Mechanical Tests and Theoretical Research on Fracture Grouting Reinforcement of Soft and Weak Coal Rock

Fracture grouting is an effective method to address the issues of unstable and disturbed collapsing of the roadway surrounding the rock during coal mining. It helps to expel water and air from the weak rock mass, aiming to prevent seepage and reinforce the surrounding rock. Coal samples were grouted with cement-based slurries and epoxy resins of varying water-cement ratios. We conducted uniaxial compression tests on the samples using acoustic emission and VIC3D monitoring systems to examine the durability, compressive strength, and visible damage features of coal samples reinforced with different grouting materials. This study presents the theoretical formula for the elastic modulus of a solid under loading and compares it with experimental results. The test results show that as the water-cement ratio decreases, the compressive strength of grouting and solid materials increases. Additionally, the strength of epoxy resin on the consolidated body shows a significant increase, but the strengthening effect remains consistent with a water-cement ratio of 0.6. An examination of the reinforced body’s failure characteristics revealed that stress concentration first occurred at the coal sample joints. As the loading time progressed, fractures developed, grew, penetrated, and finally failed, with all failure locations occurring in the non-reinforced zone. The theoretical values of elastic modulus are largely comparable with the experimental values, and the contrast between the solid elastic modulus and the unreinforced coal rock is improved, which shows that the integrity of coal rock can be improved by fracture grouting.