Unsaturated soils | Hydraulic conductivity | Shear strength | Consolidation and volume change | Waste rock | Field testing MDH operates a range of pressure plate cells designed for testing clay rich, silty or sandy materials and coarse-grained soils such as waste rock (materials containing particles up to 60 mm in diameter). A vapor extraction technique is used to extend the soil-water characteristic curve to 106 kPa. Our standard testing equipment includes 63 mm diameter pressure plate cells and our specialized equipment consists of large diameter (300 mm) cells and other specially fabricated cells for calibrating thermal conductivity matric suction sensors. Soil-water characteristic curve and predicted hydraulic conductivity function for a sandy tailings