侧阻附加弯矩对桥梁桩基水平承载力影响研究
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摘要
为研究桩身被动侧竖向摩阻力对大直径桥梁基桩的水平承载特性影响,首先在抗力矩概念基础上分别建立任意桩身横截面竖向侧摩阻力产生的附加弯矩计算公式及其影响下的桩身单元受力微分表达式。基于传递矩阵法及Laplace正逆变换,分别得出考虑侧阻附加弯矩影响时桩身弹性段、塑性段的传递矩阵系数解。结合推导的桩端水平阻力本构模型和给定的迭代求解方法,进而得出考虑桩侧竖向摩阻力影响的桥梁基桩桩身响应解。通过试验对比验证了本文方法的合理性,证明了桩侧竖向侧摩阻力所产生的附加弯矩对桩基水平承载力的影响非常显著。最后开展了附加弯矩参数影响分析,结果表明:不同τ-s曲线作用时桩身最大变形降低幅度变化规律均类似;桩身最大变形降低幅度随着桩侧摩阻力τ-s曲线极限值τu的增加、临界位移su的减小而增加;当长径比Lb/d≥4时,可忽略桩端水平阻力的影响;当Lb/d≥10时,可忽略侧阻附加弯矩效应的影响;长径比相同时,桩径越大,相应的初始阶段最大位移降低幅度也越大。
To analyze the effect of skin friction along the passive side on the lateral bearing capacity of large diameter pile foundation of bridge,the calculation formula of the additional moment caused by vertical shaft resistance for each cross-section of pile shaft is established by means of the conception of resisting moment,and the differential expression of pile element stress subjected to the effect is obtained.Furthermore,based on the transfer matrix method and Laplace transformation,this paper deduces the solutions of transfer matrix coefficients for pile in elastic and plastic state and obtains the horizontal responses of bridge pile foundation considering the influence of additional moment induced by vertical shaft resistance on the basis of the derived constitutive model of horizontal resistance at pile end and the given iteration method. The test result verifies the proposed approach and shows that the influence of resisting moment on lateral bearing capacity is significant. Finally,parametric study of additional moment is performed and the results reveal that the decreasing ratio of maximum pile deflection has the same changing patterns with different τ-s curve; the decreasing ratio of maximum pile deflection increases with increasing limit friction τuor decreasing critical displacement su of τ-s curve; the influence of horizontal resistance of pile tip can be neglected when aspect ratio of pile exceeds 4 and the additional moment effect can also be ignored when aspect ratio of pile exceeds 10. Furthermore, the larger the pile diameter is,the bigger the decreasing ratio of the maximum pile deflection at the initial stage will be under the condition of identical aspect ratio of pile.
To analyze the effect of skin friction along the passive side on the lateral bearing capacity of large diameter pile foundation of bridge,the calculation formula of the additional moment caused by vertical shaft resistance for each cross-section of pile shaft is established by means of the conception of resisting moment,and the differential expression of pile element stress subjected to the effect is obtained.Furthermore,based on the transfer matrix method and Laplace transformation,this paper deduces the solutions of transfer matrix coefficients for pile in elastic and plastic state and obtains the horizontal responses of bridge pile foundation considering the influence of additional moment induced by vertical shaft resistance on the basis of the derived constitutive model of horizontal resistance at pile end and the given iteration method. The test result verifies the proposed approach and shows that the influence of resisting moment on lateral bearing capacity is significant. Finally,parametric study of additional moment is performed and the results reveal that the decreasing ratio of maximum pile deflection has the same changing patterns with different τ-s curve; the decreasing ratio of maximum pile deflection increases with increasing limit friction τuor decreasing critical displacement su of τ-s curve; the influence of horizontal resistance of pile tip can be neglected when aspect ratio of pile exceeds 4 and the additional moment effect can also be ignored when aspect ratio of pile exceeds 10. Furthermore, the larger the pile diameter is,the bigger the decreasing ratio of the maximum pile deflection at the initial stage will be under the condition of identical aspect ratio of pile.
