A method for estimating peak and critical state friction angles of sand based on cone penetration tests

Abstract

In this study, a new method for estimating the shear strength of sand based on the cone penetration test (CPT) results is proposed. Key motivation was to utilize CPT results from vertical and inclined penetration conditions, aiming at eliminating the stress normalization process required in traditional methods, to further enhance the reliability of strength estimation. Both the critical state \(\left( {\phi_{c}^{\prime } } \right)\) and peak \(\left( {\phi_{p}^{\prime } } \right)\) friction angles were considered in the proposed method. To establish prediction models for \(\phi_{c}^{\prime }\) and \(\phi_{p}^{\prime }\), the correlative relationship between the cone resistance (\(q_{c}\)) and the coefficient of lateral earth pressure at rest (K₀) was introduced, where the ratio of vertical to inclined cone resistances was utilized. The proposed prediction models for \(\phi_{c}^{\prime }\) and \(\phi_{p}^{\prime }\) utilize the penetration resistance ratio enabling the direct estimation of strength parameters without additional experimental process for in-situ stress input. Such novelty of the proposed method leads to simplified and optimized strength estimation process at reduced time and cost. The proposed method was validated through results from centrifuge tests and coupled Eulerian–Lagrangian finite element simulations, which confirmed the accuracy and field applicability. Results were compared with those from other existing methods, which showed that the proposed method produced improved prediction.