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Analysis of lateral bearing behaviors of scoured monopile foundations considering the influence of length-to-diameter ratio
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摘要: 冲刷是海上风电单桩基础设计中需要考虑的重要因素，然而计算时通常忽略局部冲刷坑的几何形状及桩基入土段长径比（L/D）的影响，导致设计偏于保守。针对这一问题，建立考虑局部冲刷坑形态的海上风电桩基础三维有限元模型，研究冲刷作用下不同长径比桩基础的侧向承载特性变化规律，提出适用于受局部冲刷小长径比单桩基础的简化梁-弹簧分析模型并进行验证。研究结果表明：小长径比单桩基础的侧向响应对局部冲刷深度较为敏感。随着冲刷深度的增大，基底反力和桩侧垂向摩阻力等土反力分量对桩基水平承载力的贡献也随之增大，仅考虑桩侧土反力的传统API p-y曲线方法难以适用受冲刷单桩基础的计算分析，须考虑基底效应的影响。研究结果可为海上风电基础设计分析提供参考。Abstract: Scour is one of the key factors that should be considered in the design process of offshore wind turbine (OWT) monopile foundations. However, the geometry of local scour pit and embedded length-to-diameter ratio of pile (L/D) are always ignored in practice, which leads to a conservative design. A three-dimensional finite element model for OWT monopile considering the geometry of local scour pit and L/D was utilized to study its lateral bearing behaviors under the existence of local scour pit. Furthermore, a simplified beam-spring model for monopile with small L/D was proposed to predict the lateral responses of monopile under local scour and validation was also made. The results show that the lateral behaviors of monopile with low L/D are sensitive to the scour pit’s depth. With the increment of scour depth, the contribution of soil resistance components such as base reaction force and vertical shaft shear force to the pile foundation’s horizontal bearing capacity also increases. The typical API p-y curve method that only considers lateral soil resistance will no longer apply to the analysis of scoured monopile foundation, and the influence of pile base effect shall be taken into account. The research results can provide reference in practice of OWT foundation design and analysis.
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Key words:
- local scour /
- offshore wind turbine /
- monopile foundation /
- length-to-diameter ratio
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图 2 桩顶荷载-位移曲线对比
Figure 2. Comparison of pile head load-displacement curves predicted by FE model and centrifuge test
图 3 PILE2桩顶荷载-位移曲线对比
Figure 3. Comparison of pile head load-displacement curves of PILE2
图 4 不同冲刷坑形态对PILE4和PILE1桩身变形的影响（
$ F=3\;\mathrm{M}\mathrm{N} $ ）Figure 4. Influences of different scour pit’s shapes on deflection of PILE4 and PILE1 (F=3 MN)
图 6 不同冲刷工况下
$ {H}_{\mathrm{b}} $ 、$ {M}_{\mathrm{b}} $ 与$ {\tau }_{\mathrm{v}} $ 对PILE2水平承载力贡献Figure 6. The contributions of
$ {H}_{\mathrm{b}} $ 、$ {M}_{\mathrm{b}} $ and$ {\tau }_{\mathrm{v}} $ to the lateral bearing capacity of PILE2 under various scour cases
图 7 不同长径比桩基基底效应对桩基水平承载力的贡献
Figure 7. Variation of proportions of pile base effects to the horizontal bearing capacity of pile
图 9 PILE3冲刷前后同一深度处p-y曲线对比
Figure 9. Comparison of p-y curves for PILE3 at the same depth before and after scour
图 10 PILE1冲刷前后同一深度处p-y曲线对比
Figure 10. Comparison of p-y curves for PILE1 at the same depth before and after scour
图 12 受局部冲刷海上风电单桩基础的简化梁-弹簧计算模型
Figure 12. The simplified beam-spring model for OWT monopile subjected to local scour
图 13 不同模型对PILE3桩顶载荷-位移曲线计算结果对比
Figure 13. Comparison of pile head load-displacement curves of PILE3 predicted by different models
