COUPLED AND UNCOUPLED APPROACHES FOR THE ESTIMATION OF 1-D HEAVE IN EXPANSIVE SOILS DUE TO TRANSIENT RAINFALL INFILTRATION: A CASE STUDY IN CENTRAL VIETNAM

In this study, we utilized the coupled and uncoupled approaches in Geostudio commercial program to simulate the swelling of expansive soil caused by rainfall infiltration. For the coupled analysis in general, the infiltration of rainfall and subsequent heave are modeled using fully coupled formulation in SIGMA/W; specifically, the displacements and pore-water pressure changes are computed simultaneously. In the uncoupled analysis, rainfall-induced pore-water pressure change was simulated using SEEP/W alone and the resulting pore-water pressure change was employed in SIGMA/W for the volume change analysis. In other words, to analyze the problem in an uncoupled manner, the pore-water pressure changes and volume changes are computed separately. For the above purpose, the residual soil in Bac Ai district, Ninh Thuan province, South Central Vietnam, a well-known place with expansive soil problems was considered. The result shows that both proposed methods are promising tools and can be used in engineering practice for the estimation of the 1-D heave due to rainfall infiltration with respect to time.