Sensitivity of Raft Foundation’s Structural Behaviour to Changes in Geometry and Materials

Abstract

The finite element method is used to examine the sensitivity of the response of rafts subjected to concentrated loads to changes in geometry and material within the foundation. The parameters that are varied in the analysis include the mat thickness, soil modulus of subgrade reaction, concrete modulus of elasticity and spacing between columns. The structural response of the mat is studied by investigating the critical soil bearing pressure beneath the mat, as well as the internal bending moment and shear within the foundation. Findings of the study showed that the most important variables that can impact the structural behaviour of a mat are the thickness and spacing between columns, and to a lesser extent the soil modulus of subgrade reaction and concrete modulus of elasticity. Results of the sensitivity analysis are used to develop a relative mat rigidity factor that can quantitatively predict the degree of rigidity of a mat foundation, which can help in determining whether or not the traditional rigid approach can be safely used to analyse a given raft.