focus has been given to understanding how belowground sediment structures enhance dune stability. A first step in addressing this knowledge gap is to determine optimal methods to measure subsurface sediment properties in onshore sandy environments. Our team performed a comparison of geotechnical and geophysical methods on a restored beach and dune system on Florida’s Atlantic coast. Methods included two types of dynamic cone penetrometer (DCP) systems, a multi-channel analysis of surface wave (MASW) system, a ground penetrating radar (GPR), soil vibracores, and grain size analyses. Two transects were investigated, a 50-meter cross-shore transect and an intersecting 20-meter along-shore transect. The transects were selected to study the gradient of sediment properties from the swash zone to the high dune. Key findings from this study were that the PANDA DCP provided a higher resolution of measurements compared to the standard DCP, which is extremely advantageous in the shallower, less consolidated soils. MASW shear wave velocity results showed similar trends to the DCP cone tip resistance and allowed for measurement of stiffer soils where the DCP reached refusal. In addition, the results from the DCP, GPR and vibracores compared well. Thus, the use of the DCP and GPR systems as minimally intrusive testing options in fragile dune systems was verified.

Combined Monitoring Remote Sensing Systems: Ground-Based SSR and Satellite-Based SAR

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:21:28 +0200

A combined ground-based slope stability radar (SSR) and satellite-based (InSAR) monitoring system was trialled at a remote mine site in the Northern Hemisphere in order to investigate relative changes in displacement experienced by a mine waste storage facility. The relative changes in displacements along the InSAR line-of-sight (LoS) were compared to the relative changes in displacement provided by the ground-based SSR LoS. Although the two LoS are different, this study showed good agreement between the magnitude of relative displacements observed by both remote sensing technologies on the slope of the facility. Additionally, the study looked at the effectiveness of InSAR and SSR on capturing relatively shallow operational works undertaken on the tailings storage facility slope. Results showed that SSR is able to provide near real-time information about progressive trends in displacements and alert mine site personnel of potential areas that might need attention. InSAR could detect anomalies in surface deformations during the period when SSR did, but the radar signal was sufficiently low to not unequivocally attribute these responses to real surface deformations

Improvement of Apparatus for Sampling and Cone Penetration Test

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:21:04 +0200

In this paper, a new innovative method of geotechnical investigation applicable to seafloor is proposed. This method is the improved version of Sampling and Cone Penetration Test (S&CPT) to evaluate geotechnical properties by Cone Penetration Test (CPT) while collecting continuous samples quickly and inexpensively for offshore geotechnical investigations. In the previous study, demonstration tests on soft cohesive soil were conducted, and some problems were found. The purpose of this study is to modify the sampler to improve penetrability, sampling performance, workability and to examine the applicability for cohesionless soils. Using the improved samplers, demonstration tests were conducted at two sand sites (loose and medium-dense) in Japan. The results of each test were used to examine: (1) sampling performance, and (2) workability. As a result, the following conclusions are drawn: 1) In loose sand, sampling of several meters is possible. In medium-dense sand, the same level of sampling may be possible by providing an appropriate shoe to prevent blockage at the sampler tip. 2) The workability of the proposed apparatus is very high compared to the conventional Cone Penetration Test and Standard Penetration Test.

Detection of cavities in an urban environment: Case of M’Rara region (Northeast of Algeria)

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:20:48 +0200

Micro-gravimetry emerges as the most appropriate geophysical technique for cavity detection in urban or industrial settings, as it remains unaffected by surrounding electromagnetic influences. The presented study investigates the occurrence of fissures, land subsidence, collapse events, and their potential association with the formation of cavities at depth. These phenomena were observed near a sealed hydraulic drilling site located in the M’Rara area within the Northeast Algerian Sahara basin. This drilling operation was sealed off due to the inflow of saline water, with a salt layer identified at a depth of 936 m according to the stratigraphic column. A gravimetric survey was conducted to image the lateral and vertical density variation. The resulting gravimetric image allows in comprehending the observed geological phenomena and their potential correlation with the presence of cavities at the salt layer.

A Cylindrical Cavity Expansion Test on Sand

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:14:25 +0200

Cylindrical cavity expansion is one of the fundamental boundary value problems in geotechnical engineering used as a simplified analogue to the pressuremeter test, pile driving and the Cone Penetration Test. Much of the popularity of cavity expansion comes from the simplicity of modelling it numerically. All numerical models require verification and validation, but doing so for cavity expansion has been limited due the relatively small amount of physical modelling of the problem. Past cavity expansion tests in calibration chambers have often been limited in range of strains, diameter to length ratio, and the amount and type of measurements made. This paper describes a calibration chamber set up used to perform cylindrical cavity expansion tests in a dry fine sand. Instead of attempting to replicate a specific application (e.g., pressuremeter test), the goal was to create a near-perfect cylindrical cavity expansion model, with in-soil measurement of stresses and strains, to serve as baseline data for validation of numerical models. The experimental set up is described, the material properties are summarized, and results of a cavity expansion tests are presented and discussed.

