Study on the Fracture Characteristics of Sandstone and the Effect of Grouting Reinforcement under Different Confining Pressure

Grouting is an important method to control the stability of underground engineering surrounding rocks, and the study of the strength, deformation characteristics and strength recovery rate of grouting reinforcement of fractured rocks under different confining pressures is an important reference value for engineering practice. In this paper, the time-varying characteristics of different concentrations of oxalic acid and different volume ratios of urea-formaldehyde resin slurry were tested. It was found that the lower viscosity period and initial setting time of the slurry were shorter when the oxalic acid concentration was higher at the same volume ratio; the longer the lower viscosity period and initial setting time of the slurry were when the volume ratio of the slurry to oxalic acid was larger at the same oxalic acid content. The changes of force characteristics, destabilization characteristics, strength characteristics, strength recovery rate and fractal dimension of yellow sandstone and yellow sandstone grouting reinforcement with confining pressure were investigated by experiments. The results indicate that the fractal dimension decreases with the increase of the confining pressure, while the strength and strength recovery rate of the grouting reinforcement are proportional to the confining pressure, and the recovery rate can reach 27% under 8 MPa confining pressure, and the cohesion recovery rate is about 16%.