Characteristics of Stress Memory and Acoustic Emission for Siltstone under Different Previous Stresses

Abstract

A stepped cyclic loading test was designed to investigate the stress memory and acoustic emission characteristics of siltstone under different previous stress levels. This study aims to improve the applicability of the acoustic emission in situ stress measurement method in porous weak cementation strata. The stress memory failure range for siltstone and the memory stress correction formula were determined based on characteristic stress value. The analysis of acoustic emission characteristics revealed the failure mechanism of the Kaiser effect of siltstone, and the following conclusions were obtained. Crack initiation stress can serve as the failure criterion for the stress memory effect in siltstone. Therefore, the failure range for the stress memory effect in siltstone can be defined as a previous stress of less than 15.3 MPa and a memory stress of less than 13.7 MPa. The pore compaction process in siltstone and the friction-generated acoustic emission signal during this process negatively affect stress memory. The primary cause of the stress memory effect in rocks is the irreversible development of new internal cracks. The compression rebound effect of primary soft pores in siltstone mainly causes the Kaiser effect to fail. The compression rebound effect of primary soft pores in siltstone is the main reason for the failure of the Kaiser effect.