随着海上风电的大力发展，大直径管桩越来越多的应用于风电桩基，复杂海洋环境和岩土体参数使得单桩承载力预测较为困难。利用现场静力触探测试（CPT）数据推测桩基承载力是国内外规范中的常用方法，然而，在海洋环境下，由于成本和条件的制约，现场CPT数据较为缺乏，如何利用有限的CPT测试数据来预测桩基承载力是迫切需要解决的难题。针对上述难题，本文分析了影响大直径钢管桩承载力的因素，如桩周土体参数、桩-土相互作用系数、土塞效应等，建立了贝叶斯的不确定分析模型；基于现场桩基承载力试验数据，构建了三维随机有限元模型，分析了桩土相互作用机理，并提出了基于CPT数据的近海桩竖向承载力计算方法。本文的主要研究工作如下：

（1）探讨了单桩竖向承载力的不确定性来源和有效数据带来的计算误差，在此基础上，基于33根桩竖向承载力测试数据，利用贝叶斯概率理论，结合先验信息和现场CPT数据，对竖向承载力的不确定性进行定量分析；通过马尔科夫链式循环和蒙特卡洛随机抽样方法，生成竖向承载力的等效样本；根据对等效样本的统计分析，讨论了测量参数不确定性对竖向承载力的影响。

（2）基于响水风电场项目现场桩基测试结果，讨论了钢管桩内部土塞对竖向承载力的影响，分析钢管桩内部土体的土层分布不确定性；并对内侧摩阻力进行量化分析，将CPT预测桩基承载力方法进行了修正，并与国内外规范中计算方法进行对比，结果表明：修正后的方法预测的竖向承载力误差在0.4%~5.3%之间，误差远低于规范中的方法，且实测结果均位于修正后计算结果的90%置信区间之内。

（3）规范中桩侧摩阻力系数k为固定值，然而在海洋环境下，桩侧土体属性变化较大，基于固定系数k计算桩基竖向承载力会带来较大的误差。因此，基于随机有限元方法，建立响水风电场桩基的三维随机场模型，研究了土体参数空间变异性对桩基承载力的影响；并基于模型分析结果，提出了k系数的计算公式，由计算结果可知随深度变化，k系数在4 ~ 13之间波动，且在不同区域内的k系数的变化规律存在一致性。

（4）基于随机有限元模型，对桩-土之间荷载传递规律进行分析，探讨了桩-土沉降变形机理；对水平静载作用下的P ~ y曲线进行分析，并提出桩侧土体弹性系数k_py的计算方法，由计算结果可知，k_py随着土体的影响区域范围的增大而降低，随着土体弹性模量的增大而上升；同时，k_py的理论计算值与实际P ~ y曲线斜率有相同的变化趋势，能准确地对测试桩P ~ y曲线进行预测。

[1] Gokhman M R, Fedorovich D I, Targulyan Y O. Prediction of attainment of bearing capacity of piles sunk by combined method[J]. Soil Mechanics and Foundation Engineering, 1992, 28(4): 164-171.

[2] 陈佳茹, 张陈蓉, 黄茂松, 等. 砂土中扩底应力对深埋扩底抗拔桩承载力的影响[J]. 岩土工程学报, 2019, 41(S2): 89-92.

[3] Padmini D, Ilamparuthi K, Sudheer K P. Ultimate bearing capacity prediction of shallow foundations on cohesionless soils using neurofuzzy models[J]. Computers and Geotechnics, 2007, 35(1): 33-46.

[4] Xu D S, Tang Z Y, Zhang L. Interpretation of coarse effect in simple shear behavior of binary sand-gravel mixture by DEM with authentic particle shape[J]. Construction and Building Materials, 2019, 195: 292-304.

[5] 杨锋. 近海桩式风机基础——塔架动载特性与响应及桩基优化研究[D]. 北京: 中国水利水电科学研究院, 2013.

[6] Ghorbani B, Sadrossadat E, Bazaz J B, et al. Numerical ANFIS-based formulation for prediction of the ultimate axial load bearing capacity of piles through CPT data[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2018, 36(4): 2057-2076.

