A Low-Cost Automated SWCC Device and Data Analysis Procedure For Unsaturated Soils Exhibiting Volume Change

ABSTRACT: Conventionally, a soil water characteristic curve (SWCC) is measured using a pressure plate device; however, this procedure is relatively tedious, and demands manual measurements. A new system has been developed utilizing a low cost single board computer (Raspberry Pi). The following paper discusses both the operational, and practical benefits of this device as it relates to unsaturated soil mechanics. The device continuously measures volume outflow to determine matric suction equilibrium - producing a SWCC with limited user interaction. The SWCC for numerous soils were approximated. A photogrammetric procedure was employed to measure the shrinkage curve and produce volumetric SWCC’s as described by Fredlund et al. (2018). The transient outflow steps were then used to approximate the unsaturated permeability and compared to implicit methods. This device provides a preliminary framework for directly and automatically estimating unsaturated hydraulic conductivity for unsaturated soils exhibiting volume change using multi-step outflow measurement.