大倾角层状采动煤岩体重力-倾角效应与岩层控制
Gravity⁃dip effect and strata control in mining of the steeply dipping coal seam
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摘要: 大倾角煤层开采过程中,重力-倾角效应是导致细观层状煤岩体单元体主应力偏转和层间 接触面应力非均衡传递,介观层状采动模型优势破裂面方向偏移,宏观层状关键层区域迁移、岩体 结构异化的主要因素。 研究表明,在倾角 35°以上煤层采场中重力-倾角效应影响尤为明显:1 煤 岩组合界面倾角 35° ~ 60°时,非均衡传力特性逐渐凸显,界面附近煤岩体内应力传递方向发生偏 转,且偏转量随倾角增加逐渐增大;煤体破坏由压剪破坏转化为近平行于界面的滑移剪切破坏,煤 岩体的强度和弹性模量也随之减小。 2 改变了采场围岩采动应力路径演变规律,在采动应力驱动 下顶板的损伤变形与破坏运动存在明显的区域性和时序性。 3 诱发了大倾角采场顶板结构跨层 迁移转化、底板非对称破坏滑移、区段煤柱或煤壁局部-整体破坏,以上围岩失稳存在多尺度链式 时空关联性,特别是引发围岩灾变的采场关键岩块位置多变,形成采场围岩承载结构异化和泛化特 征。 理论与实践表明,重力-倾角效应作用下大倾角煤层岩层控制具有显著的多维度和多尺度特 点,突破传统开采方法与技术瓶颈,研发全新型成套装备是实现该类煤层安全高效开采的有效 途径。Abstract: Gravity⁃dip effect is a main factor leading to the deflection and non⁃equilibrium transfer of stress in the me⁃ so⁃layered coal⁃rock mass and the interlayer contact area,the directional offset of dominant fracture in the mesoscopic layered mining model, regional migration of key strata and the variation of rock structure in the macro⁃layered in the mining of steeply dipping coal seam. The research result shows that the gravity⁃dip effects are particularly obvi⁃ ous in the coal seam with dip angle above 35° including 1 the characteristics of non⁃equilibrium stress transmission at the interface of coal⁃rock combined body are obviously and the stress transmission near the interface is deflected and the amount of deflection increases gradually. The failure of coal mass is transformed from compression⁃shear to shear slip nearly parallel to the interface,and the strength and elastic modulus of coal⁃rock mass also decrease accord⁃ ingly. 2 The evolution law of the mining stress path in the stope has been changed,and the damage deformation and failure movement of the roof driven by the stress have obvious regional and time sequence. 3 It leads to the migration and transformation of roof structure,the asymmetric failure of floor slipping,and the partial⁃total failure of the coal pil⁃ lar or coal wall in the section in the steeply dipping coal seam. The instability of the surrounding rock above has a multi⁃scale chain spatiotemporal correlation and the key rock blocks in the stope that cause surrounding rock catas⁃ trophes are changeable,which results in the dissimilation and generalization of the bearing structure of the surrounding rock in the stope. Multi⁃dimension and multi⁃scale are the essential characteristics of strata control in the steeply dip⁃ ping coal seam under the action of gravity⁃dip effect. Breaking through the bottleneck of traditional mining methods and technologies,and developing new complete sets of equipment are effective ways to achieve the safe and effi⁃ cient mining of steeply dipping coal seam.