考虑串孔影响的穿层水力扩孔合理冲煤量研究

在煤层增透方面，穿层水力扩孔冲出煤量主要依据经验以及遵循“能冲尽冲”的原则，致使串孔现象严重，针对这一问题，采用理论分析、数值模拟结合工程试验的方法，阐明了串孔致因机理和串孔前后扩孔孔硐内负压损失分布特征，构建了考虑吸附膨胀应力和Klinkenberg效应的扩孔孔硐附近煤体瓦斯流动流-固耦合数学模型，利用Comsol软件，模拟了不同冲煤量下扩孔孔硐附近煤体所受应力分布和煤体渗透率的变化情况。研究结果表明:随着煤体不断被冲出，孔硐有效抽采半径相对变化率呈现衰减趋势；扩孔孔硐附近最大主应力呈现先急剧减小再增大，然后降低直至原始应力大小的趋势；渗透率的变化趋势与最大主应力恰好相反；扩孔孔硐周围煤体渗透率的增加主要受煤体的径向位移所控制，孔硐周围煤体大幅径向位移会产生串孔现象，渗透率虽得到大幅度提高，但瓦斯抽采效果和安全采掘很难保证，需要厘定出水力扩孔合理冲出煤量。

Research on reasonable coal flushing quantity of perforated hydraulic reaming considering influence of string hole

In the aspect of permeability improvement of coal seam, the coal flushing quantity of perforated hydraulic reaming mainly depends on the experience and follows the principle of “as flushing as possible”, which leads to the serious phenomenon of string hole. Aiming at this problem, by means of theoretical analysis, numerical simulation and engineering test, the causation mechanism of string hole and the distribution characteristics of negative pressure loss in the reaming hole chamber before and after the string hole were expounded. A mathematical model of fluid solid coupling for gas flow in the coal body around the reaming hole considering the adsorption expansion stress and Klinkenberg effect was constructed, and the variation of stress distribution and coal permeability of the coal body around the reaming hole chamber under different coal flushing quantities was simulated by using the Comsol software. The results showed that with the continuous flushing of coal body, the relative change rate of effective extraction radius of hole chamber decreased. The maximum principal stress around the reaming hole chamber decreased sharply first and then increased, and then decreased to the original stress, and the change trend of permeability was opposite to that of the maximum principal stress. The increase of permeability of coal body around the reaming hole chamber was mainly controlled by the radial displacement of the coal body, but the large radial displacement of the coal body around the hole chamber would produce the phenomenon of string hole, and although the permeability was greatly improved, the effect of gas extraction and safe mining was difficult to ensure, so it was urgent to determine the reasonable coal flushing quantity of the hydraulic reaming.