青藏公路下伏多年冻土的融化分析

基于青藏公路沿线高温冻土区和低温冻土区2组地温观测孔5 a的地温观测资料, 研究了路基下伏多年冻土的融化状态, 定量分析了进入路基下多年冻土内的热状况. 结果表明: 路基近地表地温明显高于对应天然地表下的地温, 路基近地表经历的融化期长于对应天然地表, 高温冻土区路基内已形成贯穿融化夹层;进入高温冻土区路基下伏多年冻土内的热收支处于持续不断的吸热状态, 进入低温多年冻土区的热收支也呈现出吸热明显大于放热的周期性变化;高温冻土区接近0℃的地温及其持续不断的热积累是引起下伏多年冻土不断融化的主要原因. 低温冻土区进入多年冻土的热积累暂时以增高地温耗热为主, 随着地温的增高, 低温冻土区也可能发生强烈的冻土融化.

Analysis on the Thawing of Permafrost underlying Qinghai-Tibetan Highway

Construction of the Qinghai-Tibetan Highway will change the heat exchange between atmosphere and ground surface, destruct the original heat balance, resulting in a heat accumulation in highway embankment and underlying permafrost and permafrost thawing. This is the greatest problem in the construction in permafrost regions. General principle for the construction of the highway is to try to keep the underlying permafrost from thawing. In order to realize the purpose, it is very important to have a good understanding of the thawing state of permafrost underlying the highway embankment. Based on two series of observations of ground temperature profile, both in high temperature and low temperature regions, the thawing state of permafrost underlying the highway is stated, and the heat penetrating into permafrost is analyzed in this paper. It is revealed that the ground temperature near the highway surface is obviously higher than that of natural ground surface, and that the thawing period of the highway embankment is longer than that of natural ground. Permanent thawed layer has formed in high temperature regions. The heat budget within the permafrost underlying the highway shows a continuous heat-taking state in high temperature regions. The heat income within the permafrost in low temperature regions is greater than the heat release from the permafrost during an annual period. It is the high temperature (near 0℃) and continuous heat accumulation in high temperature regions that induces the thawing of the performed underlying the highway. The heat accumulation within the permafrost underlying the highway in low temperature regions is temporarily performing as permafrost temperature rising, and with increasing ground temperature, considerable thawing of permafrost is also possible.