Documents published in Scipedia

• Experimental and Numerical Investigations of CPT End Resistance at Variable Penetration Rates in Mixed Soils

  A. Arafianto, Y. Tian, B. Lehane, Y. Suzuki, D. Reid

  ISC2024.

  
  

  Abstract

  This paper investigated cone penetration test end resistance under various drainage conditions in mixed soils through numerical simulations and piezocone experiments in laboratory testing chambers. The soil samples used in the laboratory tests contained various proportions of kaolin, silt, and sand. The piezocone tests were performed using a 10 mm diameter cone in consolidated soil samples. The measured variations of cone resistance and pore pressure at cone velocities varying from 0.005 mm/s to 30 mm/s are presented, which covered the full range from drained to undrained conditions. The cone resistance was evaluated using the spherical cavity expansion limit pressure predicted in Finite Element (FE) analyses that employed the NorSand (NS) constitutive model. The experimental and numerical findings allow assessment of the suitability of the normalised velocity (V) term, proposed by others, to unify cone resistances measured at variable rates.

  Abstract
  This paper investigated cone penetration test end resistance under various drainage conditions in mixed soils through numerical simulations and piezocone experiments in laboratory [...]

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• Numerical Simulations of Cone Penetration Response via Accounting for State-Dependence and Full-Strain-Range Non-Linearity of Sand

  Z. Shi*, S. Tong, M. Huang, J. Yu, B. Wang, C. Sun

  ISC2024.

  
  

  Abstract

  The penetration response of CPT is not only related to the stress and density states of sand but also influenced by the nonlinear stress-strain relations of soils from very small (10-5) to relatively large (10-1) strain levels. Appropriate considerations of the above key soil behaviours can be crucial for accurate numerical simulations of CPT response. For this purpose, an intergranular strain (IGS)-based elastic model is introduced into a critical-state-based, state-dependent plasticity model to capture the state-dependence and full-strain-range non-linearity behaviour of sand. A numerical model of the CPT penetration process is then established by combining the aforementioned constitutive model and the arbitrary Lagrangian-Eulerian (ALE) large deformation finite element technique. The latter is adopted to handle the problems of large deformations of soil and mesh distortion. Then the computed response of CPT is compared against centrifuge test observations, and the numerical model is utilized to analyse the influences of the full-strain-range non-linearity behaviour of sand on the penetration response of CPT. The results indicate that the non-linear stress-strain relations at small strains can have noticeable impacts on the tip resistance of CPT, in particular for loose sand, while having a relatively small influence on the penetration depth required to reach a steady-state penetration resistance. The above influences might be attributed to a rapid decay of soil strains with the distance from the cone tip, and consequently high stiffness and strong constraints effects of far-field soils on core soils adjacent to the cone tip

  Abstract
  The penetration response of CPT is not only related to the stress and density states of sand but also influenced by the nonlinear stress-strain relations of soils from very [...]

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• Inherent and CPTu-measured Scale of Fluctuation of Undrained Geomaterials: a Numerical Perspective

  L. Monforte*, S. Collico

  ISC2024.

  
  

  Abstract

  The vertical scale of fluctuation of soil parameters is often indirectly estimated through Cone Penetration Testing (CPTu) as the test provides nearly continuous and repeatable data. However, the variability quantified from CPTu might not be representative of a soil parameter intra-site variability, but rather the effect of the variability of soil measured through its response to the cone probe. The objective of this work -of an openly prospective nature- is to examine how the vertical inherent spatial variability of clay-like insensitive geomaterials propagates to the cone tip and friction sleeve resistance by means of numerical modelling. A total stress analysis is presented, in which the undrained shear strength is described according to random field theory. Numerical results show that the scale of fluctuation of the tip resistance and friction sleeve resistance is greater than the one assumed for undrained shear strength.

  Abstract
  The vertical scale of fluctuation of soil parameters is often indirectly estimated through Cone Penetration Testing (CPTu) as the test provides nearly continuous and repeatable [...]

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• A DEM Study on the Effect of Chamber Boundary on CPT Calibration Chamber Tests

  A. Sadrekarimi*, S. Hashemi

  ISC2024.

