Abstract: Single-point mooring (SPM) system has been widely used in China’s offshore oil development due to its superiority in overcoming severe sea conditions. However, the research on the interaction mechanism between the anchor pile and soil in underwater single-point mooring systems remains inadequate, particularly with respect to the calculation method of horizontal bearing capacity that considers the depth of padeye depth. Utilizing the composite foundation reaction force method, the flexure control equation and boundary conditions of the anchor pile of the single-point mooring system under lateral load are established, and the calculation programs are compiled using iterative methods to obtain the anchor pile load-displacement curve and the distribution curve of pile displacement and bending moment along the pile shaft at different mooring point positions. The accuracy and reliability of results are validated through comparison with numerical simulation and existing centrifugal model test results. Furthermore, the parameter analysis is conducted to consider the impact of padeye depth on the horizontal bearing capacity of anchor piles and the reference range of the optimal padeye depth is provided. The findings indicate that increasing the padeye depth leads to a significant reduction in the lateral displacement and maximum bending moment of anchor piles, while also increasing the horizontal ultimate bearing capacity of the anchor pile.

Key words: single-point mooring system (SPM), anchor pile, lateral bearing capacity, theoretical analysis