Large Soil Deformations Research Articles

Investigation of slope failure mode evolution during large deformation in spatially variable soils by random limit equilibrium and material point methods

This study investigates the occurrence and evolution of various slope failure modes during large deformation in spatially variable soils using Monte Carlo simulation combined with Limit Equilibrium Method (LEM) and Material Point Method (MPM). The proposed method takes advantage of both methods, i.e., the computational efficiency of LEM and the MPM’s capability of modeling the whole process of a landslide, particularly large deformation of soils after the landslide is initiated. The proposed method is illustrated through a two-layer cohesive soil slope. Four slope failure modes (i.e., shallow, intermediate, deep and progressive failure modes) are identified and characterized quantitatively. It is found that the evolution and consequences of these failure modes depend on spatial distribution of soil shear strength. This highlights the value of the site-specific spatial variability information obtained from site investigation.

Numerical evaluation of buckling in steel pipe piles during vibratory installation

The buckling of steel pipe piles during installation is numerically studied. Generally, numerical simulation of installation processes is challenging due to large soil deformations. However, by using advanced numerical approaches like Multi-Material Arbitrary Lagrangian-Eulerian (MMALE), such difficulties are mitigated. The Mohr-Coulomb and an elastic-perfectly plastic material model is used for the soil and pile respectively. The pile buckling behavior is verified using analytical solutions. Furthermore, the model is validated by an experiment where a pipe pile is driven into sand using vibratory loading. Several case scenarios, including the effects of heterogeneity in the soil and three imperfection modes (ovality, out-of-straightness, flatness) on the pile buckling are investigated. The numerical model agrees well with the experimental measurements. As a conclusion, when buckling starts, the penetration rate of the pile decreases compared to the non-buckled pile since less energy is dedicated to pile penetration given that it is spent mainly on buckling.

Coupled Eulerian-Lagrangian finite element method for simulating soil-tool interaction

Simulation of soil-tool interaction is challenging due to large deformations of soil around the tool, unconstrained deformation of the free soil surface and the dynamic behaviour of soil-tool interaction at the interface. An application of a coupled Eulerian-Lagrangian finite element (CEL-FE) method to the simulation of soil-tool interaction is presented. By combining the merits of both the Lagrangian and the Eulerian formulations, large deformation and unconstrained deformation of soil and the dynamic behaviour of soil-tool interaction are simultaneously simulated. Firstly, interactions between the soil and vertical tines were simulated. The results showed that the predicted soil deformation and draft force were in reasonable agreement with published data from soil bin tests. Then, in order to further validate the feasibility and effectiveness of the CEL-FE method, interactions between the soil and inclined blades at different operating conditions were simulated. Results showed that the numerically simulated and experimentally measured draft forces exhibited similar trends and average values. In addition, the predicted soil deformation was in general agreement with experimental observations. Finally, an example of simulating soil-mouldboard interaction was given and preliminary results indicated that shape complexity of this tool was not a limitation for applying the CEL-FE method. The proposed CEL-FE method provides new possibilities for simulating soil-tool interaction and it is hoped that this method will help to contribute a better understanding of the soil-tool interaction process thereby improving the design of tillage tools.

Co-seismic stress changes and damage to tunnels in the 23 October 2004 Mid-Niigata Prefecture earthquake

Recent near-field earthquakes accompanied by large soil deformations have been clouding the notion that mountain tunnels would be safe places during earthquakes. One of the recent eye-openers was the damage to railway tunnels in the 2004 Mid-Niigata Prefecture earthquake. Changes in stresses in the interior of a half-space of stratified sedimentary rocks, as a representative of the earthquake-hit region, are obtained using the authors’ previous works on co-seismic deformations of this region to study the damage mechanism of deeply embedded railway tunnels. The values of square root of the second invariant of the stress deviator tensor, [Formula: see text], and the first invariant of Cauchy stress tensor, [Formula: see text], are compared with the reported damages along the entire stretch of selected tunnels and a very good correlation is observed between the peak values of [Formula: see text] and the damaged sections of the tunnels. A yield surface is defined as the boundary between clusters of points for damaged and undamaged tunnel sections in the scatter diagram of [Formula: see text] and [Formula: see text]. This yield surface and rock–soil deformability can be used to examine the margin of safety of both existing and new tunnels as well as for hazard zonation in a given scenario earthquake.

