Underground Coal Mining On Highway Subgrade Road Surface Deformation Impact Study

China’s coal resources are very rich,and coal provides important energy for the development of China’s industry and other fields.Follow the problem is that wear under the domestic highway subsidence phenomenon more and more,because the seam is produced,the surface subsidence,makes roadbed instability,pavement cracking,plus the rain infiltration,highway roadbed damage increased,thus affect the normal driving safety.Aimed at the phenomenon of the subgrade pavement damage,this study with the nanchuan district of chongqing city to pine highway sections below coal mining activities as the basis,using FLAC3 D numerical simulation,and the road surface of the earth’s surface deformation law are analyzed,mainly do the following several aspects:(1)The simulation of three coal seams with different deep ratios shows that the deeper the coal seam is,the greater the surface subsidence will be.Will rock contour at70 ° Angle of the influence of deformation along the overburden extends to the surface,on both sides of the curve is symmetric distribution,each rock layer formed on the surface of subsidence area is greater than the actual goaf area.The surface position corresponding to the center of goaf is the largest subsidence.(2)The simulation analysis was carried out on the different dip Angle of coal seam,the results show that the rock strata movement is a continuous dynamic process,the surface deformation and dip Angle of coal seam is linear relationship,the greater the Angle,the surface affected by coal bed mining range,the greater the vertical distortion than in horizontal direction.(3)From different speed frequency analysis of the surface deformation,the results show that the deformation affected by coal bed mining road,under traffic loads,the greatest influence on pavement deformation speed of 60 km/h,with the increase of duration,surface subsidence deformation will increase.(4)To simulate the different load vehicles to the influence of the secondary deformation of road surface disturbance of mined-out area,the results show that the vehicle wheel pressure,the greater the surface subsidence,with 1.17 MPa pressure under the action of 36.4 mm maximum surface subsidence.The stress in each layer of pavement decreases with the increase of depth.When the depth reaches 0.48 m,the stress in the vertical direction is very small.(5)Analysis of longitudinal 100 m range road surface subsidence along the route,the results show that when the coalface after under the roadbed,along the route vertical subsidence will appear uneven settlement of left and right sides is symmetrical,position corresponding to the road surface subsidence in the center of the mined-out area is the largest.Therefore,it is necessary to determine the level of the influence of underground coal seam mining on the surface,and to provide basis for the construction of road wiring and scheme.(6)With integral calculation method on the surface and surface deformation calculation,modeling analysis results and the theoretical calculation results are consistent,it is concluded that the pavement deformation affects the smallest permissible value,the surface deformation: the surface of the slope is less than or equal to 3.0 mm/m,the surface horizontal deformation is less than or equal to 2.0 mm/m,for highway road surface subsidence value should not be greater than 25 mm,if more than the permissible value,need to abscission layer grouting reinforcement in deformation range of road.