Effective Stress and Compressibility of Unsaturated Clayey Soil under Drying and Wetting Cycles

Abstract

Naturally, soil moisture reduces during dry seasons when the soil is in drying state; while it increases during wet seasons when the soil is in wetting state. Previous studies have shown that for an unsaturated soil sample, soil-water characteristic curves (SWCCs) do not match in wetting and drying paths. The differences between wetting and drying paths are called the hydraulic hysteresis. The hydraulic hysteresis plays an important role in mechanical properties of soil such as shear strength, volume change, and settlement. The objective of this research is to study the effects of drying and wetting on the effective stress and compressibility of unsaturated clayey fine-grained soils. To this end, saturated and unsaturated triaxial tests were performed on the soil samples under various normal mean stresses, and matrix suctions in drying and wetting paths. It was found that soil samples bear higher levels of effective stress in the drying path than the wetting path under a same level of suction. The attained values of effective stress parameter (χ) showed that the Bishop’s effective stress parameter (χ = Sr) is not properly applicable for the clayey soil. Moreover, the resulting loading-collapse curve (LC) revealed that the effective pre-consolidation pressure in the drying and wetting stages changed even with same degrees of matrix suction.

Effects of water content change path on laboratory and field compaction of lime stabilized expansive soil

“…The determined soil water characteristic curves are shown in Figure 4. Some scholars have measured the moisture characteristic curve of clay in two different processes of wetting and drying found that under the same water content, the matric suction in the drying process is always greater than that in the wetting process (Kholghifard, 2020;Ding et al, 2022;Sarker and Wang, 2022). Figure 4 shows that the drying curves are above the wetting curves for specimens with both 5% lime and 8% lime contents.…”

“…In terms of macroscopic mechanical properties, matric suction is closely correlated with the shear strength of the soil. The relationship between matric suction and water content is described using the soil-water characteristic curve (SWCC), and scholars such as Bishop has established connections between matric suction and the strength of unsaturated soils (Kholghifard, 2020;Zhao et al, 2021). Several factors have been demonstrated to affect the SWCC, Gallage and Uchimura (2010) indicated that soils with low density exhibit lower residual suction compared to those with high density, while the influence of soil structure on SWCC can be negligible in the high suction range (Baker and Frydman, 2009).…”

Degradation Characteristics and Mechanism of Black Sandy Dolostone Subjected to Wetting–Drying Cycles

“…Some studies have proposed that chemical composition analysis theory and the damage mechanics method can effectively analyze chemical damage mechanisms in water-rock interaction [18][19][20]. The water-rock interaction has a significant time effect on the mechanical parameters of rocks, and its effect varies for different rocks [21][22][23]. It was found that an aqueous environment with higher OH − concentration causes a significant increase in the growth rate of quartz fracture [24,25].…”