基于等效深度作用的采动含瓦斯煤体劣化失稳致灾机制

There are widely thick-hard rock strata that control the movement, deformation and stress distribution of the surrounding rock in the coal-bearing strata in China. The practice proves that the underlying coal and rock mass show the similar mechanical characteristics with the mass of the larger depth for the superposition of the impact load and concentrated stress after the mining-affected thick rock roof strata are broken and thus the coupled dynamic disasters including rock burst, coal and gas outburst and abnormal gas emission are serious. By the methods of theoretical analysis, laboratory tests, numerical simulation and field verification, the equivalent-depth effects of the thick-hard rock strata breakage on the underlying coal and rock mass are researched and then the mechanical experiment paths are proposed; the damage and permeability evolution laws of the gassy coal are obtained after the synchronous stress-damage-permeability experiments based on the mechanical experiment paths; then the gas-solid coupling model and energy equation during the mining gassy coal mass damage and instability were established and the occurrence conditions of the coupled dynamic disasters are analyzed quantitatively in order to reveal the inducing-disaster mechanism base on equivalent-depth effects. The above researches could lay the theoretical foundation for the prevention of dynamic disasters under thick-hard rock strata and be of scientific significances for guaranteeing safe and efficient mining of underlying coal seams.

我国煤系地层中广泛存在着厚硬岩层，控制着采场围岩的移动变形和应力分布规律。实践证明，受采动影响的厚硬顶板岩层失稳破断后，所产生的冲击载荷与集中应力的叠加作用使得下伏煤岩体表现出与更深处煤岩体类似的力学特征，进而导致冲击、突出、瓦斯异常涌出等煤岩瓦斯动力灾害严重且往往复合发生。项目采用理论分析、实验室试验、数值模拟和现场验证相结合的方法，研究厚硬关键层破断对下伏采动煤岩体的等效深度作用机制，并提出相应的力学试验路径；在此基础上开展含瓦斯煤体应力-声发射-渗透同步试验，获得含瓦斯煤体损伤破坏与渗透演化规律；进而建立采动含瓦斯煤体损伤破坏过程的气固耦合模型和劣化失稳能量方程，定量化分析煤岩瓦斯复合动力灾害发生条件，揭示基于等效深度作用的采动含瓦斯煤体劣化失稳致灾机制。上述研究旨在为厚硬岩层下伏煤岩瓦斯动力灾害防治提供可靠的理论基础，对保障厚硬岩层下伏煤层安全高效回采具有重要的科学意义。

我国煤系地层中广泛存在着厚硬岩层，受采动影响的厚硬岩层失稳破断后，所产生的冲击载荷作用使得处于中深部的下伏煤岩体表现出与深部煤岩体类似的力学特征，易导致下伏煤层发生煤岩瓦斯动力灾害。项目采用理论分析、实验室试验、数值模拟和现场验证相结合的方法，研究了厚硬关键层破断对下伏采动煤岩体的等效深度作用及采动含瓦斯煤体劣化失稳致灾机制。主要结论如下：1）建立了厚硬关键层结构见方失稳模型，分析了厚硬关键层的应力分布特征和失稳破断规律，计算获得了厚硬关键层结构失稳的能量积聚-传播-耗散规律，揭示了厚硬关键层破断对下伏采动煤岩体的等效深度作用机制，提出了基于能量条件的致灾关键层判别准则；2）开展了等效深度作用下含瓦斯煤体应力-声发射-渗透同步试验，研究了不同加卸载方式下煤体损伤破坏形态与破断角变化规律，分析了煤体损伤与渗透协同演化特性，提出了造成塑性变形煤体损伤-渗透特性差异的本质原因，获得了加卸载方式对含瓦斯煤损伤-渗透演化特性的影响规律；3）推导了基于声发射特征和差应力比的含瓦斯煤损伤变量表达式，构建了含瓦斯煤统计损伤模型，分析了基于损伤扩容的塑性变形煤体孔隙率变化规律，建立了塑性变形煤体渗透率演化模型，揭示了等效深度作用下含瓦斯煤损伤-渗透演化机制；4）计算了厚硬关键层下伏含瓦斯煤体的灾变潜能与灾变耗能，提出了煤岩瓦斯动力灾变的能量判据与必要条件，揭示了等效深度作用下煤岩瓦斯动力灾变机制，进而提出了相应的工程防治方法。研究结果可为厚硬岩层下伏煤岩瓦斯动力灾害防治提供可靠的理论基础，对保障厚硬岩层下伏煤层安全高效回采具有重要的科学意义。