chapter  68
Calibrating NTH method for ϕ′ in clayey soils using centrifuge CPTu
ByZ. Ouyang, P.W. Mayne
Pages 7

An existing effective stress limit plasticity solution for piezocone penetration tests (CPTu) developed at the Norwegian Institute of Technology (NTH) is calibrated to evaluate the effective stress friction angle ϕ′ for clayey soils subjected to centrifuge model testing. Results from previously conducted in-flight mini-piezocone tests by various institutes were compiled for study, including readings taken from 13 series of centrifuge chamber tests on artificially prepared clays, mainly kaolin and kaolinitic-silica mixtures. Effective stress friction angles from companion triaxial compression tests (CAUC or CIUC) and/or Direct Simple Shear (DSS) tests on these soil deposits were adopted as the benchmark reference to verify the reasonableness of the NTH method in assessing ϕ′ at constant penetration rates, as well as a few special tests conducted at variable rates.