Swell–compression behaviour of compacted clays under chemical gradients

The present study examines the effect of inflow of sodium chloride solutions on the swell–compression behaviour of compacted expansive clays under a range of external loads. Inflow of sodium chloride solutions reduced the swell magnitudes and pressures and even caused the compacted clay specimens to experience compressive strains in oedometer tests. The axial strain difference of specimens inundated with sodium chloride solutions and distilled water at a constant effective stress predicted the osmotic consolidation strains of a saturated clay specimen from an increase in osmotic suction in the pore fluid. Specimens exposed to larger osmotic suction gradients (Δπ) are predicted to experience larger osmotic consolidation strains. The predicted osmotic consolidation strains exceeded the experimental osmotic consolidation strains. The free-swell and load method and the swell under load procedure predicted different swell pressures owing to differences in strain contributions at the microstructure and macrostructure levels. The increase in osmotic suction in pore water apparently acts as an equivalent net stress (ρπ) that favours a reduction in swell potential of the compacted clay specimens due to a reduction in reversible swelling strains from an increase in net stress and irreversible macrostructural component that decreases because the distance of the stress point to the load–collapse (LC) curve decreases.Key words: compacted clays, chemical gradients, osmotic consolidation, suction, swell.