Analysis Of Frost Damage Characteristics And Treatment Technology Of Subgrade In Western Section Of Lanzhou-Xinjiang Railway

In the development of economic construction in Northwest my country,the construction of high-speed railways is particularly important.However,most of the northwestern region belongs to the seasonally frozen soil area,the soil often undergoes frost heave,and the roadbed frost damage is serious.The subgrade stability of the existing lines is poor and cannot meet the train speed requirements,which seriously hinders the development of high-speed railways.In order to ensure the stability of the roadbed in the seasonally frozen soil area,it is very important to study the frost heave problem of the seasonally frozen soil and the roadbed frost damage treatment technology.In view of this,this article combines the subgrade reconstruction project of the western section of Lanzhou-Xinjiang Railway to study the subgrade temperature field and frost damage remediation issues through the analysis of the monitoring data of subgrade frost damage in the physical test section and numerical simulation methods.The main contents and conclusions are as follows:(1)Select monitoring points on the severely frost-damaged section of the subgrade Based on the monitoring data of soil temperature and moisture inside the subgrade,the law of temperature and moisture changes during the freeze-thaw cycle of the subgrade soil in the seasonally frozen soil area under the action of atmospheric temperature is analyzed,and the response of soil temperature to the atmospheric temperature is analyzed.and Study the coupling characteristics of soil temperature and moisture inside the subgrade.It is concluded that during the freeze-thaw cycle,the temperature change trend of the subgrade soil at each depth is almost the same as the change trend of the water content,but due to the influence of the soil heat capacity and the water heat capacity,the peak temperature of subgrade soil always lags behind the peak water content.(2)According to the climatic characteristics of the western section of the Lanzhou-Xinjiang Railway and the freezing depth of the roadbed in the past 3 years explore the development law of the freezing depth of the roadbed,refer to the calculation theory of railway subgrade freezing depth in seasonal frozen soil area at home and abroad,the function fitting method is used to obtain the power function relationship between freezing index and freezing depth,In addition,A method for estimating the freezing depth of the western section of the Lanzhou-Xinjiang Railway was proposed,and it was found that the freezing index showed a gradually increasing change law from east to west.(3)Based on the heat conduction theory and the finite element method,a nonsteady state roadbed temperature field model with phase change is established.Taking solar radiation,effective radiation of pavement,air temperature and convective heat exchange as upper boundary conditions,perform numerical simulation to solve and compare and verify with monitoring data,it analyzed the influence of the change of outside air temperature and the process of soil freeze-thaw phase transition on the changes of soil thermal parameters,and the distribution law of Subgrade temperature field in the process of freeze-thaw cycle is studied.(4)Through the evaluation of subgrade frost damage treatment effect in the aspects of subgrade soil temperature,moisture and deformation,it is proposed that the treatment technology of laying transverse seepage ditch and draining drainage hole should be adopted in the treatment of subgrade frost damage,in which the treatment effect of hole by hole excavation and setting transverse seepage ditch every other excavation is the best.It is found that the treatment effect of setting seepage ditch every other excavation is 80 cm and 60 cm the difference is not big,so the horizontal seepage ditch with depth of 60 cm should be selected.The comprehensive treatment technology of setting transverse seepage ditch and grouting reinforcement combination should be adopted in the transition section of road culvert,in which the combination of every other excavation and grouting reinforcement is the best.the results show that the treatment effect is better than that of every three excavation and grouting reinforcement.