| Our country is poor in oil and gas,but is rich in coal,so the coal as the main energy in our country is so much important to the economic development of china.95 percent of the coal of O ur country is produced by the way of underground mining,but the mining activities destroyed the original stress equilibrium state of underground rock mass,therefore caused the redistribution of stress,and then affected the normal production of working face because of the occurrence of a series of mine pressure phenomenon as the roadway roof caving,coal rib,floor heave and so on.For the roadway prone to happen floor heave,monorail crane affected less by roadway floor is often used as auxiliary transportation in the working face because the mine car and locomotive transportation mode is no longer suitable.However,the roof of roadway bear the action of high stress concentration under the action of monorail crane,the instability mode and supporting mechanism of roof have changed greatly.Combined with the effect of monorail crane roadway stability caused by the complex stress environment and spatial location of roadway in fully mechanized caving face,maintaining the roof stability of monorail crane roadway is so difficult.The research of this paper is based on the S1203 fully-mechanized caving face in Yuwu coal mine of LuAn mining group,the geological structure o f Working face is simple,no phenomenon with water gushing of roof,S1203 working face main mining 3# coal seam: 3 # coal is black,block structure,joint development,uneven fracture,is mainly composed of bright coal and with vitrain and durain strip,be longing to the light coal type.The coal is high quality steam coal for special low sulfur,low phosphorus,medium grey,good thermal stability,high calorific value,the types of coal is lean and the gas content of coal seam is low.In order to solve the control problem of roof stability of the mining roadway under the action of monorail crane in the process of mining face,this article has carried on the control technology research of roof stability in the S1203 face return air lane.Aiming at the research content above,obtaining the influencing mechanism to roof stability of the section coal pillar,the way of roadway layout and monorail crane loading through numerical simulation and theoretical analysis.N umerical simulation study on the distributing re gularities of the side abutment pressure and the second invariant of deviatoric stress of fully mechanized caving mining stope,obtaining the reasonable width of section protection coal pillar in monorail crane roadway by comparing and analyzing the side abutment pressure and the second invariant of deviatoric stress.Based on the analysis of the distribution structure of the anchor cable prestress field,putting forward anchoring composite deep beam bearing structure and analyzing the influencing factors o f this structure's stability by establishing roadway roof's Mechanics model of deep beam stability under the action of monorail crane;Establishing a mathematical model of deep beam based on the maximum shear stress strength criterion,obtaining the reasonable supporting parameters of monorail crane roadway roof by analyzing the shear behavior of deep beams under different parameters,ultimately determine the monorail crane roadway roof support scheme and carried on observation of field pressure.The main conclusions of this paper are as follows:(1)On the basis of analyzing the actual production geological conditions and coal seam occurrence conditions of S1202 and S1203 working face of Yuwu mine,summarized the influencing factors of roof stability of return air lane are the way of roadway layout,spatial position relationship between roadway and coal seam and monorail crane loading.(2)Through the analysis of Characteristics of overlying strata movement in fully mechanized caving mining,established the integral structure model of the lateral end of the old roof under the condition of fully mechanized caving mining,and drawing the influence on monorail crane roadway stability caused by adjacent working face mining is mainly lie in the contradiction between the integrity of roadway surrounding rock and stress concentration.(3)Through the numerical simulation of Stress field and displacement field of surrounding rock of roadway,drawing the influence law of top coal thickness on stability of roadway roof: The horizontal stress of roof strata changes suddenly at the interface of roof coal and rock,the stability of coal rock interface is poor with the increase of horizontal stress,with the increase of the thickness of the top-coal,the additional loading of the roadway roof increases,the range of plastic zone expands and the roadway deformation also increases.(4)Using FLAC numerical simulation software studying on the change rule of the side abutment pressure and the second invariant of deviatoric stress in working face with the change of coal pillar width.Under the condition of different coal pillar width,abutment pressure and the second invariant of deviatoric stress have the same change law.The coal pillar remain in the state of low support pressure when the width of coal pillar is small,that is,when gob side entry retaining.The stress is transferred to wards the deep to the solid coal rib of roadway,the solid coal rib of roadway is in a state of high concentrated stress,but coal pillar and the solid coal rib affected by adjacent mining of working face is in a wide range of shaping state,it's not conducive to the maintenance of roadway roof stability under the action of the monorail crane that the integrity,stability and bearing ability of the surrounding rock of roadway is poor.With the increase of width of coal pillar,roadway and coal pillar shaped area will gradually shrink,the stress superposition is waken that roadway influenced by the effects of adjacent working face mining,the integrity of surrounding rock mass and stress concentration degree of two coal rib are reduced,and the maintenance d ifficulty is reduced.Based on the analysis of the side abutment pressure and the second invariant of deviatoric stress of the S1202 working face,obtained the guiding function of the second invariant of deviatoric stress to the width of coal pillar,according to the theoretical analysis of the coal pillar width under the limit equilibrium theory,the reasonable coal pillar width is 30 m.