含瓦斯煤的渗透率演化模型及其影响因素研究

为了研究瓦斯抽采过程中煤体渗透率的变化规律，推导建立了考虑吸附膨胀应力的含瓦斯煤的孔隙率模型和含瓦斯煤的渗透率演化模型，通过三轴应力条件下的含瓦斯煤渗透率实验对该模型进行了验证，两者吻合度较高。基于该模型研究了在孔隙压力卸载状态下煤的弹性模量、初始孔隙率、吸附性常数、吸附膨胀应力系数等对渗透率的影响规律。结果表明：在气体卸压过程中，煤的弹性模量越小，其渗透率的变化率波动就相对越大；煤的初始孔隙率越小，其孔隙率的变化率越大，进而渗透率的变化率也就越大；煤的吸附膨胀应力系数对渗透率的影响作用与Langmuir吸附常数类似，其值越大则气体解吸所引起的渗透率增大就越强，渗透率下降就越缓慢。

Study of Permeability Evolution Model for Coal Containing Gas and Its Influencing Factors

In order to study the change rule of coal permeability during gas extraction, the porosity model and permeability evolution model of gas-containing coal with adsorption expansion stress were deduced and established. The model was verified by the experiment of coal containing gas permeability under the condition of triaxial stress, and the experimental results matched with the permeability model. Based on this model, on the condition of gap pressure unloading, the effects of coal elastic modulus, initial porosity, absorbability constant and adsorption expansion stress coefficient on permeability were studied. The results show that in the process of pressure relief, the lower the coal elastic modulus, the larger the change rate of permeability; the smaller the initial porosity, the larger the change rate of porosity, and thus the larger the permeability change rate; the influence of coal adsorption expansion stress coefficient on permeability is similar to Langmuir adsorption constant, the larger the value, the stronger the permeability caused by gas desorption and the slower the permeability decreases.