H-adaptive FE analysis of elasto-plastic nonhomogeneous soil with large deformation

Error estimation and h-adaptive finite element procedures are implemented for large deformation analyses of foundations on soil where the strength increases with depth. Errors are estimated by comparing strains at Gauss points with more accurate estimates using Superconvergent Patch Recovery (SPR). Mesh refinement using subdivision concept is then used iteratively to obtain optimal meshes, satisfying a minimum element size criterion. The Remeshing and Interpolation Technique with Small Strain (RITSS) approach is then used for large deformation analysis, with stress interpolation using either a modified form of the unique element method (MUEM), or the stress-SPR approach. Example analyses are then presented illustrating the three main aspects of mesh refinement, stress interpolation and large deformation response. Criteria are given for minimum element size and displacement increment far strip and circular foundations bearing on soil with varying degree of non-homogeneity, and computed bearing capacities are shown to compare well with lower bound estimates. The effect of soil weight on deep penetration of a strip foundation is discussed, with particular reference to the pattern of soil heave adjacent to the foundation, and the magnitude of the bearing capacity. (C) 1998 Elsevier Science Ltd. All rights reserved.