A Novel and Facile Method for Characterizing Shrinkage Geometry along the Granitic Soil Profile

Abstract

Core Ideas A simple and facile approach was proposed for measuring the anisotropic shrinkage. Subsidence was dominant for soils in the loose and aggregated structure. Horizontal shrinkage was predominant for soils with the horizontal arrangement of plate particles The shrinkage behavior of granite soils was controlled by clay content and pore structure. Soil volume change resulting from frequent drying–wetting cycles leads to severe erosion and landslides in granite regions. Limited attempts have been made to investigate the shrinkage geometry of these soils. Here, a new method was proposed for characterizing soil shrinkage behavior by testing cylindrical specimens of undisturbed granitic soils sampled separately in vertical and horizontal directions at the pedogenic layers (i.e., surface [L1], lateritic [L2 and L3], sandy [L4], and detritus [L5] layers). For L1, the coefficient of linear extensibility (COLE) was larger in the vertical than in the horizontal direction, whereas it was the opposite for L2 and L3. For L4 and L5, the COLE showed no significant differences between the two directions. A modified van Genuchten equation fitted well with the COLE curves (p < 0.01). The shrinkage potential decreased in the order of L3 > L2 > L1, L4 > L5. Subsidence was dominant for the L1 soil due to the loose‐aggregated structure, whereas cracking was dominant in the lateritic layer soils due to the horizontal arrangement of clay particles. The shrinkage geometry for L4 and L5 was largely determined by soil structure inherited from the configuration of granite rock. The shrinkage behavior of granite soils was controlled by clay content and pore structure. This new method of measuring shrinkage geometry is accurate, low cost, nondestructive, and labor saving but remains to be improved and validated on a wide range of soil types.