Viscous Effects on the Stress-Strain Behavior of Gravelly Soil in Drained Triaxial Compression

A series of special drained triaxial compression tests using a large-scale triaxial apparatus was carried out to study the viscous properties of gravelly soil. To evaluate loading rate effects on the stress-strain behavior, the axial strain rate was changed stepwise during otherwise monotonic loading (ML) at a constant strain, which resulted in a sharp increase or decrease in the deviator stress. Drained creep loading tests were also performed at several deviator stresses during otherwise monotonic loading and unloading along different stress paths. The amount of creep strain increased with an increase in the deviator stresses. The stress-strain behavior was nearly elastic for some stress range immediately after ML was restarted at a constant strain rate following each creep stage. The viscous properties of partially and fully saturated specimens were essentially the same.