Analysis On Dynamic Response Of Ballastless Track Subgrade Of High-speed Railway

In recent years, the high-speed railway has been constructed more and more quickly, with a considerable scale of achievements. The construction of high-speed railway has been still continued. Presumably, to the end of 2015 the operating mileage will run up to 18000 km and the fast-train networks with the core of the high speed railway will be weaved. By then, the total mileage will be more than 40000 kilometers. At present, Ballastless track has been widely used in the construction of high-speed railway. As a new track structure, its dynamic performance and the force transmission characteristics are quite different with the traditional form. In this paper, with CRTSⅡSlab ballastless track as an example which was widely used in the construction of high-speed railway, a dynamic analysis will be made through the establishment of three-dimensional solid finite element model. The mainly researchment will be achieved as follows:①This paper discussed the development of high-speed railway in our country, and the planning of the future analysis frantic jumble orbit in the application of the high-speed rail construction process and its importance, and summarized the high speed railway subgrade dynamic response problem of the research background and the status.②This paper analysed of the classification and characteristics of high speed railway subgrade structure, collected the measured values of the dynamic stress on the top of the bed surface and the related research materials, compared with using frantic jumble track subgrade dynamic stress is far less than that of the roof has a frantic jumble orbit, but the frantic jumble track makes the dynamic function of train loads spread more widely and the power attenuation slower.Studies of train load is analyzed using a simplified to simulate the train loads in the form of wheel/rail force combination. Writted the subroutine in Fortran language, which will make the moving load changed over time in the finite element software.③Established a roadbed model, writed a subroutine DLOAD of train load,with the contrast of time history on stress in track plate and the top of the bed surface, the reliability of the mode in this paper was verifyied. To extract the equivalent stress of track structure and acceleration time history, found on the top of the support layer bogie two rounds of stack effect significantly, there is no single wheel load peaks.Got the track plate and concrete support layer stress of lateral distribution.④Extracted the subgrade structure of equivalent stress time history, vertical displacement time history, and various structural layers in the roadbed, the acceleration time history.Found the depth, the greater the response of the transverse distribution more uniform, the dynamic response peak was not obvious.Through the analysis of the distribution and the attenuation law of vertical and horizontal, found at the bottom of bed surface and bed top surface, the maximum dynamic stress on the edge of the support layer below, supported the dynamic stress of the edge of the vertical layer of attenuation was mainly within the bed, and the bed surface and bed to the dynamic stress at the bottom of the diffusion ability existence very big difference, the former was superior to the latter.From the subgrade surface depth of 1.17 m, displacement attenuation in half.Vertical displacement produced by the deformation of subgrade, the basic unit depth of bed surface displacement was the largest.Within the scope of the support layer vertical displacement basic symmetric to the center line of the orbit, the transverse distribution difference was small, closed slightly larger than the lateral and transverse distribution on the surface of the bed surface of the bed of the underlying surface transverse distribution more uniform, each structural layer of roadbed were maximum at the center line of the orbit, outside the scope of support layer, displacement decrease rapidly.At the bottom of bed surface and bed surface, rail acceleration slightly bigger than just below the centerline orbit, difference was very small.At the top of the subgrade body surface, the center line of the orbit of the maximum acceleration.Outside the scope of support layer, add speed along the lateral subgrade rapid attenuation. In addition, with the depth deepening, vibration attenuation speed and dynamic stress and vibration attenuation was similar.⑤Analysis of the two kinds of orbital velocity influence on the results of a smooth condition was made,finding that whether considering the track irregularity, the increase of train speed increase would lead to dynamic response, the response to the increase of amplitude was put in bigger difference.The increase of the acceleration and dynamic stress was most significant.And track irregularities of the speed of dynamic stress, acceleration amplification effect was more obvious, the impact on the vertical displacement was very small.⑥In the process of dynamic response analysis, some suggestions on the project construction was put forward according to the results of the analysis on dynamic response.