A Practical Numerical Model of Embedded Mooring Chains in Clayey Soils

Abstract

Interactions between mooring chains and the seabed are crucial in the estimation of the capacities of mooring anchors for floating facilities in deep water. This paper presents a computationally efficient numerical approach to simulate the chain cutting through soil under the tension load. Following verification against analytical solutions, a more sophisticated model is implemented using the numerical approach, enabling more accurate determination of soil resistances based on mobilized displacements in both the normal and tangential directions of the chain. The variation in the mobilized friction along the chain as it cuts through the soil is presented, and the equivalent friction coefficient for use in the simple analytical solution is also studied. The interaction between the mooring chain and soil plays an important role in offshore anchoring foundation analysis because it directly determines the load magnitude and direction applied to the foundation. A more realistic assessment is achieved by analyzing the mooring anchor as an integrated system rather than treating the chain and foundation separately, which necessitates numerical modeling of the chain. This paper introduces a computationally efficient numerical approach for modeling chain–soil interactions, suitable for practical applications. The approach is verified by reproducing analytical solutions used widely and is then further developed to capture variations in mobilized friction along the chain length, providing additional insights into the very low friction mobilization for chains at deep depths near the padeye.