Abstract: A large amount of clay is deposited at the seabed of the Chengdao Offshore Oilfield, and its undrained shear strength is an important mechanical parameter for the foundation design of marine structures. In this paper, by comparing three methods for estimating the undrained shear strength of cohesive soil. Both the advantages and disadvantages of each test method are evaluated and summarized. Combined with engineering examples, a linear regression analysis of the undrained shear strength obtained by the triaxial test and the resistance of the cone penetration tip was conducted to obtain the correlations between the cone tip resistance and the calculated undrained shear strength. Then throughout the error analysis and verification, it is considered that the method is feasible and accurate for the undrained shear strength of the seabed clay in Chengdao Offshore Oilfield. Finally, a further detailed analysis was conducted to obtain the key parameter selection methods for the undrained shear strength of clay soil with buried depths of 0~5 m, 5~10 m, and 10~20 m.

Key words: Undrained Shear Strength, CPT, Triaxial Compression Test, Clay