Eulerian finite element model for stability analysis of circular tunnels in undrained clay

Abstract Traditional Lagrangian finite element (FE) method may encounter numerical problems due to severe element distortion in the analysis of tunnel stability, which requires the simulation of large deformation and post-failure behaviour of soil. To overcome these limitations, this paper presents an Eulerian FE model, developed to evaluate the stability of circular tunnels in undrained clay. An application example was first presented in detail to illustrate both the approaches and principles for the simulation. Then parametric analyses of tunnel stability using the Eulerian FE method were performed to verify the validity of the developed model. The computed limit support pressures showed good agreements with the solutions from the finite element limit analysis, demonstrating that it is applicable in the stability analysis of a circular tunnel. Meanwhile, Lagrangian FE analysis was also performed for a comparison of performance with the developed Eulerian FE model. The computed results by Lagrangian FE models were shown significantly overestimating the stability of the circular tunnels, which was found to be caused by the decrease of tunnel diameter during the analysis. The Eulerian FE method developed in this paper can inherently avoid this problem, highlighting its advantage in the stability analysis of circular tunnels.

Lateral response of piles subjected to a combination of spudcan penetration and pile head loads

The effects of spudcan penetration on adjacent laterally-loaded piles mainly manifest themselves in the additional lateral shaft loads induced by large soil deformation. This paper presents a procedure to analyze lateral response of piles subjected to a combination of spudcan penetration and pile head loads. First, the Coupled Eulerian-Lagrangian technique (CEL) is post-processed and key model parameters are investigated to generate accurate soil displacement profiles during free-field spudcan penetration. Second, the effects of spudcan penetration on the adjacent piles loaded on the pile head are analyzed in two ways: the passive pile method and the offset p-y curve method. Results of an available centrifuge model test is firstly adopted to certify the effectiveness of the procedure in analyzing piles singly loaded by spudcan penetration. Then a combined-loading 1 g model test is conducted to calibrate the procedure. Agreement between the calculated and measured results is found especially with the combination of the CEL FE method and the passive pile method.

A novel approach for simulation of soil-tool interaction based on an arbitrary Lagrangian–Eulerian description

Simulation of soil-tool interaction is a challenging task due to the large deformation of soil around the tool, the unconstrained deformation of the free soil surface and the dynamic soil-tool interaction behavior at the interface. In this paper, a novel approach based on an arbitrary Lagrangian-Eulerian finite element (ALE-FE) formulation is used for simulating the soil-blade interaction. Problems associated with severe mesh distortions in a Lagrangian description and those associated with deformable material boundaries in an Eulerian description can be solved by this formulation. By introducing the Eulerian boundaries, the cutting action is simulated as the flow of soil against a stationary blade. No element deletion is needed in ALE-FE method and thus the complete contact surface of soil is retained. The extended Drucker-Prager constitutive law is used to simulate the mechanical behavior of soil. Results indicate that the ALE-FE approach is a useful tool in investigating soil-tool interaction and it is especially suitable for cases where large plastic deformation of soil occurs. Simulations under different cutting conditions demonstrate the robustness and effectiveness of the proposed ALE-FE method. The influences of cutting angle and depth on cutting are also investigated. The failure angle, soil deformation and draft force predicted by ALE-FE model are in good agreement with the published experimental data.

Physics-Based Deformable Tire–Soil Interaction Model for Off-Road Mobility Simulation and Experimental Validation

A physics-based deformable tire–soil interaction simulation capability that can be fully integrated into the monolithic multibody dynamics computer algorithm is developed by extending a deformable tire model based on the flexible multibody dynamics approach to off-road mobility simulations with a moving soil patch technique and it is validated against test data. A locking-free nine-node brick element is developed for modeling large plastic soil deformation using the multiplicative finite strain plasticity theory along with the capped Drucker–Prager failure criterion. To identify soil parameters including cohesion and friction angle, the triaxial compression test is carried out, and the soil model developed is validated against the test data. In addition to the component level validation for the tire and soil models, the tire–soil interaction simulation capability developed in this study is validated against the soil bin mobility test results. The tire forces and rolling resistance coefficients predicted by the simulation model agree well with the test results. It is shown that effect of the wheel loads and tire inflation pressures is well captured in the simulation model. Furthermore, it is demonstrated that the moving soil patch technique, with which soil behavior only in the vicinity of the rolling tire is solved to reduce the soil model dimensionality, leads to a significant reduction in computational time, thereby enabling use of the high-fidelity physics-based tire–soil interaction model in the large-scale off-road mobility simulation.

