Key Technology And Application Of Gob-side Entry Retaining In Zhongcun Coal Mine

In mine production,there are problems such as tight mining replacement,large coal pillar loss and large disturbance of roof to roadway.Gob-side entry retaining can effectively alleviate such problems.The fracture position of overlying hard roof in gob-side entry retaining is a key factor affecting the stability control of surrounding rock.Pre-splitting roof cutting of hard roof can effectively solve this problem.Based on the engineering background of roof cutting and gob-side entry retaining(used as2407 return airway)in 2408 transportation roadway of Zhongcun Coal Mine,this thesis comprehensively uses indoor experiment,theoretical analysis,numerical simulation,field test and other research methods to analyze the blasting pre-splitting roof cutting technology,roof cutting and gob-side entry retaining technology and roof cutting and gob-side entry retaining technology,and successfully applied in 2408 transportation roadway.The main research results are :(1)Blasting pre-splitting roof cutting technology for gob-side entry retaining with hard roof : The main roof of the transportation roadway in the 2408 working face is hard medium-grained sandstone.The main roof of the goaf side has a large breaking span during the mining of the working face.The rotary motion generated after instability will make the overall surrounding rock of the gob-side entry in a high stress state,which is not conducive to the roadside support of the gob-side entry and the stability control of the surrounding rock in the roadway.Therefore,the blasting roof cutting technology is used to cut the roof and relieve the pressure on the overlying hard roof of the gob-side entry.The cutting height is determined to be11.5m,the cutting angle is determined to be 20 °,the hole spacing is determined to be2 m,the explosive parameters are : diameter 45 mm,length 300 mm,weight 450 g / roll,single hole charge quantity is 10.5kg,need 23 rolls,charge length 7.0m,sealing length4.5m.(2)Roadside support technology of gob-side entry retaining with roof cutting :The calculation formula of roadside support resistance of gob-side entry retaining with roof cutting is established.It is concluded that the support strength required for roof cutting of filling body in 2408 working face is 11.83 MN,the width of filling body is 1.8m,and the water cement ratio is 1.5 : 1.Based on the numerical calculation model,the row spacing between the tension bolts is determined to be 800 mm ×700mm,based on the numerical calculation model,the stress and deformation law of gob-side entry retaining filling body in the primary mining influence stage,stable stage and secondary mining influence stage are analyzed.The results show that the maximum deformation of roadside filling body is maintained at 225 mm after the influence of primary and secondary mining,and the supporting strength of filling body remains stable,which can meet the needs of field use.(3)Strengthening support technology in gob-side entry retaining with roof cutting : The law that the peak stress of the secondary mining side of gob-side entry retaining with roof cutting increases gradually and transfers to the deep is obtained by analysis.It is calculated that the roof subsidence of gob-side entry retaining is 218 mm,and the support resistance of coal side bolt should not be less than 0.249 MPa.It is determined that two Φ20-2200 mm high-strength rebar bolts are added between each two rows of bolts on the basis of the original support,and the row spacing between bolts is 1000 mm × 1000 mm.Therefore,the single hydraulic prop is used to strengthen the support of the roof of the retaining roadway.The support range is 120 m behind the working face,with 3 pillars in each row and a row spacing of 1000 mm.(4)Industrial test : 2408 working face of Zhongcun Coal Mine arranges measuring points in the rear entry of a mining face.It is measured that the convergence of the roof and floor of the roadway is finally stable at about 400 mm,the convergence of the two sides is finally stable at about 350 mm,the roof separation is about 19 mm,the average maximum force of the bolt is 146 k N,the average maximum force of the anchor cable is 302 k N,and the average load of the filling body is 6.8 MPa,which can meet the engineering requirements.There are 61 figures,5 tables and 60 references in this thesis.