千米深井超长工作面顶板分区破断驱动机制与围岩区域化控制研究

Regional failure mechanism of main roof and zonal method for ground control in kilometer-deep longwall panel with large face length

我国煤矿开采深度和工作面长度不断增加,矿压显现剧烈程度逐年走高。为提高深部超长工作面围岩控制效果,以中煤新集口孜东矿121304工作面为工程背景,采用现场实测、理论分析、室内试验等手段研究顶板微震活动规律,揭示顶板分区破断与动态迁移机制。结果表明:千米深井超长工作面支架阻力呈现“中间小、两端大”的谷形分布特征,顶板破断有异于常规采场的“O-X”模式;工作面不同推进阶段,顶板破断引起的高能级微震事件位置在工作面长度方向上动态变化,表明基本顶破断存在分区和动态迁移现象;工作面中部高能级微震事件携带能量小于工作面两侧,造成中部动载冲击效应弱,与支架阻力谷形分布吻合;将超前采动应力大于基本顶初始屈服强度的区域定义为峰值影响区,区内应力集中驱动超前裂隙萌生,应力释放和应力旋转促进裂隙扩展,揭示了旋转性采动应力驱动超前裂隙发育机理;构建了基本顶分区破断与动态迁移力学模型,原生裂隙和采动裂隙改变了基本顶局部边界条件,引发基本顶分区破断现象,由中部峰值影响区至工作面两侧,基本顶极限承载能力降低,导致分区破断动态迁移现象;峰值影响区基本顶破断尺寸小于非峰值影响区,解释了121304工作面支架阻力呈谷形分布的原因;根据千米深井超长工作面基本顶分区破断与动态迁移模式,提出了工作面围岩区域化控制方法,中部峰值影响区液压支架采用成组协同移架方式,其他区域采用独立移架方式,提高了121304工作面围岩控制效果。

Mining depth and face length increase gradually in coal mine.The intensity of mining pressure occurrence rises quickly.In order to improve ground control in deep longwall panel with large face length,a case study is carried out by taking 121304 longwall panel in the Kouzidong Coal Mine of Xinji Energy Co.,Ltd.,China National Coal Group Corp as the background.Roof micro-seismicity characteristics are summarized,aiming to reveal the mechanisms of regional failure and dynamic migration in main roof.The works are conducted by using field measurement,theoretical analysis and lab test.The results show support resistance presents valley-shaped distribution,characterized by small resistance in middle region and large resistance in side regions.At different face advancement,the location of roof rupture induced micro-seismic events with large magnitude changes dynamically along face length direction,indicating regional failure and dynamic migration of main roof.The energy associated with the strong event at middle section is smaller than that at side sections.Thus,dynamic impact of middle area is weakened,consistent with valley-shaped distribution of support resistance.The region where mining induced stress is larger than initial yield strength of main roof is defined as peak point influenced zone.Large stress magnitude within the zone leads to crack initiation while release and rotation of the stress lead to crack propagation,which reveals driving effect of rotational stress on fracture development.A model is developed for regional failure and dynamic mitigation of main roof.Pre-existing and mining-induced fractures change local boundary condition of main roof,leading to regional failure.Roof load-bearing capacity decreases from middle to side section,leading to dynamic mitigation of regional failure.Rupture size of main roof is smaller in peak point influenced zone,which explains valley-shaped distribution of support resistance.According to regional failure and dynamic migration in main roof,a zonal method is proposed for ground control,realized by coordinative movement of the supports within middle peak point influenced zone.Single mode is used in other areas.Ground control is effectively strengthened after application of the new method in 121304 longwall panel.