Time-sensitivity mechanism of rock stress memory properties under tensile stress

In deep underground engineering,understanding of time-related stress memory properties is critical to evaluate the in situ stress conditions of a rock mass.In this study,the time-sensitivity mechanism of the rock stress memory properties under tensile stress was investigated.It was found that the material property(Poisson’s ratio)and crack angle were the controlling factors of the Kaiser effect(KE)under tensile stress.In particular,the time-sensitivity of the stress memory properties was closely related to the crack growth path.When the failure of the rock specimen was dominated by tensile microcracks and the crack development direction was deflected by up to 30°in the successive loading process,the stress memory capacity was likely to be time-independent for a sandstone specimen.The distribution of the Felicity ratio in a Brazilian test was more discrete than that in a three-point bending test It also showed that the changes in the crack path,rather than the time interval between successive loading cycles,led to inaccuracy of the detected KE.This study provides insights into stress memory-related issues under uniaxial or more complex stress conditions and thus facilitates development of methods for testing in situ mechanical behaviors of rocks with acoustic emission(AE)technology.