摘要:

AbstractThe mechanical behaviour of a rock mass is strongly affected by discontinuities such as faults and joints. In this paper, a damage mechanics theory is proposed which deals with some sets of discontinuities distributed in a rock mass, for example, joint systems. In this theory, the distributed discontinuities are characterized by a second‐order symmetric tensor, called the damage tensor. By introducing the damage concept, the deformation and fracturing behaviour of the rock mass can be reated in a framework of continuum mechanics. A numerical procedure is developed in order to implement the damage mechanics model by using the finite element method. The theory and numerical analysis are applied to several laboratory tests and a practical underground opening problem. Numerical results are compared with measured dat

ISSN:0363-9061    

DOI:10.1002/nag.1610120102

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe subject of this paper is the nonlinear analysis of heat and moisture transfer in partly saturated soil. In particular, an extension of the previous work of the author to two‐dimensional applications is presented. Problems of greater complexity and engineering significance can hence be solved. The theoretical basis of the problem is first outlined before the two‐dimensional formulation of the numerical solution is given. The finite element method is employed to give the spatial distributions of the variables, with a finite difference scheme being used to predict the temporal variations. The method allows the nonlinear nature of the soil parameters to be modelled, predictions being given of the coupled transient simultaneous transfer of heat and volumetric moisture content. The two‐dimensional nature of the work is illustrated for the case of surface evaporative soil moisture losses from sloping ground. Subsoil conditions of a uniform deposit of loam are considered with values of representative material parameters assumed after a literature search. The coupled nature of heat and mass transfer is illustrated by means of an analysis of the moisture migration patterns that occur. Two‐dimensional moisture flow, out of and into the soil, is shown to tak

ISSN:0363-9061    

DOI:10.1002/nag.1610120103

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA computational method, based on an advanced elasto‐plastic large strain formulation, well suited for the analysis of the cone penetration problem, is presented.A new approach of finite strain elasto‐plastic analysis is employed.13The basic (non‐rate) constitutive relations are developed in a spatial reference space to preserve their physical significance. They are subsequently transformed in Lagrangian co‐ordinates, and through simple time differentiation, their rate equations are introduced. The method is computationally implemented with the finite element method and special provisions are taken to allow for the moving boundary conditions of the

ISSN:0363-9061    

DOI:10.1002/nag.1610120104

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper describes a technique for computing lower bound limit loads in soil mechanics under conditions of plane strain. In order to invoke the lower bound theorem of classical plasticity theory, a perfectly plastic soil model is assumed, which may be either purely cohesive or cohesive‐frictional, together with an associated flow rule. Using a suitable linear approximation of the yield surface, the procedure computes a statically admissible stress field via finite elements and linear programming. The stress field is modelled using linear 3‐noded traingles and statically admissible stress discontinuities may occur at the edges of each triangle. Imposition of the stress‐boundary, equilibrium and yield conditions leads to an expression for the collapse load which is maximized subject to a set of linear constraints on the nodal stresses. Since all of the requirements for a statically admissible solution are satisfied exactly (except for small round‐off errors in the optimization computations), the solution obtained is a strict lower bound on the true collapse load and is therefore ‘safe’.A major drawback of the technique, as first described by Lysmer,1is the large amount of computer time required to solve the linear programming problem. This paper shows that this limitation may be avoided by using an active set algorithm, rather than the traditional simplex or revised simplex strategies, to solve the resulting optimization problem. This is due to the nature of the constraint matrix, which is always very sparse and typically has many more rows that columns. It also proved that the procedure can, without modification, be used to derive strict lower bounds for a purely cohesive soil which has increasing strength with depth. This important class of problem is difficult to tackle using conventional methods. A number of examples are given to illustrate the effectiveness of th

ISSN:0363-9061    

DOI:10.1002/nag.1610120105

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAttention is focused on the mechanical behaviour of rock‐like materials. Developments and applications of a constitutive model based on damage theory are presented. The internal damage model is calibrated for a hard brittle rock, Bushveld Norite, and through this process the identification of the material parameters is carried out. Emphasis is placed on the identification of the material parameters in the damage evolution law. The uniqueness of solutions in the softening regime is investigated through finite element mesh sensitivity studies of non‐uniform deformation triaxial compression te

ISSN:0363-9061    

DOI:10.1002/nag.1610120106

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA numerical approach to bifurcation problems in soil mechanics is described. After locating the bifurcation point by a combination of an incremental‐iterative loading procedure and an eigenvalue analysis of the tangent stiffness matrix, the solution is continued on the localization path by a suitable combination of the fundamental solution and the eigenvector belonging to the lowest eigenvalue. The procedures are applied in a bifurcation analysis of a cohesionless soil in a biaxial testing device. The results suggest that a diffuse bifurcation mode with a short wavelength is encountered whereupon a shear band gradually develops. The inclination angle of the shear band compares well with analytical formulae and with empirical dat

ISSN:0363-9061    

DOI:10.1002/nag.1610120107

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610120108

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610120109

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610120101

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY