Mining response and dynamic reinforcement for narrow coal pillar next to goaf in working face 1402 of Xin’an coal mine

With the increase of integrating coal mines under national coal de-capacity policy, the mining instability phenomenon of narrow coal pillar next to goaf is increasingly prominent, which has seriously restricted the safety and efficient production in coal mines. Therefore, stability control engineering problem of narrow coal pillar next to goaf, near No.5 drilling field on air return roadway of repeated mining face 1402 in Xin'an coal mine was as study object, a method of combining numerical simulation and theoretical analysis was used to explore the mining disturbance response characteristics of narrow coal pillar stability next to goaf, near No.5 drilling field, then dynamic grouting reinforcement technical scheme for narrow coal pillar next to goaf, near No.5 drilling field was put forward and field application and effect test were carried out. The study results showed that: the stability of narrow coal pillar next to goaf, near No.5 drilling field was slightly affected by air return roadway excavating in working face 1402. While in the mining period of working face 1402, within the range of 18-6 m from No.5 drilling field, the concentrated vertical stress in narrow coal pillar next to goaf gradually transformed from asymmetrical saddle-shaped distribution into arched distribution. When working face was 6 m away from No.5 drilling field, the superimposing vertical stress in narrow coal pillar next to goaf exceeded coal strength, and the plastic zone was completely connected, which was extremely easy to failure and even destabilization. In the field, MP364 type grouting material and special grouting equipment were applied to conduct dynamic grouting reinforcement 5 m of front area and rear area in narrow coal pillar near No.5 drilling field, which was always 10 m ahead working face. Good grouting curing effect of coal pillar next to goaf was verified through the deep hole peeping and gas monitoring, and ensured the working face mined safely, provided a significant reference for similar condition of coal pillar stability control in integrating coal mines of our country.