Characteristics of Soils with Low Plasticity: Intermediate Soil from Ishinomaki, Japan and Lean Clay From Drammen, Norway

Two soils with low plasticity are investigated; intermediate soil from Ishinomaki, Japan and lean clay from Dram- men, Norway. Since both the soils were retrieved using the Japanese sampling method, the test results from these samples are comparable. Though they have the same order of plasticity index (Ip), there is a significant difference in the grain size distribution characteristics between these soils. Ishinomaki intermediate soil contains a lot of sand or silt sized particles, its Ip value being nearly proportional to its clay content. On the other hand, Drammen clay consists of a large proportion of rock flour, which contains little clay mineral. The study shows that the unconfined compression test significantly underestimates the undrained shear strength for both soils, and their residual effective stress (p'r) is also very low. It has been found that to compensate for loss of p'r, recompression tests are useful methods to evaluate the strength of such soils.