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采动巷道软弱顶板塑性破坏演化规律与支护方案

Evolution law and control method of plastic zone in soft weak roof of mining roadway

  • 摘要: 软弱顶板条件下,巷道在原岩应力与采动应力叠加作用下会出现深度较大的塑性破坏区,引发剧烈的巷道围岩变形,甚至出现冒顶隐患。为掌握采动过程中塑性区在软弱顶板中的演化规律,以敏东一矿回采巷道为工程背景,系统研究了采动前后巷道围岩塑性区分布与演化特征,结果表明:在本工作面超前支承压力和上区段工作面采空区侧向支承压力的叠加影响下,采动巷道周边两个主应力比值急剧升高,同时,受邻近工作面覆岩移动影响,巷道围岩周边应力中的最大主应力方向也将发生大幅度的偏转。伴随着软弱顶板采动巷道围岩主应力大小和方向的不断演化,最大塑性破裂深度逐渐扩展且朝向顶板,塑性区扩展过程中会出现隔层分布现象,顶板剧烈变形主要是由塑性破坏产生,各层位顶板的破裂顺序依次为浅部塑性破坏、高位软岩塑性破坏和中位岩层的破裂。中部层位的断裂破坏一般滞后于高位穿透塑性区的形成。期间巷道围岩出现严重的非均匀性大变形,支护难度极大。据此提出了以注浆锚索为核心的顶板控制方法,注浆层位应主要集中在采动期间发生高位穿透塑性破坏的层位,注浆覆盖范围应不小于高位穿透塑性破坏的分布范围,巷道顶板变形监测结果表明,顶板控制效果良好,顶板未出现安全隐患且变形量在允许范围内。

     

    Abstract: Under the condition of weak roof, the mining induced roadway will have a large depth of plastic failure zone under the superposition of the original rock stress and the mining stress, which will cause severe deformation of the surrounding rock of the roadway, and even the hidden danger of roof fall. In order to grasp the evolution law of the plastic zone in the weak roof during mining, taking the mining roadway of Mindong No. 1 Mine as the engineering background, the distribution and evolution characteristics of the plastic zone of the roadway surrounding rock before and after mining have been systematically studied. The results show that:under the superimposed influence of the advanced supporting pressure and the side supporting pressure of the mined-out area in the upper section, the ratio of the two principal stresses around the mining roadway increases sharply. At the same time, the surrounding rock of the roadway is affected by the migration of the adjacent coal face. The direction of the maximum principal stress in the peripheral stress will also be largely deflected. With the continuous evolution of the magnitude and direction of the main stress of the surrounding rock in the mining roadway with a weak roof, the maximum plastic fracture depth gradually expands towards the roof. During the expansion of the plastic zone, the distribution of barriers will appear. The severe roof deformation is mainly caused by plastic failure. The rupture sequence of the roof of each layer is shallow plastic failure, high soft rock plastic failure, and middle rock rupture. The fracture failure of the middle layer generally lags behind the formation of the high-level penetrating plastic zone. During this period, the surrounding rock of the roadway appeared serious non-uniform large deformation, and it was extremely difficult to support. Based on this, a roof control method with grouting anchor cable as the core is proposed. The grouting layer should be mainly concentrated on the layer where high penetration plastic failure occurs during mining, and the grouting coverage should not be less than the high penetration plastic failure. The roof deformation monitoring results of the roadway show that the roof control effect is good, the roof has no safety hazards and the deformation is within the allowable range.

     

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