The Stability Evalution Of Mining Subsidence Area And The Analysis Of Influence On The Upper High-speed Railway Line

China is a big country of coal resources reserves and consumption,the exploitation of coal resources has produced a large number of mined-out areas.In some areas,the construction of high-speed railway is inevitable to pass through the mined-out areas.Therefore,the surface stability of mined out area is related to the safety of railway construction and operation.The paper relys on Guinan high-speed rail(Nanning section)line engineering above er Tang Coal Mine Goaf,by adopting the methods of field investigation,theoretical analysis,numerical simulation and data monitoringto Combined with the characteristics of the soft rock in the area,carried out systematic and in-depth study.The main research contents and conclusions are as follows:(1)The mined-out area was explored by using field investigation,comprehensive geophysical prospecting,seismic imaging method and high density resistivity method and drilling method,Made clearthat the distribution,mining depth,range,boundary and filling condition of the coal-mining area which the high speed railway passes through.Dapanjing goaf has the greatest influence on the selected high-speed rail lines,in addition,the subsidence and bending deformation of overlying rock mass in goaf have been basically completed.The mined-out area has been filled with mudstone or silt,the,the filling time is long and the packing has high density;(2)The paper analyzed the surface movement deformation and failure mode of the mined out area.Mainly include cracks and steps,collapse pits and moving basins.to summarize the theory of mining subsidence prediction.Studied the principle of probability integral method and calculation formula of surface movement and deformation emphatically.The "activation" mechanism of the overlying strata in the goaf and the effect on the surface lines are analyzed;(3)The prediction model of mining subsidence is established by using probability integral method,to study on Surface Movement and Deformation of Mined-out Area Caused by Coal Seam Mining.The maximum surface subsidence caused by mined out area is about 1310 mm,the maximum horizontal movement is about 320 mm.The affected length by the mined-out area of the High-speed rail line 2 is about 1200 m and the line 3 is about 700 m.The surface movement continuation time of Datang well mining area in Ertang coal mine is about 500 days,The mining area mining terminal time has reached 35 years,Dapan wells subsidence area has been in overall stability.The surface residual deformation value after the mining movement period was calculated as 140 mm,The remaining 25 mm in the future for a long time to complete,the settlement rate of residual settlement is-2mm/y,to monitor the ground subsidence rate by PS-In SAR technology of-4 ~ 4mm/y is basically the same.It can be determined that the residual settlement of mined out area is basically completed;(4)This paper establishes 3D geological model of goafs in Dapanjing with finite element software MIDAS/GTS,analyses the mobile deformation of strata and surface in goafs,the maximum of 1275 mm,the maximum horizontal displacement of 330 mm,the results from numerical simulation and probability integral method are basically identical.At the same time,this paper simulates the effect of high-speed dynamic load in mined-out area with finite element software MIDAS/GTS.The result of simulation is that there are 1.78 mm residual settlement in goafs under high-speed moving load.It shows that the stability of goaf foundation within the scope of the standard;(5)This paper analyses the stress and attenuation rule of high railway base under dynamic load of dynamic.High railway speed is 350km/h,train axle load is 200 KN,subgrade’s dynamic stress amplitude is 106.6k Pa,the longitudinal distribution of length is 1.44 m,dynamic load impact depth is about 5m,The critical safety depth is 23 m,the dynamic load of high speed railway has no influence on goafs,because the depth of the mined-out area is 100 m.And puts forward the treatment measures of mined-out area for the safety of railway subgrade.