青藏高原高等级道路路基路面温度变化特征

连续观测了青藏高原多年冻土区道路结构不同层位和天然大地不同深度处温度, 分析了不同层位日均温度的时空变化趋势、实时温度的频率分布特性与不同结构层材料的冻融特性。分析结果表明: 空气、面层、基层、路基和天然大地温度年度变化趋势均呈现明显的热季与冷季之分, 转换时间分别是4月份和9月份; 观测周期年内, 沥青混凝土路面路表日平均温度为-17 ℃~40 ℃, 水泥混凝土路面路表温度为-18 ℃~17 ℃, 沥青混凝土路面下的路基顶面以下0.8 m处温度波动范围为-2.8 ℃~6.3 ℃, 水泥混凝土路面下的路基顶面下0.7 m处温度波动范围为-3.4 ℃~5.4 ℃; 空气、沥青混凝土面层、水泥混凝土面层的温度和温度梯度频率分布均呈现出明显的单峰形态, 且峰值对应的温度或温度梯度与相应的年均值存在偏差; 基层、垫层和路基的温度频率分布均呈现多峰并存的形态, 分别与冷季、热季、冷热季转换期相对应; 分析周期年内沥青混凝土路面和水泥混凝土路面的路表冻融次数分别为182、178; 沥青混凝土与水泥混凝土冻结融化持续时间频率分布均呈现主峰+多副峰的形态, 主峰对应的持续时间分别为0~2 h和18~20 h。可见, 在多年冻土区, 可优先选择水泥混凝土路面, 以利于冻土的保护, 沥青混凝土与水泥混凝土配合比设计均应验证抗冻融耐久性能。

Temperature variation properties of pavements and subgrades for high-grade roads on Qinghai-Tibet Plateau

The temperatures of different deeps of roads and natural ground were continuously measured in permafrost regions on Qinghai-Tibet Plateau, and the variation tendencies of daily mean temperature (DMT) with time and depth, and the frequency distributions of real-time temperature and the freeze-thaw properties of different structural layers were analyzed.Analysis result shows that the annual change rules of DMTs of air, surface layer, base layer, subgrade and natural ground demonstrate high-temperature periods and low-temperature periods, and the corresponding shifting times are April and September.The DMT of surface layer of asphalt concrete pavement varies from-17 ℃ to 40 ℃ in yearly observation period, and the DMT of surface layer of cement concrete pavement varies from-18℃to 17℃.At 0.8 m-depth from the top surface of subgrade under asphalt concrete pavement and 0.7 m-depth from the top surface ofsubgrade under cement concrete pavement, the DMTs vary from-2.8 ℃to 6.3 ℃ and from-3.4 ℃to 5.4 ℃, respectively.The frequency distributions of temperatures and temperature gradients of air, surface layer of asphalt concrete pavement and surface layer of cement concrete pavement display obvious single-peak shapes, and there are deviations between the temperatures or temperature gradients corresponding to the peak values and the annual mean values.The frequency distributions of temperatures of base layer, sub-base layer and subgrade present multipeak shapes, and the peak values correspond to low-temperature period, high-temperature period and their transition period, respectively.The freeze-thaw cycles of surface layers of asphalt concrete pavement and cement concrete pavement are 182 and 178 in yearly observation period, respectively.The frequency distributions of freeze-thaw lasting times of asphalt concrete pavement and cement concrete pavement have one main peak and several sub-peaks, respectively, and the main peak usually appear in the interval of 0-2 hor 18-20 h.Obviously, it is given priority to choose cement concrete pavement in order to protect the permafrost in permafrost regions, and the freeze-thaw durability performance shall be verified in the mix proportion design of asphalt concrete and cement concrete.