Stability analysis of complex intersection point and supporting technology of concrete-filled steel tube pier column group

Roadway intersection point are critical in underground mining and significantly impact mine safety. To address challenges such as large unsupported roof areas, concentrated stress, and difficult support in deep complex intersection point, a study is conducted at the −650 south wing track main roadway intersection point in Yangcheng coal mine. The research combines theoretical analysis, numerical simulation, indoor testing, and field application to evaluate intersection point stability and develop composite support technologies. By analyzing geological and mechanical parameters, a variable cross-section beam support model is established, and a formula for roof deflection is derived. The roof span is identified as the primary factor affecting intersection point stability, with a defined danger zone for roof subsidence. Two composite support schemes are designed: One using concrete-filled steel tube composite frame and another using concrete-filled steel tube pier column group. Simulations show roof subsidence of 100 mm and 150 mm, respectively, indicating both schemes effectively controlled subsidence and ensured safety. A comparative analysis base on construction difficulty, cost, and allowable deformation selected the concrete-filled steel tube pier column group scheme as optimal. Field implementation confirms significant improvements in roof and surrounding rock stability. Monitoring data after 2 years and 5 years show cumulative roof subsidence of 65 mm and 126 mm, respectively, lower than predictions for the concrete-filled steel tube support scheme. This demonstrates continuous stability, good support performance, simple construction, and economic feasibility, providing valuable insights for complex intersection point support.