引文
[1]龚成中.大直径嵌岩桩基承载特性的理论分析与实验研究[D].南京:东南大学,2014.
[2] Basu D. Analysis of Laterally Loaded Piles in Layered Soil[D]. West Lafayette:Purdue University,2006.
[3] Dodds A M,Martin G R. Modeling Pile Behavior in Large Pile Groups under Lateral Loading[R]. Buffalo:Multidisciplinary Center for Earthquake Engineering Research,2007.
[4] Lam I P,Martin G R. Seismic Design of Highway Bridge Foundations[R]. Virginia:U. S. Department of Transportation,Federal Highway Administration,1986.
[5] Mcvay M C,Niraula L. Development of P-Y Curves for Large Diameter Piles/Drilled Shafts in Limestone for FB-PIER[R]. Tallahassee:University of Florida,2004.
[6]霍少磊.巨型基础承载特性的尺寸效应研究[D].南京:东南大学,2016.
[7] Alikhanlou F. A Discrete Model for The Analysis of Short Pier Foundations in Clays[D]. Lubbock:Texas Tech University,1981.
[8] Tseng T J. Laterally Loaded Rigid Piers in Sand And Sandy Soils[D]. Lubbock:Texas Tech University,1984.
[9] Gerolymos N,Gazetas G. Static and Dynamic Response of Massive Caisson Foundations with Soil and Interface Nonlinearities-Validation and Results[J]. Soil Dynamics and Earthquake Engineering,2006,26(5):377-394.
[10] Varun A D,Gazetas G. A Simplified Model for Lateral Response of Large Diameter Caisson Foundations-Linear Elastic Formulation[J].Soil Dynamics and Earthquake Engineering,2009,29:268-291.
[11]王伯惠,上官兴.中国钻孔灌注桩新发展[M].北京:人民交通出版社,1999.
[12] Ashour M,Helal A. Contribution of Vertical Skin Friction to the Lateral Resistance of Large-Diameter Shafts[J]. Journal of Bridge Engineering,2013,19(2):289-302.
[13]竺明星,龚维明,何小元,等.纵横向受荷基桩变形内力的矩阵传递解[J].岩土力学,2014,35(11):3281-3288.
[14]张玲,赵明华,赵衡.倾斜荷载下桩柱式桥墩受力变形分析传递矩阵法[J].中国公路学报,2015,28(2):69-76.
[15]竺明星.组合荷载作用下被动桩承载机理研究[D].南京:东南大学,2016.
[16]李灿.大直径钢管桩水平承载特性研究[D].大连:大连理工大学,2012.
[17]陈源.海口某深基坑支护数值模拟及土体本构模型研究[D].海口:海南大学,2014.
[18]费康. ABAQUS在岩土工程中的应用[M].北京:中国水利水电出版社,2010.
[19] Jeanjean P. Re-Assessment of p-y Curves for Soft Clays from Centrifuge Testing and Finite Element Modeling[C]. Offshore Technology Conference,4-7 May,Houston,Texas,2009.
[20] Bhushan K,Fong P T,Haley S C. Lateral Load Tests on Drilled Piers in Stiff Clays[J]. Journal of the Geotechnical Engineering Division,1979,105(8):969-985.
[21] Georgiadis K,Georgiadis M. Undrained Lateral Pile Response in Sloping Ground[J]. Journal of Geotechnical and Geoenvironmental Engineering,2010,136(11):1489-1500.
[22] Mokwa R L. Investigation of the Resistance of Pile Caps to Lateral Loading[D]. Virginia:Virginia Polytechnic Institute and State University,1999.
[23] Juirnarongrit T,Ashford S A. Soil-Pile Response to Blast-Induced Lateral Spreading. II:Analysis and Assessment of the p-y Method[J]. Journal of Geotechnical and Geoenvironmental Engineering,2006,132(2):163-172.
