Evaluation Index And Optimization Of Protection Measures For Subgrade Transverse Temperature Difference In Frozen Ground Region

With the construction and operation of railway in frozen ground region,the deformation problem of subgrade caused by the difference of transverse ground temperature is prominent.How to evaluate and eliminate or weaken the difference of transverse ground temperature and improve the long-term stability of subgrade has become the key problem to be solved urgently.In order to solve this problem,this paper puts forward the evaluation index of subgrade temperature difference in frozen ground region,and compares the common protection measures accordingly.Finally,according to the evaluation index,the measure with better performance is selected for further optimization.The main work completed is as follows:(1)This paper puts forward the evaluation indexes which can reflect the characteristics of space and time change of roadbed temperature difference,including the uniformity index of the time-range change and the the symmetry index of ground temperature at typical moments of ground temperature.By simulating the temperature field changes of roadbed with different anti-frost berms,the maximum freeze depth,uniformity evaluation index and symmetry evaluation index are calculated,the change of ground temperature difference is compared and the feasibility of evaluation indexes calculation method is verified.(2)The roadbed numerical models laying EPS insulation board and PU insulation board are established and calculated,and the basic laws of temperature change of different operating conditions during the process of freeze-thaw cycles are compared.The changes of the ground temperature differential evaluation index under different working conditions are calculated,and the advantages and disadvantages of different measures are compared accordingly.(3)A numerical calculation model of the roadbed with heat rods is established,the changes of the ground temperature distribution are studied,and the evaluation index of geothermal variability is calculated,and the results show that the uniformity index of the ground temperature time-histories change and the symmetry index at typical moment have been improved,which shows that the anti-freezing effect of the roadbed with hot rods is relatively excellent.(4)The roadbed with hot rod is optimized by the ant colony algorithm,and the hot rod is adjusted according to the change of the temperature difference indexes of the roadbed,then the optimal treatment scheme is obtained.