In situ X-ray computed tomography study on the effect of rock blocks on fatigue damage evolution of a subgrade SRM

Abstract

This study examines the effects of the rock block percentage (RBP) on the cyclic behaviors in soil rock mixture (SRM) by conducting cyclic triaxial tests at a constant stress amplitude and low strain level. The SRM samples were prepared using compaction testing with different RBPs. For the evaluation of the mesoscopic damage and stress dilatancy behaviors, the in-situ X-ray computed tomography (CT) technique was employed. It was revealed that the hysteresis loop presents a sparse-dense-sparse pattern that is caused by the plastic strain accumulation. Adding rock block to SRM influences the shape of the hysteresis loop, and the area of the hysteresis loop decreases with increasing RBP for samples at the same stress amplitude, the energy loss becomes smaller for SRM samples with a high RBP. On the other hand, after extracting cracks from the original CT images, it shows that damage of the SRM with different RBPs is different under the same loading cycle, the geometric parameters of crack decrease as the RBP increases. Localized deformation in the SRM sample results in the differential stress dilatancy behavior, there is interlocking among rock blocks and restriction of localized bands, which is affected by the different RBP in the SRM sample.