Selection Of Reasonable Support Parameters Of West Air Return Roadway Passing Through Fracture Zone In Yuandian No.2 Coal Mine

The coal mining in Huainan and Huabei mining areas in Anhui Province and other mining areas in China has entered the deep part.Due to the complex and changeable geological conditions in the deep part,the destruction of the surrounding rock is common,and it is difficult to keep the deep fault fracture zone stable with conventional support,so it is important to choose reasonable support to keep the fault fracture zone stable for the deep coal mining efficiently.This paper takes west air return straight wall semi-circular roadway passing through fracture zone in Yuandian No.2 Coal Mine in Huabei as the engineering background,evaluates the degree of deformation and safety of the roadway through the deep fault fracture zone,analyzes the formation mechanism of high-strength prestressed anchor（cables）compression arch,selects reasonable prestressed anchor（cables）parameters through field measurement,theoretical analysis and numerical simulation,and proposes an optimized new support scheme to ensure the safety of the roadway.The new support scheme is proposed to ensure the safety of the roadway and to provide guidance for the reasonable support of the subsequent deep roadway through the fracture zone.The main research contents of this paper are as follows:（1）To investigate the characteristics of loose and broken surrounding rocks of west air return straight wall semi-circular roadway passing through fracture zone;（2）to analyze the influence factors of high strength prestressing anchor（cables）on the formation of compression arch through the distribution of additional stress field formed in surrounding rocks by high strength prestressing anchor（cables）in the surrounding rocks,and to find out the key parts of surrounding rocks which are easy to"destabilize";（3）to propose the mechanism of compression arch formation by high strength prestressing anchor（cables）;（4）to establish numerical calculation model to determine the reasonable support parameters of prestressing anchor（cables）according to the thickness of compression arch.FLAC^3D5.0 numerical calculation software was used to analyze different anchor inter-row spacing（400mm,500mm,600mm）,different anchor lengths（1500mm,2000mm,2400mm,2600mm）,different anchor preload forces（50k N,70k N,90k N）,and different anchor cable lengths（1000mm,4000mm,5000mm,6300mm）.The additional stress distribution in the surrounding rock under different anchor cable lengths（1000mm,4000mm,5000mm,6300mm）and different anchor cable preloads（80k N,100k N,120k N）is concluded as follows.（1）The additional stresses based on the extent of crushing of the tunnel surrounding rock and the law of the degree of crushing found that the key parts of the excavation support of the straight wall semi-circular arch tunnel in the deep fault crushing zone is in the lower part of the arch baseline at the location of the alleyway sidewall,thus the destabilization from local to overall can be avoided by strong support.（2）The change of inter-row distance of anchor rod has no significant effect on the thickness of compression arch of surrounding rock of straight wall semi-circular arch roadway in fault fracture zone,but it has significant effect on the magnitude of additional stress in the range of compression arch,when the inter-row distance is reduced from 600mm to 400mm,the additional stress increases by 46.67%;the change of anchor rod length has significant effect on the thickness of compression arch of surrounding rock of straight wall semi-circular arch roadway in fault fracture zone,but it has no significant effect on the additional stress in the range of compression arch.There is no significant effect on the additional stress within the compression arch.When the length was increased from 1500mm to 2600mm,the thickness of compression arch increased by 88.24%;the change of anchor preload had no significant effect on the thickness of compression arch,but had significant effect on the magnitude of additional stress within the compression arch,when the preload was increased from 50k N to 90k N,the additional stress increased by 73.33%.（3）When the anchor cable length exceeds 4000mm,the additional stress in the surrounding rock and the thickness of the compression arch are not significantly improved.Therefore,when supporting the surrounding rock in the straight wall semi-circular arch roadway in the fracture zone,the pre-stressed anchor cable length should not exceed4000mm;the anchor cable pre-tightening force can significantly affect the magnitude of the additional stress in the surrounding rock of the roadway.（4）The FLAC^3Dnumerical calculation model reveals that the parameters of inter-row distance,length and prestressing force of anchor（cables）can increase the additional stress in the surrounding rock of the roadway by 0.15～0.20MPa,and the strength of compression arch can be increased by 25%,and the thickness of compression arch can be improved significantly,which proves that the high prestressing strong anchor（cables）support technology can form compression arch after parameter adjustment and optimization.This technology can be one of the best choices for the reasonable support of straight wall semi-circular arch roadway passing through deep fracture zone.The details of the reasonable support arrangement of the roadway anchor（cables）under this condition will be given in the text,and the relevant test parameters and numerical simulation analysis in this paper can provide some reference significance for the actual project implementation.Figure[56]Table[10]Reference[66]...