Effects of initial density and drying-wetting cycle on soil water characteristic curve of unsaturated loess

Soil water characteristic curve (SWCC) plays a significant role in unsaturated soil mechanics. There are several factors influencing the soil water characteristic curve, such as initial density, dry-wetting cycle and stress, etc. A series of tests are carried out by means of GCTS-type SWCC device for soil water characteristic curve for remoulded unsaturated loess specimens at different bulk densities. Based on test results, after a well-adapted selection of soil water characteristic curve model, the influence of initial bulk density on unsaturated loess soil water characteristic curves are studied through analyzing the best-fitting curve parameters. The two drying-wetting cycles tests for a specimen at certain initial density are also carried out; and the corresponding hysteretic curves are obtained. By developing the concept named "degree of hysteresis" and analyzing the differences of volumetric water content in the drying-wetting cycle test, the SWCC hysteresis behaviour of unsaturated loess is preliminarily studied. The aforesaid results may play a significant role in the investigations on stress-dependent soil water characteristic curve model and the force-water coupled constitutive model.