煤层瓦斯抽采爆破卸压的钻孔布置优化分析及应用

为解决重庆地区低透气性松软煤层瓦斯抽采率低的难题，提出煤层底板预裂爆破卸压增透新技术，指出其增透过程分为爆破应力波与爆生气体共同作用形成裂隙贯通区和爆破空腔顶部煤岩体垮落形成卸压带2个阶段。借助数值模拟对不同孔距爆破应力波的动态演变规律进行研究，发现预裂爆破影响范围分为粉碎区和贯通区，其中粉碎区范围约为爆破孔直径的6倍，而贯通区的形成则主要受大直径控制孔反射形成的拉伸波作用，最终得到预裂爆破形成贯穿裂隙且保持与控制孔同高破坏区间的最优孔距为0.9 m，并将该技术应用于重庆–煤矿K4煤层底板巷预抽瓦斯工程。应用结果表明：瓦斯抽采纯量提高2.8倍，瓦斯抽采浓度提高3.75倍，而且在爆破完成20～30 d后瓦斯抽采效果明显提高。

OPTIMIZATION ANALYSIS OF DRILLING LAYOUT BASED ON BLASTING RELEASING PRESSURE AND ITS APPLICATION

To resolve the problems of low gas draining rate in soft coal seam with low permeability，a new technology of improving seam permeability by pre-splitting blasting on floor rock is proposed. The process of increasing permeability is divided into two stages：firstly forms penetrative cranny area in the interaction of blasting stress wave and detonation gas；secondly forms releasing pressure area by coal-rock caving at the top of the blast cavity. Dynamic variation of blasting stress wave of different drilling intervals was researched by numerical simulation；and it is found that the influence sphere of the pre-splitting blasting is divided into smash area and penetrative cranny area. The smash area is 6 times of the diameter of blast hole；and the tensile wave caused by large diameter pores reflection plays the major role to connect fissures. The optimal space of forming unicom fissures and keeping same high destruction scope with the control hole is 0.9 meter，which is applied to gas pre-drainage engineering in a bottom road of a Chongqing coal mine. The application result shows that the gas drainage flow is 2.8 times of the original，and the gas drainage efficiency is improved by 3.75 times of the original. Besides，it is obvious that the much better results was achieved 20–30 days after blasting.