孤岛充填工作面初采致冲力学机理探讨

孤岛充填工作面由于要控制采空区顶板下沉而导致工作面煤体支承压力分布变得复杂，造成冲击危险性评估方法不同于常规工作面，为了提供充填回收孤岛煤柱采场围岩稳定性分析的理论依据，以山东某矿孤岛充填工作面为背景，通过对孤岛煤柱覆岩结构及演化特征进行研究，建立了孤岛充填开采条件下“充填体-煤柱-顶板”力学模型，得到了充填工作面超前支承压力估算方法，提出了孤岛充填工作面煤体冲击失稳的判据。研究结果表明:① 采空区充填效果决定了上覆岩层下沉运动的空间以及与两侧采空区覆岩发生水平联动的范围，是影响孤岛煤柱覆岩结构演化特征的关键因素;② 受回采巷道切割及大直径钻孔卸压工程的影响，工作面煤体承载能力呈现明显的区域差异性，弹性承载区煤体是上覆岩层传递载荷的主要承载体，工作面开采边界条件和回采巷道布置方式是影响工作面煤体静态稳定性的主要控制因素;③ 充填材料受到采空区顶板下沉运动中压应力作用下发生压缩变形，当顶板和充填材料达到力学平衡时顶板下沉运动终止，充填材料固结体压缩变形量和弹性模量是影响工作面煤体动态稳定性的主要控制因素;④ 决定孤岛充填工作面冲击危险性的关键因素是工作面弹性承载区煤体静态支承压力和采空区顶板下沉量。针对这类冲击地压的致灾机理，通过煤层注水、高压水压裂及优化工作面布置以降低工作面弹性承载区煤体静态支承压力和提高采空区充填率、优化充填材料固结体压缩性能以减小采空区顶板下沉量等措施，可有效降低孤岛充填工作面的冲击危险性。该研究成果可为类似开采条件下冲击地压的防治提供参考。

Study on mechanical mechanism of rock burst at isolated backfilling working face during primary mining

To control the roof subsidence in gob,the longwall panel is generally backfilled after mining.The rock burst risk evaluation method of the island backfill longwall panel (IBLW) is different from that of the normal longwall panel due to the complex distribution of its abutment pressure.In order to provide a theoretical basis for the stability analysis of surrounding rock during the retrieval of IBLW,by establishing a “filling body island pan el roof ” model based on the evolution of the overburden structure,the evaluation method of abutment pressure in front of the working face and the criterion for rock burst were obtained.Research results are as follows:(1) The subsidence of the overburden strata above IBLW and the horizontal associated movement of the overburden strata above the gobs on both sides were determined by the filling effect which was also a key factor of overburden structure evolution.(2) Influenced by roadway tunneling and the de stressing of large diameter boreholes,the obvious regional difference of bearing capability of IBLW was observed.The load transferred from the overburden strata was mainly born by the elastic area of IBLW.The stability of IBLW was affected by its boundary conditions and layout of the roadways.(3) The filling materials deformed due to the subsidence movement of the roof,which stopped when mechanical equilibrium was reached.The stability of IBLW was mainly controlled by the compres sive deformation and elastic modulus of the filling material.(4) The rock burst risk of IBLW was dependent on the static abutment pressure in the elastic area and subsidence of the roof above the gob.To prevent this kind of rock burst,the static abutment pressure can be reduced by injecting water into the coal seam,hydrofracturing and op timizing the layout of longwall panels.Also,the roof subsidence can be controlled by improving the filling rate of the gob,optimizing the consolidation and compressive properties.This research result provides a technical guidance for rock burst prediction and control.