• Geomechanics and Engineering
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• v.18 no.2
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• pp.153-159
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• 2019

This paper examines the results from three-dimensional dynamic finite element analysis undertaken to develop a new dynamically installed anchor (DIA). Several candidate shapes of new DIAs were selected after an investigation into previous researches of existing DIA designs. The performances of selected DIAs during the installation and loading in non-homogeneous clay were investigated through large deformation finite element (LDFE) analyses. Findings were compared to the current anchors in operation (i.e., Torpedo and Omni-Max DIA) to assess the viability of the new designs in the field. Overall, the anchor embedment depths of the novel DIAs lied under the results of OMNI-Max DIA. And also, the tracked anchor trajectory confirmed that, the novel DIAs dove deeper with stiffer travelling angle, compared to the OMNI-Max DIA. These elements are more critical and beneficial especially in a field where the achieved embedment depths are generally low.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.11a
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• pp.110-121
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• 2001

The interest in suction piles by the oil industry was risen in the middle of 1980's. Recently, suction piles have been applied increasingly in offshore engineering due to its low cost, simplicity, efficiency, and reliability. Suction piles have normally been used as anchors of floating structures and foundations of marine structures in deep-water locations. Suction piles have several technical advantages over conventional piles and anchors; fast and easy installation at any depth of water, extremely large resistance due to its huge size, and easy retrieval by applying a positive suction pressure inside the pile, etc. Daewoo E&C Co., Ltd. has conducted a series of field suction pile installation and loading tests inside the Okpo harbor located in Geojedo and the Onsan harbor in Ulsan, Korea, during the summer of 2001, which may provide additional validation of the analytical solutions previously developed by the US Naval Facilities Engineering Service Center. This is a brief description of the general mechanisms of suction pile installation and loading capacity based on the study conducted by the US Navy and Daewoo E&C Co., Ltd.

• Journal of Wind Energy
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• v.14 no.1
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• pp.21-28
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• 2023

This paper investigates the resistance performance of drag anchors used for aqua farms installed in southwestern offshore wind farms in Korea. These anchors have been employed for a long time without any quantitative evaluation. Experimental campaigns were performed at the target site and the results were used to validate the numerical model by changing the penetration depths in the uniformly distributed seabed (i.e., flat). Based on the validated model with good agreement with the experiments (ARE 1.8 %), the resistance of the anchor with different pullout angles was thoroughly examined. It is worth noting that the Coupled Eulerian-Lagrangian (CEL) technique was applied to account for the large deformation of the anchor; Eulerian for the seabed and Lagrangian for the structure. The numerical results indicated that the pullout resistance is vulnerable to horizontal inclined force rather than vertical inclination, implying that the optimum performance is ideally expected to be 0-degree force applied.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.324-332
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• 2018

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.648-656
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• 2019

The ecological changes in the ocean due to the drastic global warming require that action be taken to sustain the productivity of fisheries. Proper ocean facilities could help prevent the loss of the expenditures made on marine aquaculture and reduce the related compensation for various ocean conditions. The aim of this study was to develop a floating ocean wave-breaker using an eco-friendly concrete and conducting a site survey, a structural analysis, and a test of towing the tank. As a result, the wave at the fish farm would be reduced. The results of the holding power of anchors and the capability of moving the floating structures were considered in the design of the wave-breaker. The analyses of the material properties of concrete and the steel structures, as well as the CAPEX and OPEX analyses of the manufacturing and operation processes confirmed the superiority of the floating concrete wave-breaker. In particular, this study demonstrated that the concrete floating breakwater can protect the fish farm against typhoons and reverse-waves, thereby reducing losses of the fish.

