Deformation Mechanism And Control Technology Of Weak Semi-coal Rock Roadway In Nanyaotou Mine

Aiming at the problem of violent deformation and instability of surrounding rock in weak semi-coal rock return airway in fourth mining area of Nanyaotou Coal Mine,the deformation and failure characteristics of surrounding rock in weak semi-coal rock return airway were studied and analyzed by field investigation,theoretical analysis,numerical simulation and field industrial test.The deformation and failure mechanism was revealed.The numerical calculation method of bolt bearing fracture was developed.The fracture law of bolt in weak semi-coal rock return airway under mining action was obtained.The anchor,grouting and bottom arch support technology of weak semi-coal rock return airway was proposed,and the field application effect was remarkable.The detailed research results are as follows :(1)The deformation and failure mechanism of weak semi-coal rock roadway in Nanyaotou Mine is revealed.The deformation and failure mechanical analysis model of weak semi-coal rock roadway in Nanyaotou Mine was established,and the key influencing factors and influencing laws of the stability of semi-coal rock roadway were obtained.The stability was determined by the upper coal body,the lower sandy mudstone and the structural plane between them of two sides.Multiple dynamic pressure disturbances,repeated excavation and repair,insufficient support strength induce the roadway in frequent loading and unloading state,deformation and failure to two sides of deep development,until the occurrence of large deformation and failure.(2)The evolution law of surrounding rock stress distribution of weak semi-coal rock roadway in Nanyaotou Mine was determined.During the excavation: in the left side and right side of the roadway(The belt roadway was in the right side 35 m of the return airway)the peak stress position were 12 m and 15 m from the side,the peak stress size were 16.8MPa and 18.4MPa.After two mining superposition,the peak stress of the two sides were 27.6 MPa and 30.1 MPa,and the peak positions were 19 m and 17 m,respectively.(3)The mechanical criterion of CABLE element stress fracture in FLAC3 D was determined,and the traversal algorithm of CABLE element stress fracture under engineering scale was developed.During tunneling,with the increase of surrounding rock deformation,the bolt load gradually increases,but both are in the elastic stage,and the axial force of the bolt on both sides is greater than that of the roof bolt.Under the action of two mining superposition,the bolt load of the two sides and the roof of the roadway is greater than the breaking load,and the bolt breaking of the two sides is earlier than the roof bolt,and the left side is earlier than the right side.(4)The deformation characteristics of surrounding rock in stages of semi-coal rock return airway in Nanyaotou Mine are obtained.During tunneling: the strength of both sides and floor is small,and the deformation speed and final deformation are higher than the roof.Under the influence of mining on both sides of the working face,the stress of the surrounding rock of the roadway increases,and the surrounding rock is further deformed and destroyed.The destruction of the two sides and the bottom plate makes the roof subsidence increase significantly.The deformation of the roof,floor,left and right sides of the roadway are 643.3 mm,578.8 mm,732 mm and 727.3mm,respectively.(5)Anchor-grouting reinforcement technology for weak semi-coal-rock return airway in Nanyaotou Mine was proposed.The control technology of high-strength bolt,anchor cable support and grouting reinforcement the roof and two sides of the roadway was determined.The back-bottom arch and anchor-grouting support control technology was used for the floor.After adopting this technology,the relative displacement of the roof and floor of the roadway and the relative displacement of the two sides were less than 110 mm,which effectively controlled the stability of the surrounding rock of the return airway in the fourth mining area,and provided reference for the control of the surrounding rock of the roadway under similar production geological conditions.There are 54 figures,2 tables and 94 references in this paper.