Long-term role of cooling the underlying permafrost of the crushed rock structure embankment along the Qinghai-Xizang railway

Understanding the long-term role of cooling the underlying permafrost of the crushed rock structure embankment (CRSE) along the Qinghai-Xizang Railway (QXR) is crucial for the railway's safe operation. The thermal regime of the permafrost under the CRSE is analyzed here using monitoring data of soil temperature from 2005 to 2015. The results show that the CRSE plays an important long-term role in cooling the underlying permafrost under the present climate change conditions; however, different types of CRSEs have different cooling effects. A U-shaped crushed rock embankment and a crushed rock berm embankment with debris rock revetment can maintain the cooling of the permafrost underlying the embankment under a future climate warming of 1.0 degrees C. Moreover, under an increase in air temperature of 0.5 degrees C, a crushed-based rock embankment and a crushed rock revetment embankment can maintain the cooling of the underlying permafrost when its mean annual ground temperature is below -1.0 degrees C. The long-term role of cooling the underlying permafrost of CRSEs indicates that the QXR must use reinforcing engineering techniques to ensure its safe operation and adaptation to a temperature increase of 1.5 degrees C.