• Geotechnical Engineering
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• v.12 no.3
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• pp.63-72
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• 1996

Plate anchors are often used for various types of offshore construction and maintenance works. When the plates are embedded in soft clay and subjected to sustanined allowable loads, creep may develop. This paper presents some results from laboratory model test designed to study the creep effect that develops with time for a shallow circular anchor subjected to sustained net loads that are less than the net ultimate uplift capacity. Based on the model test results, relationships among the net load, the rate of strain, and time are developed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.895-906
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• 2014

A fundamental study of the dynamically penetrating anchor (DPA - colloquially known as torpedo anchor) embedded into deep seabed was conducted using measurement data and numerical approaches. Numerical simulation of such a structure penetration was often suffered by severe mesh distortion arising from very large soil deformation, complex contact condition and nonlinear soil behavior. In recent years, a Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this study, 3D finite element analyses using the CEL formulation are carried out to simulate the construction process of dynamic anchors. Through comparisons with results of field measurements, the CEL method in the present study is in good agreement with the general trend observed by in-situ measurements and thus, predicts a realistic large deformation movement for the dynamic anchors by free-fall dropping, which the conventional FE method cannot. Additionally, the appropriate parametric studies needed for verifying the characteristic of dynamic anchor are also discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.3
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• pp.182-189
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• 2015

The Embedded Suction Anchor (ESA) is a type of permanent offshore foundation that is installed by a suction pile. To increase the loading capacity against pullout, three wings (vertical flanges) are attached along the circumference at 120 degrees apart. Analytical parametric study using the proposed analytical solution method has been conducted to identify the effects of several parameters that are thought to influence the behavior of ESAs. The analysis results show that the pullout capacity increases as the anchor depth and the soil strength increase, and decreases as the load inclination angle increases. The anchor having square projectional area and being pulled horizontally at the middle of its length provides the highest pullout capacity.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.4
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• pp.1129-1135
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• 2015

The stow net is a stationary gear made from netting, usually in shape like trawl net without wings. The nets are fixed by means of anchors, placed according to the direction and strength of the current. And the commercial fishing is associated with high rate of fatal and non-fatal occupational injury. The hazard factors analysis for the fishermen's safety of offshore stow nets vessel was conducted to serve as a basic data for improving the healthy and safe working environment of fishermen using fishermen's occupational accidents of the national federation of fisheries cooperatives (NFFC) from 2012 to 2014 (n=1,144). As a result, the average occupational accident occurrence rate of this fishery was 206.9‰ in all industries 36.9 times the rate of that. In addition, average death and missing rate was found to have a very serious level management to 50.4‰ in all industries of death of 42.0 times. The accident occurred in 84.5 to 94.6% was happened at sea. The struck by object, slipping, contact with machinery, contact by object or gear and others occurred more frequently in order on the frequency of accident occurrence pattern. However, the occurrence rate of death and missing did not match the frequency of accident pattern. In other words, slipping occurred frequently higher while death and missing risk was not high. And the contact with fishing gear and fall in the waters was low while death and missing risk was high. The results are expected to contribute for identification and assessment of safety hazard occurred in offshore stow nets vessel.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.25-33
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• 2011

Suction buckets have been widely used for offshore structures such as anchors for floating facilities, and the foundations of offshore wind energy turbines. However, the design guidelines for suction buckets have not been clearly suggested. Therefore, this study performed the numerical analysis by using ABAQUS (2010) to evaluate bearing capacities and load-movement behaviors of the suction bucket in NC clay. For the numerical analysis, the depth ratio L/D (L=embedded length of skirt; D=diameter of a bucket) was varied from 0.25 to 1.0. The analysis results showed that the L/D ratio has a significant effect on the bearing capacity, and the vertical and horizontal capacities respectively increased by about 40% and 90%, when L/D ratio increased from 0.25 to 1.0. At the vertical loading, the bucket showed the similar failure mode with a deep foundation, so the shaft and toe resistances can be separately evaluated. At the horizontal loading, the bucket with L/D=O.25 showed the sliding failure mode and the bucket with $L/D{\geq}0.5$ showed the rotational failure mode.