顶板应力波扰动下倾斜煤层异形巷道破坏特征及支护技术

Failure characteristics and support technology for a special-shaped roadway in an inclined coal seam under disturbance by roof stress waves

  • 摘要: 为分析倾斜煤层异形巷道围岩动力响应特征与破坏规律,以四川川煤华荣能源有限责任公司大宝顶煤矿21194工作面异形巷道为工程背景,采用数值计算与理论分析相结合的方法,研究了顶板应力波扰动作用下巷道围岩破坏失稳的影响因素,分析了倾斜煤层异形巷道应力波传播过程及围岩振动加速度响应特征。结果表明:① 在倾斜煤层开采中,异形巷道围岩不仅受开采扰动作用,亦承受顶板断裂形成的应力波动载作用,导致巷道顶板下沉量增大、下沉峰值向低帮侧迁移。② 顶板振动加速度波传播过程分为初振期、波动期和残余期:在初振期内,振动加速度波持续扩散;在波动期内,振动加速度波传播至巷道围岩表面,导致两帮产生非对称振动现象,巷道围岩振动加速度峰值从大到小依次为顶板、低帮、高帮、底板;在残余期内,振动加速度波强度持续衰减。③ 受振动加速度波传播影响,巷道围岩破坏范围经历了前稳态、非稳态和后稳态3个阶段:在前稳态阶段,巷道两帮塑性区破坏深度呈高帮大于低帮的非对称分布特征;在非稳态阶段,巷道顶板、两帮塑性区破坏深度增加,两帮塑性区破坏深度转变为低帮大于高帮的非对称分布特征;在后稳态阶段,巷道围岩塑性区破坏深度不再增加。基于此,提出了“长短锚索+锚杆+混凝土喷层”多级支护体系,现场监测结果表明,采用多级支护体系后,顶板、底板、高帮、低帮变形量分别降低了85.7%,74.8%,70.1%,72.9%,两帮变形的非对称性明显减弱,异形巷道围岩稳定性得到显著改善。

     

    Abstract: To analyze the dynamic response characteristics and failure behavior of the surrounding rock of a special-shaped roadway in an inclined coal seam, the special-shaped roadway of working face 21194 at Dabaoding Coal Mine of Sichuan Chuanmei Huarong Energy Co., Ltd. was taken as the engineering background. Numerical calculations and theoretical analysis were combined to investigate the factors influencing the failure and instability of roadway surrounding rock under disturbance by roof stress waves and to analyze the stress wave propagation process in a special-shaped roadway in an inclined coal seam and the vibration acceleration response characteristics of the surrounding rock. The results showed that: ① during mining of an inclined coal seam, the surrounding rock of a special-shaped roadway was subjected not only to mining disturbance but also to dynamic loads induced by stress waves generated by roof fracturing, thereby increasing roadway roof subsidence and shifting the peak subsidence toward the low sidewall. ② The propagation process of roof vibration acceleration waves comprised initial vibration, fluctuation, and residual stages. During the initial vibration stage, the vibration acceleration waves continued to spread. During the fluctuation stage, they reached the surface of the roadway surrounding rock, causing asymmetric vibration of the two sidewalls, and the peak vibration accelerations of the roadway surrounding rock decreased in the order of roof, low sidewall, high sidewall, and floor. During the residual stage, the intensity of the vibration acceleration waves continued to decay. ③ Under the influence of vibration acceleration wave propagation, the extent of failure in the roadway surrounding rock evolved through three stages: pre-steady-state, unsteady-state, and post-steady-state. In the pre-steady-state stage, the failure depths of the plastic zones in the two sidewalls exhibited an asymmetric distribution, with that in the high sidewall greater than that in the low sidewall. In the unsteady-state stage, the failure depths of the plastic zones in the roadway roof and the two sidewalls increased, and the asymmetric distribution in the two sidewalls changed to one in which the depth in the low sidewall was greater than that in the high sidewall. In the post-steady-state stage, the failure depth of the plastic zone in the roadway surrounding rock no longer increased. On this basis, a multilevel support system consisting of long and short anchor cables, rock bolts, and a shotcrete layer was proposed. Field monitoring results showed that after the multilevel support system was implemented, the deformations of the roof, floor, high sidewall, and low sidewall decreased by 85.7%, 74.8%, 70.1%, and 72.9%, respectively. The asymmetry of deformation between the two sidewalls was markedly reduced, and the stability of the surrounding rock of the special-shaped roadway was significantly improved.

     

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