图 14 不同模型对PILE3桩身变形与弯矩计算结果对比（F=3 MN）
Figure 14. Comparison of deflection and moment along PILE3 predicted by different models (F=3 MN)
表 1 仿真桩基参数
Table 1. Pile parameters used in FE model
桩基编号 入土深度/m 入土段长径比 土/桩刚度比 桩基属性 PILE1 45.00 16.4 414.25 柔性 PILE2 22.00 8.0 23.66 偏刚性 PILE3 19.25 7.0 13.87 偏刚性 PILE4 16.50 6.0 7.49 偏刚性 
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表 2 仿真冲刷工况设置
Table 2. Scour cases used in FE model
冲刷形态 工况编号 冲刷深度/m 冲刷坑坡度/（°） 无冲刷 N-1 0 0 局部冲刷 L-1 0.5D 30 L-2 1.0D L-3 1.5D 整体冲刷 G-1 0.5D 0 G-2 1.0D G-3 1.5D
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[1] LIN Y J, LIN C. Effects of scour-hole dimensions on lateral behavior of piles in sands[J]. Computers and Geotechnics, 2019, 111: 30-41. doi: 10.1016/j.compgeo.2019.02.028 [2] WHITEHOUSE R J S, HARRIS J M, SUTHERLAND J, et al. The nature of scour development and scour protection at offshore windfarm foundations[J]. Marine Pollution Bulletin, 2011, 62(1): 73-88. doi: 10.1016/j.marpolbul.2010.09.007 [3] PEDER HYLDAL SØRENSEN S, BO IBSEN L. Assessment of foundation design for offshore monopiles unprotected against scour[J]. Ocean Engineering, 2013, 63: 17-25. doi: 10.1016/j.oceaneng.2013.01.016 [4] DNV GL AS. Support structures for wind turbines: DNV-GL-ST-0126[S]. Oslo: DNV GL AS, 2018. [5] RP A P I. Geotechnical and foundation design considerations[S]. Washington D. C.: API RP 2GEO. API, 2014. [6] LIN C, JIANG W Y. Evaluation of vertical effective stress and pile tension capacity in sands considering scour-hole dimensions[J]. Computers and Geotechnics, 2019, 105: 94-98. doi: 10.1016/j.compgeo.2018.09.013 [7] 漆文刚, 高福平. 冲刷对海上风力机单桩基础水平承载特性的影响[J]. 中国科学: 物理学 力学 天文学,2016,46(12):83-92 QI Wengang, GAO Fuping. Effects of scour on horizontal bearing behavior of monopile foundations for offshore wind turbines[J]. Scientia Sinica (Physica, Mechanica & Astronomica), 2016, 46(12): 83-92. (in Chinese) [8] 陈静, 田德, 闫肖蒙, 等. 局部冲刷作用下海上风电机组支撑结构响应[J]. 太阳能学报,2019,40(5):1401-1407 CHEN Jing, TIAN De, YAN Xiaomeng, et al. Support structure response of offshore wind turbines under local scour[J]. Acta Energiae Solaris Sinica, 2019, 40(5): 1401-1407. (in Chinese) [9] QI W G, GAO F P, RANDOLPH M F, et al. Scour effects on p–y curves for shallowly embedded piles in sand[J]. Géotechnique, 2016, 66(8): 648-660. [10] BAYTON S M , BLACK J A . The effect of scour on monopile lateral behaviour[C]∥XVII European Conference on Soil Mechanics and Geotechnical Engineering-ECSMGE. Reykjavik: International Society for Soil Mechanics and Geotechnical Engineering, 2019. [11] CHORTIS G, ASKARINEJAD A, PRENDERGAST L J, et al. Influence of scour depth and type on p-y curves for monopiles in sand under monotonic lateral loading in a geotechnical centrifuge[J]. Ocean Engineering, 2020, 197: 106838. doi: 10.1016/j.oceaneng.2019.106838 [12] LIANG F Y, ZHANG H, CHEN S L. Effect of vertical load on the lateral response of offshore piles considering scour-hole geometry and stress history in marine clay[J]. Ocean Engineering, 2018, 158: 64-77. doi: 10.1016/j.oceaneng.2018.03.070 [13] ZHANG H, CHEN S L, LIANG F Y. Effects of scour-hole dimensions and soil stress history on the behavior of laterally loaded piles in soft clay under scour conditions[J]. Computers and Geotechnics, 2017, 84: 198-209. doi: 10.1016/j.compgeo.2016.12.008 [14] HONG Y, HE