Analysis of Variations of Pavement Subgrade Soil Water Content: Fid-Bau Portal

Analysis of Variations of Pavement Subgrade Soil Water Content

Heydinger, Andrew G. / Davies, B. O. A.

Seasonal Monitoring Program (SMP) data available in the Long Term Pavement Performance (LTPP) database DataPave was analyzed to investigate the variations of volumetric water content. The SMP data includes volumetric water contents from time domain reflectometry (TDR) probes in pavement sections located in the United States and Canada. Water content, or the associated degree of saturation, is used to compute resilient modulus for unsaturated unbound base and subgrade soils in the Mechanistic-Empirical Pavement Design Guide (M-EPDG) that was developed for the Federal Highway Administration. The purpose of this paper is to discuss results of analysis of volumetric water content data from the most recent release of DataPave (Release 19) and the resulting variations in resilient modulus that would occur. Results from analysis of the data indicate that there are variations of volumetric water content that occur over time. For a few of the pavement sections, the variations of volumetric water content were seasonal. For most of the sections, it was not possible to determine consistent trends in the moisture variations on a temporal scale or when comparing the different climate zones, soil types (coarse or fine-grained), pavement types or depth to the water table. The volumetric water content variations typically were greater than 3 percent and less than 9 percent. These findings indicate that subgrade soils undergo varying degrees of saturation. The resilient modulus, computed using the water content variations and an empirical equation developed for the M-EPDG, can vary by as much as a factor of 2. The resilient modulus variations are generally higher in wet climates than in dry climates.