| Under the effect of vertical short distance and large dynamic pressure,which aggravates the development of surrounding rock deformation,section contraction,support structure failure and other phenomena,the difficulty of surrounding rock stability control becomes more and more prominent and the surrounding rock of deep roadway often shows weak rheological characteristics.The repeated strong mining stress can causes the stress concentration in the plastic zone of the surrounding rock of the short-distance tunnel,and the stress field of the rock mass may occur or even redistribute many times,which makes the deformation and failure mechanism of the surrounding rock more complex.To realized the effective control of the deformation of the floor roadway,minimize the maintenance cost and ensure the safe use of the dynamic pressure roadway,the influence of vertical dynamic pressure on the mechanical support mechanism of roadway deformation is deeply analyzed on the basis of full field investigation by conducting field test,laboratory test,theoretical analysis,numerical calculation,model experiment and industrial field test,and the track roadway of575 m bottom plate is taken as the engineering background in the upper vertical distance of 58 working face.Besides,this study reveals the influence of local weak support on deformation and failure of vertical short distance high dynamic pressure roadway,and puts forward the idea of local strengthening support.The main contents and conclusions are as follows:(1)Under the influence of working face mining dynamic pressure,the surrounding rock of 575m floor track roadway is located in the engineering background,the stress and deformation law of roadway surrounding rock by setting station were detected and analyzed.Meanwhile,the in-situ stress test was conducted and the damage evolution of the dynamic rock mass by using the geological radar and borehole peeping technology were also detected and analyzed;Besides,The ground stress level,surrounding rock loose ring and damage range of roadway were determined according to the test.(2)The static mechanical parameters and impact mechanical properties of the rock in the dynamic pressure tunnel are tested in the laboratory through the field sampling,then,the microstructure and internal components of the rock sample are alos tested.According to the test results,the rock composition,internal structure and the fracture damage parameters of the surrounding rock are determined.(3)Treated with dry and wet cycles for the sandstone samples,a series of uniaxial compression tests and multi-stage loading creep tests were carried out to study the change rule of uniaxial mechanical strength of samples.Besides,the uniaxial creep test was carried out to study the laws of axial creep strain and instantaneous creep rate,and the creep parameters and failure morphology of the specimen in the failure stage were also discussed.Based on the SEM tests,the microstructure evolution of red sandstone was observed and analyzed under different dry-wet cycles,and the strength damage evolution law of sandstone affected by dynamic pressure under dry and wet conditions was explored.(4)Based on the mechanical model of vertical short-range dynamic pressure roadway,the basic equation and analytical expression of stope floor stress are given.Combined with the project site,the internal mechanism of roadway deformation under the influence of vertical short-range dynamic pressure is studied.Besides,the influence of soft rheology of surrounding rock,development and change of surrounding rock plastic zone,lack of support and dynamic pressure environment on roadway deformation is analyzed.(5)According to the uniform support mechanical effect of dynamic pressure roadway and the three-dimensional stress analysis,it is proposed that the elastic-plastic radius of the weak support area of the floor under the weak support effect of dynamic pressure roadway becomes larger,which is the inducement of floor heave and surrounding rock deformation.Moreover,through the analysis of the mechanical effect of the local strengthening support of the roadway,it is found that the larger the resistance and the scope of action of the local strengthening support is,the more obvious the tangential stress reduction of the roadway floor and the two sides is,which is helpful to ensure the stability of the roadway,but the economic feasibility should also be considered.(6)The theoretical model of space grid structure is established,which is simplified as the thin shell structure with hinged short columns.And the analytical solution expression of the stress of the theoretical shell is derived.(7)Based on the orthogonal experimental design,the arc length method is used to calculate 16 groups of space grid models,and the optimal model design parameters of steel grid are obtained through the range analysis and gray correlation analysis.(8)Based on the experimental study of space truss model,it is concluded that the ultimate load of bearing capacity is 1388 KN,and the failure form is shear-pressure failure.Besides,the radial displacement of the model structure is small,the primary and secondary arc bars of the space grid are all in the yield state under the ultimate load,and the concrete reaches the ultimate strength,which indicates that the short reinforced element with good force and can decompose the load into the space arrangement,and the material strength is brought into full play.(9)The numerical simulation results show that the vertical short distance dynamic pressure of space grid bolting and shotcreting affects the roadway,the convergence deformation and stress of surrounding rock are small,and the stress of grid structure is uniform and in a safe state,which can reduce the stress concentration of surrounding rock,improve the stress distribution of surrounding rock and reduce the deformation of surrounding rock.(10)According to the conclusion of model test,numerical calculation and theoretical analysis,the study optimizes the structure of bolting and shotcreting support of space grid in vertical short distance dynamic pressure roadway,and carries out industrial test,indicating that the structure has the advantages of active support,provides greater support resistance for surrounding rock to become better radial compressibility,which meets the basic requirements of soft rock dynamic pressure roadway support.The monitoring results show that the interaction between the space grid structure and the surrounding rock is coordinated,and the mechanical properties of the material are brought into full play.The deformation of surrounding rock of deep vertical close range dynamic pressure roadway is small,the stress of steel bar is even in safe state,and the effect of industrial test section is good.In this paper,the evolution mechanism of surrounding rock deformation mechanics under the influence of deep vertical short distance and large dynamic pressure is analyzed.Besids,based on the analysis of the mechanical effect of weak support in dynamic pressure roadway,the idea of local strengthening support for weak support is proposed.Moreover,the space grid bolting and shotcreting supporting structure suitable for deep dynamic pressure roadway is designed by optimizing the parameters of space grid,carrying out model test and numerical simulation research.The research results have certain academic significance,and also have certain reference significance for similar projects.Figure 128 Table34 Reference 158... |
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