| Deep mining is not only the inevitable trend of mining industry,but also the important development direction of "Deep earth" in our country.Rock mass shows high nonlinearity in geological environment with high In-situ stress,and a series of dynamic disasters such as rock burst and microseismic will be induced when mining under strong disturbance.The nature of these disasters is the nonlinear evolution of energy,Therefore,it is more effective to study roadway instability from the angle of energy.In this paper,theoretical analysis,laboratory experiment,numerical simulation and downhole test are combined to systematically study the energy field evolution mechanism of the surrounding rock mass and the dynamic energy absorption characteristics of the new type energy-absorbing bolt during the failure process of deep roadway instability.(1)The nature of surrounding rock deformation and failure is the result of the combined effects of energy accumulation,dissipation and release.Under the framework of elastic mechanics theory,according to the Hoek-Brown strength criterion,the distribution of elastic strain energy accumulation and release of rock mass at different positions away from the free surface is derived;From linear elastic fracture mechanics,the frictional heat energy and surface energy of crack propagation are studied using the compression-shear slip model.Considering that the plastic properties dissipated by the plastic deformation of the crack tip of the rock mass become more prominent under the high stress environment,the boundary curve equation of the plastic zone of the ?-? compound crack tip and the plastic properties of the plastic deformation are determined according to the double-shear unified strength theory.Based on the energy balance of crack growth,the energy distribution of each part is analyzed in combination with calculation examples.(2)In view of the complexity of the spatial-temporal evolution of rockburst disasters,bidirectional loading tests of circular model roadways with different hole diameter ratios were carried out to reproduce the rockburst phenomenon.During the test,the micro camera,acoustic emission,3D-DIC and other monitoring means were used to obtain the characteristic parameters such as the failure mode,spatial position and acoustic emission energy parameters of the tunnel wall.According to the experimental study,the evolution of rockburst is characterized by "energy accumulation energy release" cycles,and with the increase of input energy,the cycle time is shortened and the released energy is increased;With the increase of curvature radius,the tensile failure ratio of surrounding rock increases due to size effect;the strain field evolves in the shape of uniform distribution?X-shape?two sides V-" with the increase of axial load.(3)Considering the influence of fracture development degree and stress state on surrounding rock accumulation and release mechanism at different positions from the free face,granite samples with equivalent damage factor D=(0.16,0.36,0.51,0.89)were prepared by high temperature heating.The uniaxial and triaxial compression tests of intact granite and fractured granite are designed.The rock mechanical characteristic parameters,failure modes,energy storage capacity and dissipative energy conversion rate under different fracture development degrees and stresses are analyzed.At the same time,with the help of particle flow software PFC3D,the development process of rock fracture field is displayed,and the mesoscopic characteristic energy threshold value related to rock deformation and failure is analyzed.It is determined that when the fracture degree D=(0.4?0.5),it provides the basis for judging the support opportunity of roadway.(4)In view of the fact that there is no obvious deformation precursor for deep hard rock burst,a high damping energy absorption bolt suitable for deep hard rock mass support is developed based on the high impedance characteristics of high damping rubber material in impact engineering,so as to absorb and transfer impact energy in time.The effects of impact rate,impact frequency and thickness diameter ratio on dynamic mechanical properties and energy absorption properties of energy absorbing materials were studied by drop weight impact test and SHPB impact test.The dynamic mechanical response and tensile properties of different specifications of high damping energy absorbing bolts were studied by drop weight impact system,and the energy absorption mechanism of high damping energy absorbing bolts was revealed.Finally,from the theoretical point of view,the energy consumption mechanism of high damping energy absorbing bolt and surrounding rock support is analyzed,and the failure energy criterion of supporting roadway is obtained.(5)On the basis of the above analysis,taking sanshandao-780m horizontal section roadway stability control as the research object.Taking in-situ stress as boundary condition,FLAC3D dynamic module is used to analyze the deformation and failure law of open roadway,ordinary bolt and new energy absorbing bolt support under dynamic and static load,which preliminarily verifies the effectiveness of the new energy absorption bolt buffer energy absorption support.Based on this,exploratory study on the combined support of borehole pressure relief and new energy absorbing bolt is carried out,which realizes the deep transfer of surrounding rock energy.It is expected to further improve roadway support and reduce rock burst and other dynamic disasters. |
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