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The undrained shear strength is an essential parameter in the foundation design of marine structures. Due to the complex marine environment and technical limitations, it is difficult and costly to obtain offshore samples. Piezocone penetration tests (CPTU) are relatively low-cost compared to drilling and sampling methods. Therefore, based on the soil behavior type index (Ic) derived from CPTU results, a model for estimating cone factors (Nkt, Nke) is proposed to improve the accuracy of estimation of undrained shear strength. The result shows that the soil behavior type index (Ic) and cone factors take on a negatively correlated exponential relation. Incorporating a cone factor that varies with the soil behavior type index (Ic) significantly enhances the accuracy of undrained shear strength predictions compared to the conventional method of using a constant cone factor. This approach reduces the root mean square error (RMSE) for Nkt (Nke) from 0.124 (0.126) MPa to 0.056 (0.06) MPa, and the mean absolute error (MAE) from 0.0154 (0.016) MPa to 0.0032 (0.0036) MPa. The method was validated at an additional location and the predictions were in high agreement with the results of the consolidated quick direct shear test. The developed method can serve as an effective tool used in the design of foundations of marine structures. [ABSTRACT FROM AUTHOR]

In shallow water regions, ocean waves commonly propagate in the form of cnoidal waves, with the response induced in the seabed obviously being different from that involving conventional linear waves. Computational models of waves and seabeds were established based on cnoidal wave theory and Biot's completely dynamic consolidation theory, respectively. A semianalytical solution for the dynamic response of the multilayered, transversely isotropic (TI), poroelastic seabed induced by cnoidal waves was derived via the scalar potential function and the dual variable and position method. The reliability and accuracy of the developed semianalytical solution was verified against existing solutions and experimental data. This parametric study demonstrated that cnoidal waves have a significant effect on the dynamic response of the seabed compared to linear waves. Also, the induced pore pressure/stresses and corresponding liquefaction potential were significantly affected by the anisotropy and layering of the seabed material. The newly developed solution can serve as a useful tool for estimating the liquefaction potential of a TI and multilayered poroelastic seabed in shallow water. [ABSTRACT FROM AUTHOR]