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浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2024, Vol. 58 Issue (3): 570-578    DOI: 10.3785/j.issn.1008-973X.2024.03.014
    
Experimental investigation on pile-soil interaction of monopile under multidirectional load in soft foundation
Puxiu DAI1(),Kaifu LIU2,*(),Xinyu XIE1,3,Yuedong XU2
1. Research Center of Coastal and Urban Geotechnical Engineering, Zhejiang University, Hangzhou 310058, China
2. School of Civil Engineering and Architecture, Zhejiang Sci-Tech University, Hangzhou 310018, China
3. Institute of Wenzhou, Zhejiang University, Wenzhou 325035, China
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Abstract  

A 1g large-scale model test was carried out, in order to further study the lateral deformation response and pile-soil interaction mechanism of large-diameter monopile under multidirectional cyclic load. The lateral stress and the deformation response of the pile under different vertical and lateral cyclic load ratios were discussed. Test results showed that applying vertical cyclic loads would increase the development rate of lateral displacement of the monopile. The maximum bending moment appeared at the depth of 2.0 times the pile diameter, and the bending moment of the pile body showed a decreasing trend with the increase of the number of cycles. The position of the maximum soil resistance gradually moved from 1.5 times the pile diameter depth to 2.0 times the pile diameter depth under cyclic load, and the degradation of cyclic soil resistance-pile lateral deformation (p-y) curve mainly occured in the surface soil. Applying vertical cyclic load would increase the initial stiffness of the pile-soil interface, but it would also accelerate the stiffness degradation of the pile-soil system. Special attention should be paid to the adverse effects of vertical cyclic load on pile displacement and pile-soil interaction under long-term cyclic load in the design of large-diameter monopile for offshore wind turbines.

Key words： 1g model test      monopile      complex loading      p-y curve      pile-soil interaction     
Received: 01 March 2023      Published: 05 March 2024
CLC:  TU 43  
Fund:  国家自然科学基金资助项目(52078465)；浙江省公益技术应用研究资助项目(LGG22E080015).
Corresponding Authors: Kaifu LIU     E-mail: daipuxiu@zju.edu.cn;liukaifu@zstu.edu.cn
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Puxiu DAI
Kaifu LIU
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Yuedong XU
Cite this article:

Puxiu DAI,Kaifu LIU,Xinyu XIE,Yuedong XU. Experimental investigation on pile-soil interaction of monopile under multidirectional load in soft foundation. Journal of ZheJiang University (Engineering Science), 2024, 58(3): 570-578.

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https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2024.03.014     OR     https://www.zjujournals.com/eng/Y2024/V58/I3/570


软基中多向受荷大直径单桩桩土相互作用试验研究

为了研究多向循环受荷大直径单桩的水平变形响应及桩土相互作用机理，开展多向受荷大直径单桩的1g大比尺模型试验，探讨不同竖向和水平循环荷载比下的桩侧受力及变形响应. 试验结果表明，施加竖向循环荷载会增大桩身水平位移的发展速率；最大弯矩出现在2.0倍桩径深度处，随着循环次数的增大，桩身弯矩表现出减小的趋势；在循环荷载作用下，最大土抗力所在的位置随着循环次数的增大逐渐从1.5倍桩径深度处向2.0倍桩径深度处移动，循环土体抗力-桩身水平变形（p-y）曲线的退化主要发生在表层土体；施加竖向循环荷载会增大桩土界面的初始刚度，但同时也会加速桩土体系的刚度退化. 建议在海上风电大直径单桩的设计中，特别注意竖向循环荷载对长期循环荷载作用下桩身位移及桩土相互作用的不利影响.


关键词： 1g模型试验,  大直径单桩,  复杂荷载,  p-y曲线,  桩土相互作用 
土体类型w/%$ \gamma $/(kN·m?3)e$ c $/kPa$ \varphi $/(°)$ {w_{\text{L}}} $/%$ {w_{\text{P}}} $/%$ {I_{\text{L}}} $$ {I_{\text{P}}} $
粉砂11.017.50.71—33.0————
淤泥质黏土44.018.61.1311.427.445.124.60.9520.5
Tab.1 Physical parameters of test soil
Fig.1 Curve of undrained shear strength of muddy clay with depth
Fig.2 Geotechnical disaster simulation system
Fig.3 Arrangement and test of model pile
Fig.4 Arrangement of static and multi-directional cyclic loading model tests
Fig.5 Schematic diagram of cyclic load
荷载类别试验编号$ \mu $$ \eta $$ \lambda $N
静力S1————
S2————
循环C1-10.300.210000
C1-20.300.310000
C1-30.300.410000
C2-10.30.10.210000
C2-20.30.10.310000
C2-30.30.10.410000
Tab.2 Test program of static and multi-directional cyclic loading
Fig.6 Load-displacement curves of cyclic tests
Fig.7 Displacement curve of cyclic tests
Fig.8 Normalized displacement curve of cyclic tests
Fig.9 Moment distribution curve of pile under different cycle numbers
Fig.10 Comparative analysis of pile bending moment under different cyclic loading ratios(N=10000)
Fig.11 Normalized analysis of maximum bending moment
Fig.12 Distribution of soil resistance under different cycle numbers
Fig.13 Comparative analysis of soil resistance under different cyclic loading ratios(N=10000)
Fig.14 Cyclic p-y curves at depth of 2.0D ($ \lambda $=0.2)
Fig.15 Comparison of measured peak values of static p-y curves and cyclic p-y curves with API recommended value at different depths
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