Dynamic behavior of soil and rock mixture using cyclic triaxial tests and X-ray computed tomography

This paper aims at investigating the meso-scale mechanisms that result in damage evolution in soil and rock mixtures (SRM). Although the macroscopic cyclic stress–strain response of SRM has been well investigated, the mesoscopic damage cracking mechanisms are still not well understood. In this work, artificial SRM sample with a rock block percentage (RBP) of 30% (mass ratio) was investigated by carrying out cyclic triaxial compression tests with a constant stress amplitude and low strain level, under tomographic monitoring using a 450 kV industrial X-ray computed tomography (CT). A series of 2D CT images were obtained at different loading stages throughout the test and from different positions in the sample using CT scanning. The results show that the hysteresis loop presents a sparse–dense–sparse pattern caused by the accumulation of plastic strain during the test. Besides, parameters of damping ratio and resilient modulus vary as increasing cycles, much energy loss, and decreasing resilient ability occur with large plastic strain. The study also finds that a linear relationship exists between the hysteresis loop area and total crack area extracted from the CT images. Volumetric dilatancy caused by the damage cracking behavior has closed link with the evolution of hysteresis loop, which are controlled by the meso-structural changes during sample deformation.