, Former University Researcher, Soil, Water & Climate
Time domain reflectometry is used to monitor water content in situ under pavement at the MnROAD site. The current TDR system exhibits excessive signal loss in probes and transmission line, hampering accurate interpretation of the TDR waveform. Consequently, standard calibrations to calculated water content yield unreliable data. A specific calibration is needed to convert TDR output of this particular TDR system into water content, which then allows interpretation of the massive TDR data recorded between 1993 and 1996. A laboratory study is proposed to simulate the lossy TDR system and develop a calibration procedure taking into account the different soil types, transmission line lengths, bulk densities and temperatures. In addition, different TDR system configurations will be evaluated to make a recommendation on an improved TDR system for use by MnDOT for monitoring water content in soil material underneath pavements.