Potential use of time domain reflectometry for measuring water content in rock

Abstract

Quantifying water movement through bedrock materials requires a technique which can accurately measure water content at precise locations within the medium. Time Domain Reflectometry (TDR) is widely used to measure the water content of soil and has a measurement sensitivity which is tightly confined to the area immediately surrounding the probes. This study applies TDR to the measurement of water content in rocks. The technique was evaluated using sandstone and welded tuff in a series of laboratory experiments. A block of each rock type was instrumented with a series of evenly spaced TDR probes. Each block was first saturated with water and then allowed to air dry. The water content was determined gravimetrically using the TDR over a period of several weeks. The results indicate that the TDR technique can be used to determine the water content of rock with an accuracy comparable with that reported for the technique used in soils.