Study On Surrounding Rock Stability Control Technology Of Three Level Underground Rail In Pingmei No.6 Mine

Based on the engineering background of the three-level underground rail in Pingmei No.6 mine,the instability causes,stress distribution and plastic zone shape of the surrounding rock of the three-level underground rail are studied by using the comprehensive research methods of indoor similar simulation test,theoretical analysis and numerical simulation.On this basis,the support scheme of the three-level underground rail is improved.Through the similar simulation test of the surrounding rock of the roadway with prefabricated fractured rock specimens,the influence of the number,inclination and spacing of fractures on the rock strength is analyzed,and the strength change and failure characteristics of the rock under the condition of uniaxial compression cyclic loading and unloading are studied.The results show that:(1)the strength of the rock mass is related to the number,inclination and spacing of joints and fractures in the rock mass,and with the change of fracture inclination,The strength of rock decreases first and then increases,that is,there is a specific angle to minimize the strength of rock mass.With the increase of crack spacing,the number of cracks in a certain volume of rock mass will also decrease,so the strength of rock mass will increase;On the contrary,the decrease of crack spacing will lead to the decrease of rock mass strength.(2)Under the action of pressure,the original cracks in the rock mass begin to extend and produce secondary cracks at the same time.The extension direction of the cracks is generally consistent with the pressure direction,and finally failure occurs.The failure form of rock is related to the dip angle of crack.With the increase of crack dip angle,the specimen begins to appear shear failure,and the failure form will gradually change from tension failure to tension shear mixed failure.The fissure has a certain protective effect on the rocks in between.(3)After being affected by external disturbance,the strength of roadway surrounding rock will increase temporarily.If support is carried out at this time,the difficulty of support can be reduced;With the passage of time,the strength of surrounding rock will continue to decrease.If the support is not carried out in time,the roadway will be seriously deformed and damaged.Based on the geological data of the three-level underground rail in Pingmei No.6 mine and combined with the test results,the causes of the instability of the surrounding rock of the three-level underground rail are analyzed;Based on elastic-plastic mechanics,the stress expression of surrounding rock and the boundary equation of plastic zone of three-level underground rail are derived;Based on the mechanical parameters of the surrounding rock of the three-level underground rail,the shape parameters of the plastic zone are calculated,and it is judged that the shape of the plastic zone is oval.FLAC3 D numerical simulation software is used to simulate the three-level underground rail,which can be used as a reference for support design;Combined with the test results,theoretical analysis and numerical simulation results,the support design of three-level underground rail in Pingmei No.6 mine is carried out again;Finally,the comprehensive support method of "Anchor bolt,reinforcement mesh,shotcrete,ordinary anchor cable and bottom plate anchor grouting" is adopted.After the implementation of the improved support scheme for the three-level underground rail,the support effect of the improved support scheme is verified by monitoring the three-level underground rail.The monitoring results show that the improved support scheme can effectively reduce the deformation of surrounding rock and improve the phenomenon of roof separation.During the monitoring period,the deformation of roadway surrounding rock can meet the requirements of mine safety production.