青藏高原公路路面结构水热差异变化分析
Analysis on hydrothermal difference changes of highway pavement structure on the Qinghai-Tibet Plateau

通过对青藏高原北麓河地区大气降水以及沥青路面和砂砾路面下部浅层土体水热变化的连续监测,分析路面结构中降水、地温以及水分变化之间的关系.结果表明,在降雨时段,5 cm深度土体水分增加,沥青路面下部土体的水分增量约为砂砾路面的2倍.砂砾路面20 cm及以下深度范围水分增加,而沥青路面下部水分变化量小于0.3%.砂砾路面下部土体间存在良好的水力联系,沥青路面结构中的隔水层阻隔了层中水热交换.面层中水分的波动与降水密切相关,基层水分变化受地温控制.路面结构的隔水层增加了面层的蒸发量,同时造成层下水分的大量聚集和路基储热量的增加,表现为基层地温明显高于面层.水热交换的差异是造成沥青路面热效应的重要原因之一.
By continuously monitoring the precipitation and soil hydro-thermal changes in a shallow part under the asphalt and sand pavement in Beiluhe area on the Qinghai-Tibetan Plateau, the relationships between precipitation, temperature and moisture change in pavement structure are analyzed. The results show that during the rainfall period, the moisture of the soil of 5 cm depth under pavement increases, and the moisture increment in the soil under asphalt pavement is twice over that under sand pavement. In the deeper part of more than 20 cm depth, the moisture of the soil under sand pavement increases, while that under asphalt pavement varies only by less than 0.3%. Under sand pavement, there is a good hydraulic connection between the soil bodies in roadbed. However, in the asphalt pavement structure, the impermeable layer inhibits hydrothermal exchange obviously. Moisture changes are closely related to precipitation in the surface layer and controlled by the ground temperature in the base course. The impermeable layer of the asphalt pavement structure increases the evaporation capacity in the surface layer and causes abundant moisture accumulation under the impermeable layer and the increase of heat storage in roadbed. As a result, the temperature in the base course is significantly higher than that in the surface layer. Therefore, the difference between hydrothermal exchanges is one of the important reasons for asphalt pavement thermal effects