Seismic bearing capacity factors for spread foundations

Abstract

The effect of horizontal earthquake body forces on the bearing capacity of foundations has been examined computationally in a rigorous manner by employing the method of stress characteristics. The bearing capacity factors Nc, Nq and Nγ, due to the components of soil cohesion, ground surcharge pressure and soil unit weight respectively, have been plotted as a function of earthquake acceleration coefficient (αh) for different values of soil friction angle (ϕ). The inclusion of earthquake body forces causes a considerable reduction in the bearing capacity factors. The bearing capacity factors Nc and Nq are seen to be approximately of the same magnitude as those reported in the literature on the basis of different solution methods. However, the obtained values of Nγ are found to be significantly smaller than the available results. The nature of the pressure distribution along the footing base and the geometry of the observed failure patterns vary with the consideration of earthquake body forces.