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浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2024, Vol. 58 Issue (11): 2347-2354    DOI: 10.3785/j.issn.1008-973X.2024.11.016
    
Experimental investigation on local scour of bucket foundation considering exposed height and hydraulic condition
Peng YUE1,2(),Ben HE3,Yujie LI1,2,Yongqiang ZHU4,Qiang XU2,5,*(),Zhen GUO2,4
1. Ocean College, Zhejiang University, Zhoushan 316021, China
2. Hainan Institute, Zhejiang University, Sanya 572025, China
3. Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province, Hangzhou 310058, China
4. College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
5. Ocean Academy, Zhejiang University, Zhoushan 316021, China
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Abstract  

Wave-current flume experiments were conducted to analyze the scour temporal evolution, scour hole pattern, scour depth, and equilibrium scour time of the bucket foundation under various conditions, including different exposed heights and hydraulic conditions aiming at the low placement rate of the suction-bucket foundation, the issue of prominent seabed exposed bucket roof during suction penetration and the foundation’s susceptibility to local scouring. Results showed that the scouring phenomenon was symmetrically distributed along the flow direction under current-only conditions. The front and back of the foundation remained unaffected by penetration. The maximum scour depth occured in front of the foundation. The maximum scour depth reached one-third of the foundation burial depth when the ratio of exposed height to cylinder diameter was 0.1 and the flow velocity was 0.3 m/s. The sand lifting capacity was enhanced, leading to the formation of sand ripple terrain around the bucket foundation when combined waves and currents were present. The scouring and deposition remained symmetrically distributed despite these changes. The maximum scour pit depth exhibited regular fluctuations after reaching equilibrium. Both the maximum scour depth and the ultimate equilibrium scour time increased with increasing exposed height. A calculation formula for determining the ultimate scour equilibrium time applicable to different exposed heights was proposed.

Key words： suction bucket foundation      local scour      combined wave and current      exposed height      scour characteristic      equilibrium scour time     
Received: 01 September 2023      Published: 23 October 2024
CLC:  TU 475  
Fund:  国家自然科学基金资助项目（52238008）；浙江省自然杰出青年项目（LR22E080005）；中央高校基本科研业务费专项资金资助项目(226-2023-00090).
Corresponding Authors: Qiang XU     E-mail: yuepeng@zju.edu.cn;05clkxxq@zju.edu.cn
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Peng YUE
Ben HE
Yujie LI
Yongqiang ZHU
Qiang XU
Zhen GUO
Cite this article:

Peng YUE,Ben HE,Yujie LI,Yongqiang ZHU,Qiang XU,Zhen GUO. Experimental investigation on local scour of bucket foundation considering exposed height and hydraulic condition. Journal of ZheJiang University (Engineering Science), 2024, 58(11): 2347-2354.

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https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2024.11.016     OR     https://www.zjujournals.com/eng/Y2024/V58/I11/2347


考虑暴露高度和波流条件的筒基冲刷试验研究

针对吸力式筒型基础负压沉贯过程中到位率低、筒顶暴露突出海床，基础易出现局部冲刷的问题，开展大断面波流水槽局部冲刷试验，研究不同暴露高度和波流条件下筒型基础的局部冲刷发展过程、最终冲刷形态及深度、冲刷平衡时间等特征规律. 研究结果表明，纯流条件下，筒基周围冲淤沿来流方向对称分布，前后冲刷坑不贯通，最大冲刷深度往往出现在筒前. 当暴露高度与筒径的比值为0.1，流速为0.3 m/s时，最大冲刷深度可达基础埋深的1/3. 波流耦合作用时，掀砂能力增强，筒基周围出现砂纹地形，冲淤仍对称分布，最大冲刷坑深度达到冲淤平衡后会出现规律性波动. 最大冲刷深度和极限冲刷平衡时间随着筒型基础暴露高度的增大而增加，提出考虑暴露高度的筒基极限冲刷平衡时间计算公式.


关键词： 吸力筒基础,  局部冲刷,  波流耦合,  暴露高度,  冲刷特征,  冲刷平衡时间 
Fig.1 Schematic drawing of wave-current flume used in present test
Fig.2 Local scour test instrument for bucket foundation
相似准则相似比尺计算值相似比尺
重力相似几何比尺$ {{ \lambda }}_{\text{l}} $=$ {{ \lambda }}_{\text{h}} $160
流速比尺$ {{ \lambda }}_{\text{u}} $=$ \sqrt{{{ \lambda }}_{\text{h}}} $12.65
时间比尺$ {{ \lambda }}_{\text{t}} $=$ {{ \lambda }}_{\text{l}} $/$ {{ \lambda }}_{\text{u}} $12.65
Tab.1 Local scour test similarity scale for bucket foundation
参数原尺度/m缩尺/cm
吸力筒直径32.020.0
吸力筒高度10.06.5
上部塔筒直径5.54.0
水深48.030.0
Tab.2 Dimension of test prototype and model
Fig.3 Particle size distribution curve of sand used in present test
Fig.4 Flow velocity distribution curve of flume section
Fig.5 Exposed height of suction bucket foundation model
序号H/cmh/cmUmean/(m·s?1)Hwave/cmT/st/h
T-13000.2006
T-23000.3002
T-33000.3512
U-1300.50.2006
U-23010.2006
U-33020.2006
U-4300.50.3002
U-53010.3002
U-63020.3002
U-7300.50.3512
U-8300.50.31012
U-93010.3512
U-103010.31012
Tab.3 Setting of local scour test condition parameter for bucket foundation
Fig.6 Scour temporal evolution under different hydraulic condition
Fig.7 Scour pattern under current-only clear-water condition
Fig.8 Scour pattern under current-only live-bed condition
Fig.9 Scour pattern under combined wave and current condition
Fig.10 Curve of scour temporal evolution
Fig.11 Sand transport rate per unit width around bucket foundation model after scouring
Fig.12 Relationship between maximum scour hole pattern and exposed height
Fig.13 Relationship between ultimate equilibrium scour time and exposed height
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