Objective and Method During the rapid excavation process using shield tunneling machines in coal mines, the advance detection of concealed geological anomalies encounters challenges of limited space and insufficient accuracy. To overcome these issues, this study investigated highly-located drainage roadway 3211 in the Tiandi Wangpo Coal Mine in Jincheng City, Shanxi Province using the long-distance tunneling and detection technology, the core of which is long directional boreholes combined with comprehensive borehole geophysical prospecting. This roadway is located in the roof of the No.3 coal seam, and it is necessary to conduct shield construction in the stable sandstone layer located from 15 m to 19 m above the coal seam. Therefore, highly accurate geological positioning is required. By establishing the technical system of long directional boreholes combined with comprehensive borehole geophysical prospecting and considering the actual geological conditions, this study conducted the numerical simulations of boreholes under heterogeneous media and cross-layer conditions. Accordingly, it analyzed the characteristics of geophysical prospecting signals under different geological scenarios, revealing the structural response patterns and the effectiveness of the technology. Specifically, the synergetic detection of low-resistivity anomalies, geological structures, and coal-rock interfaces was carried out using the retreating branch drilling technology, combined with borehole transient electromagnetic (TEM) method, borehole radar, and borehole gamma-ray (GR) logging.
Results and Conclusions A long horizontal borehole was drilled at a directional drilling site adjacent to it. This horizontal borehole consisted of one main borehole and two branch boreholes, with a cumulative directional run length of 594 m and a reaming length of 440 m. Concurrently, comprehensive borehole geophysical prospecting was conducted. The detection results reveal the presence of one major low-resistivity anomaly and three structural anomalies. Furthermore, the spatial distributions of four sandstone intervals were accurately characterized. Field verification shows that the positioning deviations of the sandstone horizontals ranged from 0.01 m to 1.02 m, suggesting a significantly improved accuracy of geological interpretations and an effectively reduced multiplicity of solutions. The long-distance tunneling and detection technology applied in this study enables the synergy between continuous shield tunneling and comprehensive borehole detection, enhancing the accuracy and efficiency of advance detection under complex geological conditions while also providing significant technical support for safe and efficient shield tunneling in coal mines.
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