摘要
由于缺乏合适的激振和接收位置,传统竖向低应变反射波法在检测带承台或未凿桩头的桩基动力特性时存在明显不足。为进一步拓展低应变检测波法应用范围,基于Timoshenko梁理论,考虑桩身材料阻尼、附加轴力及桩顶等效质量作用,建立了一种横向激励条件下承台-桩-土耦合振动模型,并求解了该模型的频域内解析解及其时域半解析解。进一步地,考虑了Timoshenko梁在低应变测试条件下2种剪切波的激发与传播。基于频散效应分析得出,在低应变检测条件下主要以第1类剪切波的传播为主,而第2类剪切波在截止频率以下尚未被激发,此时可认为模型等效剪切波速略小于一维剪切波速。通过和室内模型试验结果的比较,进一步验证了所假设的有效性和理论解的合理性。基于解析结果,分别对桩底约束条件、桩-土模型参数、承台特征以及测试信号宽度等对桩顶水平激振响应的影响进行了时域分析。结果表明:对于横向激振下桩身质点时域速度曲线而言,桩底反射均呈现与激振信号“同向-反向-同向”的反复震荡区间,桩底约束条件主要影响震荡区间范围;承台特征、桩/土的材料参数主要影响桩底反射波的幅值;激振频率主要影响速度波的宽度,且高频条件下,第2类剪切波将会被激发。参数分析结果可以为带承台或未凿桩头桩基检测工程提供理论支持及指导作用。
Owing to the lack of suitable excitation and receiving locations,the traditional vertical low-strain reflected wave method has obvious deficiencies in detecting the dynamic characteristics of pile foundations with pile caps or unchiseled pile heads.Based on Timoshenko beam theory,and further considering the pile material damping,additional axial force,and pile top equivalent mass effect,a cap-pile-soil coupling vibration model under lateral excitation was established,and analytical and semi-analytical solutions of displacement in the frequency and time domains were obtained.Furthermore,this study investigated two shear waves of the Timoshenko beam under low-strain test conditions where the wave propagation basically depends on one type of shear wave,and the other shear wave is depressed under the cut-off frequency;it can be considered that the model equivalent shear wave velocity is slightly smaller than the one-dimensional shear wave velocity.A comparison with the indoor model test results further validates the hypothesis and the rationality of the theoretical solution.Based on the theoretical solution of this study,a time-domain analysis of the effects of the constraint conditions at the bottom of the pile,the parameters of the pile-soil model,the characteristics of the bearing caps,and the width of the test signal on the horizontal excitation response of the pile top was performed.The responses of horizontal velocity measured by different depths of model piles show that the pile bottom reflections have oscillation intervals“in the same direction-reverse direction-same direction”with the excitation signal,and the constraint conditions at the bottom of the pile mainly affect the scope of the oscillation interval;the characteristics of the cap and the pile/soil material parameters mainly affect the amplitude of the reflected wave at the bottom of the pile;the excitation frequency mainly affects the width of the velocity wave,and under high-frequency conditions,the second type of shear wave is excited.The results of the parameter analysis in this study can provide theoretical support and guidance for the inspection of pile foundations with caps or uncut pile heads.
作者
邱欣晨
吴君涛
赵爽
王奎华
涂园
QIU Xin-chen;WU Jun-tao;ZHAO Shuang;WANG Kui-hua;TU Yuan(Research Center of Coastal and Urban Geotechnical Engineering,Zhejiang University,Hangzhou 310058,Zhejiang,China;Key Laboratory of Soft Soils and Geoenvironmental Engineering of Ministry of Education,Zhejiang University,Hangzhou 310058,Zhejiang,China)
出处
《中国公路学报》
EI
CAS
CSCD
北大核心
2022年第4期166-176,共11页
China Journal of Highway and Transport
基金
国家自然科学基金项目(51779217)
中央高校基本科研业务费专项资金项目(2020QNA4027)
中国博士后科学基金项目(2020M681857).
