Using Time Domain Reflectometry (Tdr) and Radio Frequency (RF) Devices to Monitor Seasonal Moisture Variation in Forest Road Subgrade and Base Material

This report outlines the laboratory and field test programs conducted by the U.S. Department of Agriculture Forest Service and the U.S. Army Cold Regions Research and Engineering Laboratory to monitor soil moisture and pavement stiffness, and it describes instrumentation used for the study. It discusses observations, analyses, and results from the laboratory and field tests as part of an overall effort to develop a reliable, objective, cost-effective method to determine when to place and remove load restrictions associated with periods of critical pavement weakening (i.e., spring thaw). The technique is applicable to any secondary road subjected to seasonal freezing.