Showing papers in "International Journal of Geomechanics in 2002"
TL;DR: Theoretical and experimental studies have proven that stone columns can be used for accelerating the consolidation rate of soft soil by providing a drainage path and reducing stresses in the soil as mentioned in this paper.
Abstract: Theoretical and experimental studies have proven that stone columns can be used for accelerating the consolidation rate of soft soil by providing a drainage path and reducing stresses in the soil. ...
125 citations
TL;DR: In this article, the authors used two layer perceptrons trained using the Levenberg-Marquardt algorithm, based on backpropagation of error, for the prediction of landslide velocity.
Abstract: This article presents the use of neural networks for the prediction of movement of natural slopes. The aim is to predict velocity changes of a moving soil mass using climatological and physical data, such as rainfall and pore water pressure, which are used as input parameters in an artificial neural network (ANN). The network is designed to function as an alarm and is a decision-making tool for persons in charge of landslide monitoring. The raw data were obtained from a continuously monitored landslide, located in Salledes, near Clermont–Ferrand (France), and include daily precipitation, evaporation, pore water pressure, and landslide velocity values. The various networks used in this study are two layer perceptrons trained using the Levenberg–Marquardt algorithm, based on backpropagation of error. The most sophisticated model presented in this article was developed by cascading two recurrent networks of the same type. This model permits a satisfactory 3-day prediction of landslide velocity if qu...
78 citations
TL;DR: In this article, a new method of analysis of piled raft foundations in contact with the soil surface is presented, where the soil is divided into multiple horizontal layers depending on the accuracy of solution required and each layer may have different material properties.
Abstract: This article presents a new method of analysis of piled raft foundations in contact with the soil surface. The soil is divided into multiple horizontal layers depending on the accuracy of solution required and each layer may have different material properties. The raft is modeled as a thin plate and the piles as elastic beams. Finite layer theory is employed to analyze the layered soil while finite element theory is used to analyze the raft and piles. The piled raft can be subjected to both loads and moments in any direction. Comparisons show that the results from the present method agree closely with those from the finite element method. A parametric study for piled raft foundations subjected to either vertical or horizontal loading is also presented.
73 citations
TL;DR: The problem of cavity expansion from zero radius has no characteristic length and therefore possesses a similarity solution, in which the cavity pressure remains constant and the continuing deforma... in this article.
Abstract: The problem of cavity expansion from zero radius has no characteristic length and therefore possesses a similarity solution, in which the cavity pressure remains constant and the continuing deforma...
66 citations
TL;DR: The bearing behavior of footings on layered soils has received significant attention from researchers, but most of the reported studies are limited to footings resting on the surface of the soil an....
Abstract: The bearing behavior of footings on layered soils has received significant attention from researchers, but most of the reported studies are limited to footings resting on the surface of the soil an...
55 citations
TL;DR: In this paper, the authors analyzed the load-settlement response of vertically loaded footings placed in sands using both the finite element method with a nonlinear stress-strain model and the conventional elastic approach.
Abstract: The settlement of foundations under working load conditions is an important design consideration. Well-designed foundations induce stress-strain states in the soil that are neither in the linear elastic range nor in the range usually associated with perfect plasticity. Thus, in order to accurately predict working settlements, analyses that are more realistic than simple elastic analyses are required. The settlements of footings in sand are often estimated based on the results of in situ tests, particularly the standard penetration test (SPT) and the cone penetration test (CPT). In this article, we analyze the load-settlement response of vertically loaded footings placed in sands using both the finite element method with a nonlinear stress-strain model and the conventional elastic approach. Calculations are made for both normally consolidated and heavily overconsolidated sands with various relative densities. For each case, the cone penetration resistance qc is calculated using CONPOINT, a widely ...
52 citations
TL;DR: In this paper, a software program is used to transform 3D contact stresses occurring between the road surface and the tire that were measured with the South African Vehicle Road Surface Pressure Transducer Array (VRSPTA) device under a moving wheel are transformed to a corresponding force/stress pattern representing the actual contact stress state under the tire by means of software program.
Abstract: Three-dimensional (3D) contact stresses occurring between the road surface and the tire that were measured with the South African Vehicle Road Surface Pressure Transducer Array (VRSPTA) device under a moving wheel are transformed to a corresponding force/stress pattern representing the actual contact stress state under the tire by means of a software program. In combination with a dynamic load function such force patterns derived from these Stress-in-Motion (SIM) measurements with the VRSPTA device are used to introduce a more advanced load representation of the tire-pavement interface into a three-dimensional (3D) finite element (FE) model. Further, a method is presented to derive viscoelastic material properties of asphalt concrete (AC) mixes from dynamic frequency sweep shear (FS-S) tests of lab specimens or field cores that can be used to define material behavior of the AC layers in the 3D FE pavement model. Linear elastic layered theory is utilized to validate the results of the FE computati...
