上行采动影响下遗留群柱动态稳定性研究

Dynamic stability of residual coal pillars under upward-mining-induced influence

揭示上行开采对柱式采空区遗留群柱体系稳定性的动态扰动特征是保障蹬空遗煤安全开采的关键科学问题之一。选取元宝湾煤业9^(#)煤层柱式采空区上覆6^(#)蹬空遗煤开采为研究对象,通过数值模拟研究蹬空遗煤上行复采过程中遗留群柱的应力演化规律,评价遗留群柱的动态稳定性;在此基础上,运用结构力学基础理论,建立上行扰动载荷与遗留群柱载荷之间的关系,并揭示上行扰动载荷对遗留群柱稳定性的影响。结果表明:蹬空遗煤推进距离较小时,传递至遗留煤柱的支承压力不足以破坏其整体稳定性,使得应力分布形态保持“马鞍”形;随着蹬空遗煤推进距离增大,传递至遗留煤柱的支承压力与原有集中应力发生叠加,促进关键柱最早发生失稳,并使得其应力分布形态由“马鞍”形演变为“下开口抛物线”形;关键柱发生失稳后,覆岩载荷会发生转移,随着蹬空遗煤持续推进,邻近遗留煤柱在原有集中应力、转移应力和支承压力的叠加影响下,依次经历“增压-卸压”的演变路径,并按从左往右的次序发生失稳破坏;上行扰动影响下“遗留群柱-覆岩”耦合承载结构可以简化为均布载荷q和移动集中载荷F_(1)叠加影响下的多跨连续梁力学模型;运用“遗留群柱-覆岩”耦合承载结构的力学模型,结合上行扰动载荷与遗留群柱载荷之间的关系,可以发现上行扰动荷载的位置和大小变化均会引起柱式采空区遗留群柱荷载的传递与转移,并影响遗留群柱体系稳定性的动态演变。本研究可为柱式采空区蹬空遗煤开采遗留群柱的失稳防控提供良好的理论支持。

To ensure safe mining of residual coal,it is a key scientific issue to reveal characteristics of dynamic disturbance of upward mining on residual pillar system stability in pillar-mining gobs.With mining of overlying 6^(#)coal seam above 9^(#) pillar-mining gobs in Yuanbaowan Coal Mine as research object,stress evolution law of residual coal pillars during upward mining was studied through numerical simulation to evaluate its dynamic stability.On this basis,relationship between upward-mining-induced load and pillar load was established with structural mechanics theory.The influence of upward-mining-induced load on stability of residual coal pillars was revealed.Results have shown that mining-induced stress is not enough to destroy overall stability of residual coal pillar when advancing distance of overlying seam is small,making stress distribution remain saddle shape.With the increase of advancing distance,mining-induced stress and original concentrated stress are superimposed,which promotes the earliest instability of key pillars and causes stress distribution pattern to change from saddle shape to downward-parabola shape.Overburden stress transfers after failure of key coal pillar.As mining of residual coal advances,superimposed by original concentrated stress,transferred stress,and mining-induced stress,adjacent residual pillars undergo pressurization-relief evolution path,and lose stability from left to right.Under upward-mining-induced disturbance,coupled load-bearing structure of residual coal pillars and overburden can be simplified as a multi-span continuous beam mechanical model under superimposed influence of uniformly distributed load q and moving concentrated load F_(1).Application of coupled load-bearing mechanical model of residual coal pillars overburden strata,and relationship between upward-mining-induced load and pillar load indicate that change in position and magnitude of upward disturbance load can cause pillar load to transmit and transfer,and affect dynamic evolution of stability of residual coal pillar system.This study can provide good theoretical support for instability prevention and control of residual coal pillar during upward mining.