Field-Monitoring System for Suction and Temperature Profiles under Pavements

Abstract

The purpose of this paper is to describe the development of and typical results from a new field-monitoring system to evaluate changes in matric suction and temperature profiles in subgrade soil layers beneath constructed pavement systems over an extended period of time. This monitoring system involves the placement of sensors capable of inferring the volumetric water content and temperature of soils into a borehole in the shoulder of an existing pavement. High-permeability silica flour is used to backfill the borehole around the sensors so that changes in matric suction with depth in the subgrade can be inferred through the soil-water retention curve of the silica flour. The monitoring results from a pavement site in Arkansas with low-permeability clay subgrade are compared with predictions from the Enhanced Integrated Climatic Model (EICM). The measured and predicted temperature distributions match well, but the EICM did not capture the fluctuations in matric suction inferred from the monitoring system. This can be attributed not only to the fact that the monitoring system captured the two-dimensional water flow near the pavement shoulder but also to the possibility that the EICM may not have adequately represented the water-flow process through the asphalt and base-course layers. Profiles of matric suction and temperature obtained using the monitoring system provide real-time, site-specific feedback on interactions between the atmosphere and pavement systems. Comparison of results from multiple pavement sites with clay subgrades across Arkansas demonstrates the variability in matric suction and temperature changes in different climatic settings.