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采用多质点弹簧-阻尼模型模拟列车,将板式轨道运动学方程引入到桥梁模型中,推导了桥梁振动半解析模型,结合群桩基础模型,建立了列车-轨道-桥梁-桥墩-群桩基础半解析耦合模型。基于傅里叶变换和频域内弹性半空间Green函数求得高铁高架桥群桩基础地面波动场,研究了上软下硬和上硬下软地基环境振动规律,分析了桩径、桩长对地面振动衰减的影响。结果表明:车速较低时,轨道中心处上硬下软地层比上软下硬地层振动大;上软下硬地层,车速较高时因接近表层软土剪切波速而增大地面振动,故应避免车速接近表层土的剪切波速;群桩基础地面振动随桩长和桩径增大而增大,且车速越大地面振动增速越快;桩体具有好的减振效果,群桩范围内地面振动由于几何阻尼和桩体散射作用迅速衰减,且桩径越大振动衰减速度越快,但受桩长影响较小;群桩基础外上硬下软地层比上软下硬地层的地面振动幅度小,表明上硬下软地层减振效果好;合理设计桩基可控制轨道中心处地面振动,并能有效降低高架桥远处的环境振动。 相似文献
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海洋环境中的导管架平台承受着风浪、地震等水平荷载,而平台的稳定对桩基础有严格要求,故研究水平荷载下导管架平台桩-土系统变形规律和相互作用机制具有重要意义。研制了1套导管架平台桩-土相互作用试验系统,主要由导管架平台试验模型子系统、电动伺服加载子系统、传感器与数据采集子系统、振动测试子系统组成,可用于研究冲击荷载、静载、循环荷载下导管架平台的桩身变形规律、桩基周围土体响应及平台的振动特性。通过初步试验结果表明,该系统能够如实反映水平荷载下桩-土间的相互作用和导管架平台的振动特性,验证了该系统的有效性。 相似文献
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A series of centrifuge shaking table model tests are conducted on 4?×?4 pile groups in liquefiable ground in this study, achieving horizontal–vertical bidirectional shaking in centrifuge tests on piles for the first time. The dynamic distribution of forces on piles within the pile groups is analysed, showing the internal piles to be subjected to greater bending moment compared with external piles, the mechanism of which is discussed. The roles of superstructure–pile inertial interaction and soil–pile kinematic interaction in the seismic response of the piles within the pile groups are investigated through cross-correlation analysis between pile bending moment, soil displacement, and structure acceleration time histories and by comparing the test results on pile groups with and without superstructures. Soil–pile kinematic interaction is shown to have a dominant effect on the seismic response of pile groups in liquefiable ground. Comparison of the pile response in two tests with and without vertical input ground motion shows that the vertical ground motion does not significantly influence the pile bending moment in liquefiable ground, as the dynamic vertical total stress increment is mainly carried by the excess pore water pressure. The influence of previous liquefaction history during a sequence of seismic events is also analysed, suggesting that liquefaction history could in certain cases lead to an increase in liquefaction susceptibility of sand and also an increase in dynamic forces on the piles. 相似文献
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In this paper, the frequency domain dynamic response of a pile embedded in a porous medium subjected to SH seismic waves is investigated. The surrounding porous medium of the pile is described by Biot’s poro-elastic theory, while the pile embedded in the porous medium is treated as a beam and described by a beam vibration theory. Using the Hankel transformation method, the fundamental solution for a half-space porous medium subjected to a horizontal circular patch load is established. According to the fictitious pile methodology, the second kind of Fredholm integral equation for the pile is established in terms of the obtained fundamental solution and free wave field. The solution of the integral equation yields the dynamic response of the pile to plane SH waves. Numerical results indicate that the parameters of the porous medium, the pile and incident waves have considerable influences on the dynamic response of the pile and the porous medium. 相似文献
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考虑地基沉积过程中产生的竖向和水平向力学性质的差异,对横观各向同性地基中管桩扭转振动频域响应进行了理论研究。基于横观各向同性材料的本构关系以及桩-土耦合扭转振动,建立了桩土系统定解问题,通过Laplace变换和分离变量法求得了桩周土和桩芯土扭转振动位移形式解。通过桩-土接触面的连续条件,求得了管桩扭转频域响应解析解,并得到了桩顶复动刚度和速度导纳的表达式。将所得解退化到横观各向同性地基中实心桩解以及均匀地基中管桩解,并与已有文献进行了对比,验证了解的合理性。通过数值算例,分析了桩周土和桩芯土的横观各向同性力学参数对桩顶扭转复刚度及速度导纳的影响。 相似文献
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The behaviour of single vertical piles subjected to lateral loading at the pile head was analysed. Based on the assumption of beam on elastic foundation, the analysis was made by using the method of direct analysis which is a numerical approach making direct use of governing physical laws without explicitly utilizing the differential equation of vibration. The analysis provides short-time pile response to pulse loadings. These results indicate, among others, that an interaction between the dilatation and shear waves results in a stress discontinuity of considerable magnitude which may deserve special attention in pile design. 相似文献
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In the present study an analytical procedure based on finite element technique is proposed to investigate the influence of vertical load on deflection and bending moment of a laterally loaded pile embedded in liquefiable soil, subjected to permanent ground displacement. The degradation of subgrade modulus due to soil liquefaction and effect of nonlinearity are also considered. A free headed vertical concrete elastic nonyielding pile with a floating tip subjected to vertical compressive loading, lateral load, and permanent ground displacement due to earthquake motions, in liquefiable soil underlain by nonliquefiable stratum, is considered. The input seismic motions, having varying range of ground motion parameters, considered here include 1989 Loma Gilroy, 1995 Kobe, 2001 Bhuj, and 2011 Sikkim motions. It is calculated that maximum bending moment occurred at the interface of liquefiable and nonliquefiable soil layers and when thickness of liquefiable soil layer is around 60% of total pile length. Maximum bending moment of 1210 kNm and pile head deflection of 110 cm is observed because of 1995 Kobe motion, while 2001 Bhuj and 2011 Sikkim motions amplify the pile head deflection by 14.2 and 14.4 times and bending moment approximately by 4 times, when compared to nonliquefiable soil. Further, the presence of inertial load at the pile head increases bending moment and deflection by approximately 52% when subjected to 1995 Kobe motion. Thus, it is necessary to have a proper assessment of both kinematic and inertial interactions due to free field seismic motions and vertical loads for evaluating pile response in liquefiable soil. 相似文献
