深部沿空巷道锚固围岩破坏失稳能量驱动机理

Energy-driven mechanism of failure and instability of anchored surrounding rock in deep gob-side entry

深部沿空巷道受侧向顶板断裂所产生的动载影响,锚固围岩易产生大变形,甚至破坏失稳。以山东省孙村煤矿31120工作面上平巷为工程背景,首先采用YTJ20型岩层探测记录仪获得了锚固顶板裂隙发育规律及以脆性张裂破坏为主的破坏方式。然后,通过相似材料模拟试验方法获得了深部沿空巷道侧向顶板前期、过渡期和后期3个运动阶段典型特征,并分析了不同阶段锚固围岩破裂演化及能量释放规律;其中过渡期运动阶段锚固围岩内部应力、变形量急剧增大,裂隙发育明显,能量释放显著,对沿空巷道锚固围岩稳定性影响最大。最后,构建了侧向顶板断裂运动下沿空巷道结构力学模型,给出了锚固围岩输入能量与可抵抗能量定量计算方法,揭示了侧向顶板断裂诱发锚固围岩破坏失稳能量驱动机理,并定义了失稳能量判据,即当作用在沿空巷道锚固围岩上的能量大于锚固围岩可抵抗能量时,将发生破坏失稳。进一步地,提出了锚固围岩失稳风险等级划分方法和相应地控制技术,计算结果表明,31120工作面沿空巷道锚固围岩失稳风险等级为中风险。采取加强支护措施后,沿空巷道顶底板及两帮移近量分别减小35.47%和35.71%,锚索受力减小23.43%,变形速度明显降低,锚固围岩能量积聚程度减小。

Affected by the dynamic load induced by the fracture of lateral roof in the deep gob-side entry,the anchored surrounding rock is prone to produce large deformation,even failure and instability.Taking the tailgate of the 31120 work-ing face in the Suncun Coal Mine as an engineering background,firstly,the development law of cracks in the anchored roof and the main failure mode of brittle tension crack were obtained by using the YTJ20 rock detection recorder.In addi-tion,based on the similar material simulation test,the typical characteristics of three stages of lateral roof movement in the deep gob-side entry were obtained,and the fracture evolution and energy release law of anchored surrounding rock in dif-ferent stages were analyzed.It is noted that the internal stress and deformation of anchored surrounding rock increase sharply,the cracks develop obviously and the energy is released significantly in the transitional movement stage,which has the greatest influence on the stability of anchored surrounding rock in the gob-side entry.Finally,the structural mech-anical model of gob-side entry under lateral roof fracture movement was constructed,the quantitative calculation method of input and resistant energy of anchored surrounding rock were firstly provided,the energy-driven mechanism of failure and instability was revealed,and the instability energy criterion was defined,that is,when the energy applying on anchor-ing surrounding rock in gob-side entry is greater than the resistant energy of anchoring surrounding rock,the instability will occur.Accordingly,the instability risk classification method of anchoring surrounding rock and the corresponding strengthening control technology were put forward.The calculation results show that the instability risk level of anchored surrounding rock in the gob-side entry of the 31120 working face was medium risk.After strengthening the support,the deformation of roof and floor and the two sides of gob-side entry were reduced by 35.47%and 35.71%,respectively,the force of anchor cable was reduced by 23.43%,the deformation speed was obviously reduced,and the energy accumula-tion degree of anchoring surrounding rock was reduced.