A computer model has been developed that computes the temperature and suction profiles beneath highway pavements (or other similar covered areas) throughout a specified time period of simulation. The model is referred to as the "integrated computer model" because several modules that were developed for specific tasks have been broughttogether to form one complete package. Using 30 years of accumulated weather data as a basis, the model generates its own weather patterns that are representative of typical climatic conditions for a particular region of the united states. As the pavement structure and subgrade respond to the changing climatic conditions throughout the year, the model computes the corresponding changes in temperature andsuction. Specific boundary conditions at three locations are required: (a) the top pavement surface, (b) the bottom boundary--an extended distance into the subgrade, (c) an intermediate boundary--the topof the subgrade. The pavement surface boundary uses a heat and moisture flux condition that depends on climate. The bottom boundary requires temperature and moisture conditions that are either constant or that may vary in a specific manner. The intermediate boundary requires an initial temperature and a moisture condition that may be either suction (head) or moisture flux. The concept of a transfer coefficient between the granular base and the fine-grained subgrade has been developed to describe the process by which water from the base course and subbase infiltrates the subgrade. This transfer coefficient cannot be measured experimentally, but the selection of an appropriate value controls not only the changes in moisture conditions, butalso the temperature profile computed in the subgrade. Three instrumented sites in the united states with widely varying climatic and soil conditions are used to provide comparisons between measured and computed values of temperature and suction profiles. This paper appears in transportation research record no. 1307, Pavement analysis, design, rehabilitation, and environmental factors 1991.
Abstract