挤压断裂带含瓦斯煤体失稳破坏机理研究

In compressive fault zone, the gassy coal measure is seriously damaged due to the action of squeezing and shearing during tectonic movement and has the characteristics of high tectonic stress, high gas content and strong sorption capability. This has brought great challenge for the coal mine production safety. In order to reveal the instability mechanism of gassy coal of compressive fault zone, the microstructure and mechanical damage of gassy coal of compressive fault zone under static loading are firstly studied based on the evolution characteristics of permeability and elastic wave velocity. Then the instability mechanism of this gassy coal excited by dynamic loading is investigated to reveal the impact of mining disturbance on stability. In detail, the deformation and mechanical characteristics under the combined action of dynamic loading, static in-situ stress and gas pressure are studied, and a fatigue model is developed to describe the fatigue failure of gassy coal of compressive fault zone under field alternating loading. Subsequently, the methane desorption and seepage behavior of this gassy coal under the coupling of external stress and gas are characterized to identify the gas source of coal and gas disaster. At last, the architecture of gassy coal in compressive fault zone, the stability zoning characteristics by mining disturbance as well as impact factors are investigated. The change of permeability with the distance to the fault is functionally determined and the overlapping locality of fracture zone of compressive fault and mining disturbed zone is identified. A non-dimensional criterion is finally proposed to evaluate the stability of gassy coal of compressive fault zone. This study can provide new theoretical basis for coal pillar optimization and key control of regional coal and gas disaster in compressive fault zone.

挤压断裂带含瓦斯煤体受挤压、剪切作用产生了构造软煤，并具有高构造应力、高瓦斯含量、强瓦斯吸附解吸性能的特点，给煤矿安全生产带来了极大地挑战。本项目以挤压断裂带含瓦斯煤体失稳破坏机理为研究目标，首先研究其细观结构特征，获得静态加载条件下基于渗透率、弹性波速的力学损伤规律；其次，研究动态加载条件下该煤体的变形及力学特性，建立交变载荷下的挤压断裂带含瓦斯煤体疲劳损伤力学模型，以期揭示采掘扰动诱发煤体失稳的机理；然后，研究应力-瓦斯耦合作用下的瓦斯解吸及渗透规律，以确定灾害过程中的瓦斯来源；最后，研究挤压断层自身煤岩结构分区、采掘扰动围岩稳定性分区特征及其影响因素，获得渗透率随距离断层远近的变化关系，判别采掘扰动区与断层自身裂隙发育区叠加的临界位置，提出挤压断裂带含瓦斯煤体稳定性的无量纲判据。该研究将为优化断层保护矿柱、煤岩瓦斯灾害区域重点防治提供新的理论依据。

煤岩瓦斯动力灾害是煤的物理力学性质、地应力、瓦斯等因素综合作用下所发生的一种严重的矿山工程地质灾害，且与区域地质构造有着显著的关。挤压断裂带煤体瓦斯富集、区域地应力异常升高，在采掘扰动下很容易发生动力灾害。本项目针对挤压断裂带含瓦斯煤体易于发生煤岩瓦斯动力灾害的特点，研究煤体在瓦斯耦合条件下的失稳破坏的机理。通过实验室实验、理论等相结合的研究方法，开展了煤体细观结构特征研究，分析了静态加载条件下含瓦斯煤体力学损伤规律及强度特性度，揭示了工作面开采扰动下含瓦斯煤体力学特性；研究了外界扰动和瓦斯压力共同作用下煤体细观结构、弹性模量、泊松比等损伤演化规律，揭示了含瓦斯煤体疲劳损伤机理。揭示了不同粒度煤粉瓦斯解吸规律研究。研究了工作面前方支承压力区煤体孔隙压力对煤岩损伤的作用机制，揭示了在受载变形过程中孔隙压力对地应力方位及大小的改变规律，得出了挤压断裂带含瓦斯煤体失稳的物理力学机制。即在采掘扰动下，距离工作面较远的煤体首先经受低幅值外载作用，孔隙流体的排出导致煤体沿水平方向产生收缩变形，一方面会减小煤层局部的渗透性；另一方面，会降低煤层水平应力从而降低煤岩的三轴抗压强度。而排出的孔隙流体在煤体中发生局部迁移和富集，当流体富集区域经受后期高幅值外载作用时容易形成局部高孔隙压力，进而改变煤层受力状态，加速煤岩动力灾害的孕育，并加剧煤体在动态失稳中粉末化。同时，研究发现，断层岩石的裂纹密度随着受载水平增加而呈现指数增长规律，且微裂纹方向逐渐向载荷方面偏移。瓦斯的存在加速了断层区应力旋转现象，且断层核附近的应力旋转速率大于损伤区边界处的应力旋转速率。该研究为煤矿优化断层保护矿柱、挤压断裂带煤岩瓦斯动力灾害区域重点防治等提供理论依据。