Soil-water characteristics of unsaturated undisturbed loess under isotropic compression condition

Abstract

Using triaxial apparatus for unsaturated soils, the isotropic compression tests at constant water content are conducted on unsaturated undisturbed loess in Xi'an under different water contents. The maximum of net confining pressure is 400 kPa. Matric suction is measured by an elevated all round air pressure and with measured pore-water pressure under zero-applied stress and applied stress. Influences of net confining pressure on matric suction characteristics of unsaturated undisturbed loess are determined and illustrated during isotropic compression at constant water content. The formula of soil-water characteristics of unsaturated undisturbed loess is obtained to determine the matric suction under zero-applied stress. Experimental results show that the influence of net confining pressure on matrix suction is related to water content. When water content is smaller than shrinkage limit, the relationship between matrix suction and net confining pressures is different from that larger than Shrinkage limit. The influence of net confining pressure is large when water content is between shrinkage limit and plastic limit, and it is slight when water content is smaller than shrinkage limit or larger than plastic limit. The relation between matric suction and degree of saturated related to net confining pressure with water content smaller than shrinkage limit is different from that related to water content. The influence of degree of saturated related to net confining pressure on matric suction is much smaller than that related to water content. Net confining pressure has relatively large influence on the relation between degree of saturated and matric suction. When net confining pressure is smaller than 400kPa, its influence on he relation between water content and matric suction is negligible, and the soil-water characteristics of undisturbed loess is illustrated by the logarithm function relation between water content and matric suction under zero-applied stress.