Deformation behaviour and influence mechanism of thaw consolidation of embankments on the Qinghai-Tibet Railway in permafrost regions

Abstract With the thermal disturbance caused by engineering construction and global warming, thaw consolidation has become a primary source of subgrade deformation in permafrost regions. Based on the large-strain consolidation theory described by the updated Lagrangian, we study the thermal stability and the thaw consolidation in an ordinary subgrade at the warm and ice-rich permafrost (WIRP) site of the Beiluhe Qinghai-Tibet Railway (QTR) by establishing a thermo-mechanical coupled model. The research results are as follows: The initial mean annual ground temperature (MAGT) of the site influences the permafrost degradation on the Qinghai-Tibet Plateau due to construction and climate warming, exacerbating the thaw consolidation and creep of the ice-rich permafrost. The settlement rate and subgrade settlement increase with increasing embankment height, ice-rich permafrost layer thickness, and initial MAGT. Railway maintenance methods, such as ballast filling and track lifting, increase the subgrade weight, thus increasing the WIRP subgrade settlement. Furthermore, we predict the thaw consolidation of the DK1136 section of the QTR for the next 50 years. The prediction formulas of the cumulative settlements of the subgrade top and permafrost are established, and various suggestions for maintaining the railway subgrade of the WIRP site are proposed.