Determination of design shear strength of clay based on the comparison between unconfined compressive strength and the strength obtained by triaxial test

To determine the design shear strength of seabed, the method by unconfined compressive strength with the combined use of triaxial CU test (combined method) had been proposed. The combined method was used in 4th runway project of Tokyo International Airport and in the construction project of breakwater in Sakai-Minato Port. In the 4th runway project, it was found that the quality of high plastic clay taken by fixed piston thin wall sampler or Denison type triple tube samplerr was fairy good and that the combined method was effective to avoid the underestimation of strength of low plastic clay. In the case of Sakai-Minato Port, although the breakwater had been constructed on improved ground previously, the breakwater could be constructed without any improvement, because the strength of intermediate soil was evaluated correctly by the combined method.