Winkler spring stiffness distribution for the structural analysis of mat foundations in clay under drained conditions

Abstract The interaction between mat foundations and the supporting soil is often simplified in design practice by assuming that the mat rests on Winkler springs. Most of previous studies aimed at determining the spatial variation of the spring constants or the modulus of subgrade reaction that is needed to obtain realistic and accurate results regarding the bending of the mat assuming that the soil behaves as a purely linear elastic material. This paper investigates the effects of plastic strains and volume changes that happen due to the consolidation of clayey soils under long-term conditions on the distribution of the equivalent spring constants and the bending moment diagrams. For this purpose, three-dimensional finite element analyses are performed for fully drained conditions with the soil simulated using the Modified Cam-Clay constitutive model. The results show that the presence of plastic yielding significantly influences the mat-soil interaction and the assumption of a linear elastic soil overpredicts the soil stiffness and the bending moments in the mat foundation. The semi-analytical Discrete Area Method could be adopted to obtain comparable results to those generated by elastoplastic finite element analysis.