Behaviour of a Laterally Loaded Rigid Pile Subjected to One-Way Cyclic Loading

• Published in: Geotechnical and geological engineering 2024-08, Vol.42 (6), p.4931-4951
• Main Authors: Thangavel, Jegadeesh Kumar, Rathod, Deendayal
• Format: Article
• Language: English
• Subjects: Amplitudes; Civil Engineering; Constitutive models; Cyclic loading; Cyclic loads; Earth and Environmental Science; Earth Sciences; Finite element method; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Lateral forces; Mathematical analysis; Mathematical models; Numerical analysis; Offshore; Original Paper; Piles; Soil; Soil density; Soil dispersion; Steel construction; Steel pipes; Stiffness; Strain analysis; Terrestrial Pollution; Turbines; Waste Management/Waste Technology; Wind power; Wind turbines
• ISSN: 0960-3182; 1573-1529
• DOI: 10.1007/s10706-024-02822-4

Monopiles serve as the foundational support for offshore wind turbines and are constructed as large, hollow, and rigid steel pipes. Given their offshore installation, these foundations experience cyclic lateral forces from wind and waves. This paper focuses on investigating the cyclic lateral capacity of monopiles through experimental and numerical analysis. The study examines varying factors such as slenderness ( L/D ) ratios of 2, 4, and 6, load amplitudes ( ξ b ) of 40%, 30%, and 20%, and different densities of sand (RD) at 35%, 55%, and 75%. One-way cyclic loading at a frequency of 0.25 Hz was applied during the experiments using a pneumatic cylinder setup to the model piles. Numerical analysis was conducted on the prototype piles using PLAXIS 3D finite element software. The analysis utilised a hypoplastic model with an intergranular strain concept as the constitutive model. The model was validated against the experimental results of MLD2/LA40/RD55 and exhibited similar behaviour. The experimental findings indicate an initial 40% increase in stiffness during the first 10 cycles, leading to a higher accumulation of displacement. However, as the number of cycles increased, the rate of stiffness increase decreased due to soil getting dispersed around the pile, resulting in an increased rate of accumulated displacement. This behaviour was observed across various L/D ratios, load amplitudes, and soil densities. Additionally, an increase in load amplitude and L/D ratio, as well as a decrease in soil density, resulted in higher accumulated displacement and reduced stiffness.