Evaluation of undrained shear strength of marine clay by constant-volume direct box shear test: Case study of D-runway construction project of Tokyo International Airport

The applicability of the strength obtained by consolidated constant-volume box shear test, was examined using the data of geotechnical investigation carried out for D-runway construction project of Tokyo International Airport. It was confirmed that the design shear strength obtained by 0.85su(DST0) of undisturbed specimens, which is sheared at 0.25mm/min after the consolidation with the in-situ effective overburden pressure. Regarding the strength development by the consolidation, the comparison was made on the shear strength normalized to the consolidation pressure (strength increase rate) obtained by the constant-volume box shear and the consolidated-undrained triaxial test. It was found that 70% of the strength obtained by the consolidated-undrained triaxial test should be used to estimate the strength increase after consolidation.