  
  

  Abstract

  Laboratory-scale cone penetration tests are often carried out to calibrate the response of cone penetration, and in particular cone tip resistance to soil characteristics. However, because of the limited sample size, sample boundaries can often affect the measured cone resistance in laboratory tests. This paper presents numerical simulations using the discrete element method (DEM) to study the effect of boundary condition on cone penetration calibration chamber tests. Numerical simulations were performed under flexible (BC1) and laterally-constrained (BC3) boundary conditions on K0consolidated models at different relative densities and vertical stresses. Additional models were simulated with periodic boundaries (BC5) to model the free-field condition. To track the radial stress variations in different sections of the chamber, scattered representative volume elements (RVE) were embedded in the models. Particle displacements and contact force chains were examined to determine the relation between microscopic variables and macroscopic response of the specimens subjected to cone penetration under different boundary conditions. Larger cone resistances were obtained under BC3 condition than those in BC1 condition. For the chamber-to-cone diameter ratio of 25 adopted in this study, the influence of the lateral boundary was found to be negligible in loose to medium-dense assemblies, while the effect of chamber boundary amplified in dense to very dense samples with increasing relative density and reduced with increasing vertical stress. This was attributed to the higher radial stress induced along the cone penetration path in laterally-constraint BC3 models. Based on these findings, a correction factor is proposed to better estimate free-field penetration resistance from calibration chamber experiments.

  Abstract
  Laboratory-scale cone penetration tests are often carried out to calibrate the response of cone penetration, and in particular cone tip resistance to soil characteristics. [...]

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• The evolution of Menard pressuremeter cavity preparation in France

  B. Hamidi, S. Varaksin*

  ISC2024.

  
  

  Abstract

  Since Louis Ménard invented his first pressuremeter prototype in 1954, the pressuremeter and its placement techniques into the ground have gone through numerous advancements. In this paper, the authors review the cavity preparation developments in France from the early days of developing the pressuremeter to contemporary times. Pressuremeter probes were initially installed using hand augers, which was quite time consuming and cumbersome. Soon after, drilling was mechanized using drilling rigs with various abilities and capacities in the form of rotary and percussion drilling. Specific techniques such as STAF, RotoSTAF, and similar devices have now been developed to create holes with minimum disturbance in the ground.

  Abstract
  Since Louis Ménard invented his first pressuremeter prototype in 1954, the pressuremeter and its placement techniques into the ground have gone through numerous advancements. [...]

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• Subsurface Characterization of Coastal Deposits using Measurement While Drilling

  B. Souza, J. Regan, J. Benoît*, A. Carr, K. Pelham, C. Buerkle

  ISC2024.

  
  

  Abstract

  Measurement While Drilling (MWD) is a promising in situ test method that has gained increasing popularity in recent years. MWD can continuously characterize the subsurface while drilling any type of borehole in soil or rock without interfering with normal drilling operations. The latest MWD equipment gathers real-time data on numerous parameters that capture all aspects of the drilling process (e.g., depth, down thrust, rotation, torque, mud flow, and mud pressure). This paper summarizes MWD assessments performed in the coastal deposits of New Hampshire, USA. Profiles of individual and combined drilling parameters were used to differentiate between different soil layers and characterize subsurface conditions in complement with conventional, standardized geotechnical testing (e.g., SPT, CPTU) performed at adjacent boreholes. The results from this experimental campaign demonstrate the applicability of MWD systems to evaluate a broad range of geological conditions, from granular soils with erratic boulders to sensitive clays.

  Abstract
  Measurement While Drilling (MWD) is a promising in situ test method that has gained increasing popularity in recent years. MWD can continuously characterize the subsurface [...]

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• Using Drilling Data to Derive Geotechnical Properties of Variably Cemented Materials

  S. Sharma*, J. Rice, P. Suzuki, A. Bertrand

  ISC2024.

  
  

  Abstract

  Geotechnical site characterisation of variably cemented material is often challenging due to lack of data. Drilling data is routinely measured as a part of standard geotechnical site investigation and can provide an alternative method to derive continuous ground profiles with depth. This paper examines the use of drilling data for site characterisation purpose. Based on the drilling data obtained from an offshore windfarm project site, where variably cemented materials were found, it is shown that the borehole specific energy calculated using the drilling data reasonably captures the variation in material types with depth. Also, the results show that borehole specific energy can be correlated with the laboratory test data in a similar manner to cone penetration test. Based on the results obtained from different locations covering a range of material types and in-situ state conditions, generalised relationships between different geotechnical parameters and borehole specific energy are presented. An example of how the generalised relationships developed using borehole specific energy can be used to derive design profiles for a selected site is also shown. The data and interpretation approach presented in this paper provide a useful guide for how the drilling data can be used to assess the continuous ground profile for variably cemented sites where only limited or no in-situ test and intermittent sampling data are available.

