Seismic bearing capacity of a circular footing on a heterogeneous cohesive soil

This study concerns the determination of the seismic bearing capacity of a circular footing resting on a purely cohesive heterogeneous soil layer. The problem is treated using the kinematic approach of the Yield Design theory. The soil strength is modelled by the Tresca criterion with C ₀ the cohesion at the soil surface and G the vertical cohesion gradient. The loading process of the system is described by four loading parameters: an inclined force (N: vertical component, V: horizontal component), a moment (M) acting at the center of the footing and horizontal uniform inertial forces (F _h) acting in the soil volume during the seismic excitation. Two cases are considered for the soil: a soil with an infinite tensile strength and a soil with zero tensile strength. The soil-footing interface is considered purely cohesive with zero tensile strength. The study presents optimal upper bounds for the ultimate combinations of the dimensionless loading parameters (N, V, M, F _h) by the examination of a series of three-dimensional virtual kinematic mechanisms of failure. The results are presented in the form of surfaces in the space of the parameters (N, V, M) for a range of values of F _h.