## About

130

Publications

81,238

Reads

**How we measure 'reads'**

A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more

7,304

Citations

## Publications

Publications (130)

Geological trace lines including rock joints and fractures are important characteristics of tunnel faces. Fully recording and analyzing this information is very helpful for evaluating the state of the tunnel from engineering geology prospective. Based on the digital images of a tunnel face, the paper studied rock mass trace line extraction and grou...

In this work, the Finite Particle Method (FPM) which is a typical meshfree particle method is formulated for static deformation and plastic flow problems. The novel formulation utilizes the Lagrangian-type kernel, which guarantees the method being free from the tension instability. A pseudo-viscosity is introduced into the particle system to preven...

The assessment of soil slope stability is an important task in geotechnical designs. This study uses finite element upper bound (UB) and lower bound (LB) limit analysis (LA) methods to investigate inhomogeneous soil slope stability on the basis of the conventional Mohr–Coulomb parameters. The obtained stability numbers are presented in inhomogeneou...

Seismic effect is one of the most commonly considered factors in rock slope safety design. This study adopts the finite element lower bound limit analysis method to study the seismic stability of disturbed rock slopes considering inhomogeneity caused by rock mass disturbance. Moreover, this research investigates different earthquake magnitudes by c...

For deterministic scenarios, adaptive finite element limit analysis has been successfully employed to achieve tight bounds on the ultimate load of a geotechnical structure in a much more efficient manner than a dense uniform mesh. However, no probabilistic studies have so far considered finite element limit analysis with adaptive remeshing. Therefo...

Recently, the authors investigated the effect of spatial variability on the undrained stability of an unlined circular tunnel. However, no studies have been conducted so far for the undrained stability of an unlined square tunnel in spatially variable soil. This study, therefore, aims to extend the previous research by the authors in the area of pr...

Slope stability analysis has traditionally been performed using a deterministic approach. However, it has strongly been debated that the use of only the factor of safety in slope stability analysis does not explicitly account for all the uncertainties in soil parameters. Therefore, to investigate the effect of uncertainties in the stability of a fi...

The problem of particle dynamics simulation is interpreted in the framework of computational plasticity leading to an algorithm which is mathematically indistinguishable from the common implicit scheme widely used in the finite element analysis of elastoplastic boundary value problems. This algorithm provides somewhat of a unification of two partic...

This study employs the finite element upper bound and lower bound limit analysis methods to investigate the stability of inhomogeneous rock slopes. The differences in the stability numbers of the upper and lower bound solutions are bracketed within ±10.5% or better, and the stability numbers obtained are presented in rock slope stability charts. Th...

This paper investigates the effect of spatial correlation length on the behavior of an eccentrically loaded strip footing (or a footing subjected to combined vertical and moment (VM) loading) resting on spatially variable soil, using a combination of adaptive finite element limit analysis and random field theory. The results of Monte-Carlo simulati...

This paper utilizes finite-element limit-analysis methods to investigate the stability of slopes of various properties and in nature. Specifically, a slope with a soft (weak material) band, a postquake slope, and rock slopes were investigated. The conventional Mohr-Coulomb failure criterion and the Hoek-Brown failure criterion are utilized for soil...

The analysis of rock slope stability is a classical problem for geotechnical engineers. However, for practicing engineers, proper software is not usually user friendly, and additional resources capable of providing information useful for decision-making are required. This study developed a convenient tool that can provide a prompt assessment of roc...

The efficiency of parallel preconditioned conjugate gradient (PCG) algorithm for
solving large sparse linear systems arising from application of interior point methods to conic
optimisation problems in the context of nonlinear finite element limit analysis (FELA) for
computational geomechanics is studied. For large 3D problems, the use of direct so...

This paper uses the finite element upper and lower bound limit analysis methods to investigate the three-dimensional (3D) slope stability of two-layered undrained clay slopes. The solutions obtained from the slope stability analyses are bracketed to within ±10% or better. For comparison purposes, results from two-dimensional (2D) analyses based on...

