Research On Optimization Design Of Bolting Support In Deep & High Stress Roadway

With the shallow coal resources depleted, most of mine would be transferred or would be transferred to the deep mining, and deep mining will become the inevitable trend of the development of coal mining. In stage of deep coal mining, affected by deep geological environment, great changes took place in the mechanical properties of surrounding rock mass,characteristics of unique conducive to the mechanical characteristics of roadway stability,which brought great difficulties to the roadway surrounding rock control. At present, the lack of scientific basis for the design of bolt support parameters of deep roadways in high stress area, and there was a certain blindness, which lead to support strength and cost not reasonable. Therefore, it should also carry out a large number of experimental and theoretical research work on the project.This paper rely on National Natural Science Fund Project of "Research on weaken rules of surrounding rock and its controlling mechanism of high-strength bolting in deep roadway",and in close connection with practical field engineering, to carry on lots of field investigation study on surrounding rock large deformation failure characteristic of deep high stress roadway,to consider that roadway mainly characteristic of surrounding rock with large deformation,deformation rate fast, deformation of obvious plastic deformation and last for a long time,squeeze seriously in two sides, support body part or complete failure and destruction and produced larger floor heave deformation and failure. Using the elastic plastic mechanics,engineering mechanics, rock mechanics theory to analyze surrounding rock stability mechanics state after roadway excavation, and the mechanical calculation model was established, derived from the deep roadway surrounding rock loose circle radius calculation formula, to provide basis on choice of bolt length.Using numerical analysis method, and based on orthogonal test method, combined with Pingdingshan Coal Mine ten working face driftway actual situation to carry on orthogonal numerical test of anchorage supporting parameters, identified 13 factors and 3 levels toatal 27 different calculation models, to carry on numerical simulation respectively, and to carry on multiple index range analysis of the simulation results, and the optimal supporting scheme for roadway was obtained: Roof support parameters: bolt length 2.6m, bolt diameter 22 mm, bolt Spacing of 0.75 m × 0.8m, bolt pretension 60 KN, cable length 7.3m, cable diameter17.8mm, cable spacing of 2m×3m, cable pretension 150KN; two sides support parameters:bolt length 2.4m, bolt diameter 22 mm, bolt spacing of 0.8m×0.8m, the angle between the bolt and roof was 25 degrees, and the angle between the bolt and bottom was 25 degrees.Using MATLAB software to carry out the matrix calculation, the regression equation and the corresponding regression coefficient of help shift amount, roof subsidence, roof and floor shift were obtained, through the regression equation of two sides roadway shift amount, roof subsidence and roof and floor shift nearly amount of energy to approximate quantitative prediction. By the method of numerical simulation for pressure pipe different pressure points to carry on the simulation analysis, high strength prestressed pressure bolt optimal point to150 k N.By means of numerical simulation method to analyze deformation failure characteristics,stress distribution rules and displacement distribution rules of surrounding rock after using the optimal support scheme in deep high stress roadway. In the roadway excavation process,vertical stress peak did not change significantly, generally with 28 MPa fluctuation. Stress concentration in front of heading face, the peak stress was about 25.2MPa. During the excavation process, the vertical displacement changes along with the excavation, the roof and floor displacement increased gradually, roof and floor displacement in the 25 m was nearly128 mm, the top floor displacement of surrounding rock increased about 80 mm.The optimal support scheme was applied to the field practice, stress of roadway surface displacement and bolt force during the monitoring, in the early stage of the nearer quantity of top floor and the convergence between the two sidewalls severe changes of surrounding rock,and then gradually stabilized, the final value in the range of allowable in roof bolt, help bolt force was increased gradually and finally tended to be stable, respectively, the roof bolt can make the pressure, but due to the existence of the pressure pipe, effectively prevent the bolt broken. Field application showed that bolt supporting parameters design were reasonable and effective, and support scheme optimization decision result was reasonable, the support scheme can completely meet the requirement of roadway in the service period of production.