The deformation and failure of strip footings on anisotropic cohesionless sloping grounds

Abstract

Footing foundations are sometimes built on sloping grounds of natural sand which is highly anisotropic. The anisotropic mechanical behaviour of sand can significantly influence the bearing capacity of a foundation and the failure mechanism of its supporting slope. Neglecting sand anisotropy may lead to overestimated bearing capacity and under-design of foundations. A numerical investigation on the response of a supporting slope under a strip footing is presented, placing a special focus on the effect of sand anisotropy. A critical state sand model accounting for fabric evolution is used. The nonlocal method has been used to regularize the mesh-dependency of the numerical solutions. Predictions of the anisotropic model on the bearing capacity of strip footings on slopes are validated by centrifuge test data on Toyoura sand. Compared to the centrifuge test data, an isotropic model may overpredict the bearing capacity of the footing by up to 100% when the model parameters are determined based on test data on a horizontal bedding plane case. When the isotropic model parameters are determined based on test data where the bedding plane is vertical, the predictions of bearing capacity can be improved for some cases but the settlement at failure may be significantly overestimated. The soil body tends to move along the bedding plane upon the footing loading due to the non-coaxial strain increment caused by fabric anisotropy. The slip surface appears to be deeper with lower bearing capacity when the preferred soil movement direction caused by bedding plane is towards the slope.