SEASONAL INSTRUMENTATION OF SHRP PAVEMENTS - THE UNIVERSITY OF TOLEDO

Seasonal Monitoring Program (SMP) instrumentation was installed in five sections at the Ohio Test Pavement in Delaware County, Ohio using Strategic Highway Research Program (SHRP) protocols developed for the Long-Term Pavement Performance (LTPP) group of the Federal Highway Administration (FHWA). The SMP instrumentation monitors pavements for temperature and pavement bases and subgrade soils for variations of moisture, temperature and frost penetration. Time Domain Reflectometry (TDR) instrumentation was installed onsite in two sections for monitoring the moisture. Thermal conductivity sensors (TCS) were installed in four sections to measure soil moisture suction. Laboratory soil-water characteristic tests were conducted on remolded subgrade soil. The TDR volumetric moisture contents typically varied by 10% to 15% from the driest to the wettest periods, but sometimes the variations were larger. The lower water contents occurred during the late winter/early spring months and the higher contents occurred during the late summer early fall months. This reflects the climatic conditions that occurred. Some of the TDR moisture contents exceeded 40%, which is greater than the soil porosity and therefore not possible. An equation for TDR volumetric water content developed for the FHWA yields lower water contents. Most of the TCS are no longer within calibration. Data from sensors in calibration indicate very low matric suctions, which is consistent with high water contents. Soil-water characteristic relationships were obtained for the subgrade soil using triaxial and pressure plate apparatus. The relationships from the two tests are comparable. The soil exhibits some hysteresis when comparing drying and wetting curves.