Abstract: In order to evaluate and treat the distress of silt subgrade by rainfall of Beijing-Jiulong railway in Yellow-River alluvial plain area, the basic physico-mechanical properties of silt were investigated by a series of laboratory experiments, for varying compactnesses and water contents; the deformation and strength behaviors of compacted silt were studied. Results indicate that the silt is poor graded and difficult to be compacted, even at its maximum dry density, compacted silt also has high volume ratio of air. For specimens at optimum water compactness of 90 %, the deformation character is softening. However, with water content increasing, the deformation character of compacted silt changes to hardening, especially for specimens at high confining pressure and at high water content, the plastic shear deformation is more significant. For specimens at compactness lower than 85 % and water content not less than optimum water content, the deformation character is always hardening. Cohesion of compacted silt descends sharply with compactness decreasing or water content increasing; but internal friction angle reduces insignificant. There is remarkable slaking deformation of compacted silt due to wetted; and compactness plays a very important role in slaking deformation.

Key words: silt, strength, deformation, compactness, water content, subgrade