Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests

In order to study the mechanical behaviors and fracture process properties of granite under confining pressure unloading with constant axial pressure, RMT-150B rock mechanics test system acoustic emission detector were used characteristics deeply buried specimens different combinations initial pressures rates. The results show that when rate is small, deviatoric stress-strain curve will yield an platform, significant ductility; large, brittleness. Besides, strain increases increase rate, fluctuates. ratio increment decreases a faster higher restrain deformation sample. normalized decreased parameter specimen pressure. When relatively high, it plays dominant role in compressive strength specimens. Mohr–Coulomb criterion can better reflect unloading. cohesion internal friction angle rate. Notably, presents weakening effect on strengthening specimen, former stronger than latter one. ringing count more evenly, damage develop slowly; maximum instantaneously at stage unloading, damaged rapidly, showing characteristic sudden fracture. mode affected by At same high typical tensile characteristics, while low mainly suffer from shear or shear-tension composite With transition