A procedure for strength reduction analysis using finite-element limit analysis is presented. The scheme is completely general and does not require decision making regarding the loads needed to drive the system to failure. Rather, the scheme is based on the ability of modern interior-point methods to detect infeasibility in a controlled and reliabl...

A new failure criterion, the generalised Tresca criterion, for undrained total stress analysis is presented. The criterion is consistent with an underlying effective stress Mohr-Coulomb model. It involves two parameters: the undrained shear strengths in triaxial compression and extension. As such, the model predicts different strengths in compressi...

The limit analysis and the finite element method are powerful tools for analysing the bearing capacity of foundations. Previous research mainly focused on the foundations in uniform soils. In realistic conditions, soil properties are always varying spatially due to complex physical, chemical, and biological process in earth evolution. This paper in...

This paper investigates slope stability and produces a set of stability charts for three-dimensional (3D) slopes for a specific case in which frictional fill materials are placed on purely cohesive clay. As slopes are not usually plane strain in nature and are influenced by physical boundaries, this study uses a 3D analysis using the finite-element...

This paper presents a hybrid preconditioning technique for Conjugate Gradient method and discusses its parallel implementation on Graphic Processing Unit (GPU) for solving large sparse linear systems arising from application of interior point methods to conic optimization problems in the context of nonlinear Finite Element Limit Analysis (FELA) for...

In practical geotechnical engineering the factor of safety is still determined by means of simple limit equilibrium analysis in many cases. However, because displacement finite-element analysis is routinely applied for assessing displacements and stresses for working load conditions, this technique is increasingly being used to calculate ultimate l...

The ultimate bearing capacity of a strip footing on soil reinforced by a trench has been studied in the framework of limit analysis. Existing contributions were reviewed and were compared with numerical results predicted by two methods. The main finding was how the numerical tools performed in predicting closed lower-bound (LB) and upper-bound (UB)...

Stability charts for soil slopes, first produced in the first half of the twentieth century, continue to be used extensively as design tools, and draw the attention of many investigators. This paper uses finite-element upper and lower bound limit analysis to assess the short-term stability of slopes in which the slopematerial and subgrade foundatio...

Rainfall induced landslides can vary in depth and deeper the landslide, greater is the damage it causes. This paper investigates, quantitatively, the risk of rainfall induced landslides by assessing the consequence of each failure. The influence of the spatial variability of the saturated hydraulic conductivity on the risk of landslides is studied....

In the study of landslides, it is generally assumed that an impermeable boundary exists at a certain depth and failure occurs at this boundary. In reality this is not always the case and failures can occur at any depth. This paper aims to study the effect of boundary conditions on landslides, using a series of seepage and stability analyses perform...

The pullout capacity of plate anchors has been studied extensively over the past 40 years. However, very few studies have attempted to calculate the pullout capacity of anchors in sandy slopes. In this paper, three upper bound approaches are used to study the effect of a sloping ground surface and friction angle on pullout capacity and failure of p...

The stability of dual square tunnels in cohesive-frictional soils subjected to surcharge loading has been investigated theoretically and numerically assuming plane strain conditions. From the viewpoint of the efficient utilization of underground space for human activities, noncircular openings and tunnels should be preferred in the design stage. De...

The problem of finite element simulation of incompressible fluid flow in porous medium is considered. The porous medium is characterized by the X-ray microtomography technique in three dimensions. The finite calculus-based stabilization technique is reviewed to implement the equal order finite element interpolation functions for both velocity and p...

It is known that rock masses are inhomogeneous, discontinuous media composed of rock material and naturally occurring discontinuities such as joints, fractures and bedding planes. These features make any analysis very difficult using simple theoretical solutions. Generally speaking, back analysis technique can be used to capture some implicit param...

This paper uses the finite element upper and lower bound limit analysis to assess the stability of slopes mostly found in embankment cases where frictional materials are filled on purely cohesive undrained clay. For comparison purposes, the commonly used stability assessment method, limit equilibrium method (LEM) is also employed. The final results...

Some common criteria for predicting the plastic failure of geomaterials, including the Mohr-Coulomb model, can be represented as conic constraints. Thus, by formulating finite element limit analysis (FELA) problems with such materials as second-order cone programs (SOCPs), solutions to small-and medium-scale problems are readily obtained using curr...

