Abstract:The cyclic force characteristics of seabed foundation soils and their evaluation methods are recognized as critical scientific issues in the design and stability analysis of marine engineering structures such as dikes, offshore wind turbines, subma-rine pipelines, offshore oil platforms, and breakwaters. To systematically investigate the cyclic strength of marine clay and its evaluation method, undrained cyclic triaxial tests and in-situ cone penetration test CPTu were conducted on clay from the Yangjiang offshore area. The primary objective of this study is to provide more reliable geotechnical investigation guidance for the rapid development of offshore wind farms. The results showed that the cyclic characteristics of marine clay significantly differed from those of onshore Fujian standard sand. Marine clay mainly exhibited tensile failure under cyclic loading. The double-amplitude axial strain (εda) of samples under cyclic loading showed two development patterns: slow-sudden and rapid-stable. The power-law relationship between εda and the number of cycles (N), and that between excess pore pressure ratio and cyclic ratio (N/NL) conformed to a hyperbolic relationship. The applicability of existing liq-uefaction evaluation methods based on CPTu data for undisturbed marine fine-grained soils was analyzed. Based on the correlation between field and laboratory stress conditions of unit soil, an evaluation method for the cyclic strength of ma-rine clay was developed using CPTu data and burial depth (H).
