Geomechanics and Engineering

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Centrifuge modeling of dynamically penetrating anchors in sand and clay

  • An, Xiaoyu (State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University) ;
  • Wang, Fei (National Engineering Laboratory for Port Hydraulic Construction Technology, Tianjin Research Institute for Water Transport Engineering) ;
  • Liang, Chao (State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University) ;
  • Liu, Run (State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University)
  • Received : 2022.06.24
  • Accepted : 2022.08.30
  • Published : 2022.09.25
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Abstract

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.

Keywords

Acknowledgement

The authors would like to acknowledge the financial support provided by the Fundamental Research Funds (Nos. TKS20200309 and TKS190203) for the Central Public Welfare Research Institutes and grant 51809132 of NSFC of China.

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