Simulation analysis of deformation for unsaturated expansive soils based on fluid-solid coupling characteristics

An elastic-plastic constitutive model for unsaturated expansive soil was derived with single variable theory in effective stress principle,which includes the unsaturated characteristics of the soil.Appropriate soil-water character curves and permeability coefficient equation were selected in derivation.The swelling or shrinking behavior of expansive soils was treated as a coupling dynamic process according to the theory and method of fluid-solid coupling mechanism,from which a seepage-deformation coupling model was established.This model considers the changes of void ratios and permeability parameters(including the influence of effective stresses) induced by fluid-solid coupling effect and moreover,and the absorption and losing of water of expansive soils were simulated by setting boundary void water pressure(or matrix suction).The reliability and correctness of the proposed model were verified by laboratory loading test for expansive soil in terms of seepage and deformation.The result indicates that the numerical simulation is able to well calculate and predict the expansive soils(swelling or shrinking) with good accuracy.