50 citations
TL;DR: In this article, a compromise between analytical rigor and analysis features (e.g., multiple wheels, seasonal property variations, material nonlinearity) is made to approximate multiple wheel effects via superposition.
Abstract: Flexible pavement structural analysis for design usage must consider (as a minimum) multiple wheel/axle loading configurations, seasonal variations of material layer properties, and the nonlinear behavior of unbound materials. Although these requirements are all easily within the capabilities of three-dimensional finite element analysis, the required computation times may be impracticably long for routine design. Compromises between analytical rigor (e.g., three-dimensionality) and analysis features (e.g., multiple wheels, seasonal property variations, material nonlinearity) must be made. One compromise is to retain seasonal property variations and material nonlinearity within an axisymmetric single wheel finite element model and to approximate multiple wheel effects via superposition. Although this superposition of nonlinear solutions is undeniably invalid from a rigorous theoretical viewpoint, the errors may be well within acceptable magnitudes for practical design. The paper investigates this ...
42 citations
TL;DR: In this paper, boundary integral equations and Laplace transform domain fundamental solutions to the u-p formulation of two-dimensional dynamic poroelasticity are derived based on the Cleary reciprocal theorem.
Abstract: In this article, boundary integral equations (BIE) and Laplace transform domain fundamental solutions to the u-p formulation of two-dimensional dynamic poroelasticity are derived. Time domain fundamental solutions have been derived based on the Cleary reciprocal theorem. A set of numerical results is presented to highlight the salient features of the transient fundamental solutions, their components, and accuracies of proposed approximations. Several comparisons with Chen's solution are made.
42 citations
TL;DR: In this article, a detailed analysis using 3D and 2D FE has been made of tire/pavement contact pressure effects on rutting, including tread pattern and constant and varying contact pressure.
Abstract: The Indiana Department of Transportation/Purdue University accelerated pavement testing (APT) facility has been utilized in a number of studies of hot mix asphalt (HMA) rutting performance. The benefit of using APT is that rutting performance can be established in a few days of testing. Finite element (FE) models have been developed for relating APT to in-service pavement performance. Factors addressed in the models include pavement geometry, boundary conditions, materials, loads, test conditions, and construction variables. Determining the effects of these factors provides a means for better interpreting APT test results and HMA rutting performance. A detailed analysis using 3D and 2D FE has been made of tire/pavement contact pressure effects on rutting. The analyses include tread pattern and constant and varying contact pressure. A creep model is used to represent the HMA time-dependent material behavior. Based on test data, the material constants in the creep model were back calculated. Result...
42 citations
TL;DR: In this article, an extensive experimental, analytical, and numerical investigation on the response of asphalt concrete is currently in progress at Delft University of Technology, which includes the formulation and finite element implementation of a three-dimensional, strain-rate sensitive, temperature and loading history-dependent constitutive model, and development of the necessary experimental set-ups, testing procedures, and data analysis methods for determination of the model parameters.
Abstract: An extensive experimental, analytical, and numerical investigation on the response of asphalt concrete is currently in progress at Delft University of Technology. The objectives of this Asphalt Concrete Response (ACRe) project are: (a) the formulation and finite element implementation of a three-dimensional, strain-rate sensitive, temperature- and loading history-dependent constitutive model, and (b) the development of the necessary experimental set-ups, testing procedures, and data analysis methods for determination of the model parameters. These objectives are strongly interrelated: on the one hand, the model dictates what should be measured in a test, while on the other hand, the response observed in the tests sets the requirements for the model. As a result, model development/verification and experimental testing have been progressing in parallel throughout the project. In this contribution both the finite element and the experimental aspects of the project will be presented. The constitutive...
TL;DR: In this paper, the constitutive equations for geo-materials, in which the elastic moduli depend on the plastic strain, are derived from basic thermo-mechanical principles, and the resulting rate forms of the equations have a symmetric stiffness matrix (tensor).
Abstract: Previous analyses are amplified to demonstrate that when the constitutive equations for geo-materials, in which the elastic moduli depend on the plastic strain, are derived from basic thermo-mechanical principles, the resulting rate forms of the equations have a symmetric stiffness matrix (tensor). This result is at odds with existing analyses, which have concluded that these matrices should be non-symmetric. The consequences of these results for stability, bifurcation, and shear band formation are discussed.
