厚松散层薄基岩综放开采覆岩破坏与地裂缝发育规律

Patterns of overburden failure and ground fissure development of thick loose layer and thin bedrock

  • 摘要: 开采引起的覆岩移动、破坏及地表变形裂缝的研究对于煤矿安全生产和采动损害保护具有重要意义。以郑煤集团某矿12203工作面为工程背景,采用理论分析、现场实测与数值模拟等方法分析了覆岩受采动影响演化机制,给出了回采距离与覆岩发育高度之间的函数关系以及覆岩充分破坏埋深与回采距离之间关系,分析了该地质情况下的地裂缝分布特征。结果表明:①厚松散层薄基岩覆岩破坏演化可分为开始、快速增加阶段、缓慢增加及稳定4个阶段;覆岩破坏高度与回采距离存在Logistic函数关系、与煤层厚度存在线性函数关系,该地质条件下覆岩充分破坏时,回采距离等于埋深;②覆岩裂隙演化中,基岩部分比松散层部分破坏程度剧烈;③地裂缝形态主要为拉伸裂缝与台阶裂缝,二者交互存在,工作面边缘裂缝整体随工作面回采呈现椭圆形—圆形—椭圆形动态变化;地裂缝发育超前工作面一段距离出现,动态超前裂缝距为84.07 m,动态超前裂缝角为73.15°。

     

    Abstract: Studies on mining-induced overburden rock movement, damage and surface deformation cracks are essential to the safety production of coal mines and mining damage protection. Taking the 12203 working face of a mine of Zhengzhou Coal Group as an example, this study analyzed the evolution mechanism of overburden rock affected by mining via theoretical analysis, on-site measurement and numerical simulation. We investigated the functional relationship between back-mining distance and height of overburden development and between sufficiently destructive depth of overburden and back-mining distance. Moreover, we analyzed the distribution of the ground cracks in this geological conditions. Results show that: ① The overburden destruction of thin bedrock in thick loose layer encompasses 4 stages: the beginning, rapid increase, slow increase and stabilization; the overburden destruction height shows a Logistic relationship with back-mining distance, and a linear relationship with the thickness of the coal seam. The back-mining distance is equal to the depth of burial when the overburden is sufficiently destroyed in this geologic condition. ② In the evolution of overlying rock fracture, bedrock is more violently damaged than the loose layer. ③ The cracks in the ground are mainly tensile cracks interacting with step cracks. The cracks at the edge of the working face show an "elliptical-circular-elliptical" dynamic variation pattern along with the back mining of the working face; the development of cracks in the ground occurs at a certain distance in front of the working face. The distance of the dynamically overrunning cracks is 84.07m, and its angle is 73.15°.

     

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