Effect of dry density on the relationship between water content and TDR-measured apparent dielectric permittivity in compacted clay

Abstract

The volumetric water content, θV, is a key variable in unsaturated soil mechanics and needs to be measured both in the laboratory and the field. Time domain reflectometry (TDR) is a technique that can be successfully used for this purpose. This technique is based on the measurement of the dielectric permittivity of the soil, Ka, which is in turn related to the volumetric water content through a suitable calibration curve. An empirical calibration curve was presented by Topp et al. (1980) suggesting a unique relationship between Ka and θV. However this curve was developed for agriculture soils which have dry densities typically lower than compacted soils used in geotechnical engineering. The purpose of this study is to investigate the effects of dry density on the Ka - θV relationship.