高强度采动地裂缝形成与演化规律及减损方法

Formation and evolution law of high-intensity mining ground fissures and damage reduction method

  • 摘要: 神东矿区高强度开采造成覆岩和地表损伤严重,威胁矿区生态安全。科学认识地裂缝演化规律和采动覆岩−地表损伤传导机理是实现井下安全减损开采、含水层自修复与地表生态环境治理的关键。综合采用现场实测、理论分析、数值模拟和物理模拟等手段,首先分析了工作面矿压规律、覆岩结构特征和地裂缝宽度变化规律。然后考虑周期来压大小和覆岩结构特征,详细阐明了地裂缝宽度的动态发育过程呈“M”型双峰形态,深刻揭示了地裂缝产生机制。最后从工作面、覆岩和地表3个方面提出了采动损伤系统减损方法。研究表明,双关键层结构工作面存在大小周期来压,亚关键层破断影响小周期来压,主关键层失稳控制大周期来压,大周期来压步距为小周期来压步距的 2~4 倍,大周期来压载荷为小周期来压载荷的1.07~1.13倍;中部动态裂缝呈“双峰”分布,具有自修复现象,边缘裂缝呈“单峰”分布,对地表破坏性更严重;加快推进速度可减弱采动损伤程度、加快顶板下沉速度;从关键岩块回转下沉方面解释了中部动态地裂缝张开—闭合—张开—闭合演化过程;揭示了高强度开采导致压力拱结构失稳是地裂缝产生的根本原因;提出了推进速度优化、注浆成拱减损与地裂缝分区治理的系统减损方法。研究成果为煤炭规模化开采与生态环境保护相协调发展提供了理论与技术支撑。

     

    Abstract: High-intensity mining in the Shendong mining area has caused serious overburden and surface damage, which threatens the ecological security of the mining area. Scientific understanding of the evolution law of ground fissures and the conduction mechanism of mining induced overburden-surface damage is the key to realize underground safety mining, aquifer self-repair, and surface ecological environment treatment. Comprehensively adopting on-site measurement, theoretical analysis, numerical simulation, and physical simulation methods, the mining pressure law of the longwall face, the characteristics of the overburden structure, and the variation law of the width of ground fissures were first analyzed. Then, considering the magnitude of cyclic pressure and the characteristics of overburden structure, the dynamic development process of ground fissure width was explained in detail in an “M” - shaped bimodal shape, and the generation mechanism of ground fissures was revealed in depth. Finally, a reduction method for mining damage system was proposed from three aspects: working face, overlying rock, and surface. Finally, a methodology for the systematic reduction of mining damage was proposed in terms of the longwall face, overburden and surface. The result shows that there are large and small cyclic pressure in the longwall face of double key layer structure, the breakage of sub-critical layer affects the small cyclic pressure, and the instability of the main key layer controls the large cyclic pressure, the step of large cyclic pressure is 2-4 times of that in the small cyclic pressure, and the load in the large cyclic pressure is 1.07-1.13 times of that in the small cyclic pressure; The dynamic cracks in the central region exhibit a “bimodal” distribution with self-healing phenomena, while the boundary cracks exhibit a “unimodal” distribution, which is more destructive to the surface; Accelerating the advancement speed can reduce the extent of mining damage and accelerate the rate of roof subsidence; The dynamic cracks in the centre opening-closure-opening-closure evolution process was explained in terms of rotary subsidence of the key block; The instability of the pressure arch structure caused by high-intensity mining is the fundamental reason for the generation of ground cracks; A systematic damage reduction method of advancement speed optimization, grouting arch reduction damage and zoning treatment of ground cracks was proposed. The research results provide theoretical and technical support for the coordinated development of large-scale coal mining and ecological environmental protection.

     

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