路基温度场长期模拟中的地表热边界条件研究

Upper boundary conditions in long-term thermal simulation of subgrade

在路基温度场模拟中,地表热边界常基于"附面层原理"确定,即假设一定深度(附面层厚度)的土体温度函数等于大气日平均温度函数加上一个温度增量。目前,附面层厚度和温度增量一般通过实际观测值回归分析得到,尚未建立起相应的理论和参数确定方法,无法定量分析路面材质、路面结构、太阳辐射、路面辐射对附面层厚度和温度增量的影响。首先通过理论分析,建立了附面层厚度的确定方法;然后建立了一维路面路基结构温度场模拟模型,并通过路基温度场反演分析,验证了数值模型的正确性;进而通过数值分析,研究了太阳辐射、路面辐射、对流换热和路面结构等因素对附面层底部温度增量的影响,给出了温度增量的确定方法和相应的设计图表和计算公式。

In the numerical simulation of a long-term temperature field in subgrade, the upper thermal boundaries are often determined by the boundary-layer theory, in which the temperature at a certain depth, i.e., the thickness of boundary layer, can be used as a temperature increment plus an average temperature of atmosphere. Because of the lack of a model, the boundary-layer thickness and the temperature increment are usually extracted from the monitored data of subgrade temperature in field. The objective of this study is to develop a model for the determination of the boundary-layer thickness and temperature increment. A theoretical derivation is carried out and leads to a solution of the thickness of boundary layer. Then a numerical model is established to simulate the temperature field in pavement and subgrade. The numerical model is verified through the back analysis of a case study. Furthermore, a sensitive study is carried out to study the impact of solar radiation, pavement materials, pavement structure and pavement radiation on the temperature increment, resulting in an empirical equation and a design chart.