Effect of microstructure on water retention behavior of lateritic clay over a wide suction range

To investigate the effects of soil structrue and dry density on water retention behavior of lateritic clay over a wide suction range, the axial translation technique (ATT), filter paper technique (FPT) and vapour equilibrium technique (VET) were combined to obtain soil-water retention curves (SWRCs) of specimens with different structures and dry densities. Measured SWRCs indicate that the air-entry value (AEV) and descent gradient in terms of saturation degree versus suction relationship are smallest for undisturbed specimens, and are largest for pre-consolidated specimens. The SWRCs obtained from compacted specimens with different dry densities illustrate that the AEV and descent gradient of saturation degree versus suction relationship increase with increasing the dry density. However, the effects of soil structure and dry density on the water retention behavior can be negligible at high suctions, which are verified by the curves of gravimetric water content (w) verusus suction (s) coincided after a limiting suction for specimens with different structures and dry densities. In addition, the water retention behavior can be well illustrated by pore size distributions (PSDs), obtained from mercury intrusion porosimetry (MIP). The AEVs depend on the diameters that corresponding to dramatically increase in differential intruded void ratio. And the descent gradients in the saturation degree versus suction relationship depend on their distinct PSD ranges and incremental peaks in the dominant pore sizes. Furthermore, the consistences of the AEVs and limiting suctions, deduced from the PSDs and SWRCs, demonstrate that the water retention behavior is highly dependent on the PSDs, and the SWRC features can be captured well by the PSDs.