Experimental Study on Stress Relaxation Characteristics under Shearing Condition for Nanning Unsaturated Expansive Soil

On the basis of a series of indoor stress relaxation tests for Nanning expansive soils, the characteristics of stress relaxation under the condition of direct shearing for the unsaturated remolded expansive soils have been investigated. The results show that relaxation curves of stress belong to non-completed decay type under different water contents, and the stresses tend to be stable. The relaxation curves can be obviously divided into three stages: accelerating relaxation stage, uniformly speeding relaxation stage and stable relaxation stage. The nonlinearity degree of stress-strain isochronal relationship curves are increased gradually with the increase of water content, while the ultimate displacements at soil's failure are smaller. Through the comparative analysis of experimental relaxation model and test data, we find that this experimental model could well reflect nonlinear relaxation characteristics of Nanning unsaturated remolded expansive soil.