Experimental study on dynamic mechanical and failure behavior of a jointed rock mass

In order to study the dynamic mechanics and failure behavior of jointed rock masses, impact tests were carried out on sandstone specimens with intersected jointed and unjointed intact sandstone specimens using a modified split Hopkinson pressure bar (SHPB) with confinement. The effects of intersected artificial joints on the dynamic properties and failure mechanism of sandstone samples were analyzed. The dynamic stress-strain curve of sandstone specimen was obtained from the test, as well as the fracture failure behavior of specimen under different loading rates and confining pressures. The results show that the dynamic compressive strengths of the unjointed intact rock specimens and the jointed rock specimens both increase with the increase of the loading rate and the confining pressure. With the increase of loading rate, the jointed rock specimens showed more obviously plastic deformation ability than the intact rock specimens, and the size of the broken pieces of the jointed rock samples became smaller. The dynamic failure modes of the jointed rock samples are irregular and mainly appear tensile and compressive shear failures. Next, the dynamic initiation and development process of cracks in the jointed rock specimens were analyzed by using the UDEC numerical simulation software. The process of initiation and development of meso-cracks is affected by intersected joints. Combined with the effective stress contour map, five typical crack types are defined to reveal the macroscopic fracture behavior of sandstone samples.