Monopiles are the most commonly used foundation type for offshore wind turbine (OWT) structures and are characterized by relatively large geometric dimensions, compared with offshore pile foundations typically used in the oil and gas industries. To date, there are no established technical guidelines tailored for the design and analysis of OWT monopiles. This paper first identifies various intrinsic drawbacks involved with the existing design and analysis methodologies as applied to OWT monopiles. Next, a comprehensive experimental program of 1g repeated lateral load tests, performed on a scaled rigid monopile installed in dry sand beds, is presented to investigate its behavior under various loading scenarios. The experimental results provide insights into the various blurry issues in the existing literature related to monopile behavior under long-term repeated lateral loading. Lateral soil resistance profiles were determined from the measured pile bending strain data and found to be markedly depen...

Model Studies on Monopile Behavior under Long-Term Repeated Lateral Loading

This paper includes a brief review of analytical, experimental and numerical studies carried out on conventional and innovative piles subjected to monotonic and cyclic lateral loads. State-of-the-art developments and the important approaches relevant to the field of laterally loaded pile was discussed. The observations from small-scale experiments confirmed that monopiles embedded in cohesionless soil undergoes progressive accumulation of displacement and the rate of accumulation does not approach zero even after 10,000 cycles. The accumulated rotation of the foundations under the offshore loading conditions mainly depends on the characteristics of cyclic loading such as the magnitude of maximum and minimum load during a cycle. The review of existing works showed that there are hardly any studies addressing the effect of gentle seabed slope and also the effect of multi-directional loading on the magnitude of accumulated rotation of rigid monopiles. It is critically suggested to consider the influence of strong vertical loads and moments on stiff monopiles installed on gentle seabed slopes. The current study reveals the use of finned and helical piles in improving the lateral resistance and reducing the pile head deflections. However, further investigations are required to validate their performance in varying soil conditions and also to optimize and ease the design through the development of cyclic p–y curves.

A Review on Conventional and Innovative Pile System for Offshore Wind Turbines

An experimental study and numerical modeling of laterally loaded regular and finned pile foundations in sandy soils

Experimental and numerical studies of laterally loaded piles located near oil-contaminated sand slope

Two scaled-model tests were carried out to investigate the pile–soil–pile interaction during a lateral loading process. Two instrumented piles, termed the active pile and the passive pile, were installed into loose sand. The active pile head was subjected to lateral loads, and the passive pile was set at twice pile width away from the active pile center. To study the effect of the direction of lateral loading on the pile–soil–pile interaction, the passive pile was set in front of and behind the active pile in Tests 1 and 2, respectively. Experimental results showed that the leading passive pile produced much stronger effects on surrounding ground deformation and on response of active pile as compared with the trailing passive pile. The intermediate soil between the active and passive piles was the most susceptible to be affected by the leading passive pile. Within this zone, the larger magnitude of ground heave (by up to 50 %) was caused by the leading passive pile. The leading passive pile also enhanced the lateral resistance of the active pile by up to 70 %. The underlying reason is that the leading passive pile was located in the passive influence zone of the active pile and hence restrained the intermediate soil between the two piles. As a result, the relative stiffness ratio between soil and pile increased, leading to a stronger soil resistance.

Investigation on 3D ground deformation and response of active and passive piles in loose sand

Large lateral loads may act on pile foundation supporting structures, such as bridge abutments, retaining walls, and structures subjected to wind–earthquake loads. A pile with fins is a newly devel...

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Papers

Experimental and theoretical studies of laterally loaded finned piles in sand