| Railrway foundation project is a strip of geotechnical structures built on the ground.The construction of the roadbed project will change the local landscape,while inevitably subject to the long-term role of natural camp forces,resulting in changes in the performance of the service state of the roadbed project.A high-speed railrway in the northwest seasonal permafrost zone traverses different topographic features,climate zones and geological environments.In the operation process under the action of different natural forces,will appear all kinds of engineering disease.Such as freezing and thawing line deformation,such deformation once over the limit,will seriously affect the smoothness of the line,hinder the safe operation of the railrway,and even threaten the safety of people’s lives and property and regional economic development,therefore,must carry out seasonal permafrost area high-speed railrway roadbed deformation caused by freezing and deformation of the disease problem of targeted research.In this paper,a combination of theoretical analysis,field investigation and finite element simulation is used to investigate the frost damage of the roadbed of a high-speed railrway JM zone in the northwest seasonal permafrost zone.According to the data of temperature,ground temperature and line deformation observation during 5 years from 2017 to 2021,we analyze the frost damage characteristics of different structural forms of roadbed,explore the influence of factors such as roadbed filler,water content status,climate environment and ground temperature on the frost damage of roadbed,and use finite element software to carry out numerical simulation of temperature field during the freezing period for a typical section in the interval.The main research results are as follows:(1)2017-2021 during the interval roadbed frost damage problem is prominent.From the analysis of the number of freezing damage and freezing height perspective,it is found that a total of 435 freezing damage occurred in the zone within 5 years,70.3% of the freezing damage freezing height in the range of 4-5mm,28.1% of the freezing damage freezing height between 5-10 mm,very individual in more than 10mm;from the analysis of the structural form of the roadbed,it is found that the number of embankment,road graben and transition section roadbed freezing damage in the zone shows a decreasing law,that is,embankment >transition The road embankment > transition > road graben;from the perspective of different freezing periods,the number of frost damage during the 5 years decreased,frost damage was controlled.The analysis of embankment form roadbed frost damage found that the number of frost damage occurred in the same month during the five-year period is close,and the frost damage occurred in the early January.In addition to this,during the freezing period of2017-2018,the maximum freeze up height of the interdistrict embankment form roadbed was found in early February 2018.(2)Analysis of the fine particle content,moisture content and external temperature conditions of the interdistrict roadbed filler revealed that: for the roadbed filler,the largest percentage of freeze up was found in the bottom layer of the bed through field tests,followed by the top layer of the bed.Sieving experimental results show that the roadbed bed bottom layer is mostly fine particle content of Group B filler,and some fillers do not meet the specification requirements,easy to cause roadbed frost swelling;water content state,the average annual precipitation of 381.2 mm,random sampling found that the water content of the roadbed between 9% to 14%,and rainfall and frost damage number there is a certain degree of correlation,frost swelling characteristics test results show that the filler frost swelling rate and The results of the freezing and swelling characteristics test show that the freezing and swelling rate of filler and water content are obviously positively correlated;in terms of temperature distribution state,the freezing period is from November to March every year,with 110～134 days of freezing and extreme low temperature-25 ℃.The maximum number of freezing damage was found in the first freezing period,and a significant correlation was found between the number of freezing days and the number of freezing damage to the roadbed.(3)The form of roadbed in each section within the study interval is mainly low embankment,so the 1.3 m high low embankment section is selected for simulation analysis,and the results show that: the number of freezing days in the freezing period of 2017-2018 is104 days,which is similar to the measured ground temperature data of 115 days;the freezing rate is larger when the roadbed soil starts to freeze,and then gradually decreases;in mid-February 2018,each part of the section successively reaches the maximum freezing depth.The maximum freezing depth at the shoulder,line centerline,natural ground and slope foot are 3.86 m,3.76 m,3.15 m and 2.97 m respectively,and there is an obvious pattern in the size of freezing depth at each location,i.e.shoulder > line centerline > natural ground > slope foot.Model verification results show that the simulation results are basically in line with the measured data,except for the simulation time point of the maximum freezing depth,which is one month earlier than the measured value.(4)The maximum freezing depth of the roadbed after the addition of XPS insulation material is significantly smaller than the original roadbed section,and the laying of XPS panels at 40 cm,60cm and 80 cm below the roadbed surface can provide good insulation effect.Compared with the other two schemes,the roadbed soil with 80 cm scheme is the first to reach the maximum freezing depth and has the best thermal insulation effect.Therefore,for low embankments with a roadbed height of about 1 m,it is recommended to lay the insulation panels at a depth of 80 cm below the roadbed surface to achieve a better insulation effect. 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