3-D Bearing Capacity Analysis of Square Foundation in Spatially Variable Cohesive Frictional Soil

Abstract

Natural soil variability is a well-known issue in geotechnical design particularly in footing design. When subsoil must be characterized in terms of mechanical properties, random finite element method (RFEM) can be effectively adopted. This method had been widely considered in two-dimensional case (plane strain condition) focusing on soil strength variability in two dimensions and assuming no variability along the direction perpendicular to the considered plane by default. This limitation can significantly influence probabilistic bearing capacity evaluations and emphasizes the importance of three-dimensional (3-D) analysis in such stochastic characterization. The 3-D analysis in stochastic context has not fully explored as such analysis is time-consuming and different stochastic conditions can be considered. The purpose of this paper is to use RFEM for the bearing capacity assessment of a square shallow foundation to endorse our understanding of the influence of 3-D analysis on bearing capacity and on failure mechanisms. In this study, soil shear strength properties (i.e. soil cohesion and friction angle) are assumed to be independent and correlated random fields. Results show that the influence of correlation between shear strength properties can be significant and lead to more realistic estimates of bearing capacity. A probability distribution of bearing capacity was then estimated and used to calibrate safety factors for reliability purposes.