Study On The Influence Of Uneven Settlement Of High Speed Railway Subgrade On The Stress Deformation And Cracking Of Monolithic Track Bed

As a structural form of ballastless track in high-speed railway,monolithic track bed has been widely used in the construction of high-speed railway in China due to its high smoothness,high stability and less maintenance.However,as a reinforced concrete slab laid on the roadbed,the uneven settlement of the roadbed will lead to deformation,cracking and other problems.This will not only change the mechanical performance of the monolithic track bed due to the action of the train load,resulting in the ride irregularity and insecurity,but also affect the durability of the monolithic track bed.In view of this situation,combined with the specific situation of a high-speed railway in Northwest China,this paper studies the deformation and cracking of the monolithic track bed caused by the uneven settlement of the high-speed railway subgrade,as well as the relationship between the settlement of the subgrade,the running speed of the train and the mechanical performance of the monolithic track bed,and on this basis,studies and determines the limit value of the uneven settlement of the subgrade.The main research work is as follows:1)Based on the field investigation of the cracking status of the monolithic track bed of two high-speed railways within the jurisdiction of Lanzhou Railway Bureau,this paper makes a scientific summary of the investigated data,analyzes the cracking type,crack location and crack form of the monolithic track bed,and probes into the relationship between the subgrade settlement and the cracking mechanism of the monolithic track bed in combination with relevant theories.2)Through the established finite element model,the uneven settlement value of the roadbed when the first,second and third cracking of the ballast slab concrete is analyzed,and the variation laws of the crack distribution,the stress of the ballast slab and the displacement of the ballast slab under the three settlement conditions are studied;In this paper,the cracking of Monolithic Track Bed Slab under different settlement conditions,such as 0,5,10,15,20,25,30,35,40(unit mm / 20 m),and the displacement of Track Bed Slab and the stress of Track Bed Slab under this settlement condition are analyzed and studied.On this basis,the mapping relationship between the uneven settlement of high-speed railway subgrade and the stress deformation and cracking of track bed slab is obtained.3)Through the established finite element model,combined with the mapping relationship between the uneven settlement of subgrade and the stress deformation and cracking of monolithic track bed slab,the vertical acceleration,rail displacement,bed plate displacement and bed plate stress of the monolithic track bed under different train operation speed and subgrade settlement are discussed and analyzed.Based on this,the influence of subgrade settlement and train operation speed on the mechanical performance of the monolithic track bed is obtained.4)Through the established finite element model,combined with the mapping relationship between the uneven settlement of the railway subgrade and the stress deformation and cracking of the track bed slab,and the influence of the settlement of the subgrade and the running speed of the train on the stress performance of the monolithic track bed,based on the four angles of train safety,dynamic characteristics of track structure,passenger comfort and adjustable error of structure,the limit value of uneven settlement of Subgrade of ballastless track bed plate is obtained.