Documents published in Scipedia

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

  K. Fakharian*, F. Kaviani-Hamedani, M. Bahrami, H. Vaezian, I. Attar, M. Hashemi, A. Osouli, T. Bahrami

  ISC2024.

  
  

  Abstract

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

  Abstract
  Precast concrete piles are adopted as a foundation solution in liquefiable silty sand and sandy silt layers of north of Oman Sea shorelines for large diameter liquid tanks. [...]

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

  J. Sosnoski*, A. Meier, G. Dienstmann, H. Nierwinski, E. Odebrecht, F. Mantaras

  ISC2024.

  
  

  Abstract

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

  Abstract
  The present paper aims to validate the applicability of a piezoball test equipped with pressure transducers at the probe’s tip, middle, and equator faces to estimate the [...]

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

  K. Fuławka*, L. Stolecki, I. Jaśkiewicz-Proć, R. Kołodziej

  ISC2024.

  
  

  Abstract

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

  Abstract
  Seismic activity and related rockbursts are currently one of the most dangerous threats negatively affecting work safety and continuity of operation in Polish underground [...]

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

  I. Entezari*, J. Sharp, P. Mayne

  ISC2024.

  
  

  Abstract

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

  Abstract
  This paper is an extension of our previous research investigating the potential of machine learning models to estimate shear wave velocity (Vs) from piezocone penetration [...]

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• A Data Driven CPTu-PINNs Method to Predict Soil Settlement

  H. Li, Z. Ouyang*

  ISC2024.

  
  

  Abstract

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

  Abstract
  Obtaining soil parameters through laboratory tests and solving the governing equations that describe soil settlement can be time-consuming, making immediate on-site predictions [...]

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• Can Seabed Spatial Uncertainty Be Quantified Using Advanced Statistical Approaches?

  J. Valderrama*, M. O'Neill, F. Bransby, P. Watson, M. Bertolacci, A. Zammit-Mangion

  ISC2024.

  
  

  Abstract

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

  Abstract
  Knowledge of seabed properties away from investigated locations is often required, for example, when geotechnical surveys are sparse or when the field layout changes between [...]

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

  E. Revelo-Obando*, R. Ghose, M. Hicks

  ISC2024.

  
  

  Abstract

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

  Abstract
  Capturing the spatial variability in soil is crucial for ground response analyses in the context of seismic hazard mitigation. The lateral variability in thickness and properties [...]

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

  G. Pinto*, M. Araujo, A. Faria, J. Carneiro, M. Junior

  ISC2024.

  
  

  Abstract

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

  Abstract
  The Cone Penetration Test (CPTu) can be used to evaluate the soil behaviour and properties through correlations (empirical and/or analytical), and the results must be compared [...]

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

  F. Patino-Ramírez*, J. Salomon, Y. Yang, A. Holmes, C. O’Sullivan

  ISC2024.

  
  

  Abstract

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

  Abstract
  The exploration, characterisation, and monitoring of the subsurface is relevant to a wide range of applications, from environmental monitoring and in-situ characterisation [...]

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• Particle Crushing and Liquefaction Resistance of Crushable Aragonite Sands

  M. Saqib*, A. Das, N. Ranjan, P. Patra

  ISC2024.

  
  

  Abstract

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

  Abstract
  The influence of soil crushability on the strength parameters of aragonite sand under cyclic undrained conditions is investigated in this study. The investigation used aragonite [...]

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