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.