Numerical simulation and engineering application of grouting reinforcement for surrounding rocks of chamber in deep of 1 000 m by L-shaped boreholes

This paper takes the L-shaped grouting borehole reinforced surrounding rocks of the large section chamber in a 1 000 m deep coal mine of Huaibei Mining Group as the engineering background. The porous media seepage theory is used to establish a fluid solid coupling model of continuous medium grouting with considerations of characteristics of high pressure and near horizontal penetration of rock strata. By using numerical simulation, the relationship between grouting pressure, slurry diffusion radius and rock permeability coefficient under the condition of isolated hole and three-hole grouting are obtained. Moreover, the diffusion law of pre grouting slurry in deep rock strata under high ground stresses is also revealed. The numerical simulation results show the linear relationship between the grouting volume and the grouting pressure, the permeability coefficient and grouting time, and square root relationship between the spread radius of the slurry and the grouting pressure, the permeability coefficient and the grouting time of isolated hole. The simulation results also demonstrate that under the same grouting parameters, the grouting volume of single hole of three-hole grouting is lower than that of the isolated hole grouting; and the slurry diffusion radius is greater than that of the isolated hole grouting. Based on above mentioned results, the grouting reinforcement scheme and reasonable selection of grouting parameters are decided; and the expected results are achieved. The in-situ applications can be a reference for the design and construction of similar projects in the future.