Evaluation of Factors of Safety against Basal Heave for Deep Excavations in Soft Clay Using the Finite-Element Method

Abstract

This study investigates basal heave stability of deep excavations in soft clay using FEM with reduced shear strength. Three failure and one excessive deformation case histories are utilized. Three methods of estimating factors of safety against basal heave are employed, including the convergence criterion method involving numerical convergence, the angle method of quantifying the kick-out phenomenon of the wall, and the intersection method of examining the behavior of nodal displacements. Results show that the convergence criterion method and the angle method overestimated the factors of safety (FS) against basal heave. The intersection method, on the other hand, resulted in good agreement with the field observations because the calculated factors of safety were close to unity. The intersection method was also verified by a parametric study wherein its factors of safety increased linearly with the undrained shear strength of soil.