Experimental investigation of jetting effect on spudcan extraction from soft clay |
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| Institution: | 1. College of Ocean Science and Engineering, Shanghai Maritime University, 1550 Haigang Rd., Shanghai, 201304, China;2. Institute for Ocean Engineering, China University of Petroleum, 18 Fuxue Rd., Beijing, 102249, China;3. Department of Aeronautics and Astronautics, Fudan University, 220 Handan Rd., Shanghai, 200433, China;1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300350, China;2. Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiaotong University, Shanghai 200240, China;3. Key Laboratory for Mechanics in Fluid Solid Coupling Systems, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;1. College of Water conservancy and Environmental Engineering, Zhengzhou University, Zhengzhou, 450001, PR China;2. Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, No. 1, Xikang Road, Nanjing, 210098, China;3. College of Civil Engineering and Architecture, Henan University of Technology, Zhengzhou, 450001, China;4. Faculty of Petroleum and Mining Engineering, Suez University, 43721, Suez, Egypt |
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| Abstract: | The jack-up unit may suffer difficult extraction from soft clay attributed to the large embedment and suction. To ease spudcan extraction, the jetting technique is extensively adopted. The jetting effect on spudcan extraction is investigated with a series of model tests. Firstly, the effectiveness of top jetting is investigated, and it is found that the top jetting is not effective in reducing extraction resistance. Secondly, the efficiency of different jetting procedures are studied. It is revealed that jetting prior to extraction reduces the suction by increasing the excess pore pressure at spudcan base. And the jetting after extraction begins reduces the suction by filling the gap formed under the spudcan with jetting water and eliminating cavitation. Finally, tests with different jetting times, jetting rates, jetting pressures, and jetting nozzle locations and numbers are conducted. It is found that the effect of jetting time converges as it increases. The flow rate of jetting prior to extraction has little effect on jetting efficiency, whereas the flow rate of jetting after the extraction begins has significant influences on the jetting efficiency. Jetting pressure also has great effect on jetting efficiency, and converges as it increases. The closer the nozzles are located to the spudcan edge, the sooner the post-peak extraction resistance decreases. And the jetting efficiency increases with the nozzle number. The findings from the experimental studies can serve as a reference for future studies on the operation and optimization design of a jack-up jetting system. |
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| Keywords: | Jack-up Spudcan Extraction Jetting Soft clay |
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