Slurry Leakage Channel Detection and Slurry Transport Process Simulation for Overburden Bed Separation Grouting Project: A Case Study from the Wuyang Coal Mine, Northern China

The 8006 working face at the Wuyang Coal Mine adopts grout injection into bed separation technology for surface subsidence control. Surface grout leakage occurred during the grout injection into the bed separation process of this working face. Grout leakage has adverse effects on the grouting filling effect, grouting cost and the environment. To determine the grout leakage channels and the slurry transport process, and to provide a theoretical basis for slurry leakage prevention and control, this paper first used 3D seismic exploration technology to identify the fault distribution characteristics of the study area, and then used COMSOL Multiphysics to carry out the numerical simulation of the grout transport process. The conclusions are as follows. Fifteen normal faults were identified in the vicinity of the 8006 working face. Among all the faults, the F1, F11, F18, F19 and F27 faults penetrate the surface and are the main channels for the grout to run to the surface. Based on the distribution characteristics of the faults and the spatial location relationship among the bed separation, faults and grout leakage points, the theoretical analysis of the leakage causes of each grout leakage point was carried out, and the main leakage channels of the grout injection into bed separation were proposed to be the bed separation and faults. The results of the numerical simulation of grout transport show that, as the permeability of the bed separation space and fault is much better than that of the surrounding rock, during the grout injection process the grout diffuses through the bed separation and fault in turn, and finally to the surface, where leakage occurs. The simulation results confirm that the main leakage channels for the grout are bed separation and faults.