6. Shear strength of cohesive soils

6.1 Drained and undrained behavior

While we are generally only interested in the drained characteristics of powdery soils, in the case of cohesive soils, we must examine all drained and undrained characteristics. These characteristics are determined in shear tests carried out either in the laboratory or in situ.

Drained characteristics are normally determined by consolidated undrained triaxial tests with pore pressure measurement, or by consolidated drained triaxial tests. Slow (drained) shear box tests (direct shear tests or alternating direct shear tests) are also used.

Non-drained characteristics are determined in the laboratory, using consolidated non-drained triaxial tests, or in-situ using a site scissometer. Unconsolidated, undrained...