Study on strength characteristics and failure mechanism of hard rock containing cracks with different dip angles

Abstract

Abstract To further study the strength characteristics and failure mechanism of hard rock containing open prefabricated cracks, uniaxial compression tests of green sandstone containing open prefabricated cracks of different inclination angles were carried out. The results show that the peak strength of the unclosed prefabricated cracked green sandstone is lower than that of the intact green sandstone, and the peak strength increases and then decreases with increasing β, with the highest strength at β = 75 and the lowest strength at β = 0.The characteristics of acoustic emission (AE) signals are roughly divided into two stages a stable period and an active period. When 0 ≤ β ≤ 30, the proportion of the active period is large; when 45 ≤ β ≤ 90, the proportion of the active period is small. When β increases from 0 to 90, the failure modes mainly include four types, which are slab crack failure caused by tensile stress, type I tensile failure caused by type II shear stress, shear failure along the shear slip surface and splitting failure caused by tensile stress. When β = 0, 15,a small-scale strain burst occurs, and the ejected fragments are of medium size and in the shape of 'plate'. When β = 30,45, the ejection of local small fragments occurs. When β = 60, 75, a high-strength strain burst dominated by large fragments occurs. When β = 90, the rock is mostly stripped on the surface without obvious rockburst.