Evaluation of CPTu Cone Factors for Busan Clay Using Pore Pressure Ratio

Cone factors, , and , for estimating undrained shear strength of Busan clay are evaluated in this study. For this, CPTu and field vane tests are performed for clay layers at two sites, Busan new-port and Noksan, and also triaxial tests with undisturbed samples taken from the same site are carried out. From experimental results, it is observed that the undrained shear strengths of clay increases with depth, and the undrained shear strength obtained from triaxial tests is 1.5 times higher than one obtained from vane tests. The normalized undrained shear strengths of Busan clay from triaxial and vane shear tests are and , respectively. In CPTu results, cone tip resistance () and pore pressure () linearly increase with depth, and the pore pressure ratio () of Busan clay is within the range of . The cone factors, which are determined by comparing the CPTu results with triaxial and vane shear test results, are found to be and , respectively. It is also observed that the cone factors are inversely proportional to the pore pressure ratio. From this, the prediction methods for evaluating the cone factors of Busan clay are developed.