A Finite Element Method to Design and Calculate Pier Foundations in Expansive-collapsing Soils

Abstract

A three-dimensional finite element method has been devised to calculate the movements and stresses of a pier foundation on expansive-collapsing soil isotropic, non-linear and non-homogeneous. The lack of linearity and homogeneity due to the stress state is taken into account through the dependence of the initial swelling and oedometric modulus upon the vertical stress as explained in the paper. Stress-path has a large influence in the calculated heave and tensions in pier, and is taken care of. A parametric study has been made. The parameters that have more influence in the problem are: swelling-collapse of the free soil profile, pier dimensions, net pressure for large base piers, an increase of Poisson's ratio above 0.3, the oedometric modulus of the soil and the placement of a soft material between pier shaft and soil. Conventional calculation methods underestimate wetting heave for a given value of final suction.