Analysis on Subgrade Deformation Features and Influence Factors in Permafrost Regions on Qinghai-Tibet Railway

Since the construction and operation of the Qinghai-Tibet Railway,there have been a series of influences on those projects located above the ground,because the thermal stability conditions of the permafrost under the subgrade have already been changed.The main influence factors usually include the route alignment,solar radiation,air temperature,water migration,project measures and so on.By researching,it has been found that the subgrade deformations come into being mainly in the forms of frost heaving and thaw settlement,and the thaw settlement plays a more dominant role in subgrade deformations.In addition,the subgrade deformations are closely related to the route alignment,frozen soil temperature,engineering geological features and other factors.Especially,the subgrade deformation increases with the increase of the difference between the sunny slope and the shady slope of the subgrade;the higher the frozen-soil temperature rises,the larger the subgrade deformation becomes.Moreover,the subgrade deformations mainly occur in warmer and ice-rich sections,and there is an equal ratio relationship between ice content and thaw settlement.