超高压水射流割缝煤体卸荷松弛特征及与瓦斯运移的耦合机制

Permeability enhancement is crucial for the gas disaster control and gas high-efficiency recovery of the deep low-permeability coal seam. Aimed at solving the problems existing in the high-pressure waterjet slotting such as relatively small effective influencing range and large coal dust which is easy induce borehole blockage, the ultra-high pressure waterjet slotting technique was proposed, and the unloading-relaxation characteristics of coal slotted by the ultrahigh pressure water jet and its coupling mechanism with gas migration were also investigated. The main features of this project are: the impact dynamic property of the ultra-high pressure waterjet in the coal slurry is revealed via the water hammer pressure and stagnation pressure of the ultra-high pressure waterjet in the coal slurry. The division principle of the relaxation zone and the determination method of the sub-zone of the loaded coal are proposed via the deviation of the coal relaxation judgment criteria under the coupling of ultra-pressure impact and the confining pressure. The coupling mechanism of coal unloading-relaxation and gas migration is revealed via the investigation on the spatial-temporal evolution rules of coal deformation and gas pressure at the stages of ultra-high pressure waterjet slotting and gas drainage. The research achievements aims at providing a theoretical basis for the application of ultra-high pressure waterjet in the permeability enhancement, gas disaster control and gas high-efficiency recovery of deep coal seam.

增透是深部低透气性煤层瓦斯动力灾害防治和瓦斯高效抽采的关键。针对目前高压水射流割缝增透技术有效影响范围较小，煤屑粒度大而容易引起堵孔等问题，本项目提出超高压水射流割缝增透技术，并探讨了超高压水射流割缝煤体卸荷松弛特征及与瓦斯运移的耦合机制。本项目的主要特色为：通过探究超高压水射流在煤屑混浊液淹没下产生的水锤压力和滞止压力时空演化特征，揭示煤屑混浊液淹没下超高压水射流冲击动力特性；通过推演超高压冲击荷载和围压耦合下煤体松弛判据，提出受载煤体卸荷松弛区划分原则及分带确定方法；通过探究超高压水射流割缝及瓦斯抽采阶段煤体变形和瓦斯压力的时空演化规律，揭示煤体卸荷松弛与瓦斯运移的耦合机制。研究成果旨在为超高压水射流割缝技术在深部煤层增透及瓦斯动力灾害防治和瓦斯高效抽采方面的应用奠定理论基础。

瓦斯抽采是煤矿瓦斯动力灾害防控的有效途径，深部煤层以高地应力、高瓦斯压力、低透气性为主要特征。因此，增透是深部低透气性煤层瓦斯动力灾害防治和瓦斯高效抽采的关键。水力化技术是现场验证有显著增透效果的瓦斯强化抽采措施。本项目针对目前高压水射流割缝增透技术有效影响范围较小，煤屑粒度大而容易引起堵孔等问题，采用理论分析、物理试验、相似模拟、数值分析等方法综合探究了超高压水射流割缝煤体卸荷松弛特征及与瓦斯运移的耦合机制，取得一系列研究成果。开展了超高压水射流冲击动力特性物理和数值实验，揭示了靶板形状对超高压水射流冲击动力特性的影响规律，阐明了超高压水射流冲击动力特性；获得了煤层超高压水力割缝产生煤屑粒度的分布特征，构建了超高压水射流破煤深度的预测模型，阐明了射流冲击受载煤体诱导裂纹的形态特征，推演了射流冲击荷载和围压耦合下煤的松弛判据，获得了射流冲击下受载煤体的破损特征，提出了受载煤体卸荷松弛区划分方法，分析了射流参数对受载煤体卸荷松弛特性的影响规律，阐明了受载煤体卸荷松弛特性的围压效应；研发了含瓦斯煤割缝物理模拟试验系统，通过含瓦斯煤割缝物理模拟试验阐明了割缝作用下含瓦斯煤动态响应特征，凝练了割缝作用下含瓦斯煤动态响应的描述指标，揭示了瓦斯压力和射流参数对瓦斯运移的影响规律及作用机制，揭示了割缝煤体卸荷松弛与瓦斯运移的耦合机制。研究成果为超高压水力割缝技术在深部煤层增透及瓦斯动力灾害防治和瓦斯高效抽采方面的应用奠定理论基础。项目圆满完成了计划书中规定的研究内容，取得了预期研究成果，1人入选中国科协“青年人才托举工程”，3人晋升为副教授，毕业硕士2名，正在培养硕士1名；发表SCI论文19篇，其中高被引论文5篇；申请发明专利6项，其中授权4项；获得省部级科技进步二等奖2项。