Numerical simulations of Holocene salt-marsh dynamics under the hypothesis of large soil deformations

Abstract Salt marshes are vulnerable environments hosting complex interactions between physical and biological processes. The prediction of the elevation dynamics of a salt-marsh platform is crucial to forecast its future behavior under potential changing scenarios. An original finite-element (FE) numerical model accounting for the long-term marsh accretion and compaction linked to relative sea level rise is proposed. The accretion term considers the material sedimentation over the marsh surface, whereas the compaction reflects the progressive consolidation of the porous medium under the increasing load of the overlying younger deposits. The modeling approach is based on a 2D groundwater flow simulator coupled to a 1D vertical geomechanical module, where the soil properties may vary with the effective intergranular stress. The model takes also into account the geometric non-linearity arising from the consideration of large solid grain movements by using a Lagrangian approach with an adaptive FE mesh. The numerical experiments show the potentiality of the proposed 2D model, which consistently integrates in modeling framework the behavior of spatially distributed model parameters. High sedimentation rates and low permeabilities largely impact on the mechanism of soil compaction following the overpressure dissipation.

A coupled fluid-solid SPH approach to modelling flow through deformable porous media

In this paper, a computational framework based on the mesh-free smoothed particle hydrodynamics (SPH) method is developed to study the coupled behaviour of fluid and solid in a deformable porous medium. The mathematical framework developed herein is derived from the Biot's two-phase mixture theory in which the solid is modelled as an elasto-plastic material and the pore-fluid as an incompressible fluid. The key feature of the proposed numerical framework is that both solid and fluid phases are solved simultaneously in two different Lagrangian discretisations (or two different sets of Lagrangian particles) using their own governing equations that are linked through several laws of physics. The capability of the SPH method to model large deformation of the solid materials enables the framework to account for the permeability change due to the dilatant shear behaviour of the solid phase. To obtain a stable and accurate SPH solution for the pore-fluid, an incompressible SPH (ISPH) approach is adapted to correctly simulate the pore-pressure distribution of the fluid phase inside the porous medium. The proposed coupled SPH framework is firstly validated against analytical and solutions obtained using finite element method (FEM) for a submerged soil medium subjected to a gravitational load and a seepage flow through an elastic embankment, respectively. Then, it is employed for the simulation of flows through rockfill dams and an embankment failure induced by seepage flows. Simulation results predicted by SPH show very good agreements with analytical, FEM and experimental results. This suggests that the proposed two-phase SPH framework is a promising approach for future studies of coupled problems that involve complex water free-surface/seepage flows and large deformation of soils which are difficult to be modelled using traditional FEM-based coupled two-phase flow models.

Seismic Performance of a Soil-Pile-Bridge: Three-Dimensional Finite Element Simulation

Soil-Structure Interaction (SSI) is involved in the seismic performance of pile-supported bridge. Such effect includes soil-pile interaction driven by the deformation of pile and surrounding soil. This interaction might be further pronounced due to large soil deformation during earthquake. To capture this characteristic, a three-dimensional (3D) finite element (FE) simulation is conducted considering soil-pile interaction along with the corresponding numerical details. The prototype system of a two-span reinforced concrete bridge with a single pier is demonstrated in multi-layered clay. The overall seismic response of the coupled soil-pile-bridge system are systematically investigated. The simulated results showed that the inertial effect of superstructure and transversal configuration of bridge significantly influence the pile response. The analysis technique as well as the derived insights are of significance to general pile-supported bridge system configurations.

Analysis of Piezocone Penetration under Different Drainage Conditions with the Two-Phase Material Point Method

The piezocone penetration test (CPTU) is commonly used to identify a soil’s profile and estimate its material properties. Depending on the soil type, ranging from clay to sand, undrained, partially drained, or drained conditions may occur during cone penetration. In silt and sand–clay mixtures, the CPTU penetration is characterized by partially drained conditions, which are often neglected in data interpretation. The effect of drainage on CPTU measurements has been mainly studied experimentally. Numerical analyses are rare because taking into account large soil deformations, soil–water and soil–structure interactions, and nonlinear soil behavior is still a challenging task. This paper presents and discusses numerical simulations of CPTU in saturated soils with the two-phase material point method. Soil behavior is described with the modified cam clay model. This study investigates the effects of pore pressure dissipation during penetration, cone roughness, and horizontal stress state, comparing the results with experimental data. The paper discusses the effect of neglecting partial drainage in deriving the shear strength parameters for silty soils and suggests a procedure to estimate the consolidation coefficient for performing CPTU at different penetration rates.

