青藏公路冻土路基阴阳坡热效应研究

Investigation of thermal effect of sunny-shady slope of permafrost embankment of Qinghai-Tibet highway

青藏公路多年冻土路段的阴阳坡现象会引发路基及下伏冻土地基热状况不对称分布,影响长期稳定性.为此,基于实测坡面温度数据,开展不同年平均气温和路基高度条件下冻土路基地温场分布及演化规律的模拟.结果表明,年平均气温-3℃下阴坡冻结指数约为阳坡的2倍,融化指数约为阳坡的0.83倍.路基修筑后,阴坡一侧路基下部人为上限均有一定抬升.此后,在气候变暖及沥青路面强烈吸热效应作用下,路基左右路肩下部人为上限不断下降,其中高填方路基人为上限下降速率相对较快.阴阳坡效应作用下,东西路基下部人为冻土上限呈左高右低的趋势,下伏土体温度同样为左高右低.高填方路基下伏冻土层地温分布的不对称较同期的普通填方路基显著.

The phenomenon of sunny-shady slope in the permafrost road section of Qinghai Tibet highway, inducing asymmetrical heat distribution in embankment proper and beneath-buried permafrost subgrade and affecting long-term stability of the embankment. Therefore, based on field measured temperature of embankment slopes, the temperature field distribution and evolution regularity of permafrost embankment with different height at different annual mean air temperature were investigated simulatively. The result showed that the freezing index beneath shady slope would be about 2 times of that beneath sunny slope, while the thawing index beneath shady slope would be about 0.83 times of that beneath sunny slope. After completion of embankment construction, the artificial upper limit of permafrost soil beneath shady slope would have a certain uplift at lower part of embankment. Then, due to the climate warming and significant heat absorption of asphalt pavement, the artificial upper limit of permafrost soil would continuously decline both beneath sunny and shady slopes, the decline rate of the artificial upper limit of permafrost soil would be relatively greater beneath high-filled embankment. Due to the sunny-shady slope effect, the artificial upper limit of permafrost soil at lower part of west-east oriented embankment would exhibit a trend that left high right low and the temperature of beneath-buried soil would behave just the same. The asymmetrical distribution of temperature field of high-filled embankment would be more obvious than that of ordinary embankment in the same period.