Research On Deformation Control Technology Of Subgrade Transition Section Of High Speed Railway In Seasonally Frozen Soil Area

Transition section is the key structure that affects the fast and stable operation of high-speed railway.In practical engineering,due to objective conditions or considering economic factors,graded crushed stone is often not used to fill the transition section.Laying geogrid in the filling body can improve the mechanical properties of the filling body and enhance the strength and stability of the filling body.Therefore,it is a feasible engineering measure to fill the transition section with group a filler and geogrid instead of graded gravel.In this paper,through the field investigation,the disease of the transition section of the existing railway is investigated and analyzed;through the numerical simulation analysis,the working performance of the transition section of the high-speed railway is studied under different compactness,different moisture content and different reinforcement types,and the following results and conclusions are obtained:(1)After a long period of operation,the transition section of the existing line is prone to uneven settlement.During the filling of transition section,restricted by abutment or culvert,the working surface is narrow,which is not conducive to the operation of large-scale rolling machinery,and the compaction degree of filling material is insufficient.After the train is put into operation,the transition section will be compacted and sunk under the action of train load and self weight load;in rainy season,the rainwater on subgrade surface can not be discharged in time,which can reduce the interaction between filling soil particles,and the transition section is strong When the moisture content is high in winter,frost heaving deformation will occur in the transition section;the dynamic action of train will promote the uneven settlement of rigid structures such as abutment and subgrade,and ultimately affect the stability and safety of train operation.(2)There is a negative correlation between the settlement of the transition section and the compactness of the filler.With the increase of the compactness of the filler,the settlement deformation of the transition section decreases gradually.When the compaction degree of filling is 0.95,the differential settlement of road and bridge is 2.16cm;when the compaction degree of filling is 0.93,the differential settlement of road and bridge is 2.28 cm,and the relative compaction degree is 0.95,which increases by 6%;when the compaction degree of filling is 0.93,the differential settlement of road and bridge is 2.43 cm,and the relative compaction degree is 0.95,it increases by 13%.(3)The water content has a significant effect on the settlement and deformation of the transition section.The vertical deformation and horizontal deformation of the transition section increase significantly with the increase of water content.Compared with the optimal moisture content,the differential settlement of the transition section with the fillingcompactness of 0.95,0.93 and 0.90 increases by 75%,80% and 87%,respectively,and the settlement deformation at the joint between the transition section and the general subgrade increases by 95%,96% and 99%,respectively.(4)Reinforcement measures can effectively control the settlement and deformation of the transition section.Compared with the other two kinds of reinforcement length,the effect of longitudinal equal length geogrid laying in the transition section is more significant to control the deformation of the transition section;in the transition section,longitudinal equal length geogrid laying in the transition section,the reinforcement effect increases significantly with the decrease of the reinforcement layer spacing;the influence of the compaction degree of the filler on the reinforcement effect is weak,and the reinforcement effect of different compaction degree is more significant The reinforcement effect of transition section is basically the same;the water content has a greater impact on the reinforcement effect,and the effect of reinforcement to reduce the deformation of subgrade is weak in the dry state.When the water content increases,the reinforcement measures can significantly reduce the deformation of transition section.The deformation of the transition section can be effectively controlled by laying geogrid with equal longitudinal length within the length of the transition section,and the reinforcement effect increases with the decrease of the reinforcement layer spacing.(5)Compared with the graded crushed stone filling transition section,the reinforced transition section has the advantages of small settlement deformation,convenient construction and good economic benefits,so the reinforced transition section has a good application prospect.