Undrained bearing capacity of tripod skirted foundations under eccentric loading

The undrained bearing capacity of a group of three rigidly connected skirted foundations (tripod) under vertical, moment or combined vertical-moment loading is investigated. Three-dimensional displacement finite element analyses of a single footing are first presented in order to validate the numerical modelling procedure. Various loading paths are considered and comparisons with known solutions are made. Subsequently, a series of analyses of undrained loading on a three-footing group is presented. Different footing spacings and loading directions are considered. The predominant failure mechanisms for characteristic load combinations are determined and the calculated failure loads are presented in dimensionless and normalized form. Based on the numerical results, a unique normalized failure load surface is proposed which applies to all loading directions and footing spacings for a given skirt length to footing diameter ratio.