边界条件对多年冻土路基热稳定性的影响分析

多年冻土区的年平均气温是影响冻土路基边界条件的重要因素.在附面层原理的基础上,考虑采用带有相变的控制方程和数值方法,以相同尺度的路基模型为前提,选取不同的年平均气温为影响因素,对青藏工程走廊公路路基的人为冻土上限和年平均地温进行了研究.结果表明:公路路基下年平均地温随着年平均气温的升高而升高,人为冻土上限随着年平均气温的升高而显著下降.在年平均气温为-7.16℃时,路基修筑50 a后其年平均地温为-3.61℃,其人为冻土上限为-0.97 m;年平均气温为-3.21℃的条件下,路基修筑50 a后其年平均地温仅为-0.1℃,其人为冻土上限也降至-13.11 m.因此,可以看出:在未来气候持续变暖的背景下,现有处于稳定状态的冻土路基将逐渐变得不稳定.

Influence of boundary conditions on the thermal stability of embankments in permafrost regions

Annual mean temperature plays a very important role to embankment boundary conditions in permafrost regions. On the basis of principle of the boundary layer and unified embankment sizes, governing equation, which involves phase change, and finite element method were applied to study the heat effect along the Qinghai-Tibet Highway. Different locations along the Qinghai-Tibet engineering corridor were chosen to be the studying objects. It is found that annual mean ground temperature increases when annual mean air temperature increases. However, artificial permafrost table decreases remarkably with annual mean air temperature increasing. When the annual mean air temperature is -7.16 ℃, the annual mean ground temperature will be -3.16 ℃ and the artificial permafrost table will be -0.98 m 50 years later; when the annual mean air temperature is -3.21 ℃, the annual mean ground temperature will be -0.1 ℃ and the artificial permafrost table will be -13.11 m 50 years later. Thus, the conclusion can be drawn that stable embankment will turn into unstable one as global climate warming.