Study And Application Of Roadway Rurrounding Rock Control Technology To Close Coal Seam Group Mining In Xishan Mining Area

Roadway surrounding rock to close seam mining shows unique characteristics of mine pressure,so its control theory of single seam mining is no longer applicable.This paper aims at the problems in the research on surrounding rock control technology of roadway in the near coal seam mining,as engineering background in Xishan typical near coal seam mining area,it adopts comprehensive research methods such as field measurement,theoretical analysis,numerical simulation,model test,and field practice to carry measurement of geological parameters,laws of roadway surrounding rock activity,method of roadway layout,mechanics principle of roadway surrounding rock control,and the roadway supporting field test.Results can provide technical support and theoretical basis for control of roadway surrounding rock in near coal seam mining,mainly concentrated as follows:(1)The earth stress in the Xishan mining area is medium level and is dominated by horizontal stress,the depth of mining and the lateral pressure ratio determine the type of ground stress field,when the depth of mining increases,the ground stress value increases.the horizontal maximum principal stress direction are N5°W~N89.7°W and N5.6°E~N62.7°E,large geological structures such as folds and faults have significant impact on its direction,filling the gap in stress testing in the Xishan mining area.The top plate of 2#main coal mining layer consists of mudstone,Sandy mudstone,fine sandstone,etc.,and its strength is 20-60 MPa,the top plate of 8#main coal mining layer is composed of limestone,mudstone,and sandstone,its strength is 20 to 100 MPa,the rock formation contains two types of main structure surfaces:sedimentary and tectonic,and which has mastered rock strength and structure distribution characteristics of top plate of the main coal mining layer in the Xishan coal area.(2)The simplified mechanical model of the wide coal pillar bottom plate was established,and the stress analysis of it was derived,it was found that the greater mining depth,the greater stress of it,and the value of it was gradually attenuated with bottom plate depth,but no matter with mining depth,the numerical simulation shows that mining depth and coal column width are important parameters which affect stress distribution law of coal pillar floor,determine distribution pattern,and have important reference value for establishing mechanical model.when mining depth is increased,the stress will increase,and coal column widen is increased,the stress will decrease,which is consistent with the theoretical analysis,but the stress concentration coefficient has nothing to do with mining depth and coal pillar width.The similarity model test are in good agreement with theoretical and numerical conclusions,all three methods confirm that the stress of coal pillar bottom plate is gradually attenuated with bottom plate depth,but it has nothing to do with coal pillar width and mining depth.Using theoretical analysis method to explore impact of mining depth,rock mass strength,and working face length on the bottom plate destruction depth,the study found that the greater mining depth and working face length,the greater it,and the higher rock mass strength,the lower it,numerical simulation also confirmed that mining depth and floor rock mass strength are the key parameters affecting mining failure depth.This paper discusses the characteristics of non-uniform multilithologic rock formations on bottom floor,and proposes that weighted mean of bottom floor rock strength should be used,and modify yield failure depth function of bottom floor rock mass.(3)Using similar model test method,taking typical near coal seam of Duerping coal mine in Xishan mining area as a prototype,and using a two-dimensional non-contact full-field strain measurement system,comprehensive and systematic studying stress distribution laws of coal pillar floor and characteristics of deformation and failure of bottom plate in goaf area,the results show that stress distribution of the bottom bed of coal column is similar to that of the center of coal pillar,which are consistent with theoretical analysis and numerical calculation.The displacement of bottom plate in goaf area increases first,then decreases,and finally returns to 0,which vividly reproduces deformation and destruction of floor rock layer,Accurate determining rock failure angle on both sides mining residual coal pillars,the first mining surface is 60°,and the last mining surface is 55°.(4)In view of limitations of traditional reverse internal fault arrangement method,a new type of inward fault arrangement method is proposed,model test verifies that internal fault arrangement method has good adaptability,to establish layout principle of rational position of roadway in near coal seam:both to avoid area affected by concentrated stress of coal pillar remained of upper coal seam,and to avoid area seriously affected by mining damage of it,it is confirmed that transfer depth of coal pillar floor stress exceeds mining damage depth of bottom plate.two types of determination methods for internal fault distance are proposed,if layer distance is less than depth of bottom plate damage,internal fault distance is(?);if layer spacing is greater than depth of bottom plate destruction,the internal fault distance is(?).(5)To clarify that strength of floor rock mass is characterized by progressive decay and deterioration,and propose to use deterioration rate to indicate the degree of floor rock mass mining damage,and establish calculation formula for strength deterioration rate of floor rock mass;This paper puts forward that roof of mining roadway is divided into three types:single rock formation,two rock formations,and multiple rock formations,a simple support beam mechanics model is established,and relationship between layer spacing,roadway width,mining depth and roof stability is discussed,it is found that the greater layer spacing,the more stable roof,the greater roadway span,the less stable roof,and the deeper the mining depth,the more stable roof.The mechanical model of roof reinforced by anchor and cable is established,the mechanics principle of top plate reinforced by anchor and cable is demonstrated,and top plate becoming into a composite beam by the superimposed beam is elaborated.The elastic modulus of top anchor is improved,the bending stiffness of top plate is increased,the deformation resistance of top plate is enhanced,and which ensures overall stability of roof.(6)Xishan is a typical near-coal seam mining area,in order to solve the problem of roadway surrounding rocks control in the near-coal seam mining in Duerping coal mine,it is proposed that two lanes of 73903 working room adopt same inward fault arrangement method,to determine fault distance of belt lane as 9m,and fault distance of track lane as 10m,based on stability analysis of roof and evaluation of geomechanics,it is proposed that belt roadway surrounding rock adopts control technology of prestressed anchor and cable,and design parameters of anchorage support are given,field tests and pressure monitoring show that belt roadway section meets requirements for driving and mining of working surface,field practice and theoretical research are combined organically to verify each other,and show rationality of research results.