Calibration of TDR probes for water content measurements in partially saturated pyroclastic slope

Monitoring of water content in partially saturated slopes prone to landslide could be essential for the good functioning of an early warning system. In this regard, Campania region in Southern Italy is an area with an extensive record of rainfall-induced landslides. In Western Campania, slopes consist of pyroclastic soil cover in partially saturated conditions resting on limestone. Time-domain reflectometry (TDR) allows monitoring of the soil dielectric constant, which is related to the volumetric water content. Topp et al. (1980) proposed the most popular relation between these two parameters but it does not provide satisfactory results when applied to volcanic soils. Therefore, when dealing with pyroclastic soil, ad hoc calibration is required. Here, the calibration of TDR probes in undisturbed pyroclastic soil samples collected at the Mount Faito test site (Campania, Italy) is shown and the proper relation between volumetric water content and dielectric constant is proposed. Lastly, these calibration curves are compared to those found for other pyroclastic soils belonged to different geologic contexts in Campania.