Documents published in Scipedia

• Interpretation of the undrained pressuremeter test in unsaturated condition

  J. Monnet*, L. Boutonnier

  ISC2024.

  
  

  Abstract

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

  Abstract
  The pressuremeter measures both the pressuremeter modulus and the limit pressure, which are used to estimate the bearing capacity of the foundation according to different [...]

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

  J. Rubio, L. Casas*

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  SOCOTEC Spain, together with our partner GEM (Geotecnia y Exploraciones Marítimas), has been performing one of the largest geotechnical survey investigations in the development [...]

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• Impact of better pressuremeter interpretation on the cost of geotechnical structures

  R. Granjon*, J. Monnet

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  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 [...]

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• PLENARY LECTURE - The Legacy of Michele Jamiolkowski to Geotechnical Engineering

  S. Foti*, R. Salgado, R. Lancellotta

  ISC2024.

  
  

  Abstract

  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.

  Abstract
  Michele Jamiolkowski was deeply interested in many topics in geotechnical engineering. The link between his many contributions to the discipline was his deep appreciation [...]

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• PLENARY LECTURE - Instrumental Dynamic Penetrometers for Geotechnical Characterization

  P. Breul, P. Reiffsteck

  ISC2024.

  
  

  Abstract

  The dynamic penetrometer is a common technique in geotechnical exploration and widely deployed throughout the world. However, while this technique has many advantages, it also has several disadvantages that can hinder its use and development. Indeed, it has evolved little, and its application has sometimes remained "rustic". But in recent years with the development of sensors, interpretation methods and digital technology, this technique has been adapted to improve the quality of measurement, the understanding of the phenomena occurring during the test and its exploitation. This article presents the recent developments and adaptations of this technique and their potential. After a brief review of the principle, history, and current limitations of the technique, we look at recent technological developments and the latest advances in terms of interpreting and using the test.

  Abstract
  The dynamic penetrometer is a common technique in geotechnical exploration and widely deployed throughout the world. However, while this technique has many advantages, it [...]

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• PLENARY LECTURE - Simulation-aided geotechnical site investigation

  L. Monforte*, M. Arroyo, A. Gens

  ISC2024.

  
  

  Abstract

  With the advancement of computational geomechanics over the past decades, most of the activities typical of site characterization, such as in situ testing or sampling, can be realistically simulated using appropriate constitutive models and balance equations for geomaterials. These numerical simulations are not only informative of the processes that take place during testing but can be used to assess the reliability of current practice empirical interpretation techniques or even propose new interpretation techniques. In this paper, we present two numerical analyses of long-standing geotechnical problems in which new insights are gained by means of advanced numerical modelling. The first analysis corresponds to cone penetration testing in undrained, brittle geomaterials; we describe the effect of the constitutive parameters on cone metrics, and we propose a novel procedure to estimate the initial state parameter from CPTu based on a wide-ranging parametric analysis. The second analysis involves tube sampling in undrained geomaterials. A total stress analysis allows us to describe the kinematics of the soil during tube insertion and evaluate the effect of the tube geometry on the strain path of the problem. The analysis is then extended by considering a fully coupled hydromechanical formulation and a critical state constitutive model for cemented soils; by simulating conventional laboratory tests on the soil that has entered the tube we can quantify sampling disturbance in terms of geotechnical design parameters (e.g. undrained shear strength and yield stress). The possibilities offered by numerical modelling for site characterization are far from being fully exploited. It is envisaged that in the future site-specific numerical analyses will become available, enabling a more comprehensive understanding of the subsurface conditions.

  Abstract
  With the advancement of computational geomechanics over the past decades, most of the activities typical of site characterization, such as in situ testing or sampling, can [...]

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• PLENARY LECTURE - Treatment of uncertainties in site characterization in second-generation eurocode 7

  J. Estaire, T. Schweckendiek

  ISC2024.

