Application of comprehensive support techniques to roadway tunneling in vicinity of Ordovician carbonate confined aquifers under complicated tectonic conditions

Many technical problems are being encountered in roadway tunneling processes, especially at fault bundles and fault-dense zones and in vicinity of the Ordovician carbonate confined aquifers. These complicated tectonic conditions increase the difficulty of water inrush prediction and prevention. This paper takes the roadways tunneling at Jiangzhuang Coal Mine of Shandong Province, China, as a case study. The presence of fault bundles and fault-dense zones reduces the distance between roadway tunneling and the Ordovician carbonate confined aquifer and thus increases the potential risk of water inrush. Based on characteristics of the structure and water bearing formation and hydraulic conductivity in the fault zones, a trinity technique consisting of exploration, grouting, and supporting was proposed to ensure roadway safety tunneling. Underground mine seismic prediction (MSP), underground transient electromagnetic (TEM), underground drilling, numerical simulation evaluations and roadway grouting and supporting were used to understand, reduce, and mitigate the risk of poor stability and water inrush in the roadway tunneling process. Site construction has verified that the fault position was basically consistent with the results from MSP and TEM and drilling. Conclusions from risk evaluation and numerical simulation contributed to the grouting reinforcement and road supporting. Grouting reinforcement of the fracture zone reduced hydraulic conductivity, whereas the reasonable supporting was implemented for the weak part of the surrounding rock, which effectively controlled the roadway deformations. The comprehensive application of the trinity technique provided accurate and defensible geological data for roadway tunneling in this mining area, created favorable conditions for safe and efficient construction, and provided an important reference for research on similar type of roadway construction.