Documents published in Scipedia

• Organization and Analysis of Measurement While Drilling (MWD) Data in Montana, USA

  D. Barrick*, D. O'Meara, N. Jaynes, C. Link

  ISC2024.

  
  

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• Use of a portable measurement while drilling system for shallow subsurface characterization

  B. Souza, F. Pilniere, J. Benoit, M. Bost, P. Reiffsteck*

  ISC2024.

  
  

  Abstract

  The Portable Measurement While Drilling (PMWD) equipment designed by CEREMA engineers is an innovative and lightweight tool to perform rapid assessment of shallow subsurface conditions. The equipment consists of sensors mounted on a cordless rotary drill that records depth, downforce, rotation, torque, and time. This paper presents results obtained with the portable MWD under laboratory and field conditions, which were directly compared to soil resistance profiles obtained with a lightweight dynamic cone penetrometer (LDCP – PANDA). Results from 66 PMWD profiles and 87 LDCP profiles demonstrated the potential applicability of the portable MWD in shallow subsurface investigations. A linear correlation between the Somerton Index (SD) and the LDCP tip resistance (qd) was obtained in granular soils under controlled conditions, ranging from sand (SP) to sandy gravel (GP). The obtained relationship was applied to MWD results from a 180-m long, 50-m tall grassy slope in New Hampshire, USA. It was observed that the estimated qd values from drilling parameters have a good correspondence with LDCP results at the same testing locations. Shallow subsurface characterization using MWD can potentially be used for shallow foundations, compaction control, pavement subgrade evaluation, and areas prone to geotechnical hazards not easily accessible through usual exploration methods.

  Abstract
  The Portable Measurement While Drilling (PMWD) equipment designed by CEREMA engineers is an innovative and lightweight tool to perform rapid assessment of shallow subsurface [...]

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• Prediction of Land Surface Subsidence in the U2 Metro Tunnel in Vienna

  O. Kichaieva

  ISC2024.

  
  

  Abstract

  This paper discusses the numerical and probabilistic modelling of the tunnel construction concerning some not yet completed sections of the Vienna U2 metro line. It presents the algorithm and results analysis of numerical simulation for the step-by-step tunnel construction using the New Austrian Tunnel Method (NATM) in a dense urban environment. The nature and magnitude of subsidence of the earth surface depending on a number of factors involved in the calculation scheme are determined, and all parameters of the stress-strain state of the system "tunnel - ground mass" are obtained. A methodology is proposed for determining reliability by the criterion of additional vertical subsidence of the ground surface which accompanies underground construction. By comparing the results of numerical modelling, empirical calculation and geotechnical monitoring of the metro construction site, it is shown that they correlate well enough with each other. The results of this study can be used to predict the level of the ground settlement during tunnelling works in areas of dense urban development

  Abstract
  This paper discusses the numerical and probabilistic modelling of the tunnel construction concerning some not yet completed sections of the Vienna U2 metro line. It presents [...]

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• The importance of laboratory proficiency testing schemes in assessing and improving uncertainty

  C. Wallace, J. Powell*, J. Reynolds

  ISC2024.

  
  

  Abstract

  Any site characterisation relies on at least some laboratory tests, and some of those test results (often from basic tests such as Liquid Limit and Plastic Limit) are used in initial design calculations based on correlations. However, the reliability of those correlations is heavily dependent on the uncertainty in the results of those laboratory tests. There is an inter-laboratory proficiency testing scheme that has been running for over fifteen years in the UK, with many worldwide participants. This paper presents a compilation of the scheme’s findings to allow an assessment to be made regarding the reliability of different tests. As an example, repeatability within a single laboratory for the Liquid Limit test by cone penetrometer has been shown to be ± 1 %, but between different laboratories this has risen to ± 6 %. Similar ranges have been found in the Plastic Limits which, taken together with the uncertainties from the Liquid Limits, could give rise to significant concerns over using correlations based on the Plasticity Index. Other examples of results from various test methods are given in this paper and it is argued that much of the uncertainty comes not from the test method itself, but from other factors including basic equipment maintenance, calibration, technician training and competence. It will be seen that laboratory proficiency testing schemes are crucial in highlighting these problems and giving an opportunity to allow better assessment of the quality of both test results and, arguably, the laboratories that produce them.

  Abstract
  Any site characterisation relies on at least some laboratory tests, and some of those test results (often from basic tests such as Liquid Limit and Plastic Limit) are used [...]

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• Modelling the spatial variability of karstified processes in gypsum deposits – the case of a high-speed railway bridge in the Madrid Miocene Basin

  J. Pérez-Romero, S. Sandoval*, J. Díaz

  ISC2024.

