An estimate of the bearing capacity of shallow foundations on anisotropic soil by limit equilibrium and soft computing technique

The limit equilibrium method with a multi-block failure mechanism has been utilised to study and estimate the bearing capacity of shallow foundations on anisotropic deposits. The multi-block mechanisms of Hill and Prandtl types were adapted to consider the effect of the footing-soil interface roughness. Both mechanisms composed of passive and active wedges and multiple transitional blocks between them. As an anisotropic medium, the` soil shear strength parameters were considered to entail a linear relationship with the bedding plane orientation. The dependency of the soil shear strength parameters to the depositional characteristics renders the problem to be highly nonlinear and hence, an iterative procedure was adopted to achieve a converged and optimal bearing capacity estimation. The optimisation was made by the Genetic Algorithm (GA) in an iterative process. Bearing capacity of isotropic soils was also calculated as a benchmark solution and then, extended to anisotropic soils. Some correction factors for three bearing capacity terms have been presented which cover a wide range of the anisotropy ratio. In general, the shear strength anisotropy proved to decrease the bearing capacity of a shallow foundation. The results were compared with some experimental and numerical results.