[7] Valikhah F, Eslami A, Veiskarami M. Load–displacement behavior of driven piles in sand using CPT-based stress and strain fields[J]. International Journal of Civil Engineering, 2019, 17 (12): 1879-1893.

[8] Wang C H, Osorio-Murillo C A, Zhu H H, et al. Bayesian approach calibrating transformation model from spatially varied CPT data to regular geotechnical parameter[J]. Computers and Geotechnics, 2017, 85: 262-273.

[9] 夏振华. 考虑土——结构相互作用的近海桩承结构动力分析[D]. 南昌: 南昌大学, 2016.

[10] 梁多伟. 碎石桩与抗滑桩联合加固及非埋式桩板结构加固斜坡软弱地基路堤的数值模拟[D]. 成都: 西南交通大学, 2013.

[11] Tumay M T, Fakhroo M. Pile capacity in soft clays using electric QCPT data[C]. Proceedings of a Conference on Cone Penetration Testing and Experience, St Louis, 1981: 434-455.

[12] Eslami A, Fellenius B H. Pile capacity by direct CPT and CPTu methods applied to 102 case histories[J]. Canadian Geotechnical Journal, 1997, 34(6): 886-994.

[13] Alkroosh I S, Bahadori M, Nikraz H, Bahadori A. Regressive approach for predicting bearing capacity of bored piles from cone penetration test data[J]. Journal of Rock Mechanics and Geotechnical Engineering, 2015, 5(7): 584-592.

[14] Fateh A M, Eslami A, Fahimifar A. Direct CPT and CPTu methods for determining bearing capacity of helical piles[J]. Marine Georesources and Geotechnology, 2017, 35(2): 193-207.

[15] 蔡国军, 刘松玉. 基于CPTU测试的桩基承载力预测新方法[J]. 岩土工程学报, 2010, 32 (S2): 479-482.

[16] 边晓亚, 郑俊杰, 徐志军. 考虑单桩设计方法的基桩承载力可靠度分析[J]. 岩土工程学报, 2013, 35 (S2): 1099-1102.

[17] American Petroleum Institude (API). Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms-Working Stress Design (RP2A-WSD), 18th Edition, [J], 2010.

[18] Veritas D N. Design of offshore wind turbine structures[J]. Offshore Standard DNV-OS-J101, 2014, 6: 2014.

[19] 中国建筑科学研究院. 建筑桩基技术规范 (JGJ 94-2008) [S]. 北京: 中国建筑工业出版社, 2008.

[20] Das M, Dey K D. Prediction of Bearing Capacity of Stone Columns Placed in Soft Clay Using ANN Model[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2018, 36(3): 1845-1861.

[21] Shaik S, Krishna K S R, Abbas M, et al. Applying several soft computing techniques for prediction of bearing capacity of driven piles[J]. Engineering Computations, 2019, 35(4): 1463-1474.

[22] Almeida M A, Miguel M G, Teixeira S H. Horizontal Bearing Capacity of Piles in a Lateritic Soil[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2011, 137(1): 59-69.

[23] 童立元, 李洪江, 刘松玉, 等. 基于静力触探试验的基坑开挖卸荷单桩水平承载力损失预测研究[J]. 岩土工程学报, 2019, 41(03): 501-508.

[24] 赵明华, 彭文哲, 杨超炜, 等. 斜坡地基刚性桩水平承载力上限分析[J]. 岩土力学, 2020, 41(03): 727-735.

[25] 张小玲, 赵景玖, 孙毅龙, 等. 基于圆孔扩张理论的桩基水平承载力计算方法[J]. 工程力学, 2021, 38(02):232-241.

[26] Xu D S, Xu X Y, Li W, et al. Field experiments on laterally loaded piles for an offshore wind farm[J]. Marine Structures, 2020, 69: 102684.

[27] Qian Y M, Ai S D, Wang R Z, et al. Calculation Model of Bearing Capacity of the Rigid-Body Expanded Plate Pile under Horizontal Force in Ocean Engineering[J]. Journal of Coastal Research, 2020, 111(sp1):345-351.

