Influence of intermediate principal stress on mechanics and acoustic emission characteristics of coal rock

Abstract

In order to study the safety problems caused by coal mine excavation, the self-developed ground acoustic process simulation test system was used to carry out true triaxial loading and unloading tests of coal rock under different intermediate principal stress conditions, and the acoustic emission detection system was used to record the damage evolution law of coal rock during loading and unloading. The results showed that in the true triaxial unloading test, with the increase in the intermediate principal stress, the failure state of coal rock changed from shear failure to local shear tensile failure and then to overall yield failure. In the stress-strain curve, with the increase in the intermediate principal stress, the strain in the direction of the intermediate principal stress gradually changed from compression to expansion, and the volume strain changes from contraction to expansion. Mogi-coulomb strength criterion can better reflect the strength failure characteristics of coal rock during unloading. In the AE curve, the increase in the intermediate principal stress caused the unstable exponential growth of the internal cracks in the loading stage of coal rock and made the coal rock no longer have the bearing capacity in the unloading stage.

Keywords

• true triaxial test
• intermediate principal stress
• coal rock
• mechanical properties
• acoustic emission
• damage evolution