Experimental study on the ultrasonic nonlinear damage characteristics of expansive soil during constant amplitude dry-wet cycles

Various control parameters of the dry-wet cycles can affect the development of expansive soil damage. It is important to study the fatigue damage characteristics of expansive soil under dry-wet cycles of constant amplitude. This paper considers expansive soil from Baise in Guangxi, China as the research object. Based on tests of the P-wave velocity and low-stress shear strength of expansive soil under 0{6 constant amplitude drywet cycles, the attenuation laws for the P-wave velocity were analyzed, the damage variable of expansive soil was characterized by P-wave velocity, and the rationality of this damage variable was verified by measuring the low-stress shear strength values of expansive soil specimens. Based on the experimental P-wave velocity results, a nonlinear empirical model of fatigue damage for expansive soil was constructed. As a result, the P-wave velocity of an expansive soil sample decreases nonlinearly with an increasing number of dry-wet cycles and that the damage degree increases nonlinearly with an increasing number of cycles. The cohesive force and damage degree of expansive soil show an attenuation relationship that is well t by a logarithmic function; in general, the damage characteristics of expansive soil are closely related to the dry-wet cyclic loading path.