Weakening Rule And Stability Control Of Surrounding Rock In Deep Close Range Coal Seam Roadway

During the mining of the deep close distance coal seam group,the bottom plate rock mass follows the propulsion direction of the working face.Along the inclined direction of the working surface,the concentrated stress formed in the coal column left by the overlying coal seam is transferred in the bottom rock mass to produce additional stress to the mining roadway arranged in the lower coal seam,and the main stress difference of the surrounding rock of the roadway increases sharply.In the mining roadway arranged in the coal rock mass,the ore pressure is more severe,and the maintenance is extremely difficult.Based on this,this paper to 3232 zhou yuanshan coal mine mining roadway as the research background,the deep close coal seam roadway deformation failure characteristics and cause analysis,the deep close coal seam roadway surrounding rock damage weakening law,deep close coal seam roadway surrounding rock deformation damage rule,deep close coal seam roadway surrounding rock stability control and support principle,deep close coal seam roadway support technology and engineering test,and the industrial test,roadway surrounding rock deformation was effectively controlled.The main research results of this paper are as follows:(1)The mining roadway of Working Face 3232 in Zhouyuanshan Coal Mine was selected as the research background,combined with the characteristics of roadway zoning,segmentation,and asymmetric deformation.The observation of roadway roof structure and indoor point load test of rock mass were carried out,and the basic situation of roadway roof crack development and rock mass mechanical parameters were obtained.It was found that the mechanical properties of roadway surrounding rock themselves are one of the key factors affecting roadway deformation.Secondly,according to the different occurrence conditions of the overlying strata in the roadway,the entire roadway is reasonably divided into five sections,providing a modeling basis for later two-dimensional similar simulation tests and numerical simulation research.Finally,in comprehensive consideration of previous research results on the distribution of roadway stress under different occurrence conditions,a mechanical model for the mining roadway in Working Face 3232 of Zhouyuanshan Coal Mine was constructed,and the evolution laws of the principal stress difference between the upper coal seam floor and the lower coal seam roadway surrounding rock were studied,providing a theoretical basis for roadway deformation and destruction,and further providing a theoretical basis for the stability control of roadway surrounding rock under such conditions.(2)Firstly,the concept of "disturbance factor",which can comprehensively reflect the weakening factors of surrounding rock in deep mining roadway,is proposed,and its impact on the law of rock damage and weakening is deeply analyzed;Based on the stress transfer law of surrounding rock during roadway excavation in damaged coal and rock mass,a triaxial loading unloading uniaxial reloading test of rock mass was designed,and the functional relationships between the peak strength of sandstone specimens after unloading and confining pressure,initial axial pressure loading ratio,and porosity were determined;The uniaxial reloading failure mode of the damaged sandstone specimen changes,and the failure mode of the rock is related to the loading history.The evolution law of acoustic emission amplitude during rock loading under different failure modes has a segmented development,which quantifies the corresponding relationship between strain and acoustic emission amplitude.According to the hoop strain law,the damaged rock exhibits two states:plastic hardening and plastic softening.The uniaxial reloading failure characteristics of damaged sandstone specimens have changed,and the damaged rock is mainly tensile failure.As the damage value increases,the failure mode gradually changes to shear slip failure.Based on elastoplastic fracture mechanics,the mechanical properties of micro cracks in rock are analyzed,and it is found that the micro mechanical properties of rock have a significant impact on the macro mechanical response;A three-dimensional damage evolution model of rock based on Weibull distribution is established to distinguish the damage evolution process of rock.(3)Select river sand as aggregate,gypsum + cement as cement,design considering 3factors 5 level orthogonal test,using the difference analysis,variance analysis and multiple regression analysis,studied the river sand,gypsum,cement and other key factors for similar material longitudinal wave velocity,compressive strength,tensile strength,density and the influence of elastic modulus.Further,the similar simulation test bench of deep close coal seam was built,and the monitoring of rock layer displacement,stress and damage characteristics in the mining and excavation of lower coal seam roadway was carried out.The working face is along the tendency direction,the roof of the goaf collapses seriously,and the coal pillar roof deform slightly.With the coal seam mining,the overburden rock load is transferred to the coal pillar side,and the lower floor of the goaf has a large range of pressure relief area,and the lower floor of the coal pillar has a local pressurization area.Through numerical simulation,the distribution law of the surrounding rock of 3232 working face is analyzed.Along the direction of the working face,the differential distribution characteristics of zoning and segmentation,and it provides a theoretical basis for the design of roadway zoning and segmentation support.(4)Design the anchorage test of damaged rock mass,The bolt had no effect on its failure pattern,Both show splitting disruption with low damage and shear slip disruption with high damage,But has an effect on its destructive characteristics,The destruction characteristics of damaged rock mass under the action of anchorage are more diverse;The crack extension model of rock-anchor combination is established,It reveals that the weakening of rock strength damage and the continuous expansion of internal cracks are the main causes of rock instability and deformation;The grouting test of single fissure rock mass,Characterizing of stress-strain curve under load condition of grouting specimen,The influence mechanism of surrounding pressure and grouting material on the strength strengthening and destruction mode of fracture rock is expounded,last,The calculation method of the bonding force of grouting material and structural surface strength is derived;The reinforcement test of cemented broken rock mass,The parameter sensitivity characteristics of the supporting components are analyzed,The progressive failure process of the reinforcement specimen is described,The evolution model of anchor-surrounding rock is constructed,Combined with the numerical simulation methods,The characteristics of the coupling mechanism of bolt(cable)are studied.(5)For the basic conditions of mining roadway,proposes the principle of "partition section and key parts key support",designs the "asymmetric support" scheme,monitors the deformation of the roadway roof base,further calculates the convergence rate,thus judging the deformation trend of the roadway surrounding rock,provide the basis for the supporting strength parameter design,the engineering application monitoring data results show that the supporting scheme design has certain rationality.