Non-destructive assessment of sample homogeneity in resedimented fine-grained soils by low-field NMR-spectroscopy

Sample preparation by resedimentation is a common research practice for clays. While sample inhomogeneity is well investigated for coarse soil mixtures, there is evidence that particle sorting could also occur in fine-grained soils. The homogeneity of large resedimented clay samples was assessed by comparing large-scale samples of two resedimented high-plasticity fine-grained soils. These are classified as clay and silt on the Casagrande chart despite having limited index properties and mineralogy differences. The silt sample exhibited visible inhomogeneity after resedimentation. A comparison of a combination of particle size distribution and the void ratio on specimens taken at different locations in the sample based on conventional measurements of water content and bulk density, as well as nuclear magnetic resonance measurements, indicates that particle sorting is not as significant as the different fabric that ensues. In addition, nuclear magnetic resonance measurements provide non-destructive spatial water content distribution across a sample, indicating sedimentation results in two parts with different textures rather than a continuous transition.