Theory and technology of three levels support in bump-prone roadway

In this study, the “ stress-surrounding rock-support” mechanical model of rockburst roadway was estab lished,and it revealed that the starting stress condition of rockburst is that the far-field stress is greater than the critical stress,and the stopping energy condition is that the energy absorbed by the near-field surrounding rock and the energy absorbed by the support is greater than the energy released from the far-field. Based on the dynamic response analysis of the surrounding rock and support in the process of rockburst,it was found that the damping characteristics of the surrounding rock,the impact-resistant and energy absorption characteristics of the anchored rock and the damping and stiffness of the support in the roadway have an important influence on the stability of the surrounding rock subjected to an impact loading. Considering the whole “ starting-breaking-stopping” process of the rockburst,the authors proposed some prevention and control methods on rockburst in the roadway in terms of static and dynamic mechanics. Firstly, before the rockburst starts,according to the stress condition of rockburst start,the methods of reducing the stress and the accumulation of elastic energy of coal and rock mass and improving the resistance of support to increase the diffi culty of rockburst start-up are conducted. Secondly,during the process of rockburst,according to the energy condition of rockburst stopping,the methods of changing structure and properties of coal and rock mass on the propagation path of impact stress wave are conducted to absorb or dissipate the impact energy. Thirdly,at the end of the propagation of the impact stress wave,the method of increasing the strength and damping of the supporting structure in the roadway is conducted to absorb the residual impact energy,and weaken the damage of the supporting structure caused by the im pact stress wave. It is proposed that the supporting structure of rock burst roadway should have the characteristics of yielding and energy absorption,and the impact-resistant support should be designed according to the energy character istics of rock burst. Combined with the failure characteristics of support and surrounding rock under the impact load and the support structure requirements of the rockburst roadway,the energy absorption support equipment,including energy absorption anchor cable,energy absorption O-shaped shed and energy absorption hydraulic support,have been developed. The three-level energy absorption support system was established by the combination of energy absorption components and their complementary functions. The three-level energy absorption support system has the characteris tics of radial yield,circumferential shrinkage and axial stability,and realizes the three-dimensional energy absorption function of the rockburst roadway.