Fig. 3. Bulk density images and depth distributions of the slaking crust. (a) bulk density image, (b) measured data, with the Mualem–Assouline (exponential) crusting model (plain line), the Roth (sigmoidal) crusting model (bold line) and the slumping model (dotted line), (c) data after correction for the slumping effect, with the exponential (plain line) and sigmoidal (bold line) crusting models, (d) measured data, with the combination of the slumping and the crusting models (exponential, plain line, and sigmoidal, bold line).