Suction Caissons Research Articles

Suction penetration behavior of multi-chamber suction caisson in sand

Response of Suction Caisson Foundations for Offshore Wind Turbines Subjected to Earthquake Loading: Numerical Simulations

Abstract Offshore wind turbine superstructures impart significant moment forces onto their foundations due to their elevated positioning. The pile-bucket composite foundation effectively combines the load-bearing advantages of monopiles and suction caissons, substantially enhancing the foundation system's moment resistance. Establishing an analytical upper bound formulation for its ultimate capacity is therefore crucial for advancing practical implementation. Initially, a validated finite element model was established within Abaqus, based on small-scale physical testing. Following successful validation, bearing performance and associated soil failure patterns were systematically examined across varying geometric proportions (H/D). Subsequently, employing limit analysis principles and kinematic velocity field derivation, an upper bound solution for moment capacity was established. Experimental data rigorously benchmarks the proposed model's rationality and precision. This work provides essential theoretical support for the engineering design of moment capacities in pile-bucket composite foundations.

Experimental and numerical study of a wet-towing system for multi-bucket jacket wind turbines considering air compressibility in suction caissons

Formation of soil plug in bioinspired scaled suction caissons in sand for offshore wind turbine

Suction Caisson Performance in Sand under Cyclic Loading: Numerical Modeling Using SANISAND-MS

Suction foundations, which are widely used in marine engineering for their cost-effectiveness and reusability, have evolved into modified suction caissons (MSCs) incorporating an internal caisson (IC) and an external skirt (ES). A clear understanding of their penetration behavior is essential to ensure successful installation. In this study, the coupled Eulerian-Lagrangian (CEL) method is employed to simulate MSC penetration in clay, with particular emphasis on soil flow behavior, heave formation, and variation in penetration resistance. The influence of foundation geometry, friction coefficient, and soil properties on penetration performance is systematically examined. Results show that the length-diameter ratio of the IC significantly affects the caisson’s ability to reach the target depth. An increase in ES length alters the heave distribution, resulting in greater soil heave on the outside compared to the inside of the caisson. Variations in ES width notably alter soil flow patterns. While soil properties exert a stronger influence on end resistance than the friction coefficient, the increase of undrained shear strength (s u) reduces the slope of the soil heave profile within the caisson. These insights provide a foundation for optimizing MSC design and installation in clay soil conditions.

Interface Shear Behavior Between Bio-Inspired Sidewall of a Scaled Suction Caisson and Sand Under Pull-out Load

In recent years, there has been a growing interest in the frictional anisotropy of snake scale-inspired surfaces, especially its potential applications in enhancing the bearing capacity of foundations (piles, anchor elements, and suction caissons) and reducing materials consumption and installation energy. This study first investigated the frictional properties and surface morphologies of the ventral scales of Cantor’s rat snakes (Ptyas dhumnades). Based on the findings on the snake scales, a novel snakeskin-inspired geosynthetic reinforcement (SIGR) is developed using 3D-printed polylactic acid (PLA). A series of pullout tests under different normal loads (25 kPa, 50 kPa, and 75 kPa) were performed to analyze the pullout behavior of SIGR in sandy soil. Soil deformation and shear band thickness were measured using Particle Image Velocimetry (PIV). The results revealed that the ventral scales of Ptyas dhumnades have distinct thorn-like micro-protrusions pointing towards the tail, which exhibit frictional anisotropy. A SIGR with a unilateral (one-sided) layout scales (each scale 1 mm in height and 12 mm in length) could increase the peak pullout force relative to a smooth-surface reinforcement by 29% to 67%. Moreover, the peak pullout force in the cranial direction (soil moving against the scales) was found to be 13% to 20% greater than that in the caudal direction (soil moving along the scales). The pullout resistance, cohesion, and friction angle of SIGR all showed significant anisotropy. The soil deformation around the SIGR during pullout was more pronounced than that observed with smooth-surface reinforcement, which suggests that SIGR can mobilize a larger volume of soil to resist external loads. This study demonstrates that SIGR is able to enhance the pullout resistance of reinforcements, thereby improving the stability of reinforced soil structures, reducing materials and energy consumption, and is important for the sustainability of geotechnical engineering.

