Effects of particle morphology on pore structure and SWRC of granular soils

Given grain-size distribution (GSD) and relative density, the soil–water-retention curve (SWRC) of granular soils can be straightforwardly predicted. However, the evolution of SWRC with different particle morphologies under the same GSD is still unclear. To solve this fundamental problem, herein, four sand analogues with different particle shapes under the same GSD were produced by three-dimensional printing. The SWRCs and the pore structure at mesoscale were synergetically measured by using nuclear magnetic resonance (NMR) technology and hydraulic properly analyser water potential meter. The relationship between particle morphology and SWRC was quantitatively analysed, and the soil pore structure evolution under different particle morphology was clearly observed. Compared with round particle shape soils, soils with the same GSD but higher degree of angularity were found to have a subtle higher air-entry value (AEV) at a given relative density, even though the global void ratio is larger. NMR results indicate the pore structure of specimens with different particle morphology is similar. The pore volume is increased with angularity while the maximum pore throat shows an opposite trend. The difference in maximum pore throat is the fundamental reason for the variation in AEV, highlighting the importance of particle morphology on soil–water-retention behaviours.