Micromechanical analysis of suction pile-granular soil interaction under inclined pulling load of mooring line: Mooring depth effect

Abstract

The micro-mechanism of mooing depth effect on the interactions between suction piles and granular soil remains unclear. This study investigates suction pile-soil interaction behaviour under the inclined pulling load of a mooring line, as well as mooring depth effects. The discrete element method (DEM) was used to model granular soil, while the suction pile was modelled via finite element method (FEM). Results in DEM-FEM simulations were compared with that in the model tests first. Then, the macro and micro behaviours during suction pile-soil interactions were analysed. Based on the results, the pulling force-displacement curves could be categorised into two groups according to the curve shapes associated with suction pile motion patterns. Discontinuity and occurrences of large soil deformation were successfully reproduced. Next, suction pile movement and deformation were quantitatively analysed in terms of vertical pull-out displacement, pile rotation, and effective support around suction piles. Furthermore, the particle-scale behaviours of soil were analysed, finishing with the identification of conclusive mechanical failure patterns. This study indicates that neglecting the mooring depth of the mooring lines may lead to a significant underestimation of the uplift capacity of a suction pile, as well as misinterpretation of the failure mode of the granular soil.