Research On Evolution Law Of Flexible Range In Surrounding Rock Of Mine Tunnel

With the consumption of the coal resources continue to climb，the rapid rise in ourcountry’s coal industry, and makes the mine construction task is particularly important. Theinvestment and building mines generally account for1/3of the whole building mine, areasonable support method is favorable to improve the speed of extracting and to reduce theexpense of support and maintain. It has practical engineering value and important significancefor mine sustainable development the research on evolution law of flexible range insurrounding rock of mine tunnel. This paper based on the basic mechanism of the deformationfailure of the surrounding rock, establishing the theoretical calculation model, and analysis theevolution law of flexible range in surrounding rock of mine tunnel through theoreticalcalculation and numerical simulation. The main contents and conclusion follow:(1) Through the analysis of the failure mechanism of the surrounding rock and a lot offield investigation， the paper obtained that the main deformation and failure of thesurrounding rock are section shrinkage, rip spalling, caving and floor heave. The basic failuremodes can be summarized as tensile failure and shear failure according to the failuremechanism of the surrounding rock.(2) Using the elastic theory to calculate the stress characteristics of the circular tunnel,theoretical formula of the circular tunnel surrounding rock flexible range was derived by thetheory of Hoke-Brown yield criterion. The paper obtained the evolution law of flexible rangeof surrounding rock under different lateral pressure by using the theoretical formula, theresults show that when the lateral pressure coefficient is less than1, the flexible range of thetunnel sides is obviously greater than the roof and floor, With the increase of the lateralpressure coefficient, flexible range of the tunnel sides gradually decreased, flexible range ofthe roof and floor continually expanded, When the lateral pressure coefficient is greater than1, the flexible range of the roof and floor is significantly greater than the roadway sides.(3) The evolution law of flexible range in surrounding rock of vaulted and rectangulartunnels was studied with FLAC and was obtained. For vaulted roadway, the flexible range offloor was relatively large due to stress concentration, and small in the roof; for rectangulartunnels, there will appear stress concentration phenomenon in the four rectangular tunnelcorners, under the same conditions, flexible range in surrounding rock of rectangular tunnelcorners is significantly greater. According to simulated different shape of the tunnel, we foundthat no matter what the shapes of the tunnel, when the difference between horizontal stressand vertical stress is bigger, the flexible range in surrounding rock of tunnels is larger, andwhen the lateral pressure coefficient is less than1, the flexible range of all the tunnels sides isobviously greater than the roof and floor, and When the lateral pressure coefficient is greaterthan1, the flexible range of the roof and floor is significantly greater than the roadway sides.(4) The research results on the above were applied in the roadway support design ofDongjiahe mine coal, we can determine the flexible range of the roadway, and usingmulti-point extensometer measure the flexible range of the roadway, verify the existinganchor length to meet the requirements of the flexible range support theory.