动载扰动下巷道锚固承载结构冲击破坏机制

Burst failure mechanism of roadway anchorage bearing structure under dynamic load disturbance

  • 摘要: 冲击地压是威胁我国煤矿安全高效开采的主要矿井灾害之一。作为冲击地压的最后一道防线,预紧力锚杆支护系统与其作用范围内围岩共同形成的锚固承载结构决定了巷道围岩的整体稳定性。为研究冲击地压巷道锚固承载结构冲击破坏力学机制和能量机制,以发生过冲击破坏的回采巷道为地质原型,建立了动静载联合作用下巷道锚固围岩数值模型,采用FLAC3D内置动力模块模拟分析了动静载联合作用下巷道锚固承载结构动载响应特征及冲击破坏过程;根据锚固承载结构的受力状态、强度特征、能量特征以及冲击破坏演化过程,提出了巷道锚固承载结构冲击破坏准则;基于弹性波动力学、弹塑性岩石力学,建立了动载和静载荷联合作用下巷道锚固承载结构稳定性力学和能量模型,得到了动载扰动冲击地压巷道锚固承载结构破坏的力学判据和能量判据。研究结果表明:动载扰动下巷道锚固承载结构冲击破坏演化过程为:动载扰动→浅部围岩损伤变形破坏→锚固系统失效→锚固承载结构失去对深部围岩控制→围岩损伤破坏范围骤增→深部围岩能量瞬时释放→锚固承载结构冲击破坏;动载扰动冲击地压巷道锚固承载结构冲击破坏必须满足应力和能量的双重“超载”条件,必要条件是:动载和巷道围岩静载叠加强度大于锚固承载结构的承载能力,即应力“超载”;充分条件是:动载余能和巷道围岩释放的弹性能量大于锚固承载结构冲击破坏耗能,且有盈余能量并可转化为冲击动能,即能量“超载”;从力学角度分析,锚固承载结构稳定性与锚固围岩体参数、支护强度、所受静载大小和动载荷特征(震源强度、震源距离、衰减系数)相关;从能量角度分析,锚固承载结构动态稳定性主要与动载能量、动载距离和能量衰减系数、主应力量值、锚固承载结构强度、锚杆(索)动载强度和延展性相关。最后通过冲击实例验证了力学判据和能量判据的正确性。

     

    Abstract: Rock burst is one of the main disasters that threat the safe and efficient mining in Chinese coal mines.As the last barrier to prevent rock burst, an anchorage bearing structure plays a crucial role in stability of roadway surrounding rock, which is composed of pre-tensioned bolt support system and its reinforced rock.In order to study the mechanical mechanism and energy mechanism of rockburst roadway anchorage bearing structure, a numerical model of roadway anchorage surrounding rock under the combined action of dynamic and static loads was established based on the geological prototype of mining roadway with impact failure.The dynamic response characteristics and impact failure process of roadway anchorage bearing structure under the combined action of dynamic and static loads were simulated and analyzed by FLAC3D built-in dynamic module.Based on the elastic wave dynamics and elastic-plastic rock mechanics, the mechanical and energy models of the stability of roadway anchorage bearing structure under the combined action of dynamic load and static load were established, and the mechanical and energy criteria for the failure of anchorage bearing structure of roadway under dynamic load disturbance were obtained.The results show that under dynamic load disturbance, the evolution process of impact failure of roadway anchorage bearing structure is as follows: dynamic load disturbance → shallow surrounding rock damage and deformation failure → anchorage system failure → anchorage bearing structure losing control over deep surrounding rock → surrounding rock damage and damage scope increased sharply → deep surrounding rock energy instantaneous release → anchorage bearing structure impact failure.The impact failure of anchorage bearing structure of roadway under dynamic load disturbance needs to meet the double “overload” conditions of stress and energy.The necessary condition is that the superposition strength of dynamic load and static load of roadway surrounding rock is greater than the bearing capacity of anchorage bearing structure, that is, stress “overload”.The sufficient condition is that the residual energy of dynamic load and elastic energy released by surrounding rock of roadway is greater than the energy consumption of impact failure of anchorage bearing structure, and surplus energy can be converted into impact kinetic energy, that is, energy “overload”.From the mechanical point of view, the stability of anchorage bearing structure is related to the surrounding rock parameters, support strength, static load and dynamic load characteristics(source strength, focal distance, attenuation coefficient).From the energy point of view, the dynamic stability of anchor bearing structure is mainly related to dynamic load energy, dynamic load distance and energy attenuation coefficient, principal stress value, strength of anchorage bearing structure, dynamic load strength of anchor(cable) and ductility.Finally, the correctness of mechanical criterion and energy criterion is verified by an impact example.

     

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