• Geomechanics and Engineering
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• 제34권2호
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• pp.209-220
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• 2023

In this study, a series of three-dimensional numerical analyses were carried out to investigate the penetration performance of a dynamically installed Hall anchor. The advanced coupled Eulerian-Lagrangian (CEL) technique was adopted to accurately simulate the large soil deformation during the vertical penetration of a Hall anchor. In total, 52 numerical analyses were conducted to investigate the relationship between anchor penetration depth and the initial kinematic energy. Moreover, a sensitivity analysis was performed to investigate the effects of soil shear strength and soil type on the penetration mechanism of a drop anchor under self-weight. There is a monotonic increase in the penetration depth with an increasing anchor weight when the topsoil of the riverbed is not subjected to erosion. On the other hand, all the computed depths significantly increase when soil erosion is taken into consideration. This is mainly due to an enhanced initial kinematic energy from an increased dropping depth. Both depths increase exponentially with the initial kinematic energy. An enhanced shear strength can potentially increase the side resistance and end-bearing pressure around a drop anchor, thus significantly reducing the downward penetration of a hall anchor. Design charts are developed to directly estimate penetration depth and associated plastic zone due to dynamically installed anchor at arbitrary soil shear strength and anchor kinematic energy.

• Geomechanics and Engineering
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• 제30권6호
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• pp.539-549
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• 2022

Accidental anchor drop can cause disturbances to seabed materials and pose significant threats to the safety and serviceability of submarine structures such as pipelines. In this study, a series of anchor drop tests was carried out to investigate the penetration mechanism of a Hall anchor in sand and clay. A special anchor drop apparatus was designed to model the inflight drop of a Hall anchor. Results indicate that Coriolis acceleration was the primary cause of large horizontal offsets in sand, and earth gravity had negligible impact on the lateral movement of dropped anchors. The indued final horizontal offset was shown to increase with the elevated drop height of an anchor, and the existence of water can slow down the landing velocity of an anchor. It is also observed that water conditions had a significant effect on the influence zone caused by anchors. The vertical influence depth was over 5 m, and the influence radius was more than 3 m if the anchor had a drop height of 25 m in dry sand. In comparison, the vertical influence depth and radius reduced to less than 3 m and 2 m, respectively, when the anchor was released from 10 m height and fell into the seabed with a water depth of 15 m. It is also found that the dynamically penetrating anchors could significantly influence the earth pressure in clay. There is a non-linear increase in the measured penetration depth with kinematic energy, and the resulted maximum earth pressure increased dramatically with an increase in kinematic energy. Results from centrifuge model tests in this study provide useful insights into the penetration mechanism of a dropped anchor, which provides valuable data for design and planning of future submarine structures.

• 수산해양기술연구
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• 제27권2호
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• pp.97-104
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• 1991

일반적으로 선박에서 많이 사용하고 있는 Hall형묘와 묘쇄의 파주력계수를 구하기 위하여 모형실험을 실시한 결과를 요약하면 다음과 같다. 1. 저질 뻘에서 착의 최대파주력계수는 4.05였고, 묘쇄의 파주력계수는 0.75였다. 저질 모래에서의 묘의 최대파주력계수는 3.95였고, 묘쇄의 파주력계수는 0.66였다. 저질 자갈에서 묘의 최대파주력계수는 3.61이었고, 묘쇄의 파주력계수는 0.72였다. 2. 모형묘와 착쇄의 파주력계수는 저질에 따라서 상용파주력계수의 0.3~0.6배 였고, 안전파주력계수와는 거의 같은 경향을 나타내었으며, 다만 자갈에서는 안전파주력계수보다 1.4~1.8배 높았다. 3. 풍력과 저질에 따른 각 종 파주력 곡선도를 작성하여 한계파주력을 설정하여 활용하면 선박의 안전운용에 도움이 되리라 기대된다.

• 대한조선학회논문집
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• 제48권2호
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• pp.183-187
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• 2011

As larger the commercial vessel is, and rougher the marine environment becomes nowadays, drag embedment type anchor (DEA) of more stable performance and higher holding power is requested to be applied on the vessel. But, the performance of DEA has not become well known to academy and industries so far, that the basic study of DEA performance and holding force for the development of new DEA of higher performance is insufficient that required. In this paper, three types of same holding category DEA model (HALL, AC-14, POOL-N, scale 1/10), which are generally applied on the commercial vessel nowadays, were tested by being horizontally dragged on the test tank, on which sand was being floored with sufficient depth, and measured the holding force of each anchor simultaneously using load cell and D/A converter. With the test results, the embedding motion was analyzed to have three different stages and the holding force of each anchor was analyzed with respect to the anchor geometry, such as shape and weight of each type of anchors, and final embedding depth.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권3호
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• pp.193-200
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• 2011

As larger ships and floating offshore structures are, and rougher the marine environment becomes nowadays, a drag embedment type anchor of more stable performance and higher holding power is requested. This paper describes an experimental study of the drag embedding motion and the resultant holding force of three types of drag embedment type anchor model (HALL, AC-14, SEC POOL-N, scale 1/10).