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

Dry-wet cycles can cause fatigue damage to expansive soil, and various control parameters of the dry-wet cycles (initial moisture content, number of dry-wet cycles, cycle amplitude, etc.) can affect the development of soil damage. therefore, 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 lowstress shear strength of expansive soil under 0-6 constant amplitude dry-wet cycles, the attenuation laws for the p-wave velocity were analysed, the damage variable of expansive soil was characterized by p-wave velocity, and the rationality of this damage variable was verified by measuring the lowstress 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. the results illustrate that 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 pwave velocity can be successfully used to define a representative damage variable for expansive soil.