TL;DR: In this paper, a kinematic hardening two-surface model of soil-footing interaction for pipelines under various loading conditions is presented, which provides an efficient and direct way to evaluate the behavior of a pipeline under different loading conditions.
Abstract: A kinematic hardening two-surface model of soil-footing interaction for pipelines under various loading conditions is presented. The model requires 13 parameters. Most of these parameters can be derived directly from a set of model tests or from conventional soil mechanics theory. Model performance is demonstrated through modeling the drained behavior of pipeline-soil interaction under typical loading conditions. Predictions from the model compare well with experimental data obtained in a series of loading tests on shallowly embedded pipelines. The model provides an efficient and direct way to evaluate the behavior of a pipeline under various loading conditions.
TL;DR: In this paper, an analysis of the stresses and displacements that take place in an infinite slope, consisting of an elastic-plastic Mohr-Coulomb material, due to the increase of the water table level is presented.
Abstract: An analysis is presented of the strains and displacements that take place in an infinite slope, consisting of an elastic-plastic Mohr–Coulomb material, due to the increase of the water table level. In particular, an attempt is made to establish a relationship between the displacements before failure and the slope safety factor. It is also shown that, for a slope of given geometry and mechanical properties, the strains and displacements before failure are significantly influenced by the ratio between the stress components parallel and normal to the slope. The initial state of stress plays a major role in defining the thickness of the shear zone within which the shear and volumetric plastic strains concentrate before failure.
TL;DR: In this paper, a technique in coupling FEM and DDA has been introduced, and this technique has been applied to some examples to demonstrate the effectiveness of the proposed coupling method.
Abstract: Problems governed by both continuum and discontinuum like tunnels and caverns are best analyzed by the coupling distinct element method and finite element or boundary element method. This article introduces a technique in coupling FEM and DDA; this technique has been applied to some examples to demonstrate the effectiveness of the proposed coupling method.
TL;DR: In this paper, a 3D elasto-plastic finite element model is used to examine the effect of construction over two existing tunnels and the change in lining shape are compared with the field measurements of the York-Mills Centre project constructed in 1989 over an existing Toronto subway tunnel.
Abstract: A 3D elasto-plastic finite element model is used to examine the effect of construction over two existing tunnels. Tunnel deformation and the change in lining shape are compared with the field measurements of the York-Mills Centre project constructed in 1989 over an existing Toronto subway tunnel. The criterion for potential damage to the tunnel liner is established based on the extreme fiber stresses of the lining. Typical 2D plane strain analyses were also conducted to investigate the importance of the 3D analysis in this case. Reasonable agreement is found between the observed field measurements and the predicted results using the 3D numerical simulation.
TL;DR: In this article, an automatic Newton-Raphson method for solving nonlinear finite element equations is presented. But the performance of the new automatic scheme is compared with the standard Newton Raphson scheme, the modified Newton raphson with line search, and two other automatic schemes that are based on explicit Euler methods.
Abstract: This article presents an automatic Newton–Raphson method for solving nonlinear finite element equations. It automatically subincrements a series of given coarse load increments so that the local load path error in the displacements is held below a prescribed threshold. The local error is measured by taking the difference between two iterative solutions obtained from the backward Euler method and the SS21 method. By computing both the displacement rates and the displacements this error estimate is obtained cheaply. The performance of the new automatic scheme is compared with the standard Newton–Raphson scheme, the modified Newton–Raphson scheme with line search, and two other automatic schemes that are based on explicit Euler methods. Through analyses of a wide variety of problems, it is shown that the automatic Newton–Raphson scheme is superior to the standard Newton–Raphson methods in terms of efficiency, robustness, and accuracy.
TL;DR: In this paper, a two-dimensional finite element method for the solution of the advection-dispersion transport equation for multicomponent contaminants is presented, based on a generalization of the one-dimensional Transport-Equilibrium Petrov-Galerkin (TEPG) methods presented by Sheng and Smith.
