Study On The Freezing Damage Characteristics Of Shen-shuo Railway Subgrade And Prevention Measures

The subgrade of Shen-shuo Railway suffered from the seasonal freeze-thaw cycle and heavy axle load,which resulted in uneven deformation and made the subgrade prone to deterioration failure.It affects the safety of Shen-shuo Railway operation seriously.Therefore,it is significant to study on the frost heaving characteristics of subgrade filling and reasonable anti-frost heaving measures for Shen-shuo Railway.In this paper,firstly the physical properties of subgrade filling of the Hedong section of Shen-shuo Railway were analyzed by routine soil tests.Secondly,based on the experimental results of Shen-shuo Railway subgrade filling subjected to no load,static load and dynamic load under the condition of closed frost heave,the effects of initial water content,compactness,cold-end temperature,load values and frequency of dynamic load on frost heave characteristics were discussed.Finally,by the hydro-thermal coupling and frost heave models,the variation of temperature field,moisture field and stress-strain field in Shen-shuo Railway existing subgrade was analyzed.In addition,the anti-frost heave effect of insulation layer was comparatively analyzed.The main conclusions in this paper are as follows:(1)For the subgrade filling subjected to no load,when the initial moisture content is 15%,the filling has not occured frost heave.However,when the initial moisture content are 18%and 21%,with the increase of compactness and the decrease of cold-end temperature,the frost heaving ratio of soil samples increases significantly.(2)The experiment results of subgrade filling under the condition of no load indicate that when the initial water content increases by 3%,the maximum amount of water migration increases by more than 1%in the unfrozen section.(3)Under conditions of static and dynamic loads,the frozen depth of subgrade filling changes little.Nevertheless,compared with the sample whose compactness is 0.93,initial moisture content is 18%and cold-end temperature is-5? subjected to no load,the frost heave decreases 3.59mm and 0.98mm respectively,which indicates that load has inhibiting effects on the frost heave of subgrade filling.(4)Under conditions of static and dynamic loads,the water content distributions of soil samples are roughly the same after frost heave tests.The water migrates from unfrozen sections to frozen sections,but the total water content of samples is constent.(5)For the Shen-shuo Railway existing subgrade,the temperature field under the ballast is significantly improved by laying polystyrene insulation material.The depth of 0?isotherm can reduce 0.08m,and the frost heave approximately decreases 22.3mm.According to the comprehensive comparison analysis on the calculated results of the numerical model,the 10cm thickness polystyrene insulation layer laid in the surface of ballast except the sleeper,the ballast slope and outside the basal slope lm has the most anti-frost heave effective.