多年冻土区道路边坡热状况差异对多年冻土融化形态的影响

Effect of the Differences of Thermal Regime within Roadbed Slopes on Thawing Morphology in Permafrost Regions

用数值方法模拟了在气候持续以0．02℃·a^-1速度增温下，50a运营年限内不同走向路基的融化形态可能发生的变化趋势．计算了在砂砾路面和沥青路面下，不同高度（0～5．0m）及不同走向（东西、东北-西南、南北、对称）路基的融化形态．结果表明：非对称热边界路基与对称热边界路基的融化形态差异很大．在呈阴阳坡的路基中，砂砾路面和沥青路面下：1）最大融化深度位置与运营时间关系不大，与路基高度、线路走向及路面类型关系密切，且最大融化深度偏离路基中线的距离与路基高度呈线性关系；2）最大融化深度与运营时间、路基高度、路面类型关系比较密切．路基较低时，最大融化深度与路基走向关系不大．路基较高时，最大融化深度与线路走向关系密切，且随着路基高度的增加、气候变暖及增温速率的增大而加剧；3）同一路基高度和线路走向下，砂砾路面的最大融化深度偏离路基中线的距离大于沥青路面的，沥青路面的最大融化深度大于砂砾路面的．相对于砂砾路面，沥青路面在一定程度上部分的抵消了阴阳坡效应，但加剧了路基下最大融化深度．

Numerical models are set up to analyze possible changing tendency of the thawing morphology in various pavement surfaces, heights and orientations for a period of 50 years. Pavement surface includes gravel and asphalt. Embankment height ranges from 0 m to 5.0 m with a step of 0.5 m. Embankment orientation directs east- west, southwest- northeast, south-- north and symmetric route. The thermal boundary conditions are under the assumption that the air temperature will increase by 0.02 ℃ · a^-1. The calculated results indicate that there is much difference in thawing morphology between asymmetric route and symmetric one. Among embankments with shadysunny slopes under gravel and asphalt surfaces： 1） The position of the maximum thawed depth has nothing to do with time, much to do with pavement surface, embankment height and orientation, and the range of the maximum thawed depth to the embankment centric line has a linear functional relation with the embankment height; 2） The maximum thawed depth has much to do with time, surfaces, embankment height. In terms of low embankment, it has little to do with roadbed orientation. But with regard to high embankment, it has much to do with orientation, moreover, it changes sharply with embankment height, climate warming and temperature increasing velocity; 3） Under the same parameters, the range of the maximum thawed depth to the embankment centric line of gravel pavement is larger than that of asphalt pavement. However, the maximum thawed depth of asphalt pavement is greater than that of gravel pavement. To some degree, the asphalt pavement is able to counteract shady--sunny slope effect partially, but the maximum thawed depth becomes more serious.