Strength of Fine-Grained Soils Using the Piezocone

Evaluation has been made of several theories and methods for deducing the undrained and effective stress strength of saturated fine-grained soil from piezocone test results. Bearing capacity and cavity expansion theories have been studied. For the undrained case the cavity expansion method proposed by A. S. Vesic, with slight modification, yielded the most accurate results. For the effective stress case, no method was found totally satisfactory. By directly relating the strength mobilized by a cone to that of a triaxial compression test and assuming the Vesic failure mechanism valid, an expression for the normal effective stress at failure is derived. In this way the effective stress strength parameters can be determined without laboratory tests.