Columnar structure and desiccation cracks

Abstract

The formation of three-dimensional prismatic cracks during the drying process of starch-water mixtures is investigated numerically. We assume that the mixture is an elastic porous medium which possesses a stress field and a water content field; the evolution of these fields is represented by, respectively, a spring network and a phe-nomenological model based on the water potential. As a result of numerical simulations, we reproduce the water content distribution where the drying front propagates from the surface to the interior, and the prismatic structure of cracks grows as the front progresses. The particle-diameter dependence of the columns scale and the downward coarsening process of the columnar structure are investigated. We find that the non-uniform fracture process is a conse-quenice of breaking points propagating along the sides of polygonal cross sections. We also examine the effect of the crack networks on the dynamics of the water content field. The contrast between starch columns and geological columnar joints is discussed.