Study on the mechanical properties of rock with cross fracture under biaxial compression cyclic loading and unloading.

Abstract

In this study, biaxial compression cyclic loading and unloading tests are performed on rock-like samples that contain a single group of cross cracks. The effects of angle α between the main crack and load direction, the angle between the main and secondary cracks, and the number of cycles of biaxial compression cyclic loading and unloading on the coabsmpressive strength and crack evolution of the samples are investigated. The effects of the number of groups of cross cracks and number of cycles of cyclic loading and unloading on the compressive strength and crack evolution are then examined. When both angle β between the primary and secondary prefabricated cracks and the lateral pressure are similar, the compressive strength of the specimen first decreases and then increases with α from 0° to 90°. When α is the same, the lateral pressure is the same, and β between the primary and secondary prefabricated cracks increases from 0° to 90°, the compressive strength of the sample does not significantly change. When α is the same, β is the same, and the lateral pressure is the same, the compressive strength of the specimen after cyclic loading and unloading gradually decreases with increasing number of cyclic loading and unloading. When both α and the lateral pressure are the same, the compressive strength of the specimen gradually decreases with increasing number of cross cracks in the specimen. Main crack is the main controlling factor of the strength and crack propagation of specimens with a single group of cross cracks. The interaction among multiple groups of intersecting cracks changes the state of the local stress field, and the crack propagation is more complex than that in a single group of cross cracks.