B, WANG L Z, et al. Cyclic lateral response and failure mechanisms of semi-rigid pile in soft clay: centrifuge tests and numerical modelling[J]. Canadian Geotechnical Journal, 2017, 54(6): 806-824. doi: 10.1139/cgj-2016-0356 [15] REESE L C, COX W R, KOOP F D. Analysis of laterally loaded piles in sand[C]∥Offshore technology in civil engineering hall of fame papers from the early years. Houston, Texas: OnePetro, 1974: 95-105. [16] REESE L C, COX W R, KOOP F D. Field testing and analysis of laterally loaded piles on stiff clay[C]∥Offshore Technology Conference. Houston, Texas: OnePetro, 1975. [17] BYRNE B W, BURD H J, ZDRAVKOVIĆ L, et al. PISA: new design methods for offshore wind turbine monopiles[J]. Revue Franç aise De Géotechnique, 2019(158): 3. [18] BYRNE B, MCADAM R, BURD H, et al. New design methods for large diameter piles under lateral loading for offshore wind applications[M]∥Frontiers in Offshore Geotechnics III. Florida: CRC Press, 2015: 705-710. [19] BURD H J, TABORDA D M G, ZDRAVKOVIĆ L, et al. PISA design model for monopiles for offshore wind turbines: application to a marine sand[J]. Géotechnique, 2020, 70(11): 1048-1066. [20] POULOS H G, HULL T S. The role of analytical geomechanics in foundation engineering[C]∥Foundation Engineering: Current Principles and Practices. New York: ASCE, 1989: 1578-1606. [21] MURPHY G, IGOE D, DOHERTY P, et al. 3D FEM approach for laterally loaded monopile design[J]. Computers and Geotechnics, 2018, 100: 76-83. doi: 10.1016/j.compgeo.2018.03.013 [22] 朱斌, 熊根, 刘晋超, 等. 砂土中大直径单桩水平受荷离心模型试验[J]. 岩土工程学报,2013,35(10):1807-1815 ZHU Bin, XIONG Gen, LIU Jinchao, et al. Centrifuge modelling of a large-diameter single pile under lateral loads in sand[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(10): 1807-1815. (in Chinese) [23] BHATTACHARYA S, NIKITAS G, ARANY L, et al. Soil-structure interactions(SSI) for offshore wind turbines[J]. Engineering & Technology Reference, 2017, 1(1): 24, 16. [24] WANG L Z, ZHOU W J, GUO Z, et al. Frequency change and accumulated inclination of offshore wind turbine jacket structure with piles in sand under cyclic loadings[J]. Ocean Engineering, 2020, 217: 108045. doi: 10.1016/j.oceaneng.2020.108045 [25] WANG L Z, LAI Y Q, HONG Y, et al. A unified lateral soil reaction model for monopiles in soft clay considering various length-to-diameter (L/D) ratios[J]. Ocean Engineering, 2020, 212: 107492. doi: 10.1016/j.oceaneng.2020.107492 [26] LIN C, HAN J, BENNETT C, et al. Analysis of laterally loaded piles in soft clay considering scour-hole dimensions[J]. Ocean Engineering, 2016, 111: 461-470. doi: 10.1016/j.oceaneng.2015.11.029 [27] DAI S, HAN B, WANG B G, et al. Influence of soil scour on lateral behavior of large-diameter offshore wind-turbine monopile and corresponding scour monitoring method[J]. Ocean Engineering, 2021, 239: 109809. doi: 10.1016/j.oceaneng.2021.109809 [28] LIN C, WU R. Evaluation of vertical effective stress and pile lateral capacities considering scour-hole dimensions[J]. Canadian Geotechnical Journal, 2019, 56(1): 135-143. doi: 10.1139/cgj-2017-0644 [29] 龚晓南. 桩基工程手册[M]. 2版. 北京: 中国建筑工业出版社, 2016. GONG Xiaonan. Pile foundation engineering manual[M]. 2nd ed. Beijing: China Construction Industry Press, 2016. （in Chinese） -
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