Influence of the Suction on the Stiffness at Very Small Strains: Fid-Bau Portal

Influence of the Suction on the Stiffness at Very Small Strains

Mendoza, C. E. / Colmenares, J. E.

This paper presents the results of an investigation on the variation of the stiffness at very small strains of an unsaturated clayed soil subjected to drying processes. The soil stiffness was measured by using the wave velocity technique (ultrasonic pulse transmission method and bender elements testing). The test were conduced on samples of kaolinite clay derived from volcanic ash. Those samples were prepared by using a static compaction method known as the flouting mould. Compacted samples of kaolin were allowed to dry gradually up to air-dry condition. At intermediate equilibrium stages, the Shear and Young's modulus and the matrix suction were measured. The effects of initial void ratio, compaction water content and matrix suction on the dynamic response of the soil were investigated. The experimental results suggest that suction significantly increases the stiffness at very small strains. An S-shaped relationship between the initial stiffness and the degree of saturation was observed. The modulus increased significantly at early stages of the drying process, with the changes becoming more gradual as drying continued. However, at final stages, near to air-dry condition, the effect of suction on the stiffness was important again. The initial void ratio appears to have more influence on the stiffness than compaction water content. Contours of equal suction in the plot of the modulus versus degree of saturation, during drying processes, were analyzed. Additionally, changes in the soil fabric during drying and wetting were analyzed considering changes in void ratio.