从地表能量平衡各分量特点论青藏高原多年冻土工程中的冻土保护措施

Discussion on Protection Measures of Permafrost under the Action of Engineering from the Point of Earth Surface Energy Balance Equation in Qinghai-Tibetan Plateau

多年冻土的形成、发展和存在状态与地表能量平衡中各要素的变化特征密切相关,青藏高原地表能量平衡方程中各要素的变化具有如下特点:1)年总净辐射和年总辐射量均比较高;2)地表反照率一般较低,绝大多数下垫面类型的反照率在0.4以下;3)大部分地区地表的地气热交换总量中,蒸发耗热较小,感热交换量远大于蒸发耗热量,占辐射平衡总量的70%左右;4)目前大部分多年冻土地区的土壤热通量为正值,导致多年冻土处于退化过程中.针对高原地区辐射比较强的特点,在青藏公路五道梁北坡进行了减少沥青路面辐射增温的试验.结果表明:在沥青路面刷涂白色或浅色涂料可以有效保护沥青路面下的多年冻土,其中白色路面可以使路面下4 m处的地温降低1℃以上.

Forming, developing and existence of permafrost are closely related with the characteristics of different factors of earth-- surface energy balance equation. Earth--surface energy balance in Qinghai-Tibetan Plateau has following characteristics： 1） Annual total radiation and net radiation are both higher; 2） The albedo of most underlaying surface is usually lower than 0.4; 3） Quantity of latent heat exchange is often far less than the sen sible heat exchange. The latter occupies 70% of the annual net radiation; 4） Thermal influx of soil in most permafrost area is positive. This results in the degradation of permafrost. Experiment on how to reduce the temperature rise of asphalt surface in the Wudaoliang Ridge Section of Qinghai-Tibetan Highway shows that, painting light color or white dope can effectively protect the frozen soil under the roadbed. Thereinto, after adopting white road surface, 4m ground temperature of the center bore was lowered by more than 1℃.