Dynamic behavior of a running crack crossing mortar-rock interface under impacting load

Abstract

Crack can often be observed propagating from one material to another. Due to differences in material properties, dynamic stress intensity factor, the crack propagation speed and stress field may change as the crack crossing the interface of two materials. Therefore, a side material cleavage triangle (SMCT) specimen was proposed in this paper. Green sandstone and granite were used in specimens. The dynamic loading tests were carried out using SMCT specimens under the impact loading, and crack propagation gauges (CPGs) were used to measure the crack propagation speed. The dynamic fracture toughness in the rock and mortar zone was calculated by ABAQUS code, and the finite element simulation results were consistent with the test results. It was concluded that the crack propagation speed is approximate twice in mortar as granite for the mortar-granite specimens. But the speed difference in sandstone and mortar is small for the mortar-sandstone specimens. The critical dynamic stress intensity factor (DSIF) increases with the increase of loading rate, and the increase of average critical DSIF in granite is larger than that in mortar for the mortar-granite specimens. However, the difference is small for the mortar-sandstone specimens. Meanwhile, the interface roughness also affects crack propagation. Under the same loading rate 1220 GPa/s, the crack can straightly cross the mortar-granite interface for the mortar-granite specimens with a rough interface, while for those with a smooth interface, the crack propagates along the smooth interface.