Multi-scale damage evolution characteristics of coal and rock under hydraulic coupling
LAI Xingping1，2，3，ZHANG Shuai1，DAI Jingjing1，WANG Zeyang1，XU Huicong1
(1. College of Energy Science and Engineering，Xi′an University of Science and Technology，Xi'an，Shaanxi 710054，China；
2. State Key Laboratory of Coal Resources in Western China，Xi′an University of Science and Technology，Xi'an，Shaanxi 710054，China；3. Key Laboratory of Western Mine Exploration and Hazard Prevention，Ministry of Education，Xi′an University of Science and Technology，Xi'an，Shaanxi 710054，China)
Abstract：Hydraulic coupling has an important influence on mechanical properties of deep coal and rock mass and failure mode. In order to study the softening effect of uni-axial compression of coal and rock samples and multi-scale characteristics of damage evolution. Utilizing the rock mechanical testing system and acoustical emission monitoring system，the uni-axial compression test of coal and rock samples is developed under the different water conditions. Firstly，by means of scanning electron microscopic identification of micro-structure. Secondly，the mechanical properties of coal and rock samples and failure mode is analyzed from macro scale. Thirdly，the damage evolution process of coal and rock samples is retrieved from the meso-scale based on acoustic emission parameters. Finally，the evolution characteristics of macro-and meso-scale damage is discussed under hydraulic coupling. The result shows that the macroscopic softening effects of coal and rock samples in different water-bearing states are similar. The increase of water content can effectively softening of rock mechanics parameters of coal as well as softening effect of distinct phases for the state has low water content，the softening effects of coal and rock samples in different water-bearing states are obviously different. The acoustic emission parameters of coal samples show a softening trend as the moisture content increases. Rock acoustic emission parameters，with the water rate increases，showing reduce the increasing trend in first. It shows that the water can effectively slow the damage evolution of coal sampling process. Ultimately，the impact of the coal sample bias is weakened. While the higher water content to provide rigidity and pore water coupling of water film speeds up the process of rock damage evolution. Finally，it is contrary to the theory of rock burst prevention and control to reduce the severity of rock mass failure. This study conclusion provides the theoretical basis for prevention measures of deep water softening of coal and rock burst.
2020, Vol. 39 
