| Influenced by the coal seam geological conditions,the upper part of the coal seam in Guizhou Province is casually affected by the dissolved karst area.The porous and dissolved roof with a certain argillaceous filling has the characteristics of low original rock strength,poor rock integrity,and developed fissures.Therefore,the issue of surrounding rock stability control of roadway under such conditions becomes a more difficult engineering and technical problem in roadway construction and maintenance.At present,the research on its stability and control technology is still in exploration and practice.It is necessary to carry out the research on the related support theory and support technology.In order to solve the practical problems of poor integrity of surrounding rock in roadways with dissolving roof and large water inflow in rainy seasons,this paper uses the National Natural Science Foundation of China project as the subject,with the 111701 roadway of a mine in Guizhou as the engineering background,to study the rock deformation characteristics and deformation rule under the dissolved karst roof,analyze the stability of the surrounding rock,and targeted to carry out the water-blocking compound supporting theory and supporting technology research,put forward the reinforcement of surrounding rock,improve the integrity of the roadway surrounding rock supporting measures.According to actual working condition and roadway geological influence factors,this paper puts forward the"superimposed bearing arch roadway support theory",which can cope with the complex stress environment,improve the integrity of surrounding rock,have a higher support strength,and meet the requirements of roadway waterproof and water resistance.On the basis of the given supporting theory,a supporting scheme suitable for the dissolution roof is designed.FLAC3D numerical simulation software is used to simulate and analyze the characteristics of roadway stress distribution before and after adopting composite support scheme,and analyze the distribution characteristics of stress,displacement,plastic zone and so on.Combined with the numerical simulation results,the composite support scheme was effectively verified,and the mechanical bearing characteristics of the support structure on the roof and the two sides were determined.Finally,through on-site monitoring,the support has achieved good results.The main research conclusions are as follows:(1)Based on the geological data and engineering data,the mechanical properties and engineering characteristics of the dissolved roof are described.The deformation and failure characteristics of the surrounding rock of the dissolved roof are analyzed.The deformation and failure characteristics of the surrounding rock are as follows:asymmetric deformation of the roadway,obvious phenomenon of strong mud,large flow of water from cracks,inward shrinkage of side shoulder Angle,roof subsidence,failure of anchor rod and anchor cable,tearing of metal net,serious convergence of local section,etc.The deformation characteristics of the surrounding rock of the dissolved roof are analyzed from four aspects:stress environment,rock lithology,supporting structure and physical and chemical action.(2)The surrounding rock control concept of superimposed bearing arch roadway was proposed based on the deformation and failure characteristics and laws of the surrounding rock of the dissolved roof.The surrounding rock control theory of"superimposed bearing arch"for the dissolved roof is put forward.Theory of the main principle is:500 mm thickness of grouting layer can achieve resistance and can significantly improve the integrity of the surrounding rock,water slurry infiltration to form network skeleton structure fracture zone,strengthening supporting the weak link,strengthening the bearing performance of surrounding rock and increase the broken area the residual strength of rock mass,the plastic zone of surrounding rock integrity,compressive,both high strength and moderate pressure,and can form a layer of waterproof supporting shell effectively,prevent water erosion damage to the roadway.The mechanical model of superimposed bearing arch was established,and the calculation formula of roof ultimate bearing capacity of superimposed bearing arch was deduced.Secondly,the calculation model of"superimposed bearing arch"supporting structure was established,and the formulas for solving the stress and displacement in elastic zone,plastic zone and broken zone were deduced.(3)The principle of surrounding rock support of the dissolution roof roadway was clarified.Based on the above research,the support scheme was designed and a composite support scheme of"bolt(cable)+grouting+U-shaped steel"was determined.For the grouting part in the composite support scheme,the physical and mechanical experiments of the grouting body were carried out to test the mechanical properties.The supporting mechanism of the grouting system is analyzed from three aspects:the framework structure of the rock mass network,the reduction of the range of the broken zone and the plastic zone,and the grouting interlayer to prevent the water-physical erosion.(4)The dissolution hole numerical model and the tunnel numerical model are established to analyze the stress state of the dissolution roof and the vertical displacement,horizontal displacement and plastic zone of the tunnel before and after adopting the composite support scheme.The numerical simulation results show that the"bolt(cable)+grouting+U-shaped steel"composite support scheme can effectively improve the integrity of surrounding rock,make the surrounding rock have a large support reaction in the periphery,and effectively control the settlement of the dissolved roof and the two sides of the displacement.The composite scheme can effectively coupling the rock mass with the supporting structure,improve the active bearing capacity of surrounding rock,and meet the requirements of roadway support.(5)Taking 111701 roadway of a mine in Guizhou as the engineering background,industrial tests were carried out to monitor the roadway section of the proposed composite support scheme.YJDM3.6 mining laser roadway section detector was used to monitor and record the data of roadway roof subsidence,two-side moving amount and floor heave deformation.Monitoring results show that final deformation of roof,both help and floor heave amount closer to roadway support expectations."bolt(cable)+grouting+U-shaped steel"compound supporting technology can improve the dissolved karst roof integrity,reinforces the surrounding rock of the bearing capacity,blocks the fissure water to the influx of roadway,relaxed the move to the internal space of surrounding rock,the overall stability of roadway control the desired effect. |
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