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关键层动态下沉力学模型及时空演化规律研究

Study on dynamic subsidence mechanical model and time-space evolution law of key strata

  • 摘要: 合理的沿空掘巷滞后时间是缓解采掘接续压力、提高安全开采效率的关键。基于薄板理论引入麦克斯韦模型, 将时间参数与关键层运移建立联系, 结合数值模拟和工程实践对顶板破断动态下沉力学模型进行了论证。研究结果表明, 关键层上表面的应力集中是岩层破断的关键因素, 开采步距、时间与顶板在压实期的挠度成线性相关。数值模拟结果显示, 采空区压实期(30 d内)受残余采动影响, 关键层位移发育迅速, 采空区关键层中部应力由中心向边缘传递, 并最终集中在巷道的顶板。终采后采空区短时间内应力集中显著, 仍有发生动力灾害的倾向性, 短时间(60 d内)不具备掘巷条件。现场的矿压监测与微震数据从时间与空间角度侧面证明了开采动压的残余影响, 微震事件由深部向浅部逐步发展, 证实了采空区压实期内存在由应力集中到平衡的时空演化过程。以时间参数为连接点, 将关键层运动和巷道掘进时间有机的结合起来, 对沿空掘巷时机的选择有重要的理论指导意义。

     

    Abstract: Reasonable lag time of gob-side entry driving is the key to alleviate the mine pressure and improve the efficiency of safe mining. Based on the thin plate theory, the Maxwell model is introduced to establish the relationship between the time parameters and the migration of the key strata. The dynamic subsidence mechanical model of roof breaking is futher validated using the numerical simulation and engineering practice. The results show that the stress concentration on the upper surface of the key stratum is the key factor of rock breaking, and the mining step distance and time are linearly related to the deflection of the roof during the compaction period. The numerical simulation results show that the displacement of the key strata in the goaf during the compaction period (within 30 days) is rapidly affected by the residual mining, and the stress in the middle of the key strata in the goaf is transmitted from the center to the edge, and finally concentrated in the roof of the roadway. After stopping mining, the stress concentration in the goaf is significant in a short time, and there is still a tendency of dynamic disasters. Roadway excavation is not recommended in a short time (within 60 days). The mine pressure monitoring and microseismic data in the field proved the residual influence of mining dynamic pressure from the perspective of time and space. The microseismic events gradually developed from the deep to the shallow, which confirmed that there was a spatial and temporal evolution process from stress concentration to balance during the compaction period of the goaf. Taking the time parameter as the connection point, and combining the key stratum movement and roadway excavation time organically have important theoretical guiding significance for the selection of gob-side entry driving time.

     

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