青藏公路沿线多年冻土对气候变化和工程影响的响应分析

青藏公路沿线工程和气候变化影响下多年冻土变化监测表明, 多年冻土对工程活动和气候变化的响应过程存在着较大差异, 不同年平均地温的多年冻土使这种差异变得更为明显.分析结果表明: 气候变化下低温多年冻土变化要大于高温多年冻土, 工程状态下低温多年冻土变化要小于高温多年冻土; 气候变化引起的低温多年冻土变化要大于工程对其的影响, 而高温多年冻土正好相反.造成这一结果原因主要是由于在工程建设完成初期, 相对于气候影响, 工程作用对多年冻土的影响具有放大作用, 这使得工程状态下多年冻土对气候变化基本没有响应. 按照气候影响下多年冻土温度年变化速率来推测, 低温多年冻土表面温度升温到工程状态需要50 a左右时间, 高温多年冻土需要20 a左右. 6 m深的低温多年冻土温度升温到工程状态需要20 a, 高温多年冻土仅需要5～8 a.

Response of Permafrost to Climate Change and Engineering Activity along the Qinghai-Tibet Highway

Monitoring of permafrost change due to climate change and engineering activity along the Qinghai-Tibet Highway shows that there is a large difference in the response of permafrost to climate change and engineering activity, which obvious varies with mean annual ground temperature. The change in cold permafrost is more significant than that in warm permafrost due to climate change. However, the change in cold permafrost is less significant than that in warm permafrost due to engineering activity. The effect of climate change is larger than that of engineering activity for cold permafrost, but it is just contrary for warm permafrost. The reason is that the effect of engineering activity on permafrost has an enlarging action as compared with the effect of climate change in several years after a construction completion. As a result, the response of permafrost under an engineering state to climate change becomes insensitive. Inferred from the annual ratio of permafrost temperature rising due to climate change, it is required 50 years for cold permafrost surface temperature and 20 years for warm permafrost surface temperature rising to the engineering state; it is required 20 years for cold permafrost temperature and 5 to 8 years for warm permafrost temperature at the depth of 6 m rising to the engineering state. Therefore, warm permafrost will experience the effects of both climate change and engineering activity in several years after a construction completion, but clod permafrost requires much more time to experience the two effects. It is significant important to consider the effect of climate change on permafrost for an engineering in permafrost regions.