Study on Control Mechanism of High Strength Anchor-grouting Self-forming Roadway in Deep Mining Area
Supervisor:yuan liang li shu cai wang zuo
Traditional long-wall mining needs to retain coal pillar to support the roadway,which is affected by "three high and one disturbance" phenomenon.The surrounding rock of roadway pillar is loose and fragmented,its bearing capacity is weak,support components fail frequently,roadway roof mesh is serious,the wall is heavily bulged out,the floor heave is large,and therefore roadway is frequently maintained and repaired.The coal pillar retained in mining roadway not only causes serious waste of coal resources,but also causes stress concentration in surrounding rock of working face,which leads to major safety accidents such as working rock burst,coal and gas outburst.These problems seriously restricts the safe,high-yield and efficient operation of coal mine.In view of the above problems,it is of great theoretical and engineering significance to clarify the caving mechanism of the short-arm beam of self-forming roadway in deep mining area,to study the bolting and grouting mechanism and control effect of self-forming roadway in deep mining area,and to put forward pertinent control measures for the support of self-forming roadway in deep mining area.Taking Suncun Coal Mine in Xinwen Mining Area as an engineering background,this paper studies the control mechanism of self-forming roadway bolting and grouting in deep mining area by means of theoretical analysis,numerical test.laboratory test and field test.The main research work and results are as follows:(1)Study on roof failure nechanism of anchor-grouting self-formed roadway in deep mining areaBased on the principle of self-formed roadway,the roof structure of self-formed roadway has obvious characteristics of stages.The roof of self-formed roadway is divided into four areas,namely,the preparation area,the implementation area,the influence area and the stable area.At the same time,the mechanics of different areas of the roof of self-formed roadway is established based on the upper limit analysis theory and the principle of energy transformation balance.Based on the analysis model,the caving curve equation of short-arm beam in self-formed roadway in different regions and stages is deduced,and the caving variation law of short-arm beam under different parameters is clarified.With the increase of cohesion c of rock mass,prestress of grouting anchor cable p,temporary support force F and strength pt of roadway wall pt,the falling range of short arm girder with cut roof gradually shifts to roadway side.When the distance d of grouting anchor cable,stress of surrounding rock q,angle of cut roof 0 and stress concentration factor lambda decrease λ,the falling range of cut-top short-arm beam gradually shifts to the direction of coal side.With the increase of friction angle in rock mass φ,cut-top short-arm beam b shows an increasing trend.However,the gap is not obvious,and the top-cut short-arm beam shows a significant decreasing trend.(2)Study on bolting and grouting control mechanism of self-formed roadway in deep mining area.Considering the influence of grouting surrounding rock parameters and supporting parameters of grouting anchor cable,the formula for calculating the mechanical parameters of grouting-anchor composite is derived,and the variation law of the mechanical parameters of grouting-anchor composite is revealed.The cohesion of anchor-grouting composite is positively correlated with the cohesion of grouting surrounding rock,the friction angle of grouting surrounding rock and the pre-tightening force of anchor cable,negatively correlated with the distance between rows,positively correlated with the friction angle of grouting surrounding rock and the pre-tightening force of grouting anchor cable,and negatively correlated with the distance between rows.The mechanical tests of grouting and anchorage grouting were carried out.The results show that the water cement ratio and particle size have a great influence on the strength of grouting body in broken surrounding rock.The strength of grouting body with water cement ratio of 0.5:1 is larger,and the strength of grouting body with particle size of 10～15 mm is smaller.There is a positive correlation between the pre-tightening force and the number of supporting components.(3)Study on bearing strength of anchor-grouting complex in self-formed roadway in deep mining areaBased on the surrounding rock structure of self-formed roadway,the geometric parameters of the bearing structure of self-formed roadway anchor-grouting complex are analyzed,the corresponding mechanical model of the bearing strength of self-formed roadway anchor-grouting complex is established,the calculation formula of self-formed roadway anchor-grouting complex is deduced,and the variation law of the bearing strength of self-formed roadway is revealed.The bearing strength of self-grouting roadway is positively correlated with cohesion,internal friction angle,pre-tightening force,length and diameter of grouting anchor cable,and negatively correlated with row spacing between grouting anchor cables.It is an effective way to improve the stability of self-grouting roadway by applying grouting reinforcement technology to increase pre-tightening force on surrounding rock and adjust the spacing and diameter of grouting anchor cable.(4)Study on numerical test of bolt-grouting support of self-formed roadway in deep mining areaConsidering the influence of roof slit height,slit height,grouting reinforcement range and grouting reinforcement parameters,16 kinds of contrast schemes are designed,numerical contrast test of bolting and grouting support for deep self-formed roadway is carried out,the variation law of roadway displacement,plastic zone and surrounding rock stress is analyzed.and the control mechanism of bolting and grouting for deep self-formed roadway under the influence of different factors is revealed.The results show that with the increase of the scope and grade of grouting reinforcement,the displacement and vertical stress of self-forming roadway decrease;with the increase of the height and angle of roof-cutting,the maximum displacement and peak stress of surrounding rock at different parts of self-forming roadway decrease,and the height of roof-cutting and the angle of roof-cutting are 8 m and 20°.(5)Model test of bolt-grouting support for self-formed roadway in deep mining areaGeomechanics model test of bolt-grouting support for self-formed roadway is carried out.The evolution law of stress and displacement of surrounding rock of self-formed roadway is analyzed,and the control effect of bolt-grouting support for self-formed roadway is clarified.The results show that the lateral abutment pressure increases first and then decreases with the increase of the distance from the solid roadway.The peak value of the lateral abutment pressure is 0.91 MPa and the distance from the solid roadway is 0.1 M.With the increase of the excavation footage,the internal displacement of the roof of the self-formed roadway increases sharply at first and then tends to slow down.Slowly,in the range of 0-100mm excavation footage,the displacement of the roof of the cut joint is significantly increased under the influence of the advance abutment pressure;after excavation of the working face to the monitoring section,the overburden strata of the roof subsides with the rotation of the roof of the cut joint,and the displacement further increases.The maximum deformation of the roof of the self-formed roadway is 2.5mm,respectively,indicating the surrounding rock control effect of the self-formed roadway by anchoring and injection.The fruit is remarkable.(6)Field application of bolt-grouting support for self-formed roadway in deep mining areaBased on 2215 transport roadway of Suncun Coal Mine,grouting diffusion rule test,grouting anchor cable anchorage performance test and roadway roof zoning field test were carried out.The stress of single support,grouting anchor cable force and roof separation layer were monitored,and the control effect of deep self-formed roadway bolting and grouting support was verified.The research shows that the 2215 transport roadway in Suncun Coal Mine adopts high-strength bolt-grouting and retaining roadway technology.The roadway roof surrounding rock fissures are filled densely,the anchorage force of grouting anchor cable is increased,the roof separation value is small,the advance support range of working face is reduced,the mine pressure of working face is not obvious,and the control effect of roadway surrounding rock is remarkable.