高海拔多年冻土地区宽幅沥青路面-路基体系热效应实测分析

Field observation and analysis on thermal effects of wide asphalt pavement-embankment structure in high-altitude permafrost region

为明确中低纬度高海拔多年冻土区"宽厚黑"路面结构和路面类型对路基路面体系温度场的影响规律,在青藏高原高温多年冻土区分别铺筑了窄幅和宽幅沥青路面-路基温度场监测试验段,对两种尺度路基路面体系不同深度和横向位置处以及天然大地不同深度处温度状况进行3年连续观测和统计分析。结果表明:宽幅路面沥青层年温度波动幅度高于窄幅路面,且波动幅度差异随路面结构层深度增加而减小;新建公路路基填土会经历持续2年以上的初期冻融放吸热不稳定阶段;高填方宽幅沥青路面-路基体系吸热面积与散热面积的同时增加导致宽幅路基路面体系不同横向位置和深度处温度场更为复杂;沥青路面宽度从5m增加到24.5m导致最大融化深度增加量在1.5～2.0m。在中低纬度高海拔多年冻土区设计宽幅公路路基填土高度时应考虑具体路基断面特点,计算极端天气下的宽幅路基路面体系从建设期到稳定期的温度场。

In order to reveal the influences of structures and types of wide-thick-dark pavement on the temperature field of embankment and pavement system in high-altitude permafrost region, a narrow pavement-embankment test section and a wide pavement-embankment test section were constructed, respectively,in high-temperature permafrost region of Qinghai-Tibet plateau. The temperatures at different depths and horizontal positions for these two types of road structures and the natural ground temperature below the ground surface up to 3.2 m were observed continuously and statically analyzed for three years. Results show that: the annual fluctuation amplitude of temperature in asphalt layer of wide road pavement is greater than that of narrow road pavement, and the difference of fluctuation amplitude may decrease with the depth of structural layer of pavement. The new constructed road embankment may experience an initial unstable freeze-thaw period of at least two years. The concurrent increases of solar flux-absorbing area and radiating area may result in more complicated temperature fields at different depths and horizontal positions in the road structure of high embankment and wide pavement. The widening of road pavement from 5 m to 24.5 m may lead to an increase of 1.5~2 m of thawing penetration. Consequently, when designing the height of fill embankment for wide road structure in permafrost region of the middle-or low-latitude but high-altitude areas, the specific cross-sectional characteristics of embankment shall be considered, and during the period from construction stage to stable stage under the extreme weathers, the temperature field in wide pavement-embankment structure shall be calculated to ensure the thawing penetration at the road shoulder at the sunny side may always meet the requirements.