关键词: 非饱和原状黄土, 非饱和土真三轴仪, 土-水特征曲线(SWCC), 中主应力参数b值

Abstract: Soil-water characteristic curve is the basic trait to reflect the existence state and interaction of three-phase medium in the unsaturated soil, and the soil-water characteristics of unsaturated soil will be influenced by the stress state change and the deformation development. To reveal the change rules of soil-water characteristic curve in complicated stress state, a series of isotropic consolidation and shear tests with different intermediate principal stress ratios b under constant water content is performed on intact loess with various initial suctions by using the improved unsaturated soil true triaxial apparatus. Soil-water characteristics of unsaturated intact loess under different test conditions are determined and illustrated, at the same time, the function of fitted curves is gained. The results show that saturations all increase with net mean stress, the ratio b and net confining pressure; the suctions decrease with the increase of saturations, when the saturation is larger (Sr0≥43%), the reduce rate of the suction is smaller, when the saturation is smaller (Sr0<43%), the reduce rate is larger; when the saturation is fixed, the suctions all increase with net mean stress, the ratio b and net confining pressure. The influence of small net mean stress (p≤300 kPa) on soil-water curve of intact loess after the completion of the isotropic consolidation is slight, which can be described by power function. A fitting expression of soil-water characteristic curve is obtained to reflect the combined effect of the net confining pressure and the middle principal stress after the completion of true triaxial shear. Applicability of the fitting expression is verified by relevant tests.

Key words: unsaturated intact loess, unsaturated soil true triaxial apparatus, soil-water characteristic curve(SWCC), the intermediate principal stress ratio b