ABSTRACT
The paper presents an experimental programme aimed at studying the retention properties of partially saturated silty sand in terms of the simultaneous storage of water and light hydrocarbon (LNAPL). Specifically, this study pursues a better understanding of the multi-phase flow and transport phenomena in oil-polluted unsaturated soils. Using a mixture of two natural soils (Ticino Sand and Pontida Silt), soil samples were prepared at different initial dry densities and oil and water contents. Soltrol was used as analogue of the LNAPL. The investigation was focused on both microscopic and macroscopic point of views by using mercury intrusion porosimetry and vapour transfer technique. Clear aggregation phenomena on this mixture were observed on addition of small amounts of Soltrol, which have important consequences on the retention properties. The aggregation induces a double-porosity soil structure, which is not easily erased on subsequent hydraulic cycling.
