Analysis And Experimental Study On Mechanical Characteristics Of Height-adjust Of Ballastless Track In High Settlement Section

With the rapid development of urban rail transit in our country,the subway transport capacity and local engineering quality defects lead to more and more diseases of ballastless track structure in the tunnel,especially tunnel basement subsidence diseases,such as shanghai,tianjin,guangzhou,hangzhou,ningbo and other cities belong to the soft soil area,which brings the new challenges to tunnel stability after the operation.Settlement of metro tunnel that will inevitably lead to the line in the process of uneven settlement,this causes the separation and clearance of the ballast bed and the segment,ballast bed cracking,segment breakage,which leads to the deterioration of the seepage structure,track condition,train dynamic load increasing,such as settlement of metro tunnel in soft soil area is more outstanding,eventually will affect the normal use of the subway and train operation safety.At present,the renovation and maintenance of track structure of urban rail transit in soft soil area,such as ballast bed cutting,new buried short pillows,adding rail bearing platform between pillows,and directly buried casing on track bed surface,have problems such as long maintenance and construction time,influence on normal train operation,and lack of maintenance quality and durability.Based on this,in order to develop a ballastless track structure that can be easily and quickly maintained when the contact passage and the soft soil tunnel section are in large settlement,so as to reduce the practical requirements of the settlement of the bed affecting the train operation,it is necessary to carry out an in-depth study on the restoration of adjustable ballastless track.The specific contents are as follows:(1)The fatigue load of ballastless track structure with or without settlement was calculated by establishing vehicle-track coupling dynamic model and using the time-domain samples generated by the American Level 5 spectrum as external excitation.(2)Through the establishment of height-adjust of ballastless track three-dimensional nonlinear finite element model,and calculate the track slab,base slab in the settlement of different location of the maximum tensile stress,found that the structure of the most unfavorable position in the settlement curve inflection point.Based on this,the limit value of settlement of the structure at different wavelengths is obtained.The maximum settlement of the settlement curve should not be more than 1.4 times of the corresponding settlement wavelength.(3)In order to verify the feasibility and reliability of the completion of the height-adjust of ballastless track structure settlement repair in the operation "skylight" period.The unit experiment of filling material indoor,fatigue test of vibration isolated track structure indoor and field adjustable ballastless track structure laying and maintenance test were carried out on the selected self-compacting high-strength concrete filling material.This proves the applicability of the filling material.(4)For the settlement repair scheme of height-adjust of ballastless track,this paper obtained the ultimate filling thickness,the ultimate filling times and the optimal position of the filling layer for multiple filling by analyzing the transverse stability of the track structure and the fatigue life of the filling layer structure.