(5)Through the analysis of different roof caving forms,got the instability mechanism of roadway roof under the action of Monorail crane.Draw the influence of the Monorail crane to the roadway surrounding rock displacement field,stress field and plastic zone distribution through the numerical simulation,monorail crane makes the stress and displacement of roadway roof increases.The grid of simulation unit produce deformation,the local rock mass produce the tension fracture when the loading of Monorail crane is too large,Therefore the maintenance point of the roadway roof under the action of monorail crane is the shal ow rock of monorail suspension zone.(6)Through the analysis of the stability criterion of roadway roof under the action of the monorail crane,put forward the overall control direction of monorail crane mining roadway roof in the fully mechanized caving face of Yuwu mine.To avoid the expansion of Original cracks in surrounding rock and the production of new fractures should begin to maintain the own integrity of the roof strata,make sure the anchorage point of monorail suspension anchor located in the intact stable rock.(7)Based on the distribution of prestress field under the action of anchor rope cable prestress,established the numerical simulation model under the action of multiple anchor rope.Simulation results show: the prestress field under the action of multiple anchor rope is similar to the "drum" shape that the end is narrower and the middle width is larger,with the help of shallow bolt,the prestress field is approximately rectangular.By adjusting the parameter of spacing and row spacing between the cable and the pretightening force,formed the prestress field that distributing uniformly and continuously along the axial and tangential direction of the roadway.According to the assumption of plane problems of elastic mechanics,put forward anchoring composite deep beam bearing structure under the action of prestressed anchor cable.(8)Established the simplified mechanical model of roadway roof anchor composite deep beam bearing structure under the action of the monorail crane,Calculate the uniform loading,and the stress distrib ution state in the beam under concentrated force respectively,getting the stress components at any point in the deep beam under the multi load coupling through stress superposition method and the formula for calculating the stability of deep beam.(9)Based on the analysis of the distribution of prestress field under the different parameters of anchor rope,the influence law of anchor cable parameters on the distribution of prestress field is obtained,the width of prestress field and the value of stress are negatively correlated with the length and spacing and row spacing of anchor rope,and are positively correlated with the prestressing force of anchor rope.(10)By analyzing the relationship of the prestress field of anchor rope and the roof anchor composite deep beam,the length,the spacing of anchor rope and the prestressing force are all the composite influencing factors of deep beam stability.Used numerical simulation software of MATLAB to calculate the distribution of maximum shear stress and prestress field in deep beams with different structural dimensions under the action of monorail crane and anchor rope supporting resistance.Conducted the quantitative analysis by taking the near zero stress zone of maximum shear stress and the diffusion coefficient of the prestress field of anchor rope as the measure index to the deep beam stability,drawing the following conclusions: under the action of the monorail crane,with the increase of the monorail crane loading,the range of the high stress area of the maximum shear stress in the deep beam is expanding,the stability of shallow rock mass is decreasing;the pretightening force of anchor rope not only influence the distribution of the maximum shear stress in the deep beam,and also affect the diffusion of the prestress field.According to the two analysis results,the stability of deep beam increase under the high pretightening force;The near zero stress zone of maximum shear stress in the deep beam increase in the first and then decrease,but the increase of the anchor rope spacing result in the weakness of the diffusion effect of prestress field,and the rise of difference degree along the roadway tangential of prestress field.(11)Combined with actual situation,finally determine the roadway supporting scheme in fully mechanized caving face under the action of monorail crane by carrying out the field test research.The mining roadway roof in fully-mechanized caving under the action of monorail crane adapt the dense long cable supporting,the length of a nchor cable is 8300 mm,the spacing is 900 mm * 900 mm,the pre tightening force is 200 kN.Reinforce the roof with long anchor rope to make sure the anchor point locate in the undamaged rock mass,form the composite anchor deep beam integral structure in soft surrounding rock in roadway surface and deep rock mass with the help of diffusion effect of the prestress field of anchor rope.Reinforce the shallow roadway by using bolt,restrain stress concentration under the action of monorail crane loading effective ly,control the roadway deformation,improve the stability of its own. |
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