Abstract: This article presents a two-dimensional finite element method for the solution of the advection-dispersion transport equation for multicomponent contaminants. While the approach described is general, the analysis presented here is restricted to nonlinear, equilibrium-controlled sorption and exchange of soluble inorganic ions. The finite element method is based on a generalization of the one-dimensional Transport-Equilibrium Petrov–Galerkin (TEPG) methods presented by Sheng and Smith [1]. In the TEPG methods, the reaction term is treated as a part of the mass accumulation term. This is in contrast with common formulations where the reaction term is treated as a source term. The transport equation thus contains two unknowns, the aqueous concentration and the total analytical concentration. The solution strategy adopted is to solve the transport equations coupled with chemical equilibrium equations by sequential iteration. No assumption on the reaction term is required when solving the transport equ...
TL;DR: In this paper, a numerical model was developed to predict the air losses from tunnel face and perimeter walls in compressed air tunneling, and the model can also predict the zone of ground influenced by air flow.
Abstract: A numerical model has been developed to predict the air losses from tunnel face and perimeter walls in compressed air tunneling. The model can also predict the zone of ground influenced by air flow...
TL;DR: In this article, a variational approach for the analysis of downdrag forces of pile groups undergoing soil downward movement is presented, where the theoretical load-transfer curves are employed to describe the soil load displacement relationship.
Abstract: This article presents a variational approach for the analysis of downdrag forces of pile groups undergoing soil downward movement. The theoretical load-transfer curves are employed to describe the soil load-displacement relationship. A soil with stiffness varying with depth and with stiffer end-bearing stratum at the pile toe can be easily treated using the present method. The validity of the present method is demonstrated through comparison with existing theoretical solutions and field measurements.
TL;DR: In this article, the PFC\U2D\Ncode has been used for modeling a fragmented claystone, a difficult waste material produced by open-pit coal mines in Northwestern Bohemia.
Abstract: Micromechanical modeling of a fragmented claystone—a difficult waste material produced by open-pit coal mines in Northwestern Bohemia—is presented in this article. The PFC\U2D\Ncode, which accounts for the discrete nature of geomaterials and represents them as an assembly of unbonded or bonded particles, has been used. First, synthetic claystone was generated and the deformability and strength parameters were calibrated via numerical testing and comparing the results with those of available laboratory and field tests. The pre-peak, peak, and post-peak behavior of synthetic claystone was studied, and microscopic indicators of macroscopic behavior were selected and visualized. In order to simulate the dump material, joints were introduced that divided the claystone specimen into fragments. The appropriate microproperties of synthetic dump material were selected by means of a similar numerical testing and calibration procedure. Distribution and redistribution of particle contact forces before, during, and after failure of the dump material specimen were visualized and velocities corresponding to strain localization plotted. According to the study and some previous references, the compressive contact force chain acting in the direction of major principal stress appears as a backbone of microstructure, and compression induced tension as its basic failure mode at particle level.
TL;DR: In this article, the authors present experimental results of tests on soil-structure interfaces carried out on a ring simple shear apparatus specially developed at Ecole Nationale des Ponts and Chaussees, Paris, for such studies.
Abstract: This article presents experimental results of tests on soil-structure interfaces carried out on a new “ring simple shear” apparatus specially developed at Ecole Nationale des Ponts and Chaussees, Paris, for such studies. In this apparatus strain localization takes place at or near the surface of the rotating steel drum that forms the soil-structure interface. Depending on the conditions of tests, in terms of surface roughness, special instrumentation is capable of recording local as well as global response. Three tests on Hostun gravel at different confining radial pressures have been conducted and a deviatoric hardening model with nonassociated flow rule has been adopted for their numerical simulations. The point of inception of strain localization based on various theoretical considerations has been discussed and experimentally verified. The post-peak behavior is simulated by employing a homogenization technique in which the soil sample is treated as a composite material consisting of a shear b...
TL;DR: In this paper, the structural design of flexible pavements reinforced by steel nettings has been investigated using a 3D finite element modeling (FEM) approach to estimate the gain in base material obtained by using such systems.
Abstract: This article deals with the structural design of flexible pavements reinforced by steel nettings. The purpose is to estimate the gain in base material obtained by using such systems. Most of the current pavement design methods are modeling the reinforcing system as a continuous layer. This approach is leading to cost‐ineffective solutions. To overcome these present limitations, a three‐dimensional (3D) finite element modeling (FEM) approach is suggested. The application of 3D‐FEM allows simulation of the real shape of steel reinforcing nettings. To cover as many practical cases as possible, various pavements are considered, defined by various base thicknesses and soil bearing capacities. Structures with and without base reinforcement system are compared in terms of asphalt fatigue, rutting, and deflection performance. These comparisons make it possible to draw several design charts for various asphalt thicknesses and soil bearing capacities. Such design charts will avoid time‐consuming computations with 3...