How much does the spatial variability of CPTu measurements affect the hydro-mechanical variables' estimation?

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:13:24 +0200

Using CPTu profiles for subsoil characterisation, transformation equations must be used to obtain the hydro-mechanical properties for structures and infrastructure designing. Additionally, the uncertainty and the spatial variability of measured parameters must be taken into account for a reliable geotechnical design. In this work, we used a Stochastic Simulation approach to define reliable 3D models of two geotechnical designing variables for granular soils (friction angle–’ and the Darcy permeability coefficient–k) from tip resistance (qc), sleeve friction (fs), and pore pressure (u2) profiles. The selected method – the Sequential Gaussian Co-Simulation (SGCS) – provided reliable optimized 3D models of the spatial distribution of the variables of interest and allowed quantifying the propagation of the estimation uncertainty associated with the raw measurement models through the transformation equations. Overestimation (OE) and Underestimation (UE) percentages for a confidence interval of 68% were calculated throughout the 3D model: granular soils showed a larger uncertainty than fine soils concerning the measured variables (qc, fs, and u2). In granular soils, the measured variable uncertainty varies up to 100% but the derived variables show different behavior: ’ shows UE and OE less than 25% while k reaches 100%. These differences in the propagated uncertainties depend on the transformation equations and the measured variable dependence.

A practical method to derive shear modulus from pressumereter tests in clay

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:12:24 +0200

Pressuremeter tests are an efficient tool to derive shear modulus of ground, and its decay with shear strain. Non-linear behaviour of ground during cavity expansion, and its consequence on shear modulus and stress with the distance to the pressuremeter cavity, have to be taken into account. For tests in fine soils, for which constant volume can be assumed during the test, retrofitting of unload-reload loops based on closed form solutions integrating the non-linear elastic behaviour can be implemented. In a first phase, this paper presents a practical straightforward method to derive shear modulus decay with shear strain based on the cylindric cavity expansion theory including non-linear elasticity under undrained conditions and hyperbolic ground behaviour. In a second phase, the method is applied step by step to a pressuremeter test in clay with unload-reload loops. Finally, on a third and last phase, this paper compares the previous results from to i) other interpretation methods integrating prior strains transformations, but also to ii) other investigation tests providing the initial shear modulus G0 associated with very small strain levels or the shear modulus decay with strain level.

Correlations Between The Pressuremeter And The Rigid Dilatometer Parameters In Soils

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:11:26 +0200

The Dilatometer Fondasol Test (DFT) is a unidirectional loading test in a borehole that provides an in-situ stress-strain curve. Two rigid shells are spread in the soil at a constant displacement rate by several small hydraulic jacks. First results using this probe in soils were obtained by Besson (2022) who also provided methods to compute from the stress-strain curve both a pseudo-elastic modulus and a limit stress. However, additional data were required to establish strong correlations between the dilatometer parameters and the pressuremeter parameters. This paper introduces new results obtained in various sites in France and synthetises all the results obtained so far. For each site, pressuremeter soundings and dilatometer soundings are carried out in pairs using the same drilling methods. DFT and PMT are performed at the same depths and at the same strain rate. For the computation of moduli and limit stresses, semi-automatic methods are employed to prevent subjective interpretations. Correlations are proposed between the dilatometer modulus and the pressuremeter modulus as well as between the dilatometer limit stress and the pressuremeter limit pressure. The established correlations, along with their limitations, are interpreted.

Comparative tests between Texam and Menard Pressuremeters

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:11:09 +0200

Two testing programs were undertaken for comparing results of the Texam and Menard pressuremeters with regards to the deformation modulus (E) and limit pressure (Pl). Two configurations of the Texam pressuremeter were used; one with a probe fitted with metal rings, the other with a probe fitted with polymer (vulcolan) rings. The results of the first program carried out in laboratory and presented in a previous article, have been completed and are presented here. The second testing program have been undertaken in the field. A total of 41 tests were completed in three boreholes in silty and clay materials. The comparative tests produced excellent correlations in the laboratory, with regression coefficients (R2) of 0.99, and fairly good correlations in the field (R2 ranging fron 0.64 to 0.73). The main findings are that the Texam produces equivalent or conservative results. More specifically : (1) the Texam with metal-ring probe produces comparable moduli values, (2) the Texam with polymer-ring probe produces lower moduli values, and (3) the two configurations of Texam produce lower limit pressures. The observed differences range between 10 to 20 %. Equivalence factors have been proposed.

