Abstract: Silt soils have been encountered in most of the estuary of Qiantangjiang. Based on the study of dilatant characteristic of Qiantangjiang alluvial saturated silts, general triaxial drainage tests of five groups of silts of different saturation degrees have been conducted to study the dilatancy of the unsaturated silts. The test results of the slightly dense silt show that one of the most significant properties of Qiantangjiang unsaturated silts is the dilatant characteristic; and that the amount of potential dilatancy is mainly governed by the saturation degree, and confining pressure; and that the influence of the saturation degree on stress-strain curves of silts is slight; and that the shapes of stress-strain curves are slightly softened. The ratio of residual strength to peak strength (qr / qmax )is mostly between 0.9 and 1.0. The research also makes it clear that the amount of dilatancy rises with the ascent of the saturation degree, and falls with the rise of confining pressure. There is a clear correlation between the volumetic strain and the intermediate principal stress at the critical state. Under the confining pressured of 800 kPa, the volumetic strain of slightly dense silts is in the range confined by the two almost parallel lines = 12.020 2 – 4.939 2lnp and = 15.771 7 – 5.775 1lnp. The most amount of dilatancy is less than 5%

Key words: unsaturated silt, triaxial test, stress-strain, volumetric strain, dilatancy