Numerical simulation of negative pressure penetration of suction anchor foundation based on CFD-DEM fluid solid coupling method

As a new-type and efficient marine structure foundation form, the suction anchor is widely used in ocean engineering. However, the traditional laboratory tests and the finite element numerical simulations have limitations in studying the penetration of suction anchors in granular materials such as sand. The fluid-solid coupling method based on the discrete element method and computational fluid dynamics theory (CFD-DEM) is used to numerically simulate the penetration of the suction anchors in sand. The effectiveness and accuracy of the CFD-DEM fluid-solid coupling method are verified by comparing with these of the laboratory suction penetration tests and the theoretical analysis of penetration resistance. The penetration mechanism of the suction anchors in sand is explained from the mesoscopic scale of soil particles. The changes of soil plug and sand layer inside the anchor during the penetration process are obtained, which shows that the sand layer presents a convex arc distribution in the middle, indicating the compaction effects. The soil displacement and expansion caused by the compaction effects are also part of the reasons for the soil heave. Simultaneously, the equipotential distribution of the excess pore water pressure changes and the changes in the hydraulic gradient of the sand layer during the penetration process are simulated, which confirms the "safety mechanism" of suction penetration in the sand. Finally, the change of negative pressure loss ratio is compared with the results of Houlsby and Byrne's theoretical model, and the variation law of permeability coefficient of soil inside the anchor with penetration is obtained. In this study, it is proved that the CFD-DEM is an efficient method to analyze the suction installation of the suction anchors in sand.