  
  

  Abstract

  The purpose of this paper is to introduce the geotechnical engineering community to the treatment of uncertainties in site characterization within the framework of the second-generation Eurocodes. To do so, the main uncertainties related to the Ground Model, the ground properties and the groundwater levels are described before discussion of the statistical and modelling involved. This paper also explains the determination of “representative values” of ground properties within the framework of the Second-Generation Eurocode 7, either selecting the value based on engineering judgment and comparable experience, being in this case termed a “nominal value”; or evaluating the value by statistical methods, being in this case termed a “characteristic value”. Additionally, since 2nd-Gen Eurocode 7 allows using reliability-based methods for the verification of limit states, the paper gives some guidance for choosing probability distribution types, and for assessment their parameters like the mean and standard deviation. Finally, two examples are provided to show how to deal with the new elements involved with uncertainty treatment in terms of statistical analysis and probabilistic modelling

  Abstract
  The purpose of this paper is to introduce the geotechnical engineering community to the treatment of uncertainties in site characterization within the framework of the second-generation [...]

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• PLENARY LECTURE - Recent advancements in data-driven site characterization

  J. Ching*, K. Phoon

  ISC2024.

  
  

  Abstract

  This paper reviews some recent advancements that address the challenges faced by the broad application area of datadriven site characterization (DDSC). The challenges include the ugly-data challenge, site-recognition challenge, and stratification challenge. The ugly-data challenge is about the MUSIC-3X attributes of the site investigation data, where MUSIC-3X stands for multivariate, uncertain and unique, sparse, incomplete, possibly corrupted, and 3D spatial variability (3X). The site-recognition challenge is about the site-uniqueness feature of the site investigation data. The stratification challenge is about the task of layer delineation in soil profiling. In recent years, some studies have been conducted to address these challenges with an encouraging degree of success, which are briefly reviewed in this paper. However, there are still unresolved issues yet to be addressed, which are briefly summarized in this paper as well.

  Abstract
  This paper reviews some recent advancements that address the challenges faced by the broad application area of datadriven site characterization (DDSC). The challenges include [...]

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• PLENARY LECTURE - Combined resistivity and seismic measurements along linearly extended earth structures - acquisition and interpretation approaches

  C. Comina*

  ISC2024.

  
  

  Abstract

  Geotechnical parameters of linearly extended earth structures, such as embankments and earth dams, are usually obtained from localized investigations through drilling or penetration tests, commonly time and cost consuming. Non-invasive geophysical investigations may be considered an alternative approach for the geotechnical characterization of these structures, given their surveying speed and their depth and length of investigation. Particularly, new acquisition approaches with the use of appropriate streamer cables could strongly reduce the acquisition times making geophysical surveys ideal for a preliminary screening of these structures. Specifically, resistivity and seismic methods can be adopted given that these two methodologies could offer complementary information with respect to the pore fluid properties (resistivity methods) and the solid skeleton characteristics (seismic methods). Also, through specific correlations, relevant geotechnical parameters for the evaluation of the stability of these structure and its efficiency (i.e. hydraulic conductivity, porosity and others) can be obtained. In this paper a review of the methodologies developed in recent years for data acquisition along linearly extended earth structures is reported with special focus on the use of combined electric and seismic streamer cables. Suggestions with respect to interpretation approaches and data elaboration are also analysed.

  Abstract
  Geotechnical parameters of linearly extended earth structures, such as embankments and earth dams, are usually obtained from localized investigations through drilling or penetration [...]

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• PLENARY LECTURE - Passive seismic methods for site characterization

  C. Cornou*

  ISC2024.

  
  

  Abstract

  Site characterization methods to extract the shear-wave velocity (Vs) structure over the first few tens to few hundred of meters or the soil’s resonance frequency using seismic noise recordings have become widespread over the last 40 years. Being cost-effective and easy to implement, especially in urban environment, passive seismic methods have been shown reliable to retrieve the soil resonance frequency and the Vs profile of near-surface geological layers. International efforts over the last 20 years have outlined the capabilities and limitations of passive seismic methods and lead to a series of good-of-practice, state-of-the-art and recommendations on data acquisition and processing. Recent methodological developments using three-component single-station and three-component array methods are promising approaches to better constrain Vs profiles. Also, the very high spatial and temporal resolution offered by the Distributed Acoustic Sensing (DAS) makes this emerging technology one with very high potential for near-surface site characterization, especially in urban environment.

  Abstract
  Site characterization methods to extract the shear-wave velocity (Vs) structure over the first few tens to few hundred of meters or the soil’s resonance frequency using [...]

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