Lateral thermal influences of roadway and railway embankments in permafrost zones along the Qinghai-Tibet Engineering Corridor

In permafrost zones, the ground thermal regime beneath and around foundations is of great importance to long-term stability and integrity of engineering infrastructures. In this study, ground temperatures beneath and around embankments of the Qinghai-Tibet Highway (QTH) and the Qinghai-Tibet Railway (QTR) were observed at two profiles in continuous permafrost zones on the Qinghai-Tibet Plateau. The lateral thermal influences of the embankments on natural ground in the vicinity were analyzed based on the field observed data. The results indicated that the lateral thermal influence of the QTH and QTR embankments on shallow ground in the vicinity was very slight. The permafrost table depth or freeze-thaw process in the shallow ground near the embankments was mainly determined by the ground surface conditions. Different from the case of shallow ground, the lateral thermal influence of the QTH embankment on the permafrost in the vicinity was significant. Based on the permafrost temperature distribution at - 10 m depth, the scopes of the lateral thermal influence of the QTH embankment calculated from the embankment shoulder were as much as 30-40 m at the two observation profiles. Whereas, the lateral thermal influence of the QTR embankment on the permafrost in the vicinity was slight. Because the QTR was constructed using cooling method of crushed rock embankment at the two profiles, the underlying permafrost either maintained well in thermal regime or experienced a slight cooling. The factors affecting the scope of the lateral thermal influences of embankments on permafrost in the vicinity were discussed at the end of the paper, as well as the related mitigation method. This study provides information that could aid engineering design of linear transportation projects and the assessment of environmental impacts in permafrost zones.