Session: 10-05-01 Bucket Foundations, Suction Caissons and Spudcans

Paper Number: 105425

105425 - Numerical Analysis of the Effect of Multidirectional Load on the Bearing Capacity of Suction Bucket Foundation 

With the development of clean energy, the development of offshore wind and tidal energy is being emphasized. In deeper waters, shared anchor foundations are becoming the preferred form of foundation for future energy development. Notably, multiple floating structures are simultaneously anchored by a single anchor foundation, thereby reducing the number of anchor foundations used and saving construction costs. However, the mechanical behaviors of these new foundations have not been investigated sufficiently since the shared anchor foundations are subjected to loads in multiple directions at the same time.

In this paper, suction bucket foundation is studied as an anchor of shared anchor foundation. Based on the unified constitutive model, which could describe the drained and undrained mechanical properties of sand and clay under monotonic and dynamic loads in a unified way, the effect of multidirectional loading on its bearing capacity was investigated by using the soil-water coupled finite element method analysis. First of all, the soil parameters required in the numerical simulation were confirmed through the simulation of a number of triaxial tests. Secondly, the finite element model is established and simulated, and the numerical simulation results were verified by centrifuge test results. The comparison shows that the numerical simulation results can well reproduce the effect of multi-directional loads on the bearing capacity of the suction bucket in the test. Then, based on the above model, the mechanical behaviors of the soil around the foundation are investigated when the unidirectional load is applied to the suction bucket. The simulation results show that after loading the soil around the foundation can be divided into passive earth pressure zone, shear zone and active earth pressure zone after loading. In each zone, the density of the sandy soil varies differently. In the passive earth pressure zone, the density of the sandy soil increases, while in the shear zone, the density of the sandy soil decreases greatly. In fact, under wind and wave loads, there are cases of loading in one direction and unloading in the other due to the phase difference of the multi-directional loads. In the simulation, the load F1 is first applied in one direction. After unloading, the load F2 is applied in the other direction until the suction bucket foundation reaches its load bearing capacity limit. The impacts of the angle between the two different directional loads (F₁ and F₂) on its bearing capacity are also investigated. According to the results, when the suction bucket foundation is loaded with F₁ load, the reduction of its bearing capacity will occur under F₂ load. When the angle between F₁ and F₂ is 60°, 90°, 120° and 150°, respectively, the suction bucket bearing capacity will be reduced by 1%, 8%, 14% and 14% compare with the bearing capacity of single load. The reduction of its bearing capacity is influenced by the angle between two different directional loads, the level of the load and the density of the soil. Furthermore, the stress history, degree of structure and the stress-induced anisotropy of sandy soils also have an impact on the variation of bearing capacity. Therefore, when designing a shared anchor foundation for multi-directional loads, the angle between different loads should be less than 60° and other measures should be taken when the angle between loads exceeds 90° to ensure the safety of the shared anchor foundation.

Presenting Author: Bin Yan Shanghai Jiao Tong University

Presenting Author Biography: Bin Yan received his bachelor's degree in civil engineering from Shanghai Jiao Tong University, China, in 2018. Currently, he is pursuing his Ph.D. degree in Civil Engineering at the School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, China. His research interests include soil dynamics, offshore pile foundations and triaxial testing.

Authors:

Bin Yan Shanghai Jiao Tong University
Wenxuan Zhu Shanghai Jiao Tong University
Bin Gao Shanghai Jiao Tong University
Guanlin Ye Shanghai Jiao Tong University
Yinghui Tian The University of Melbourne