高压注水煤层力学特性演化数值模拟与试验研究

NUMERICAL SIMULATION AND TEST STUDY ON MECHANICAL PROPERTIES EVOLUTION OF HIGH-PRESSURE WATER INJECTION COAL SEAM

为从细观上揭示高压注水过程中煤体裂隙扩展、应力场演化和高压水体在煤体中的渗流规律,利用考虑煤岩介质材料力学性质的非均匀性特点以及煤岩介质变形破裂过程中透气性的非线性变化特性特征并基于煤岩破裂过程固-流耦合动力学模型开发的RFPA2D-Flow软件系统对祁南煤矿721工作面煤层高压注水进行数值模拟,同时进行高压注水现场试验研究。数值模拟结果表明:在高压水挤压作用下,钻孔周围煤体逐渐损伤、破坏,裂隙进一步扩展,渗透能力大大增加,渗透系数最大可以由0.5m/d增加到1580.0m/d,在钻孔附近煤体处平均增加14倍。现场试验结果表明:采取高压注水工艺后,工作面前方煤体卸压带宽度由2.5m增加到3.5m,应力集中带向煤体深处推移1.0m,表明高压注水消突效果比较明显。

In order to get the rule of the cranny development,stress field evolution and the high-pressure water flowing in the coal seam from a microscopic view,besides fieldwork experimentation about the high-pressure water injection in the coal seam of working face 721 in Qinan Coal Mine,numerical simulation is studied by the RFPA2D-Flow code developed on the basis of the solid-flow coupling dynamic model,in which the heterogeneity characteristics of the mechanical properties of coal and rock and the nonlinear evolution characteristics of gas permeability in stressed coal and rock are considered and incorporated.According to the numerical simulation,the seepage ability of the coal body around the infusing borehole becomes greatly stronger as a result of its gradual damage and cranny expanding under the effect of the high pressure water.The value of the maximal seepage parameter of the coal body could increase from 0.5 m/d to 1 580.0 m/d and 14 times averagely in part.According to the fieldwork experimentation,after adopting the high-pressure water injection technology,the width of the stress-relaxed zone at the front of the working face increases form 2.5 m to 3.5 m and the stress concentration zone moves to the deeper position for 1.0 m,which shows that the effect of the high-pressure water injection on eliminating the coal and gas outburst is comparatively considerable.