Abstract：Using consolidation apparatus for unsaturated soils，the confined compression tests at constant water content are conducted on unsaturated undisturbed loess in Xi?an under different initial water contents. The maximum net normal stress is 1 600 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. Effects of stress state on matric suction characteristics of unsaturated undisturbed loess are determined and illustrated under confined compression condition. Experimental results show that the net normal stress change influences the matric suction state of unsaturated undisturbed loess at constant water content. The regularity of influence greatly depends on the initial water content of specimen. The degree of influence is related to the magnitude of applied stress and initial water content. The influence of small net normal stress(≤400 kPa) on matric suction of unsaturated undisturbed loess is slight under different initial water contents. The influence of stress where the initial water content of specimen is smaller than plastic limit is greater than that where the initial water content of specimen is higher than plastic limit. The relationship between matric suction and saturation degree related to applied stress is different from that related to water content. The influence of net normal stress on soil-water characteristic curve(SWCC) is related to magnitude of net normal stress. The effect of small net normal stress(≤400 kPa) on SWCC is much smaller than that of large net stress(＞400 kPa). When net normal stress is small(≤400 kPa)，the soil-water characteristics are illustrated by the relation between matric suction and gravimetric water content under zero-applied stress for the sake of convenient use in engineering；and when it is large(＞400 kPa)，they are illustrated respectively. The relation between matric suction and gravimetric water content can be illustrated by power function under different applied stresses.
HUANG S，BARBOUR S L，FREDLUND D G. Development and verification of a coefficient of permeability function for a deformable unsaturated soils[J]. Canada Geotechnical Journal，1998，35(3)：411-425.
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2011, Vol. 30 
