Multifactor Sensitivity Study on Fault-Induced Deflected Diffusion of Splitting Grout in Rock Formation

Long-borehole grouting has become a preferred method for controlling water damage to the coal mine floor. Affected by a complex geological structure, the actual grouting treatment process cannot respond well to design requirements from the deflection failure of fracturing diffusion. In this study, a numerical grouting model was established considering seepage and fracturing diffusion coupling to reveal the grouting deflection response, which was validated with grouting experimental results. The orthogonal sensitivity calculations of five factors from fault physical characteristics and geostress were conducted. The results indicate that numerical methods can match well with experimental results. Under the given grouting engineering conditions, the influence distance of the fault on grouting-splitting diffusion reaches 40 m. The explanation verified the microseismic response characteristics of grouting differences and deflection in the X4-8 hole grouting project. Affected by fault and geostress, grouting diffusion patterns are categorized into five types: circular diffusion, horizontal elliptic diffusion, vertical elliptic diffusion, partially induced diffusion, and completely induced diffusion. The two most significant factors influencing the effective diffusing area are the vertical distance between the grouting hole and the fault and the elastic modulus of the fault. These are followed by the stress ratio between vertical and horizontal, fault dip, and horizontal fault throw. The stress ratio between vertical and horizontal determines the fracture initiation direction of grouting-splitting, while the primary factor for fault-induced fracture deflection is the elastic modulus of the fault. This study provides valuable guidance regarding the different parameter of grouting design considering the geological faults.