Deriving Strength Parameters of Granitic Residual Soils from Menard Pressuremeter Tests

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:10:51 +0200

Residual soils are non-textbook materials that are hard to be modelled by traditional soil mechanics, which creates serious difficulties in the in-situ test interpretations and the consequent applications to geotechnical design. This is due to the presence of a cementation structure that is responsible for a cohesive-frictional behaviour of these soils, meaning that two strength parameters must be derived to represent the overall strength. Furthermore, cementation structure also deeply affects the stiffness behaviour, deviating from typical response of transported soils. The common interpretation of in-situ tests usually considers extreme behaviours represented by only one parameter, namely undrained cohesion for clays and angle of shearing resistance for sands, which naturally do not work in these cohesive-frictional materials. For this purpose, only tests that take two or more independent measurements can be used to solve this problem, as it is the case of SCPTu, SDMT and PMT tests, while SPT and DPSH tests cannot be effective in this determination. Portuguese research institutions have been looking over the granitic residual soil characterization through specific research works, from which resulted several publications on the subject. Following previous research works of calibration with (S)DMT (Cruz, 2010) and (S)CPTu (Cruz et al. 2018) tests performed in Polytechnic Institute of Guarda (IPG), Portugal, a new research frame was developed to settle a methodology for obtaining strength parameters of granitic residual soils from pressuremeter tests (PMT), which is presented and discussed herein.

Expansion test with one unload-reload loop and pore pressure measurement, first interpretation of dissipation tests, Larivot site

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:10:32 +0200

This paper presents an interpretation of cyclic pressuremeter tests with pore pressure measurement performed at Larivot bridge site (French Guyana). In cohesive soils, test results are in accordance with the pressuremeter theory. The times at 50% dissipation correlate closely with those obtained from dissipation tests performed using a piezocone in the immediate vicinity.

Interpretation of the undrained pressuremeter test in unsaturated condition

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:10:16 +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

CPTU Onshore Testing with Pre-Drilling and/or Re-Drilling of the Ground at the Port of Barcelona. Lessons Learned

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:10:01 +0200

SOCOTEC Spain, together with our partner GEM (Geotecnia y Exploraciones Marítimas), has been performing one of the largest geotechnical survey investigations in the development of new areas in the Port of Barcelona. This investigation includes multiple onshore and offshore tests including drilling and sampling, CPTU, and both in situ and laboratory testing. The CPTU (Cone Penetration Test with pore pressure measurement) is currently one of the most widely used in situ tests for soil characterization. Regarding the regularization of this test, all Standards specify the technical requirements of the equipment, the method of execution of the field test and the presentation of results and minimum corrections that have to be considered when performing and interpreting a CPTU. However, the current regulations do not refer to the methodology to be followed for the pre-drilling and/or re-drilling of the ground before a CPTU test, which is a common and operationally ‘standard’ procedure. In this sense, during the onsite research campaign, the results obtained in numerous onshore and offshore CPTU tests have been analyzed and, a variation in the pore pressure data recorded in the onshore CPTU tests associated with the pre-drilling and/or re-drilling operations has been identified. For this reason, the purpose of the paper is to highlight the need for a standardized procedure to execute this type of drilling operations and/or the necessary corrections to be taken into account during the interpretations of the results obtained in order to correct the anomalies associated with the injection of an artificial water flow.

Impact of better pressuremeter interpretation on the cost of geotechnical structures

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:09:46 +0200

This paper deals with the contribution of the realistic evaluation of the pressuremeter probe inflation mechanism and its technical and economic consequences for the project manager. This new approach allows to, within the framework of the Caderousse PCH studies, to significantly optimize the sheet pile modulus used by reassessing the soil characteristics in a more detailed way.

PLENARY LECTURE - The Legacy of Michele Jamiolkowski to Geotechnical Engineering

Jesús Sánchez Pinedo — Mon, 10 Jun 2024 12:05:46 +0200

Michele Jamiolkowski was deeply interested in many topics in geotechnical engineering. The link between his many contributions to the discipline was his deep appreciation for the need to develop techniques for predicting the performance of real structures. This focus on real structures was pervasive in all of his research, and led to his attention to experimental investigation of natural soils. Jamiolkowski recognized the importance of in situ tests to site characterization of natural soils, and consequently this paper focuses on this topic. Jamiolkowski was involved in many challenging projects, and he always considered each project as an occasion to improve the state of the art, to develop novel approaches in site characterization, to develop new in situ test interpretation methods, and to obtain quality experimental data. The paper summarizes major improvements to the state of the art that resulted from his contributions, as well lessons learned from major and iconic projects in which Jamiolkowski was involved.