Experimental study on failure precursory characteristics and moisture content effect of pre-cracked rocks under graded cyclic loading and unloading

It is important to analyze the damage evolution process of surrounding rock under different water content for the stability of engineering rock mass. Based on digital speckle correlation (DSCM), acoustic emission (AE) and electromagnetic radiation (EMR), uniaxial hierarchical cyclic loading and unloading tests were carried out on sandstones with different fracture numbers under dry, natural and saturated water content, to explore the fracture propagation, failure precursor characteristics and damage response mechanism under the influence of water content effect. The results show that with the increase of water content, the peak stress and crack initiation stress decrease gradually, and the decreases are…