Study on the Application of Comprehensive Gas Control Technology for Source-Separated Three-Dimensional Gas Extraction in Large Mining Faces.

In order to address the challenges of high gas outburst in both the adjacent layers and the coal seam itself faced by large mining faces, a study on the three-dimensional extraction of gas from different sources at a large mining face was conducted. Based on the research on the instability and failure characteristics of the overlying strata during mining and the gas outburst characteristics at the large mining face, a source-separated three-dimensional gas extraction system was established. A comprehensive gas management model for the large mining face, involving the extraction of gas from different sources, has been proposed. This model is suitable for gas management at large mining faces where there is a high gas emission in the adjacent layers and a complex structure of the coal seam. Through numerical simulations using FLAC, the height of the "three zones" of the overlying strata and the range of the floor fracture zone at the large mining face were obtained, providing guidance for the layout of high-level drainage roadway, low-level drainage roadway, and floor drainage roadways. Following the coordinated layout of high-level drainage roadway, inclined high-level drainage roadway, and low-level drainage roadway, the reasonable optimization of gas extraction techniques in the coal seam, and the reasonable arrangement of floor rock predrainage roadways, the methane capture efficiency of the large 15115 mining face reached 87.5%. The methane concentrations at the upper corner and in the return airflow being below 0.8%. The methane concentration extracted from the coal seam boreholes is 2.9 times higher than that from the ordinary mining face after adopting "ordinary boreholes + large-diameter boreholes". This gas management model effectively addresses the gas-related challenges of the large mining face and improves the gas extraction rate, achieving harmonious mining and extraction of coal and methane.