Abstract:

To research the strength characteristics, deformation properties, and failure regularities of sandy slate which has micro-bedding, triaxial compressed tests in loading and unloading conditions are carried out by MTS815 Flex test GT rock mechanics test system. The test results show that the peak intensities under loading are close to those under unloading condition when the bedding parallels to the maximum principal stress (parallel bedding). When the bedding is vertical to the maximum principal stress (vertical bedding), peak intensity and residual strength under unloading condition are respectively 20% and 25% lower than those under loading condition. The sandy slate with parallel bedding shows elastic brittle feature, and this brittle failure under unloading condition is stronger than that under loading condition. Failure surfaces of parallel bedding samples develop along the bedding planes direction, and the failure is caused by strong lateral expansion under tension. The failure faces of vertical bedding samples under loading condition display shear feature with diagonal transfixion plane, and the failure faces under unloading condition develop from the shear yielding planes at both ends to the center of the sample.  

Key words:  sandy slate,  loading and unloading, mechanical property, experimental study 