关键词: 青藏铁路, 路基, 多年冻土, 冻土退化

Abstract: Based on the ground temperature monitored in the Qinghai-Tibet Railway near the southern limit of permafrost during 2006-2012, the degradation of permafrost and its influence factors were analyzed. The results show that whether in the original permafrost or in the permafrost under an embankment, the permafrost table was declining and the ground temperature was rising. In the monitoring period, the permafrost table had declined 0.29 m, with a rate of 4 cm·a^-1; the ground temperature had risen 0.03℃ at the depth of 10 m, with a rate of 0.004℃·a^-1. The depth of artificial permafrost table under an embankment was larger than that under original permafrost; the ground temperature under an embankment rising at the depth of 10 m was higher than that under the original surface. It is an obvious feature that the permafrost base under the embankment was lowering, but the permafrost thickness was thinning. It is concluded that engineering effect is the major cause resulting in the permafrost degradation under the embankment in this region, and other factors, such as air temperature rising, suprapermafrost water development, etc., are also accelerating the degradation. The thawing interlayer formed under the embankment will change the connected frozen ground into detached one, which is an unavoidable stage in the degradation process of permafrost.

Key words: Qinghai-Tibet Railway, embankment, permafrost, degradation of permafrost