Study on Grouting Repair Effect of Post-Peak Coal Samples

Coal has abundant bedding and joint structures, and most of it exhibits obvious brittle characteristics, which leads to its easy cracking and failure under mining stress. This easily leads to slab cracking and roof collapse in coal mining faces, as well as large deformations in roadways. On-site grouting of fractured coal bodies can effectively prevent these disasters. To reveal this mechanism, this study has first developed a modified ultra-fine cement grouting material and high-pressure continuous grouting system, and then conducted grouting and uniaxial compression tests on post-peak coal samples. Test results indicate that the post-peak residual bearing capacity of grouted coal specimens can recover to 65~85% of the peak strength of intact raw coal. The pre-peak plastic deformation becomes significant, and the post-peak stage exhibits stable strain softening. Grouting is considered to serve to improve the internal stress state of coal samples, act as a ductile grid skeleton, coordinate their internal deformation, and enhance their post-peak bearing capacity.