不同地表条件下青藏公路对多年冻土的热影响差异研究

Study on the diversities of thermal impacts of Qinghai-Tibet Highway on permafrost under different surface conditions

在多年冻土区,道路工程会对周边的多年冻土产生热影响,但不同地表条件下的多年冻土对道路热影响的反馈差异尚不完全清楚。本研究基于青藏公路沿线两处监测场地的多年冻土监测数据,研究了不同地表条件下青藏公路对多年冻土的热影响差异。结果表明,青藏公路对多年冻土的热影响因地表条件的不同而存在差异。与植被覆盖率较高的监测场地相比,在植被覆盖率较低的监测场地,其多年冻土年平均地温更高、多年冻土活动层厚度更大,且青藏公路对多年冻土的水平热影响范围也相对更大。此外,在植被覆盖率较低的监测场地最靠近坡脚的位置处,由于地表条件的不同,其浅层土壤更易受到外界扰动,导致该位置浅层土壤与外界的热交换特征迥异于其他监测位置,这可能也是导致两处监测场地多年冻土的热状态存在差异的原因。目前,青藏工程走廊内各线性工程密布,工程间的相互影响及其与多年冻土间的关系已成为必须考虑的问题。本研究工作对于青藏高原多年冻土区工程走廊内线性工程之间的合理间距设定,以及即将建设的青藏高速公路双向路基间的合理距离设计都可提供参考,以达到减少工程热扰动,保障工程安全运营的目的。

In permafrost regions,road infrastructures have thermal impacts on adjacent permafrost,but the diversities of the feedback of permafrost under different surface conditions from road thermal impact is not totally understood. Based on the monitoring data of two monitoring sites along the Qinghai-Tibet Highway,this work studies the diversities of thermal impact of Qinghai-Tibet Highway on adjacent permafrost under different surface conditions. The results show that the Qinghai-Tibet Highway has a significant thermal impact on the permafrost on both sides,but the feedbacks from the thermal impact are different due to different surface conditions. Compared to the site with higher vegetation coverage,the mean annual ground temperature as well as the active layer thickness are respective greater,along with a wider horizontal thermal impact in the site with lower vegetation coverage. In addition,for the site with lower vegetation coverage,at the slope foot of the embankment,because of its bare surface,the topsoil is more susceptible to external disturbances,leading to form a thermal exchange pattern differing from other positions,and this may be a reason causes the different thermal states between the two sites. In present,there are many linear projects in the Qinghai-Tibet Engineering Corridor which makes it necessary to take into account the interactions between projects and their relationships with permafrost. This work can provide references for the setting of reasonable distance between linear projects in the Qinghai-Tibet Engineering Corridor in the permafrost region of the Qinghai-Tibet Plateau as well as for the reasonable distance arrangement between bidirectional roadbed of the Qinghai-Tibet Expressway to be built,so as to reduce mutual disturbances and ensure the operational safety of the them.