In order to study the failure mechanism and ultimate bearing capacity of weightless subsoil under rigid and flexible foundations

comparative studies are conducted for flexible foundation

rigid rough foundation and rigid smooth foundation in the case that the effect of soil dead-weight was negligible. Mohr-Coulomb inside-tangent circle yield criterion under associated flow rule was adopted. The ultimate failure state of subsoil from linear elasticity to plasticity gradually was modeled by incremental elastoplastic FEM. Some conclusions are drawn from computational results of three kinds of foundations mentioned above and model test results in the literature. It is shown that the weightless subsoil under rigid and flexible foundations have similar ultimate bearing capacity; while development trends of vertical stress and displacement

critical edge pressures and slip surfaces are obviously different.