  Abstract
  Geotechnical site characterisation of variably cemented material is often challenging due to lack of data. Drilling data is routinely measured as a part of standard geotechnical [...]

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• Offshore rock investigations by a remotely operated submersible drilling rig with continuous drilling recording

  A. Deu*, M. Pérez, R. del Castillo, M. Devincenzi

  ISC2024.

  
  

  Abstract

  The submersible drilling rig presented in this paper was designed and constructed with the aim to allow conducting soil or rock characterization in offshore investigations in shallow water projects when short target penetrations are required. The system is instrumented with sensing elements allowing the full control of the operation in real-time for three different purposes: (i) positioning, (ii) continuous drilling parameters (MWD, measuring while drilling) and (iii) visual inspection. The suitability in sandy and silty soils was reported by Romero et al. (2012). The system is outstanding as an interesting alternative to traditional methodologies for rock investigations in relative shallow water projects where the knowledge of the first metres of rock profile is critical (e.g., pipelines, submarine interconnections, dredging, foundations). Some benefits of the system are presented in this paper, especially in ground models composed of a rock layer underneath a soil deposit or by rocks with variable strength with depth.

  Abstract
  The submersible drilling rig presented in this paper was designed and constructed with the aim to allow conducting soil or rock characterization in offshore investigations [...]

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• Comparison of Direct and Indirect MWD Measurements

  C. Caplane, M. Rispal, G. de Oliveira Souza*, M. Peronne, P. Reiffsteck

  ISC2024.

  
  

  Abstract

  Drilling boreholes for geotechnical purposes such as sampling and in situ tests is usually performed with the aid of drilling machines. In France, typically, the machine’s drilling parameters such as applied torque and thrust are monitored in realtime and registered so that information about the subsoil’s structure can be acquired. As these machines tend to use hydraulic systems, the oil pressures fed into each motor and actuator are the parameters commonly monitored. Recently, a new type of sensor and its application in geotechnical investigations through the measuring of drilling parameters was presented. This sensor is directly mounted on top of the drill string of a drilling machine and records the actual thrust, torque, and rotation speed transmitted to the drill string and bit. This bypasses the energy losses present in the hydraulic circuit between the machine’s pressure sensors and the hydraulic actuators. This mounting position allows a more accurate measurement of the forces and, furthermore, the effective rotation speed applied to the drill bit. The data is transmitted through a wireless Bluetooth connection enabling real time monitoring. Nevertheless, finding the right balance between a soil’s resistance, the drill rig’s power and the sensor’s optimal measuring range remains a topic for further development. This analysis of several worksites with different soils throughout France contributes to a better understanding of the last generation’s sensor’s precision and application range.

  Abstract
  Drilling boreholes for geotechnical purposes such as sampling and in situ tests is usually performed with the aid of drilling machines. In France, typically, the machine’s [...]

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• Comparative Analysis of Different Methods for Interpreting MWD Profiles

  G. de Oliveira Souza*, P. Reiffsteck, F. Szymkiewicz, C. Jacquard, M. Rispal

  ISC2024.

  
  

  Abstract

  To determine a robust geotechnical model from measurements of drilling parameters is one of the great desires of geotechnical investigations. Drilling parameters have the advantage of presenting very granular data (data-points every centimetre) much like the CPT. They allow for the identification of soil samples during the drilling process and can traverse all terrain types, from soft clays to hard rocks. However, interpreting each parameter, like penetration rate or thrust, in isolation can be challenging, as these parameters can vary greatly within each soil layer due to natural heterogeneity, the drill rig’s configuration and the noise introduced by the discontinuous interaction between soil and drill bit. Various authors propose using compound parameters such as specific energy, penetration resistance and alteration index alongside cautious filtering allows for a better interpretation, giving physical meaning to the measurements. These compound parameters have been developed from simple correlations, aiming to normalise parameters heavily influenced by drilling conditions or even aiming to evaluate the work or the energy spent in excavating the soil. Beyond that, many authors have devised algorithms to automate or standardize the interpretation of drilling logs by identifying homogenous zones or the probability that a given point belongs to a certain layer. This paper presents a comparison of such methodologies for identifying soil layers based on MWD profiles proposed in the literature. Assessment of the geotechnical structure may be made through different analytic and advanced statistical methods. MWD profiles from worksites throughout France will be used to compare and qualify these methods.

  Abstract
  To determine a robust geotechnical model from measurements of drilling parameters is one of the great desires of geotechnical investigations. Drilling parameters have the [...]

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