[28] 翟恩地, 石世刚, 胡中波, 等. 基于荷载传递曲线的大直径钢管桩水平受力特性分析方法[J]. 岩石力学与工程学报, 2019, 38(02): 365-375.

[29] 万志辉, 戴国亮, 龚维明, 等. 钙质砂后压浆桩水平承载性状模型试验研究[J]. 岩土力学, 2021, 02: 1-8.

[30] 中华人民共和国交通运输部. 港口工程桩基规范 (JTS 167-4-2012) [S]. 中国建筑工业出版社, 2012.

[31] 董爱民. 风电桩基础水平承载力研究[D]. 武汉: 中国地质大学, 2017..

[32] 蒋水华, 刘源, 章浩龙, 等. 先验概率分布及似然函数模型的选择对边坡可靠度评价影响的定量评估[J]. 岩土力学, 2020, 41(09): 3087-3097.

[33] 邹海峰. 基于CPTU的软弱土空间变异性特征与桩基承载力不确定性设计方法研究[D]. 南京: 东南大学, 2018.

[34] Cao Z J, Wang Y. Bayesian approach for probabilistic site characterization using cone penetration tests[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2013, 139(2): 267-276.

[35] 田密, 李典庆, 曹子君, 等. 基于贝叶斯理论的土性参数空间变异性量化方法[J]. 岩土力学, 2017, 38(11): 3355-3362.

[36] Juang C H, Luo Z, Atamturktur S, et al. Bayesian updating of soil parameters for braced excavations using field observations[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2013, 139(3):395-406.

[37] Beck J L, Au S K. Bayesian updating of structural models and reliability using Markov chain Monte Carlo simulation[J]. Journal of Engineering Mechanics, 2002, 128(4): 380-391.

[38] Wang C H, Osorio-Murillo C A, Zhu H H, et al. Bayesian approach calibrating transformation model from spatially varied CPT data to regular geotechnical parameter[J]. Computers and Geotechnics, 2017, 85: 262-273.

[39] Wang Y, Au S K, Cao Z. Bayesian approach for probabilistic characterization of sand friction angles[J]. Engineering Geology, 2010, 114(3–4): 354–363.

[40] Zhang J, Zhang L M, Tang W H. Bayesian framework for characterizing geotechnical model uncertainty[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2009, 135 (7): 932-940.

[41] Cao Z J, Wang Y. Probabilistic characterization of Young's modulus of soil using equivalent samples[J]. Engineering geology, 2013, 159: 106-118.

[42] 徐志军. 基桩承载力的可靠度分析及可靠度优化设计研究[D]. 武汉: 华中科技大学, 2012.

[43] Beck J L, Au S K. Bayesian updating of structural models and reliability using Markov chain Monte Carlo simulation[J]. Journal of Engineering Mechanics, 2002, 128 (4), 380-391.

[44] 郭重阳, 李典庆, 曹子君, 等. 考虑空间变异性条件下的边坡稳定可靠度高效敏感性分析[J]. 岩土力学, 2018, 39(06): 2203-2210.

[45] Zhang L L, Zhang J, Zhang L M, et al. Back analysis of slope failure with Markov chain Monte Carlo simulation[J]. Computers and Geotechnics, 2010, 37 (7–8), 905-912.

[46] 闫澍旺, 董伟, 刘润, 等. 海洋采油平台打桩工程中土塞效应研究[J]. 岩石力学与工程学报, 2009, 28(04): 703-709.

[47] 黄大维, 周顺华, 宫全美, 等. 钢管压入土体施工挤土机制与案例分析[J]. 岩石力学与工程学报, 2013, 32(01): 176-183.

[48] Yan S W, Zhou Q H, Liu R, et al. Pit bearing capacity effect on status of soil plug during pile driving in ocean engineering [J]. China Ocean Eng, 2011, 25(2): 295-304.

[49] Wang T, Zhang Y, Bao X X, et al. Mechanisms of soil plug formation of open-ended jacked pipe pile in clay[J]. Computers and Geotechnics, 2020, 118: 103334.

[50] Aleksandrova N I, Kondratenko A S. Movement of an Open-Ended Pipe with a Soil Plug Under a Longitudinal Impact[J]. Geotechnical and Geological Engineering, 2020, 38: 3493–3504.

