Hysteresis of matric suction and capillary stress in monodisperse disk-shaped particles

The dependences of matric suction and capillary stress on the degree of saturation in monodisperse disk-shaped particles are established for the full range of the degree of saturation. A thermodynamic free energy approach is employed to obtain both the soil-water characteristic curve (SWCC) and the capillary stress characteristic curve (CSCC) for both wetting and drying processes. It is shown that the thermodynamic energy stability concept can lead to the establishment of hysteresis in both the SWCC and CSCC without explicit involvement of the contact angle and ink-bottle hysteresis. The air-entry pressure value and capillary condensation pressure value are quantified and their functional dependencies on the average pore sizes are established. For particle sizes ranging between 0.001 and 1 mm, the air-entry and capillary condensation pressures decrease from several hundred kPa to several kPa and capillary forces are found to range between tens and hundreds of micronewtons.