Limit analysis of the bearing capacity of fissured materials

Formulations for the upper and lower bound theorems of plasticity are presented for fissured soil and jointed rock. The methods ignore elastic deformations and are based on the assumption that the fissured soil or rock mass can be treated as an anisotropic, rigid-plastic continuum. In the upper bound formulation, velocity discontinuity multipliers are introduced to deal with the discontinuities in the velocity field. For both the upper and lower bound formulations, linearized failure surfaces for the fissured materials are developed. The illustrative examples indicate that the new procedures are very efficient even when a quite coarse mesh is used to represent the mass of failing material, and that the 'exact' failure loads are always bracketed by the upper bound and lower bound calculations. Moreover, by increasing the number of planes in the failure surface or/and refining the meshes, the accuracy of the bounds is raised. (C) 1999 Elsevier Science Ltd. All rights reserved.