动力扰动诱发巷帮煤体冲击矿压机制研究

On the mechanism of the rock-bursts at the roadway sides induced by the dynamic disturbance

基于煤岩介质的动力扰动载荷理论,对动力扰动诱发深埋巷道帮部煤体冲击矿压机制进行了研究。利用FLAC3D软件数值模拟了深埋巷道围岩,尤其是帮部煤体对动力扰动的响应。结果表明,随扰动载荷增加,巷道围岩速度、应力和位移均产生了急剧变化,两帮煤体发生严重拉伸破坏,塑性分布区明显扩大。始终维持极限平衡状态的深埋巷道帮部煤体在动载反复扰动下容易产生超高应力集中,帮壁煤体发生破坏,形成应力转移,导致深部煤体由三向应力状态迅速转化为双向或单向应力状态。同时,动载产生的强烈振动改变了顶底板对煤层的约束条件,降低了摩擦阻力,诱发深埋巷道帮部煤体冲击矿压。根据现场统计,大安山矿+550 m西二褶曲轴10下槽回风顺槽动力扰动诱发的冲击矿压为35次,约占冲击显现总数的93.3%。

The paper is aimed at looking for the mechanism of the rock-bursts on the roadway sides induced by the dynamic disturbance. Based on the theory that has been put forward, it is the stress wave that induces the rock-bursts at the deep roadways in the coalmines. In the same way, we have worked out a numerical simulation under different dynamic disturbances in response to the surrounding rocks, especially to the sides of a deep roadway by using a software known as FLAC 3D . It is supposed that with the increase of the disturbance load, such forces as the speed, the stress and displacement of the surrounding rocks, may all have been changing dramatically. In the process of the dramatic change, the two sides of the coal seam tend to break dramatically, too. Moreover, when the disturbance load reaches a certain degree, the complex superposition of the disturbance stress and the high stress in the surrounding rocks would make the coal sides break and go beyond their maximum limits. And, speaking in a more detailed way, there exist a lot of things that would push the roadway instability and deformation, and the tensile stress would in turn be transformed from the stress wave through the innumerous reflections on the surface of the roof into the coal spalls, so as to release large amounts of elastic energy, and eventually into the coal rock bursts. According to the investigations on the spot, there took place 35 times of rock-bursts induced by such dynamic disturbance in the return air roadway in the depth of＋550 m in the Xierzhe Shaft 10, in Daanshan Mine, which accounts for 93.3% of total such disturbance bursts. The investigation results we have gained show that, it would be easy for the deep roadway sides of the coal seam that has always been always keeping highly unstable state to result in such ultra-high stress and cause the spallation damage on the roadway sides. At the same time, the micro damage accumulation and the stress concentration pressure may also lead to such roadway sides or near the roadway sides under the repeated dynamic disturbances. What is more, the quantitative changes are also likely to lead to the qualitative changes, with the coal cracks expanding abruptly. And, eventually, strong vibrations generated by such dynamic loads would be able to overcome the friction on the surface of the fracture, change the constraint conditions of the roadway roof and bottom on the coal seam, instantly break the stress balance of the roadway sides and in turn lead to the rock-bursts in the deep roadway sides.