Establishing Soil-Water Characteristic Curve of a Fine-Grained Soil from Electrical Measurements

Application of a pressure membrane extractor (PME) to establish soil-water characteristic curve (SWCC) of fine-grained soils, in 0-1,500 kPa range, is well established. However, this technique requires testing of several identical specimens, corresponding to same or different pressure(s), and their subsequent removal from the PME chamber for moisture content determination. This turns out to be a cumbersome process and even the results are considered less accurate, by the research fraternity. This is mainly due to the fact that removal of the specimen before equilibration time may not incorporate the influence of the applied pressure, precisely. This calls for the development of an alternate technique that can be employed for measuring the instantaneous moisture content of the specimen when it is pressurized, sequentially, without removing it from the PME chamber. In this context, the utility of electrical measurements (i.e., the voltage) across two points in the specimen for determining moisture content was investigated and its details are presented in this paper. This technique has been found to be quite promising and hence can be employed for acquisition of the data which would yield the moisture content of the specimen, without removing it from the PME chamber, easily and quickly. Validity of the methodology has been demonstrated by comparing the obtained SWCC vis-agrave-vis those obtained by conducting studies using a dewpoint potentiameter, WP4, and by employing the fitting function and a pedo-transfer function available in the SoilVision database.