| The thickness of the overlying coal seam on the roof of the extra-thick soft coal seam roadway is large and the structure is complicated.The top coal usually has the characteristics of low strength,weak bearing capacity and poor stability.In order to solve the technical problem that the surrounding rock breakage and deformation are serious and difficult to control during the service period of this kind of roadway,this paper takes the mining roadway of Jindi Coal Industry Extra Thick Coal Seam as the research background,and comprehensively conducts field surveys and laboratory test methods.Strength characteristics and occurrence structure characteristics were analyzed;on the basis of theoretical analysis,similar simulation,numerical calculation,etc.an ultra-thick coal roadway arch-beam coupling active bearing support system was constructed,and composite beams and bearing arches were elaborated The formation and function of the bridge and the active bearing mechanism of the arch-beam coupling;at the same time,the relationship between the key parameters of the tunnel support structure and the stability of the arch-beam bearing structure was studied,and the tunnel support optimization and engineering application were carried out.And stability monitoring research.The study reached the following conclusions:(1)Roof peeping and sampling test results show that the overlying coal roadway in the extra-thick coal seam has a complex and soft broken structure,and the development of interlayer bedding,joints,and fissures is relatively high,and the number of layers of coal in the top coal is large It is accompanied by multiple delaminations;at the same time,the physical and mechanical strength of the roadway top coal is low,the compressive and shear resistance is poor,and the bearing capacity is weak.(2)Aiming at the characteristics of roadway roof in extra-thick coal seam,on the basis of the existing roadway support theory,an arch-beam coupling active bearing support system for extra-thick coal seam is proposed.When the roadway roof is supported by the arrangement and anchoring force,an arch-beam coupling bearing structure with a larger bearing capacity can be formed in the roadway roof.It can effectively suppress the development and deformation of cracks in the top coal body,and at the same time can greatly improve the strength and bearing capacity of the surrounding rock in the roadway anchorage area and reduce deformation and damage.(3)Numerical analysis and similar simulation results show that after the tunnel arch-beam coupling load-bearing structure is formed,the average compressive stress of surrounding rock in the depth range of 0.5 ? 1.5 m above the roof of the tunnel can reach 169.04 k Pa,which is more than that of the anchor beam alone.When it exists(43.06 k Pa),it increases by about 292.6%;the average compressive stress of the surrounding rock in the depth range of 3.0 ? 5.0 m above the roof is also greatly increased.Under the effect of the arch-beam bearing structure,the deformation rate and deformation of the surrounding rock of the roadway are significantly lower than that of the bolt support.The roadway can still maintain good stability with increasing burial depth.Ability improved significantly.(4)Numerical calculation and analysis show that with the change of the parameters of the roadway bolts and anchor cables,the change of the roadway arch-beam load-bearing structure is obviously different.Among them,the anchor cable has the most important influence on the shape of the arch-beam bearing structure.The length,preload,and spacing of the anchor cable have an increase of 127.1%,96.1%,and 117.8% on the volume of the arch-beam structure.The increment of the internal stress of the arch-beam structure is 28.9%,103.7%,and 151.8%,respectively,and the increment of the arc length of the arch-beam structure is 52.6%,108.8%,and 101.8%;The inter-row spacing has an increment of 45.5%,83.1%,and 46.2% for the volume of composite beams in the arch-beam bearing structure,and an increment of 23.0%,150.0%,and 92.4% for the internal stress of composite beams.(5)According to the arch-beam bearing mechanism and the analysis of its influencing parameters,a form assessment system for the stability of tunnel archbeam bearing structure was established.Based on the analysis of parameter correlation and contribution rate,the weighted calculation method was obtained The influence of key supporting parameters on the stability of arch-beam bearing structure is solved in order to solve the blindness in the optimization process.The order of influence is as follows: pitch between anchors > pretension of anchors > length of anchors > pretension of anchors > distance between anchors > length of anchors.(6)According to the arch-beam coupling support theory of the roadway in extra-thick coal seam,the parameters of the support structure of the mining roadway in Jindi Coal Industry have been optimized.The practical application of the project and the stability monitoring of the roadway show that The bolts and cables are reasonably stressed,the overall stability and bearing capacity of the surrounding rock are significantly improved,and the deformation rate and deformation of the surrounding rock are effectively controlled,which fully meets the safety production needs of the working face and realizes safe mining. |
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