EXPERIMENTAL STUDY ON SHEAR STRESS RELAXATION CHARACTERISTICS OF NANNING UNSATURATED EXPANSIVE SOIL UNDER THE CONDITION OF SHEARING

On the basis of a series of indoor shear stress relaxation tests for Nanning unsatruated manipulated expansive soils，shear stress relaxation characteristics of the unsaturated manipulated expansive soils under the condition of direct shearing were researched. The results show that shear stress relaxation curves fall into noncomplete decay type under different water content，and the shear stress gradually decreases and tends to stable values. The relaxation curves can be divided into obvious three stages: accelerate relaxation stage，uniform speed relaxation stage and stable relaxation stage. The nonlinear extent of stress-strain isochronal relationship curves is increasing gradually with an increase in the water content，and displacement values of damage of soil body are becoming smaller. The fitting curves of K-H constitutive equation well agreed with those of the observed data，which is able to reflect shear stress relaxation characteristics of Nanning unsaturated manipulated expansive soil.