  
  

  Abstract

  The presence of karstification processes in the terrain poses a threat to the safety of the foundations of structures, which in the case of gypsum materials becomes more dangerous due to the rate at which they can progress. This work describes the case of a Spanish high-speed railway bridge whose route runs over a Tertiary gypsum formation belonging to the lower Miocene unit of the Madrid Basin. These are very firm materials in a healthy state, that allow the direct support of shallow foundations, which stand out for their high heterogeneity, with the presence of massive gypsum banks as well as alternating levels of gypsum and clay. However, these materials can be affected by karst processes of dissolution, weathering, and replacement by clays, in which case there is a marked degradation of their mechanical properties, and the eventual local appearance of cavities. In these circumstances, it is necessary to carry out soil improvement treatments, such as compaction grouting, or resort to deep foundations with piles that transmit the loads of the structure to a lower substrate in a non-disturbed state. By its nature, the detection of this type of processes by drilling rotary boreholes is not trivial, and there is often uncertainty associated with its spatial variability. This communication presents the results obtained after the execution of a geotechnical research campaign, consisting of the realization of seismic tomography borehole-profiles under each support of the viaduct, supported by the execution of conventional rotary boreholes. The results of this exploration have made it possible to understand and define the spatial extent of the materials degraded by karstification and the selection of robust foundation typologies that favour the sustainable and resilient nature of the infrastructure.

  Abstract
  The presence of karstification processes in the terrain poses a threat to the safety of the foundations of structures, which in the case of gypsum materials becomes more dangerous [...]

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• A Case Study for Data-driven Soil-layer Delineation

  J. Ching*, H. Kamyab, G. Vessia, D. Di Curzio

  ISC2024.

  
  

  Abstract

  In the past, soil-layer delineation methods can usually only take a single type of input data, e.g., soil-type data at boreholes. However, this does not fit in the geotechnical engineering practice where multiple types of data are usually available during site investigation (e.g., borehole data and cone penetration test data are both available). This paper adopts a novel data-driven method for soil-layer delineation that accommodates multiple types of site investigation data. The basic idea is to include liquid limit (LL), plasticity index (PI), and fines content (FC) into the soil parameters of analysis. According to the Unified Soil Classification System (USCS), the information of (LL, PI, FC) can be used to determine whether the soil is sand, silt, or clay. As a result, the conditional random field simulation results for (LL, PI, FC) can be used to delineate sand, silt, and clay layers. If extra soil parameters (such as cone penetration test results) are incorporated, the novel method can accommodate multiple types of site investigation data. A real example of the Fucino Basin in Italy is adopted to demonstrate the application of the novel data-driven soil-delineation method.

  Abstract
  In the past, soil-layer delineation methods can usually only take a single type of input data, e.g., soil-type data at boreholes. However, this does not fit in the geotechnical [...]

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• A method to estimate the state parameter from CPTu soundings using Pocket G-PFEM

  K. Bernardo*, N. Tasso, M. Sottile, A. Sfriso

  ISC2024.

  
  

  Abstract

  The state parameter is the main variable employed for predicting the undrained behaviour of artificial soils such as tailings and hydraulic fills. Current practice involves using screening methods and CPTu data (e.g. Robertson (2010)) or cavity expansion based methods (e.g. Shuttle and Jefferies (2016)). However, these methods have drawbacks: they are based on empirical correlations for clean sands and do not consider the effect of partial drainage. This paper presents a site-specific procedure to determine the state parameter of tailings, inspired in the work by Monforte (2022). The procedure consists of: i) calibrating the CASM constitutive model using triaxial tests for different state parameters; ii) determining the plausible range of hydraulic conductivity based on dissipation tests; and iii) conducting numerical simulations of CPTu tests using the Pocket G-PFEM tool for different combinations of state parameters and hydraulic conductivities. By comparing the results of the simulations with the real CPTu data, a site-specific relationship between the state parameter and the CPTu measurements can be established. To validate the procedure, the method is applied to a real tailings deposit and contrasted against routine screening methods. In the particular case studied in this paper, the method predicts more contractive behaviour than the screening methods. While the method is still in an early stage of development, it looks very promising because it allows for using the raw CPTu data to calibrate a constitutive model, without resourcing to any kind of correlations or empirical transformation models.

  Abstract
  The state parameter is the main variable employed for predicting the undrained behaviour of artificial soils such as tailings and hydraulic fills. Current practice involves [...]

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• On the Probability of Boulder Encounters for Piles Driven in Glacial Till

  C. Cannizzaro*, A. Beijer-Lundberg, S. Larsson, J. Spross

  ISC2024.

