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1、第36卷第7期岩土力学Vol.36No.72015年7月RockandSoilMechanicsJul.2015DOI:10.16285/j.rsm.2015.07.014桩基动刚度影响因素分析1,22322马蒙,刘建磊,孙宁,柯在田,李林杰(1.北京交通大学土木建筑工程学院,北京100044;2.中国铁道科学研究院铁道建筑研究所,北京100081;3.铁科院(北京)工程咨询有限公司,北京100081)摘要:动刚度是桩基动测分析中一个重要指标,研究动刚度的影响因素有着现实的工程意义。为了分析完整桩
2、和缺陷桩单桩动刚度的变化规律和影响因素,推导并求解了竖向简谐荷载作用下考虑两个变截面桩的导纳响应解析解。利用测试数据验证了该模型能有效计算导纳共振频率值和动刚度值。同时,对513根相同型式桥桩进行机械阻抗法测试,并对其动刚度进行统计分析。研究表明:(1)桩端支撑刚度和桩长对动刚度影响较大,端承桩动刚度随桩长增加而降低,纯摩擦桩情况与之相反。摩擦桩在桩长较长时其动刚度可能大于端承桩。(2)桩身缺陷体积改变量与动刚度变化成正相关。(3)动刚度对桩身缩颈缺陷敏感度较高,在一定程度上可以用于判断桩身完整性
3、和承载能力。关键词:桩基;动刚度;缺陷桩;竖向振动;解析解中图分类号:TU473.1文献标识码:A文章编号:1000-7598(2015)07-1939-06Analysisoffactorsinfluencingdynamicstiffnessofpilefoundations1,22322MAMeng,LIUJian-lei,SUNNing,KEZai-tian,LILin-jie(1.SchoolofCivilEngineering,BeijingJiaotongUniversity,Bei
4、jing100044,China;2.RailwayEngineeringResearchInstitute,ChinaAcademyofRailwaySciences,Beijing100081,China;3.BeijingEngineeringConsultationCo.,Ltd.,ChinaAcademyofRailwaySciences,Beijing100081,China)Abstract:Dynamicstiffnessisanimportantindexinpiledynami
5、cmeasurementandanalysis.Inpracticeitisimportanttoanalyzeandidentifythefactorsthatinfluencethedynamicstiffnessofpilefoundation.Toanalyzethedynamicstiffnessoftheintactanddefectedpiles,ananalyticalmodelofadmittanceresponseunderverticalharmonicloadsisdeve
6、lopedandsolved.Inthismodel,twovariablecrosssectionsareconsidered.Themeasuredresultsshowthatthemodelcanbeeffectivelyusedtocalculatethevaluesofresonancefrequencyanddynamicstiffness.Moreover,513bridgepilesofthesametypearemeasuredusingmechanicalimpedancem
7、ethod.Thedynamicstiffnessforallpilesisanalyzedstatistically.Itisshownasfollows.(1)thesupportingstiffnessofpiletipandthepilelengthsignificantlyeffectdynamicstiffness;thedynamicstiffnessofend-bearingpiledecreaseswithitslength,whereasthatofpurefrictionpi
8、lesincreaseswiththepilelength.Iffrictionpilehasalongerlength,itsdynamicstiffnessmayexceedthatofend-bearingpile.(2)Fordefectedpiles,thevolumetricchangehasthepositiverelationwiththevariationofdynamicstiffness.(3)Dynamicstiffnessisverysensitiveto