AE and Damage Characteristics of Coal with Different Water Soaked Depths Under Uniaxial Compression

The stability of remnant coal pillars is of great significance for safe mining of coal resources around them. The remnant coal pillars are often soaked in mine water with a certain height. Different water levels (or depths) may affect the stability of remnant coal pillar differently. In this paper, uniaxial compression tests were carried out on coal specimens with different water soaked depths. Deformation and damage characteristics of coal specimens under loading were analyzed through acoustic emission (AE) and digital image correlation techniques. The results show that the AE energy curve of each partially soaked coal specimens presents double peak, while that of fully soaked coal specimen has only single peak. As the soaked depth increases, the AE b value gradually decreases, which indicates that the micro-fracture of coal specimens decrease with the increase of water soaked depth. During deformation and damage, partially soaked coal specimens have obvious localized strain, and the local strain concentration area is basically distributed in the dry-wet transition area. While the surface of the fully soaked coal specimen presents relatively uniform deformation. Partially distributed water within coal matrix increases the heterogeneity of the coal specimens. These results reveal the deformation and damage characteristics of coal with different water soaked depths, and provide a useful reference for reasonably evaluating the stability of coal pillars.