采动煤岩渗透率演化模型及数值模拟

为描述采动煤岩渗透率演化过程，引入强度退化指数，基于Hoek-Brown强度准则，建立了考虑围压影响的煤岩应变软化力学本构模型。给出了体积应变和渗透率的关系方程，结合应变软化模型建立了采动煤岩渗透率演化模型，并在FLAC下予以实现。通过数值模拟研究了不同围压下圆柱岩样的峰后应变软化力学行为和某煤矿工作面开采过程中煤岩的渗透率演化过程，结果表明：（1）该模型能较好地反映围压对煤岩峰后应变软化行为的影响；（2）随着工作面推进，越来越多的煤岩单元破坏，渗透率也不断增长，逐渐成为瓦斯等流体运移的主要通道。（3）模型能再现采动煤岩渗透率演化的动态过程，从而为煤与瓦斯共采、煤层瓦斯抽放和瓦斯灾害防治提供指导。

Permeability evolution model of mined coal rock and its numerical simulation

To describe the permeability evolution process, the strength degradation index is introduced based on Hoek-Brown strength criterion; a strain softening constitutive model with confining pressure for coal rock is established. The relationship between volumetric strain and permeability is given; and combining the strain softening model, a permeability evolution model is proposed. Then the model is implemented in FLAC. Numerical cases are simulated including the post peak strain softening behaviors of a cylinder rock sample under different confining pressures and the permeability evolution of overburden rock during mining, The results show that: (1) The effects of confining pressure on post peak strain softening mechanical behaviors and permeability evolution can be better reflected by the model proposed. (2) With the advancing of working face, more and more coal rock elements fail and the permeability also increases. Gradually the main channels of gas flow appear. (3) The model is capable of reproducing the permeability evolution process of mining coal rock, poviding a reference for the practice of simultaneous extraction of coal and gas, methane recovery and gas disaster prevention.