Undrained shear strength assessment using piezocone and shear wave measurements

Abstract

In this paper, a new approach is proposed to determine the undrained shear strength of intact clays using the undrained rigidity index inferred from piezocones and shear wave velocity measurements based on the theory of spherical cavity expansion. The derived cone factors are further simplified for young, uncemented (non-structured) clays to be solely expressed in terms of the cone behaviour type index. Moreover, an empirical expression is suggested to relate the undrained shear strength of fissured clays to the cone and shear wave measurements. The proposed approach is used to assess the values of undrained shear strengths in several well-reported test sites. The estimated strengths are found to be in a good agreement with the related field and laboratory measurements in intact clays, whereas in fissured clays, the estimated undrained strengths are shown to match less favourably with the laboratory measurements. This may be attributed to the strong dependence of the undrained shear strength of such clays on the site-specific orientations and properties of the prevailing fissures.