Two-phase Material Point Method applied to the study of cone penetration

This paper presents numerical simulations of Cone Penetration Test (CPT) in water-saturated soft soils taking into account pore pressure dissipation during installation. Besides modelling interaction between soil skeleton and pore fluid, the problem involves large soil deformations in the vicinity of the penetrometer, soil–structure interaction, and complex non-linear response of soil. This makes such simulations challenging. Depending on the soil’s permeability and compressibility, undrained, partially drained or drained conditions might occur. Partially drained conditions are commonly encountered in soils such as silts and sand–clay mixtures. However, this is often neglected in CPT interpretation, which may lead to inaccurate estimates of soil properties. This paper aims at improving the understanding of the penetration process in different drainage conditions through advanced numerical analyses. A two-phase Material Point Method is applied to simulate large soil deformations and generation and dissipation of excess pore pressures during penetration. The constitutive behaviour of soil is modelled with the Modified Cam Clay model. Numerical results are compared with experimental data showing good agreement.

Numerical study of partially drained penetration and pore pressure dissipation in piezocone test

The piezocone penetration test (CPTU) is commonly used as a fast and economical tool to identify soil profile and to estimate relevant material properties in soils ranging from fine to coarse-grained. Moreover, in the case of fine-grained soils (clays and silts), the consolidation coefficient and the permeability can be estimated through the dissipation test. Undrained conditions are commonly assumed for the interpretation of CPTU in fine-grained soils, but in soils such as silts, penetration may occur in partially drained conditions. This aspect is often neglected in data interpretation thus leading to an inaccurate estimate of soil properties. This paper investigates numerically the effect of partial drainage during penetration on the measured tip resistance and the subsequent pore pressure dissipation response contributing to a more accurate interpretation of field data. A realistic simulation of the cone penetration is achieved with the two-phase Material Point Method, modelling the soil response with the modified Cam-Clay model. The approach takes into account large soil deformations induced by the advancing cone, soil–water, and soil–structure interactions, as well as nonlinear soil behavior.

Development of 3D particle method for calculating large deformation of soils

Development of 3D particle method for calculating large deformation of soils

함수비 증가에 따른 모래질 점토기둥의 붕괴실험 및 입자법 시뮬레이션

현장 지반에는 점토 또는 모래만 존재하기 보다는 다양한 크기의 흙이 서로 섞여 존재하는 경우가 많다. 본 연구에서는 이와 같이 모래가 포함된 점토에서 함수비 증가에 따른 흙의 유동 특성을 예측하기 위해 흙기둥 붕괴실험과 이를 위해 개발한 입자법으로 대변형 시뮬레이션을 실시하였다. 먼저 카올리나이트에 모래 함유량을 0, 10, 25, 그리고 50%까지 증가시키면서 직경 7cm, 높이 13cm의 흙기둥 붕괴실험을 실시하였으며, 시간에 따른 흙기둥의 형상 변화를 관찰하였다. 모래 함유량이 다른 각각의 흙기둥에 함수비를 40, 60, 그리고 80%로 증가시키면서 총 12 종류의 흙기둥 붕괴실험을 실시하였으며, 본 연구에서 개발한 입자법으로 시간에 따른 흙기둥의 변화를 시뮬레이션하였다. 점토의 함수비와 모래 함유량에 따른 비배수전단강도와 소성지수의 변화를 고려한 최대소성전단계수를 입자법의 점성항에 적용하여 토사 대변형을 시뮬레이션하였다. 실험 결과 모래 함유량이 동일한 경우 함수비가 증가할수록 변형이 크게 발생하였으며, 동일한 함수비라도 모래 함유량이 증가함에 따라 흙기둥의 변형은 크게 발생하였다. 최대 변형은 함수비 80%, 모래 함유량 50%인 흙기둥의 직경이 7cm에서 22cm로 3배 이상 발생하였으며, 이와 같은 흙기둥 실험에서 관찰된 토사의 대변형 거동 및 응력 변화를 개발한 입자법이 비교적 잘 예측할 수 있었다. Clay or sand does not exist alone but various sizes of soil are mixed in the field. In this study, the effect of water content on large deformation of such mixed soils is studied by using soil column tests and a particle method. A soil column with 7 cm in diameter and 13 cm in height, which was made out of kaolinite with sand content of 0, 10, 25, or 50%, was tested for large deformation. Its deformation was monitored with time. While increasing its water content from 40, 60, to 80%, a total of 12 types of soil column tests were carried out. The particle method simulated their deformation with time. A maximum plastic shear modulus, which was a function of undrained shear strength and plasticity index for soils with different water contents, was associated with soil viscosity to simulate large deformation of soil column. When a sand content of soil column was constant, the deformation of soil column increased with increasing water content. When a water content of soil column was constant, large deformation occurred with increasing the sand content. The maximum deformation, which was 22 cm in diameter, was observed in the case of water content of 80% and sand content of 50%. The particle method was able to relatively well simulate such large deformation and stress change of soils.

