Dynamic Response Analysis Of High Railway Subgrade In Seasonal Frozen Region

With the construction and transportation of high-speed railways in seasonal frozen ground areas,the stability of roadbeds has become increasingly prominent.It is necessary to study the stability and development trends of subgrades under the influence of freeze-thaw cycles and train loads to ensure safe and smooth operation of the railway.Taking the roadbed to deep-seasonal frost region as the research object,on the basis of previous research results,theoretical analysis and numerical simulation,of ground temperature distribution law of the roadbed was analyzed,and the freeze-thaw was studied.Development trend of ground temperature field,stress field and dynamic displacement of roadbed under cycling loads are studied.The research results are helpful for deep understanding of the development and changes of the stability of the high-speed railway subgrade in the deep seasonal frozen ground,and provide references for improving the design of the high-speed railway embankment in the seasonal frozen ground and the measures for frost damage remediation.This research can be summarized in the following:2D model of railway embankment with ballastless track based on a prototype of embankment in Harbin-Dalian high speed railway in northeast of China is established by means of numerical simulation with ABAQUS.Subsequently,the model is used to evaluate efficacy of the mitigation measures.The extent of stiffening block and effect of material modulus are investigated.Generally,the stiffness of surface layer of subgrade bed increasing is found to be effective in reducing the subgrade vertical acceleration.when the roadbed surface layer modulus is over 5 GPa,its effect on reducing vibration is not obvious,which means that 5 GPa have positive influence on vibration isolation and costs relatively less.Block thickness increasing appears to be highly effective for vibration isolation.Vibration mitigation weakens as the distance deepening and the vibration of subgrade even increase when the depth is over 1 m~1.6 m.Overall,the conducted study highlights the potency of vibration mitigation by installing a stiffening block in an appropriate extent beneath track.3D model of numerical analysis has built to study the influence of high speed railway dynamic response on the subgrade in seasonal frozen region.According to the statistical values of land surface temperature from Harbin-Dalian,and taking into account the rising trend of ground temperature,the distribution of the temperature field of the Harbin-Dalian subgrade has been predicted.The numerically calculated steadystate temperature field results(calculated based on temperature for 30 years)are added as initial conditions to the subgrade calculation model(ballast and ballastless models)to realize the coupling of the temperature field and the stress field.And then the influencing factors for subgrade dynamic response(dynamic stress,and dynamic displacement)was calculated including of embankment in different height and in different slope,ballast and ballastless track,and,different cases of axle load of highspeed train.