Field vane shear strength is pressented for sevem Japanese soft clays and comppared with strength obtained from unconfined compressive test. It has been reported that the vane strength normalized with the consolidation yield pressure, Su/Pc is dependent on plasticity index. Ip. However, the Su/Pc rations obtainedfrom the Present study were generally constant with Ip, with values ranging from 0.25 to 0.35 Bjerrum's correction factor μ is commonly used to determine the shear strength for stability analysis from the vane shear strength.
　The shear strength modified by method, however, was found to be considerably conservative for Japanese clays, when compared with the unconfined compressive strength that has been proved to provide an appropriate shear strength for practical use in Japan.