[24]肖宏彬.竖向荷载作用下大直径桩的荷载传递理论及应用研究[D].长沙:中南大学,2005.
[2] Basu D. Analysis of Laterally Loaded Piles in Layered Soil[D]. West Lafayette:Purdue University,2006.
[3] Dodds A M,Martin G R. Modeling Pile Behavior in Large Pile Groups under Lateral Loading[R]. Buffalo:Multidisciplinary Center for Earthquake Engineering Research,2007.
[4] Lam I P,Martin G R. Seismic Design of Highway Bridge Foundations[R]. Virginia:U. S. Department of Transportation,Federal Highway Administration,1986.
[5] Mcvay M C,Niraula L. Development of P-Y Curves for Large Diameter Piles/Drilled Shafts in Limestone for FB-PIER[R]. Tallahassee:University of Florida,2004.
[6]霍少磊.巨型基础承载特性的尺寸效应研究[D].南京:东南大学,2016.
[7] Alikhanlou F. A Discrete Model for The Analysis of Short Pier Foundations in Clays[D]. Lubbock:Texas Tech University,1981.
[8] Tseng T J. Laterally Loaded Rigid Piers in Sand And Sandy Soils[D]. Lubbock:Texas Tech University,1984.
[9] Gerolymos N,Gazetas G. Static and Dynamic Response of Massive Caisson Foundations with Soil and Interface Nonlinearities-Validation and Results[J]. Soil Dynamics and Earthquake Engineering,2006,26(5):377-394.
[10] Varun A D,Gazetas G. A Simplified Model for Lateral Response of Large Diameter Caisson Foundations-Linear Elastic Formulation[J].Soil Dynamics and Earthquake Engineering,2009,29:268-291.
[11]王伯惠,上官兴.中国钻孔灌注桩新发展[M].北京:人民交通出版社,1999.
[12] Ashour M,Helal A. Contribution of Vertical Skin Friction to the Lateral Resistance of Large-Diameter Shafts[J]. Journal of Bridge Engineering,2013,19(2):289-302.
[13]竺明星,龚维明,何小元,等.纵横向受荷基桩变形内力的矩阵传递解[J].岩土力学,2014,35(11):3281-3288.
[14]张玲,赵明华,赵衡.倾斜荷载下桩柱式桥墩受力变形分析传递矩阵法[J].中国公路学报,2015,28(2):69-76.
[15]竺明星.组合荷载作用下被动桩承载机理研究[D].南京:东南大学,2016.
[16]李灿.大直径钢管桩水平承载特性研究[D].大连:大连理工大学,2012.
[17]陈源.海口某深基坑支护数值模拟及土体本构模型研究[D].海口:海南大学,2014.
[18]费康. ABAQUS在岩土工程中的应用[M].北京:中国水利水电出版社,2010.
[19] Jeanjean P. Re-Assessment of p-y Curves for Soft Clays from Centrifuge Testing and Finite Element Modeling[C]. Offshore Technology Conference,4-7 May,Houston,Texas,2009.
[20] Bhushan K,Fong P T,Haley S C. Lateral Load Tests on Drilled Piers in Stiff Clays[J]. Journal of the Geotechnical Engineering Division,1979,105(8):969-985.
[21] Georgiadis K,Georgiadis M. Undrained Lateral Pile Response in Sloping Ground[J]. Journal of Geotechnical and Geoenvironmental Engineering,2010,136(11):1489-1500.
[22] Mokwa R L. Investigation of the Resistance of Pile Caps to Lateral Loading[D]. Virginia:Virginia Polytechnic Institute and State University,1999.
[23] Juirnarongrit T,Ashford S A. Soil-Pile Response to Blast-Induced Lateral Spreading. II:Analysis and Assessment of the p-y Method[J]. Journal of Geotechnical and Geoenvironmental Engineering,2006,132(2):163-172.
[24]肖宏彬.竖向荷载作用下大直径桩的荷载传递理论及应用研究[D].长沙:中南大学,2005.