Role of osmotic suction in volume change of clays in salt solution

The volume change behaviour is usually expressed by different curves of e–p when concentrated pore fluids are introduced to clays. Increase in effective stress from osmotic suction in salt solution and increase in inter-particle attraction from the pore-water salt concentration in salt-clay system. The void ratio is smaller in the salt solution with higher concentration under the same vertical overburden pressure, and it results the different curves of e–p in salt solution with different concentration. This paper aims to express the e–p relationship using a unique curve for clays in salt solution with different concentration. A conceptual model is proposed to explain the influence of osmotic suction on the volume change of clays in a quantitative way. A new formula for effective stress is proposed as pe = p + pπ incorporating with osmotic suction (π), and pπ = (p/π)D ‐ 2π. Experimental data for volume change of clays in NaCl solution with different concentration can be expressed by a unique curve using the proposed effective stress.