The Location Optimum and Permeability-Enhancing Effect of a Low-Level Shield Rock Roadway

High (low)-level roadways are effective gas control measures for coal seams with high outburst potential and low permeability. The spatial location of the low-level roadway directly determines the gas drainage efficiency and can affect the success of the whole engineering project. Currently, determining the location of a low-level roadway is based mostly on empirical engineering analogies and lacks relevant theoretical support. In this work, based on the Ji-15-24080 engineering project at the No. 10 Coal Mine of Pingdingshan Tian'an Coal Industry Co., Ltd., a numerical model for the location of a low-level roadway was established using ANSYS numerical software to analyze the stress distribution in the rock surrounding the conveyor roadway for the mining face and assess the permeability-enhancing effect of the low-level roadway when it is placed at different locations. A location directly beneath the conveyor roadway was found to provide a good location for a low-level shield roadway. In addition, a quantitative distance between the conveyor roadway and the low-level roadway can also be determined. These optimization results were then directly applied in the field. Relevant industrial field tests were conducted to determine fracture development, gas pressure and stability of the surrounding rock. The field test results confirm that the proposed location for a low-level shield roadway is reasonable. We recommend that when the low-level shield roadway is placed directly beneath a conveyor roadway, it should be within 50m of the working face, and an effective support structure should be employed to support the rock surrounding the conveyor roadway to ensure the stability of the rock. We further recommend that, in the area in front of the working face, particularly within 25m of the working face, densely distributed gas drainage boreholes should be drilled to drain gas from the coal seam to reduce the gas pressure and lower the outburst risk. The results of this work will provide guidance for similar engineering projects to determine the location of a low-level roadway and to ensure gas control.