The mechanical properties of natural materials such as rocks and soils vary spatially. This randomness is usually modelled by random field theory so that the material properties can be specified at each point in space. When these point-wise material properties are mapped onto a finite element mesh, discretization errors are inevitable. In this stud...

In this paper, numerical limit analysis and semianalytical rigid block techniques are used to investigate the effect of the tunnel spac-ing on the stability of two circular tunnels excavated side by side. The tunnels are modeled under plane-strain conditions, which implies that they are assumed to be infinitely long. Bounds on the stability of the...

Trench stability is a conventional geotechnical problem; however, current evaluations are often based entirely on empiricism. This paper uses numerical finite-element upper and lower bound limit analysis to produce stability charts for two-dimensional and three-dimensional homogeneous and inhomogeneous undrained diaphragm wall trenches. Using the l...

In this paper, an adaptive dynamic relaxation technique is proposed as an efficient method for large scale nonlinear geotechnical problems. Dynamic relaxation is a numerical method to solve static problems involving highly nonlinear differential equations. Extremely simple implementation and cheap computation resulting from the underlying explicit...

The efficiency of several preconditioned Conjugate Gradient (PCG) schemes for solving of large sparse linear systems arising from application of interior point methods to nonlinear Finite Element Limit Analysis (FELA) is studied. Direct solvers fail to solve these linear systems in large sizes, such as large 2D and 3D problems, due to their high st...

The displacement finite element, lower and upper bound finite element limit analysis and analytical upper bound plasticity methods are employed to investigate the undrained limiting lateral resistance of piles in a pile row. Numerical analyses and analytical calculations are presented for various pile spacings and pile–soil adhesion factors. The nu...

Risk may be estimated by multiplying the probability of failure by the consequence. This is acceptable for systems that have a single mode of failure. For systems that have multiple failure modes, such as landslides, the consequences should be assessed individually for each of the failure modes. This paper proposes a new framework of quantitative l...

Design equations are presented for the calculation of the ultimate lateral resistance of two-pile groups
in clay under a general loading direction. Analytical upper bound solutions, numerical upper and lower
bound limit analyses and displacement finite-element analyses are first presented for the case of two
piles loaded parallel to the pile-to-pil...

The ultimate earth resistance for a group of two side-by-side piles that are laterally loaded in clay is investigated using four different methods of analysis: three numerical (the displacement finite-element
method, and the upper- and lower-bound finite-element limit analysis methods) and one analytical (an
analytical upper-bound plasticity method...

Numerical techniques for the computation of strict bounds in limit analyses have been developed for more than thirty years. The efficiency of these techniques have been substantially improved in the last ten years, and have been successfully applied to academic problems, foundations and excavations. We here extend the theoretical background to prob...

This study extends the limit analysis techniques used for the computation of strict bounds of the load factors in solids to stability problems with interfaces, anchors and joints. The cases considered include the pull-out capacity of multi-belled anchors and the stability of retaining walls for multiple conditions at the anchor/soil and wall/soil i...

This paper proposes a statistical multiscale homogenization method to extract effective elastic properties of cement paste on the basis of X-ray microtomography images. The procedure starts at the nanolevel of the C-S-H matrix. Because the highest resolution of current X-ray microtomography is at micrometer scale, C-S-H and CH remains unsegmented....

The efficiency of several preconditioned Conjugate Gradient (PCG) schemes for solving of large sparse linear systems arising from application of second order cone programming in computational plasticity problems is studied. Direct solvers fail to solve these linear systems in large sizes, such as three dimensional cases, due to their high storage a...

This paper combines the random field methodology with the upper and lower bound finite element limit analysis algorithms (Sloan 1988, 1989) to study the bearing capacity of undrained clays with spatially varying shear strength. The results of the Random Field Limit Analysis (RFLA) analyses are compared with existing results obtained by elastic-plas...

The ultimate bearing capacity and the failure mechanism of cohesive-frictional soils with the inclusion of dual circular tunnels have been theoretically and numerically investigated assuming plane strain conditions. Unlike the case of a single tunnel, the center-to-center distance appears as a new problem parameter, which plays a key role in tunnel...

