| This thesis is on the background of extremely soft coal roadway anchor-net support engineering of No.5 coal track dip in Xiangshan coal mine south 1 mining area,through deepgoing field investigation,summarizing failure characteristics of anchor unit body and surrounding rock of the extremely soft coal roadway caused by unmatched strength of the metal net with bolts,analyzes metal mesh's important role in controlling of surrounding rock in extremely soft coal roadway from the angle of crack propagation.The MCS400 bolt dynamometer and the self-developing WSL-100 metal mesh dynamometer are used to measure the supporting load of the bolt and the metal mesh respectively,to explore the actual force evolution law of the bolt and steel mesh in the process of coal deformation,and to analyze the synergistic control effect of anchor-net on the deformation of the soft coal.In order to obtaine reasonable metal mesh type and other component assembly methods,theoretical analysis and Abaqus numerical simulation are carried out about the problem of determining the parameters of metal mesh support.Based on this,the coupling anchor-net surrounding rock control technology of the No.5 coal track dip in the south 1 mining area of Xiangshan coal mine is put forward and successfully applied in the test roadway.The main conclusions of this paper are as follows:(1)Through the field investigation and by comparing crack propagation situation of surrounding rock of bolt anchored directly and indirectly zone in the extremely soft coal roadway,it is known that anchored indirectly zone is the weak link of anchor net supporting overall bearing structure and anchor net support overall bearing structure failure in extremely soft coal roadway often happens starting from the coal flow in anchore indirectly area then developing to the whole supporting system failure.The destruction form caused by above-mentioned failure can be divided into metal net yield deformation and metal mesh breakage failure.(2)Field measured data prove that when the soft roadway surrounding rock reinforced with metal mesh is deformed and damaged,the supporting load of metal mesh and bolt increase synchronously,and the growth rate of the supporting load of metal mesh increases with the increase of the deformation.In this process the sum of the increment of the supporting force of the four bolts in the anchoring unit in extremely soft coal roadway is from 11 times to 15 times of the increment of the bearing load of the metal mesh.When the metal mesh starts to be broken locally,the supporting load decreases rapidly.At this time,the bolt supporting force increases rapidly due to the sudden increase of the deformation of surrounding rock.But soon,with the total breaking of the metal mesh and further scattering of loose coal,the boltsupporting force decreases rapidly to60% of peak value.(3)Through Abaqus theoretical calculation results,it is known that under the same load,metal mesh of smaller eyes side length and larger diameter of the cross section of the steel wire has the greater ultimate bearing capacity and deformation resistance,and equilateral hexagonal gabion mesh has better ultimate bearing capacity and deformation resistance than the quadrilateral ordinary metal mesh.When assembling steel belt,the anti-deformation ability of metal mesh increases about 2 times.When the reinforcing anchor cable is assembling,the anti-deformation ability of the metal mesh increases about 12 times.(4)By modifying the knitted and welded mesh of eyes side length of 65×65 mm and wire section diameter of 6 mm and enhancing anchor cable compensation supporting.the widespread phenomenon of metal mesh fracture failure is effectively solved.The field experiment shows that this measure effectively guarantees the reliability of the bearing overall structure of the anchor-net support,and achieves the goal that not to repair No.5 coal track dip in the whole service period in the south 1 mining area of Xiangshan coal mine.The thesis has 42 figures,20 tables and 91 references. |
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