Study on coal pillar failure mechanism and surrounding rock control technology under influence of secondary mining

In view of the difficulty of controlling the roadway with severe coal pillar destruction under the influence of secondary mining, the No.11315 working face of Xiaojihan coal mine was taken as the engineering background, and the secondary mining faced by the working face was analyzed by using theoretical analysis and numerical simulation methods. The spatial structure of the overlying rock underwent the succession process of “O” shape changing to “厂” shape, which revealed the destruction mechanism of the surrounding rock affected by secondary mining, and proposed the differentiated surrounding rock support technology of the roadway, and adopted on-site monitoring and the reliability of measures was verified by field monitoring. The results show that: ①The control of coal pillar deformation and destruction under the influence of mining is an important guarantee to ensure the rapid excavation and safe recovery of roadway section. ②The coupling effect of stress superposition and high-strength mining, the unreasonable matching of roadway section and supporting parameters, and the incongruity of mining advance speed are the main factors leading to the instability of coal pillars. ③The strong deformation of the surrounding rock in the remaining section of No.11213 working face is effectively controlled by the combination of long anchor cable, high pre-stressed anchor cable and steel belt, which basically meets the use requirements of the roadway. However, due to the influence of mining stress, the roof on the side of the mining side sinks 0.3 m, the roof on the side of the coal pillar sinks 0.15 m, and the maximum roof subsidence is about 0.42 m. But the integrity of the surrounding rock of the roadway is good, which will not affect the transportation and the mining of the working face. This technology also provides a useful reference for the safe mining of similar working faces.