Numerical Simulation of Rigid Cylindric Plate's Sinkage on Soil Based on SPH/FEM Method

Based on smoothed particle hydrodynamics (SPH) and FEM method, the dynamic simulation of rigid cylindric plate's sinking process on soil is studied with LS-DYNA software, and MAT 147 material model is used to describe soil's attributes. The stress distribution and flowing trend of the soil are compared at different period. The simulation results show that the SPH/FEM method is useful to analyze large deformation of soil, and our findings can give helps to the mechanical design of the components interacting with soil.

Numerical modeling of coupled seabed scour and pipe interaction

Scouring of the seabed by ice masses poses great threat to structural integrity and safety of buried structures such as oil and gas pipes. Large ridge motions and large seabed deformations complicate study of the seabed scouring and pipe interaction using classical Lagrangian methods. We present a new numerical approach for modeling the coupled seabed scour problem and its interaction with embedded marine pipes. In our work, we overcome the common issues associated with finite deformation inherently present within the seabed scour problem using a rheological approach for soil flow. The seabed is modeled as a viscous non-Newtonian fluid, and its interface described implicitly through a level-set function. The history-independent model allows for large displacements and deformations of the ridge and seabed, respectively. Numerical examples are presented to demonstrate the capabilities of the method with regard to seabed scouring and the ensuing large soil deformation.

Numerical modeling of large deformations in soil structure interaction problems using FE, EFG, SPH, and MM-ALE formulations

Present design practice for soil structure interaction (SSI) problems most frequently assumes linear elastic properties of the soil and disregards geometrical nonlinearities, treating the displacements as small. However, there are numerous problems that require a more advanced approach. This paper presents an application of such numerical approaches to modeling SSI problems in the presence of large soil deformations. Simulations using Lagrangian finite element, element-free Galerkin, smoothed particle hydrodynamics (SPH), and multi-material arbitrary Lagrangian Eulerian (MM-ALE) approaches were performed for two previously conducted experimental tests: (1) large-scale steel pad penetration into silty clay with sand and (2) standard cone penetration test performed on poorly graded sand. In this paper, the usefulness and the efficiency of the methods was assessed in terms of modeling robustness and computational cost. Results show that to some extent each of the utilized methods is able to capture large deformations. However, the most robust turned out to be SPH and MM-ALE methods as the only two that were successful in simulating both experiments.

Coupled Eulerian-Lagrangian (CEL) 방법을 이용한 Dynamically Penetrating Anchor의 동적 거동 분석

대수심 부유 구조물의 하부기초 기술 중 하나인 dynamically penetration anchor (DPA 또는 흔히 torpedo anchor로 칭함)의 거동특성을 시험결과 및 수치 해석적 접근을 통해 분석하였다. 기존의 유한요소 해석기법으로는 이러한 대수심 anchor 구조물의 거동 특성을 적절히 모사하기 어렵기 때문에 본 연구에서는 이러한 부분을 해결하기 위해 Coupled Eulerian-Lagrangian (CEL) 법을 통해 지반-구조물 사이에서 발생하는 메쉬(mesh)의 distortion 현상 및 경계조건 등의 문제점을 대변형의 관점에서 해결하고자 하였다. 실측치와의 비교를 통해, CEL 기법의 타당성을 검증하였고, 그 결과 본 연구에서 적용한 CEL 기법이 기존 유한요소 기술로는 구현이 불가능한 대수심 anchoring system의 자유낙하에 의한 전반적인 거동 및 지반의 변형특성을 적절히 예측함을 알 수 있었다. 또한 검증된 기법을 바탕으로 dynamic anchor의 거동에 영향을 주는 여러 요소들에 대한 매개변수 연구를 추가로 수행하였다. A fundamental study of the dynamically penetrating anchor (DPA - colloquially known as torpedo anchor) embedded into deep seabed was conducted using measurement data and numerical approaches. Numerical simulation of such a structure penetration was often suffered by severe mesh distortion arising from very large soil deformation, complex contact condition and nonlinear soil behavior. In recent years, a Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this study, 3D finite element analyses using the CEL formulation are carried out to simulate the construction process of dynamic anchors. Through comparisons with results of field measurements, the CEL method in the present study is in good agreement with the general trend observed by in-situ measurements and thus, predicts a realistic large deformation movement for the dynamic anchors by free-fall dropping, which the conventional FE method cannot. Additionally, the appropriate parametric studies needed for verifying the characteristic of dynamic anchor are also discussed.