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

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 FLAC^3D 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.