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Fig. 2. Schematic representation of (a) the volumetric shrinkage of the unitary prism (a = prism side dimension, h = prism height dimension, 
a and h = decrease of prism dimensions), and (b) crack opening (horizontal shrinkage) and subsidence (vertical shrinkage) phenomenon in the grassland field. Layer 1 = solid state (W [gravimetric water content] < Wp [plasticity limit]), crack opening and subsidence operate simultaneously. Layer 2 = plastic to "pseudo liquid" state (W > Wp), only subsidence operates (
b = wet density of the clayey matrix, 
= microporosity of the clayey matrix, fracture area = horizontal shrinkage (cracks) at the soil surface, a1/3 = calculated aperture of crack, WSTS = wet season topographic surface, DSTS = dry season topographic surface).
