Influence of pore structure characteristics on soil-water characteristic curves under different stress states

Since traditional instruments cannot apply stress in soil-water characteristic curve tests, we develop a suction controlled triaxial apparatus, by which soil-water characteristic curve tests are performed under different stress states. Further, the influence of stress state on the pore characteristics is discussed. The results show that both consolidation pressure and matrix suction can lead to the irreversible contraction deformation of soil. The soil under a larger consolidation pressure has a denser structure and a less void, leading to a smaller pore size and quantity. So it results in a worse permeability. Accordingly, it shows a better water retentivity. Air can hardly enter and water can hardly drain out, which give rise to a larger air entry value and a smaller slope of the soil-water characteristic curve. The soil-water characteristic curve of a compacted soil mainly depends upon current void ratio, not directly upon stress state. The influence of consolidation pressure on the soil-water characteristic curve is embodied in pore distribution properties. For similar pore distribution properties, the soil-water characteristic curve should be similar regardless of stress state. A larger consolidation pressure causes a less hysteresis.