[51] Cao Z J. Probabilistic Approaches for Geotechnical Site Characterization and Slope Stability Analysis[D]. Hong Kong: City University of Hong Kong, 2012.

[52] 阮永芬, 魏德永, 杨均, 等. 用Bayes法及后验分布极限确定土力学参数[J]. 岩土工程学报, 2020, 42(03): 438-446.

[53] Eslami A. Bearing capacity of piles from cone penetrometer test data[D]. Ottawa: University of Ottawa, 1996.

[54] Almeida M S, Danziger F A. Use of the piezocone test to predict the axial capacity of driven and jacked piles in clay[J]. Can Geotech J, 1996, 33(1): 23-41.

[55] Yan S W, Zhou Q H, Liu R, et al. Pit bearing capacity effect on status of soil plug during pile driving in ocean engineering[J]. China Ocean Eng, 2011, 25(2): 295-304.

[56] Wang Y, Au S K, Cao Z. Bayesian approach for probabilistic characterization of sand friction angles[J]. Engineering Geology, 2010, 114(3–4): 354–363.

[57] 黄传胜. 地铁深基坑开挖变形预测方法及工程应用研究[D]. 长沙: 中南大学, 2011.

[58] Cheng L L, Alfredo C, Lang Z Q et al. An output-only ARX model-based sensor fusion framework on structural dynamic measurements using distributed optical fiber sensors and fiber Bragg grating sensors[J]. Mechanical Systems and Signal Processing, 2021, 152.

[59] 李豪杰, 朱鸿鹄, 朱宝, 等. 基于光纤监测的埋地管线沉降模型试验研究[J]. 岩石力学与工程学报, 2020, 39(S2): 3645-3654.

[60] Xu D S, Liu H B, Luo W L. Evaluation of interface shear behavior of GFRP soil nails with a strain-transfer model and distributed fiber-optic sensors[J]. Computers and Geotechnics, 2018, 95: 180-190.

[61] 李嘉琪. 用于BOTDA光纤传感系统的数据处理方式的研究[D]. 长春: 吉林大学, 2020.

[62] Xu D S, Tang J Y, Zhou Y, et al. Macro and micro investigation of gravel content on simple shear behavior of sand-gravel mixture[J]. Construction and Building Materials, 2019, 221: 730-744.

[63] Gabar M, ALasefir W, Amer H. The Effect of Cemented Clay on the Performance of Raft Foundations Using Plaxis 3D Software[J]. Journal of Progress in Civil Engineering, 2020, 2(9).

[64] Gong W P, Tang H M, Wang H, et al. Probabilistic analysis and design of stabilizing piles in slope considering stratigraphic uncertainty[J]. J Geotech Engrg, 2019, 259: 156-167.

[65] 江浩. 钙质砂中桩基工程承载性状研究[D]. 武汉: 中国科学院研究生院(武汉岩土力学研究所), 2009.

[66] 万志辉, 戴国亮, 龚维明, 等. 钙质砂后压浆桩水平承载性状模型试验研究[J]. 岩土力学, 2021, 42(02): 411-418+429.

[67] 李炀, 吴曙光, 张四平, 等. 水平受荷桩桩身响应的线性方程解及应用分析[J]. 岩土工程学报, 2020, 42(S1): 70-74.

[68] 罗仑博, 王媛, 翟恩地, 等. 基于现场试验的钢管桩分层土p-y曲线研究[J]. 太阳能学报, 2019, 40(11): 3258-3264.

[69] H?rning S, Bárdossy A. Phase annealing for the conditional simulation of spatial random fields[J]. Computers and Geosciences, 2018, 112: 101-111.

[70] 廖蔚茗. 循环荷载作用下粘土场地近海风机单桩式基础变形与受力特性研究[D]. 成都: 西南交通大学, 2018.

[71] Xu D S, Tang Z Y, Zhang L. Interpretation of coarse effect in simple shear behavior of binary sand-gravel mixture by DEM with authentic particle shape[J]. Constr Build Mater, 2019, 195: 292-304.