A CPT-based method for estimation of undrained shear strength of sands and transitional soils

This paper presents a practical approach for developing a site-specific CPT-based method for monotonic undrained shear strength (s_u) in sands and transitional soils, using results of laboratory undrained triaxial compression (CU) tests on reconstituted and undisturbed specimens as reference. The methodology includes use of net cone resistance values normalised to vertical effective stress, a procedure for pairing of CPT data with CU test results, and definition of a practical failure criterion for deriving s_u from CU test data. The presented approach is particularly useful for application in offshore wind, where the economics of wind farm development favour performing only a single cone penetration test (CPT) per wind turbine location. This setting drives development of CPT-based methods for key geotechnical parameters for foundation design.