The mechanics of air entry of drying-cracking soils: Physical models

Abstract

Because of common exposure to high temperatures and forced ventilation of geomaterials in energy production and storage, failure mode of these materials often involves intense drying and constrained shrinkage associated cracking. Previous experiments show that drying-cracking occurs when the materials are completely saturated, practically simultaneously with the onset of air entry and start of desaturation. Computer assisted experiments are presented focusing on the phenomenon of air entry into drying granular meso-scale material models. A critical value of capillary adhesion force is assessed associated with the first (and subsequent) unstable air entries (Haines jumps) into drying capillary water of granular materials, as well as the corresponding saturation. The entries are recognized as precursors of drying cracks. The evaporating models with different separations of grains are photographed every 10 s and the images of menisci are computer-processed to follow the evolving water body geometry and cluster saturation. Energy released during subsequent instabilities is also assessed.