Estimating clay undrained shear strength using CPTu results

Estimation of the undrained shear strength S-u of clays using piezocone penetration test (CPTu) results has been based mainly on the cone factor N-k. In this study a new CPTu-based method for estimating S-u is proposed and evaluated. It is aimed at reducing uncertainties in the estimation of S-u and enhancing the application of CPTu results. To develop the method, a selected site on a marine clay deposit was subjected to an extensive experimental testing programme. The proposed method defines a direct correlation between S-u and the cone resistance q(t), involving the initial in situ pore pressure but excluding the need for overburden pressure calculation and therefore the need for undisturbed soil sampling. To verify the proposed method, additional test sites and example sites from the literature that encompass a variety of soil conditions are selected and examined. Values of s(u) obtained from the proposed method are in good agreement with measured values of su for all the selected verification cases.