Factors and Failure Patterns Analysis for Undrained Seismic Bearing Capacity of Strip Footing Above Void

Abstract

This study aims to predict the undrained seismic bearing capacity and failure mechanisms of a shallow strip footing that is placed on homogeneous and heterogeneous cohesive soils above a single unsupported rectangular void using finite-element limit analysis (FELA). Upper and lower bounds will be computed for a comprehensive range of geometries, horizontal earthquake accelerations, materials, void shapes, and size combinations. In addition, parameter studies will be carried out to quantify the effect of various factors on the bearing capacity of the footing to finally derive a design table that could be used to quickly predict the bearing capacity of the desired footing. The results show that according to the void condition, earthquake acceleration, and soil characteristics, there are four modes of failure: footing bearing failure without void failure; footing bearing failure with roof void failure; footing bearing failure with side; and roof void failure and void collapse without bearing failure. Finally, a sensitivity analysis will be carried out to show that the void depth and soil undrained shear strength are the most important parameters for the ultimate footing bearing capacity.