Temperature Based Water Content Measurement in Mud (Soil) With Fiber Optics

Abstract

This research has demonstrated the applicability of a DTS system to estimate the volumetric water content in saturated mud material. 2 samples of synthetically generated mud and 1 sample of natural mud from the port of Rotterdam were investigated, first by conventional methods and subsequently also with DTS. The system set-up and heating strategy were optimized by testing with different media (air, water) and with different FO coil diameters. A step-by-step approach was then designed to translate the thermal response recorded in the muds into volumetric water contents. Early- and late- time cutoffs were applied to the slope selection procedure (∆T vs ln(t)), and a mud dependent correction factor was applied to obtain the effective heat flux. The average VWC’s (ϴ) subsequently derived from the DTS data were in good agreement with those obtained by conventional methods (core sampling); the standard deviation in the VWC’s (ϴ) of all three tested muds was between 0.030 and 0.040 m³/m³. For saturated conditions, Sayde et al. (2010) and Striegl and Loheide (2012) published larger standard deviations of 0.046 m³/m³ and >0.050 m³/m³ respectively. The approach detailed in this investigation has enabled DTS to perform as a guideline on the continuous volumetric water content profile in saturated muds.