Suction caisson uplift behavior in multilayered sand under varying drainage conditions

Enhancing CPT-Based Suction Caisson Penetration Design: Insights from Back-Analysis of Large-Scale Field Installation Data

With the continuous expansion of global offshore wind power, suction caissons are increasingly becoming a significant foundation form due to their advantages such as low installation noise, convenient construction, and reusability. However, localized seepage induced soil disturbance and strength changes during their installation remain underexplored, leading to uncertainties in their capacity assessment. This paper presents a series of experimental investigations in loose saturated sand, comparing suction and embedded installations for caissons with varying length-to-diameter (L/D) ratios coupled with Cone Penetration Tests (CPT) to evaluate soil strength changes inside and outside the caissons. For both installations, the results reveal similar lateral load-bearing capacities (0.12 kN) for shorter caissons (L = 120 mm), whereas for longer suction installed caissons (L = 240 mm), the capacity was reduced by approximately 80%, due to internal soil weakening and an upward shift of the rotation centre. CPT data further revealed compaction enhancement outside and seepage-induced reduction in soil strength inside the caisson, jointly affecting failure behavior. Based on these findings, the conventional bearing capacity formula for fully embedded caissons was modified to account for partial embedment and external-internal soil strength differences, and a novel mechanically-derived failure criterion was proposed, accurately capturing non-linear load responses and improving prediction of suction caisson capacity for various load eccentricities and L/D ratios, thus supporting optimized offshore foundation design.

Analysis of the effect of pullout rate on the tensile capacity of suction caisson anchors in sand using a three-dimensional displacement method

ABSTRACTThis study presents an experimental investigation into the influence of anchor–soil interaction on the dynamic behaviour of tension leg platform (TLP)–type floating wind turbines. A 1/100 scale model of the NREL 5‐MW reference wind turbine was fabricated using a 3D printer, with scaling parameters determined based on Froude scaling laws to ensure dynamic similarity between the model and prototype. A comprehensive discussion of the applied scaling principles is provided, along with a detailed description of the calibration procedures for the custom‐developed six‐axis sensors used in the experiments. Free vibration tests were performed on the scaled model to evaluate the influence of different anchoring systems—suction caissons, triple‐suction caissons and gravity anchors—under varying seabed conditions. Throughout the experiments, six‐axis sensors installed on both the nacelle and within the floating platform captured time‐dependent accelerations along the x, y and z directions, as well as rotational responses about the same axes. To ensure the robustness and repeatability of the results, each test was conducted a minimum of three times, mitigating potential experimental uncertainties. The experimental findings demonstrated a pronounced influence of anchoring systems and seabed conditions on the dominant surge and pitch frequencies of the floating wind turbine model. Specifically, relative to the fixed‐bottom case, the first peak frequency was reduced by 20.3% with suction caissons, 8.5% with triple‐suction caissons and 28.1% with gravity anchors. Additionally, an increase in seabed relative density from 30% to 68% led to a 19.6% rise in the dominant frequency, attributed to the increased soil stiffness and lateral resistance. These results highlight the critical role of anchor–soil interaction in shaping the dynamic behaviour of TLP‐type floating wind turbines, emphasizing the necessity of integrating these effects into their design and analysis to enhance predictive accuracy and ensure structural reliability.

The installation of suction caissons often encounters the problem of soil plugs, which prevent the caisson from reaching the design depth, potentially leading to insufficient bearing capacity and deviations from design expectations. Measures like enlarging the contact area between the caisson and soil or adjusting suction have been proposed, but soil plugs still exist. Therefore, a method for eliminating soil plugs during the installation of suction caissons is proposed. The soil plug inside the caisson is transformed from a solid state to a slurry state using a stirring device, after which the slurry is pumped out to eliminate the soil plug. Feasibility tests have demonstrated that this method effectively eliminates soil plugs. A series of installation tests were conducted to evaluate the effects of stirring rate, suction rate, soil relative density, and suction caisson aspect ratio. Results indicate that the stirring rate is a critical factor, and an appropriate stirring rate is necessary. This is because an insufficient stirring rate fails to transform the soil plug into a slurry, and an excessive stirring rate compromises the seal, both of which increase the installation risks. This method is expected to provide a valuable reference for the installation of suction caissons.

Interfacial shearing characteristics between siliceous sand and the various scales of bioinspired scaled suction caisson during penetration

Kinematic response of flexible suction caissons for offshore wind turbines to vertically incident shear waves

Installation of suction caissons in calcareous silt

Lateral bearing characteristics of modified suction caisson embedded in layered soil

An experimental investigation of the pullout capacity of a composite suction caisson for underwater compressed hydrogen energy storage accumulator in saturated sand