Study On Rock Burst Control Based On Fast Active Support

Rock burst is a kind of unstable geological disaster in which tunnels under high ground stress conditions have accumulated high elastic strain energy and encountered excavation and unloading,and the energy stored in the rock mass is suddenly released.For rock burst hard rock,the main problem of the current support system is that the displacement of the surrounding rock and the support structure is small and the support force is small.Therefore,this paper is based on a fast active support method,using theoretical analysis as the main method and numerical simulation as the auxiliary research method to discuss evolution law of stress field and energy field of the surrounding rock during the 3D tunnel excavation and support process with elastic constitutive model and rheological constitutive model.At the same time,based on fracture mechanics,the mechanism and prevention of rock burst,which is greatly affected by geological structure,were studied.The main research results are as follows:(1)During the excavation and support of the tunnel,the stress of the original rock at a distance works on the surrounding rock and the strain energy of the internal surrounding rock near the cave wall increases,The supporting force of the supporting structure and the virtual supporting force of the excavation face work together to make negative work on the surrounding rock and hinder the increase of the strain energy of the surrounding rock.In the process of elastic tunnel excavation and support,the application of active support will not affect the size of the passive support force.The active support structure support force can be obtained by superimposing the active support force and the passive support force.Comparing the evolution law of the surrounding rock stress field and energy field with different support positions and methods,it is proved that the support structure needs to be quickly applied at the tunnel excavation surface to maximize the support effect of the passive support structure,and active support greatly reduce the tangential stress concentration and strain energy accumulation of surrounding rocks,and reduce the rock burst intensity level.(2)During the excavation of the rheological tunnel,the work of the external force on the surrounding rock is converted into rock burst strain energy,rheological dissipation energy,long-term strain energy and hysteretic deformation energy.The strain energy grows faster in the initial stage of excavation,at which time the rapid accumulation of strain energy can easily lead to rock burst.The strain energy remains stable in the later period,but the continuous increase of the dissipated energy in the later period will increase the rheological damage of the surrounding rock,reduce the rock strength and energy storage capacity,and cause a lagging rock burst.Under the influence of the spatial effect of the excavation face,in the initial stage of the support structure,the wall of the surrounding rock cave quickly converged,and the support force increased rapidly.As the excavation face advances,the spatial effect of the excavation face becomes smaller,the rheological effect becomes greater,the internal stress is readjusted,the wall rock wall convergence is slowed down,and the contact pressure fluctuates.In the later period of support,the support structure mainly bears the rheological pressure from the surrounding rock,and the contact pressure increases steadily.(3)During the occurrence of a rock burst that is greatly affected by the geological structure,the active supporting force provided by the prestressed anchor can significantly inhibit crack propagation and rock buckling.At the same time,the application of the anchor rod can greatly increase the shear strength of the rock structural surface,prevent the rock block from popping out under pressure,and play a buffering role when the rock block pops up.(4)The results of numerical analysis show that there is stress concentration and energy concentration at the junction of the tunnel excavation surface and the cave wall,which is the high incidence of rock burst.Moreover,the surrounding rock and the supporting structure have not come into contact here,and the passive support cannot play a role.The rapid active support can significantly reduce the stress concentration and energy accumulation there,and play a better role in preventing and controlling rock burst.The strain energy density decreases rapidly as you move away from the tunnel wall,and the supporting effect of the support structure also gradually decreases as you move away from the tunnel wall.Explosion prevention should be carried out within this range.Except for the junction between the tunnel excavation face and the cave wall,the numerical solution agrees with the theoretical solution in Chapter 2.The spatial effect formula of the excavation face is applicable in different support positions and methods.The results of numerical analysis can preliminarily interpret the rock burst record data of the diversion tunnel of Jinping Hydropower Station.