  
  

  Abstract

  Considering that a large part of Sweden is covered by glacial till, which is classified as an unsorted sediment formed by glaciers that can contain fragments of rock known as boulders, driving piles constitutes a substantial economic risk. Piles driven into glacial till may encounter boulders and undergo structural damages leading to premature refusal and to the loss of piles. Even though geotechnical investigations as of today form a solid basis for the design of pile foundations, the unpredictable presence of boulders and their hard resistance to breakage, makes it challenging to penetrate boulders by standard investigation methods. Currently, the only available source of information used by the Swedish construction industry to confirm the existence of boulders is a dynamic penetration test known as soil–rock sounding. Relying on the results from only one testing method may for most projects underestimate the existence of boulders and their potential impact to piles, leading to an unsuitable design of the entire piling system. This paper discusses the benefit in using the input from soil–rock soundings for quantifying the probability of boulder encounters in glacial till based on Poisson point process.

  Abstract
  Considering that a large part of Sweden is covered by glacial till, which is classified as an unsorted sediment formed by glaciers that can contain fragments of rock known [...]

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• An Elaborate Seismic Study of Beirut: Integrating 3D Multidisciplinary Geotechnical Model Definition, Machine Learning Enhancements, and Numerical Simulations

  M. Safa*, E. Bertrand, M. Brax, R. Abreu

  ISC2024.

  
  

  Abstract

  In seismic hazard assessment, reliance on Vs30 proxies and 1D shear wave velocity profiles often leads to underestimated ground motion. This is particularly evident in areas with complex geological structures, such as Greater Beirut (GB). The metropolis, situated near active seismic faults, experienced significant nearby earthquakes in 551, 1202, and 1837. It is characterized by diverse soil compositions, that vary from sandy terrains to limestone formations, demanding a detailed geotechnical model for seismic hazard studies. Our research developed a comprehensive 3D geotechnical model for GB, integrating data from around 500 boreholes, 700 geophysical measurements, refined DEM, and geological insights. The model delineates variations in bedrock elevation and geological strata, some sites exhibiting sediment depths up to 80 meters. We performed an iterative data analysis by combining the horizontal to vertical spectral ratio method (H/V measurements) with borehole data. This approach enabled us to estimate the average shear wave velocity (Vs-mean) in the sedimentary layer and the depth of the bedrock across the model. To address data gaps in southern GB, we used a Random Forest machine learning model, trained on interpolated points from Kriging in the central model part, ensuring continuous representation of sedimentary units even in data-limited areas. Ongoing work involves seismic simulations predicting ground motion amplification in Beirut. Using a 3D hexahedral mesh generated via Python code, we will conduct full 3D numerical simulations of seismic wave propagation. These simulations aim to provide insights into Beirut's seismic response, contributing to earthquake preparedness and risk mitigation. We will present preliminary results in predicting the seismic motion in Greater Beirut using SPECFEM3D, a spectral-element method software designed for 3D seismic wave propagation simulations.

  Abstract
  In seismic hazard assessment, reliance on Vs30 proxies and 1D shear wave velocity profiles often leads to underestimated ground motion. This is particularly evident in areas [...]

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• Material Subgrade Variability In Site Characterisation

  B. Look*

  ISC2024.

  
  

  Abstract

  Delineation of areas into a “uniform” harvestable quality material is required for cut and fill earthworks projects. Mixing or inadvertent contamination with onsite high-quality material with adjacent poor quality is unacceptable. Importing material from off-site sources have significant cost associated. Two case studies are presented to highlight the design and contractual interpretation of a “unform” site. The first case study compares when a characteristic design value is used versus the day to day on site requirements to meet these design requirements. The required coefficient of variation (COV) of material parameters is discussed from both a design and construction perspective for section delineation. A major highway road widening had 4 sections as part of the upgrade. The tender documents were based on balanced cut to fill. On site material variability had pockets of good and bad material. Statistical analysis pre and post tender were compared in the contractual dispute which followed. The contractor was obligated to then import material to significant subgrade depths for these sites. To do otherwise would be contra to both the design material requirements specified in the contract documents and the requirements of the Earthworks specifications. The second case study is for a major 13 km rail upgrade to illustrate how the COV can be used in site characterisation and spatial variation at a cutting. The COV values adopted for both design and construction assessment are different as the intent is different. A quality control COV is different for a characteristic design COV.

  Abstract
  Delineation of areas into a “uniform” harvestable quality material is required for cut and fill earthworks projects. Mixing or inadvertent contamination with onsite high-quality [...]

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