Study On Combined Support Technology Of Return Airway In 12109 Fully Mechanized Caving Face In Wangjialing Coal Mine

Wangjialing Coal Mine’s fully mechanized caving face has a large roadway section.Due to multiple influences such as excavation disturbance,adjacent fully mechanized caving face mining disturbance,and mining disturbance of the current face,roof coal cracks,step sinking,large-area net pockets,and anchor cable failure have occurred.Broken and deformed sides,failure of anchor rods,bulging and cracking of bottom plate,and even roof fall,etc.,affecting normal production.Based on field investigations and laboratory experiments,this thesis first analyzes the structural characteristics of the overlying strata of the strong mining coal roadway,and determines the reasonable coal pillar width through theoretical calculations and numerical simulations.It is proposed to adopt asymmetric"multi-anchor cable-groove"The“Steel”support form supports the surrounding rock of the roadway and determines the support plan;finally,the support plan is tested and observed to verify the coal pillar width and the reliability of the support plan.The main results of this thesis are as follows:(1)Through statistical analysis of experimental data,the physical and mechanical parameters of 2#coal are obtained:coal compressive strengthσ_c=13.33MPa,cohesive strength c=2.48MPa,internal friction coefficient tanφ=0.89,internal friction angleφ=41.78°,resistance Tensile strengthσ_t=1.034MPa;roadway roof rock compressive strengthσ_c=59.70MPa,cohesion c=6.2MPa,internal friction coefficient tanφ=1.12,internal friction angleφ=48.20°,tensile strengthσ_t=7.969MPa.(2)By analyzing the surrounding rock structure of a fully mechanized coal roadway under strong mining,theoretical calculations show that the key rock block B is fractured at 6m within the coal pillar;the ultimate strength calculation method is used to calculate the section coal pillar width under strong mining conditions,Theoretically obtain a reasonable coal pillar size of 7.67m;establish a three-dimensional numerical model of fully mechanized caving face,use the second and third invariants of deviator stress,analyze the deviator stress field and data curve distribution law under different coal pillar widths,Determine the reasonable narrow coal pillar width is 8m.(3)The high prestressed cable anchor truss system and supporting principle are analyzed,and the asymmetric"multi-cable-channel steel"support form is proposed to support the surrounding rock of the roadway.With the aid of numerical simulation software,the relationship between the deformation characteristics of the roadway surrounding rock and the depth of the plastic failure zone of the roadway surrounding rock and the relationship between the length of the anchor cable,the span of the anchor cable truss and the eccentricity of the anchor cable truss are analyzed,and the following support parameters are obtained:When the eccentricity of the anchor cable truss is 400mm,the length of the anchor cable is 8m,and the spacing of the anchor cables in the anchor cable truss system is 1.6m,the lateral resistance of the supporting structure can be fully exerted,and the surrounding rock control effect is the best.(4)According to the above-mentioned data,design the 12109 return airway support plan and conduct tests and field observations.The maximum sinking amount of the roof is 100mm and the maximum deformation of the two sides is 138mm through on-site measurement.No obvious separation of the roof is found.In terms of stress,the stress concentration coefficient of the two sides increases slowly with the advancement of the working face.The rock deformation shows obvious asymmetry along both sides of the central axis of the roadway.It is concluded that the asymmetric support of the anchor cable truss can effectively control the deformation of the surrounding rock of the roadway and solve the problem of the influence of multiple disturbances.