千米深井解放层开采卸压机理及效果分析以华丰煤矿为例

Pressure relief mechanisms and effects of liberation seam mining in 1000-m-deep coal mines: A case study of the Huafeng coal mine in Tai’an, China

  • 摘要: 解放层开采是煤与瓦斯突出、冲击地压等煤矿动力灾害防治的重要措施,以山东泰安千米深井华丰煤矿2613、2412工作面为背景,采用物理模拟与数值模拟相结合的方法,围绕解放层开采卸压机理、卸压效果评价等工程科学问题开展研究,明晰解放层开采后上覆岩层运动规律及矿压变化特征,厘清被解放层采动过程中采场应力与岩层位移演化规律,进而对解放层开采卸压效果和被解放层开采可行性进行指标化评价。结果表明:(1)解放层开采过程中,上覆岩层逐渐垮落形成漏斗状、非对称的多固支梁状结构,解放层开采结束后,采场左右两端分别形成对被解放层起永久性卸压保护的类悬臂梁结构,左右保护角分别为54°、60°。(2)解放层上覆岩层划分为“永久性卸压保护区”和“采空触矸压实区”,两种应力分布区对应解放层顶板应力最大值约20、36 MPa,对应被解放层内最大应力值约29、24 MPa,被解放层受两种应力区的叠加影响。(3)解放层开采结束后,工作面两端出现应力积聚,其他区域上覆岩层整体处于卸压状态,“采空触矸压实区”的持续发育已影响到被解放层,被解放层50~100 m区域沉降量约等于采高。(4)被解放开采过程中,覆岩板裂指数f为0.5,小于临界值0.7,不具有发生强矿压动力灾害的倾向,上覆岩层扰动范围较开采前变化极小,同时结合覆岩破坏形态,可知,被解放层开采始终处于解放层卸压范围内,解放层卸压充分,被解放层开采具有可行性。

     

    Abstract: Liberation seam mining serves as an important approach to the prevention of deep dynamic disasters such as coal and gas outbursts, as well as rock bursts. Based on the Nos. 2613 and 2412 mining faces of a 1000-m-depth coal mine in the Huafeng Coal Mine in Tai’an, Shandong, this study investigated the engineering scientific issues such as the pressure relief mechanisms and effect evaluation of liberation seam mining through physical and numerical simulations. As a result, it determined the movement law of overburden strata and the characteristics of underground pressure after the mining of the liberation seam and ascertained the evolutionary laws of the stope stress and stratum displacement during the mining of the liberated seam. Accordingly, it evaluated the pressure relief effect of the liberation seam mining and the feasibility of the liberation seam mining based on various indices. The results are as follows: (1) During the mining of the liberation seam, the overburden strata gradually collapsed, forming a funnel-shaped, asymmetric multi-end fixed beam structure. After the liberation seam mining, quasi-cantilever beam structures, which provided permanent pressure relief protection for the liberated seam, were formed at the left and right ends of the stope, with left and right protection angles of 54° and 66°, respectively; (2) The overburden strata of the liberation seam can be divided into the protection zone of permanent pressure relief and the compaction zone of gangue in the goaf. Corresponding to the protection zone and the compaction zone, the maximum stress on the roof the of liberated seam was about 20 MPa and 36 MPa, respectively, and the maximum stress within the liberated seam was approximately 29 MPa and 24 MPa, respectively. The liberated seam was subjected to the combined effects of the two stress zones; (3) After the mining of the liberation seam, stress accumulated at both ends of its mining face, and the overburden strata in other zones were in the pressure relief state. The continuous propagation of the compaction zone affected the liberated seam, whose subsidence at distances of 50-100 m from the liberation seam roughly equaled the mining height; (4) During the mining of the liberated seam, the overburden rock showed a palling index (f) of 0.5, which was less than the critical value 0.7, indicating that the dynamic disaster of high underground pressure was unlikely to happen in the liberated seam. Moreover, the overburden strata’s disturbance range varied slightly compared to that before mining. In combination with the failure morphology of the overburden strata, it can be concluded that the liberated seam was always within the pressure relief range during its mining. Therefore, due to the sufficient pressure relief of the liberation seam, the mining of the liberated seam is feasible.

     

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