Undrained Shear Behavior of Low-Plasticity Intermediate Soils Subjected to Simulated Tube-Sampling Disturbance

This paper presents a laboratory investigation of the influence of simulated tube-sampling disturbance on lightly overconsolidated intermediate soils by varying their plasticity and degree of sampling disturbance. Samples consisting of varying proportions of kaolin and silica silt that produce five plasticity indexes of 0%, 4%, 9%, 16%, and 32%, are mixed as slurry and then consolidated to an overconsolidation ratio of 1.8. All specimens are tested in a stress-path triaxial cell using the ideal sampling approach (ISA), which involves applying undrained shearing with axial strain cycles of $\pm 0.5\%$, $\pm 1.0\%$, and $\pm 3.0\%$, corresponding to three different degrees of tube-sampling disturbance. The results show systematic trends in the soil response with decreasing plasticity to the induced ISA disturbance. At the same degree of ISA disturbance, the subsequently measured undrained shear strength for the low-plasticity soils increases compared with the reference undisturbed specimen and the percent change increases with decreasing plasticity. This is significantly different from the reported findings from ISA testing of clays, indicating that intermediate soils and clays can have contrastingly different responses to sample disturbance.