Probabilistic evaluation of slope failures is increasingly seen as the most appropriate framework for accounting for uncertainties in design. This paper performs reliability assessments for rock slopes based on the latest version of the Hoek–Brown failure criterion. The purpose of this study is to demonstrate the use of a new form of stability numb...

A granular contact dynamics formulation for elastically deformable particles is detailed. The resulting scheme bears some similarity to traditional molecular dynamics schemes in that the consideration of a finite elastic contact stiffness implies the possibility for inter-particle penetration. However, in contrast to traditional molecular dynamics...

A class of variational formulations for discrete element analysis of granular media is presented. These formulations lead naturally to convex mathematical programs that can be solved using standard and readily available tools. In contrast to traditional discrete element analysis, the present granular contact dynamics formulation uses an implicit ti...

SUMMARYA new methodology for computational plasticity of nonassociated frictional materials is presented. The new approach is inspired by the micromechanical origins of friction and results in a set of governing equations similar to those of standard associated plasticity. As such, procedures previously developed for associated plasticity are appli...

Stability of multiple underground openings (tunnels) in
cohesive-frictional soil subjected to surcharge pressure has been
theoretically and numerically investigated assuming plane strain
conditions. Unlike the case of a single tunnel, the center-to-center
distance appears as a new problem parameter, which plays a key role in
tunnel stability. A con...

The probability of failure of a rock slope is generally estimated by using the Limit Equilibrium Method (LEM) in conjunction with a reliability analysis. Although the LEM is relatively simple and time efficient, recent studies have indicated that using the LEM may overestimate the factor of safety by 21%, when based on a non-linear failure criterio...

This paper focuses mainly on the stability of a square tunnel in cohesive-frictional soils subjected to surcharge loading. Large-size noncircular tunnels are quickly becoming a widespread building technology by virtue of the development of advanced tunneling machines. The stability of square tunnels in cohesive-frictional soils subjected to surchar...

In spite of the development of more sophisticated constitutive models for soil, the Mohr–Coulomb yield criterion remains a popular choice for geotechnical analysis due to its simplicity and ease of use by practising engineers. The implementation of the criterion in finite element programs, however, presents some numerical difficulties due to the gr...

Solutions for the ultimate bearing capacity of footings on purely cohesive slopes are obtained by applying finite element upper and lower bound methods. In a footing-on-slope system, the ultimate bearing capacity of the footing may be governed by either foundation failure or global slope failure. The combination of these two factors makes the probl...

This paper investigates the undrained stability of a plane strain circular tunnel in clay, where the shear strength profile is assumed to increase linearly with depth. Stability solutions for a variety of geometries and soil conditions are found using rigid-block upper bound methods as well as finite element limit analysis (which gives both upper a...

The stability of circular tunnels in cohesive-frictional soils subjected to surcharge loading has been investigated theoretically and numerically assuming plane strain conditions. Despite the importance of this problem, previous research on the subject is very limited. At present, no generally accepted design or analysis method is available to eval...

The ultimate bearing capacity and the failure mechanism of cohesive-frictional soils with the inclusion of dual tunnels have been theoretically and numerically investigated assuming plane strain conditions. A continuous loading is applied to the ground surface. For a series of tunnel geometries, shapes and material properties, rigorous lower and up...

Rigorous plasticity solutions for the ultimate bearing capacity of a strip footing resting on a sand layer over clay soil are obtained by applying advanced upper and lower bound techniques. The study compares these solutions with other published results and investigates the effect of various strength and geometry parameters. Assuming the soil layer...

In many geotechnical stability problems it is important to account for interface conditions between two or more adjoining bodies, e.g. retaining walls and footings with no-tension contact between soil and structure. These interfaces can be considered as discontinuities in stress and velocity fields developed in the system undergoing plastic collaps...

This paper uses finite element upper and lower bound limit analysis to produce chart solutions for three-dimensional (3D) natural slopes for both short-and long-term stability. The presented chart solutions are convenient tools that can be used for preliminary design purposes. The rigorous limit analysis results in this paper were found to bracket...