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为探究覆水饱和砂土场地中土-群桩基础-桥梁结构体系动力相互作用规律,自主设计并制作了直（斜）群桩基础-桥梁结构物理相似模型,开展了不同地震动强度和不同特性地震波输入下的离心机振动台试验,分析了群桩基础-桥梁结构动力特性指标,探究了覆水饱和砂土地基超孔隙水压力发展规律和桩-土相互作用动力响应特性。研究结果表明：覆水的存在对地基土-桥梁结构体系的基本周期和阻尼影响很小,但会导致直群桩基础桥梁结构的振动幅值增加20%,而斜群桩基础桥梁结构的振动幅值降低10%;斜群桩基础模型阻尼比是直群桩基础模型的2倍。上覆水导致饱和砂土地基由受低频振动液化深度更大变为受高频振动地基液化深度更大,同时导致小震作用下促进超孔隙水压力发展,而大震作用下则反之。上覆水会增大桥梁上部结构的动力响应和桩身弯矩。上述研究结果可为覆水场地中桥梁工程抗震设计提供关键参考依据。 相似文献
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In this paper, frequency domain dynamic response of a pile embedded in a half‐space porous medium and subjected to P, SV seismic waves is investigated. According to the fictitious pile methodology, the problem is decomposed into an extended poroelastic half‐space and a fictitious pile. The extended porous half‐space is described by Biot's theory, while the fictitious pile is treated as a bar and a beam and described by the conventional 1‐D structure vibration theory. Using the Hankel transformation method, the fundamental solutions for a half‐space porous medium subjected to a vertical or a horizontal circular patch load are established. Based on the obtained fundamental solutions and free wave fields, the second kind of Fredholm integral equations describing the vertical and the horizontal interaction between the pile and the poroelastic half‐space are established. Solution of the integral equations yields the dynamic response of the pile to plane P, SV waves. Numerical results show the parameters of the porous medium, the pile and incident waves have direct influences on the dynamic response of the pile–half‐space system. Significant differences between conventional single‐phase elastic model and the poroelastic model for the surrounding medium of the pile are found. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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The dynamic response of an end bearing pile embedded in a linear visco‐elastic soil layer with hysteretic type damping is theoretically investigated when the pile is subjected to a time‐harmonic vertical loading at the pile top. The soil is modeled as a three‐dimensional axisymmetric continuum in which both its radial and vertical displacements are taken into account. The pile is assumed to be vertical, elastic and of uniform circular cross section. By using two potential functions to decompose the displacements of the soil layer and utilizing the separation of variables technique, the dynamic equilibrium equation is uncoupled and solved. At the interface of soil‐pile system, the boundary conditions of displacement continuity and force equilibrium are invoked to derive a closed‐form solution of the vertical dynamic response of the pile in frequency domain. The corresponding inverted solutions in time domain for the velocity response of a pile subjected to a semi‐sine excitation force applied at the pile top are obtained by means of inverse Fourier transform and the convolution theorem. A comparison with two other simplified solutions has been performed to verify the more rigorous solutions presented in this paper. Using the developed solutions, a parametric study has also been conducted to investigate the influence of the major parameters of the soil‐pile system on the vertical vibration characteristics of the pile. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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A simplified method of numerical analysis has been developed to estimate the deformation and load distribution of piled raft foundations subjected to ground movements induced by tunnelling and incorporated into a computer program ‘PRAB’. In this method, a hybrid model is employed in which the flexible raft is modelled as thin plates, the piles as elastic beams, and the soil is treated as interactive springs. The interactions between structural members, pile–soil–pile, pile–soil–raft and raft–soil–raft interactions, are modelled based on Mindlin's solutions for both vertical and lateral forces. The validity of the proposed method is verified through comparisons with some published solutions for single piles and pile groups subjected to ground movements induced by tunnelling. Thereafter, the solutions from this approach for the analysis of a pile group and a piled raft subjected to ground movements induced by tunnelling are compared with those from three‐dimensional finite difference program. Good agreements between these solutions are demonstrated. The method is then used for a parametric study of single piles, pile groups and piled rafts subjected to ground movements induced by tunnelling. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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A comprehensive analytical solution is developed in this paper to investigate the torsional vibration of an end bearing pile embedded in a homogeneous poroelastic medium and subjected to a time-harmonic torsional loading. The poroelastic medium is modeled using Biot’s two-phased linear theory and the pile using one-dimensional elastic theory. By using the separation of variables technique, the torsional response of the soil layer is solved first. Then based on perfect contact between the pile and soil, the dynamic response of the pile is obtained in a closed form. Numerical results for torsional impedance of the soil layer are presented first to portray the influence of wave modes, slenderness ratio, pile–soil modulus ratio and poroelastic properties. A comparison with the plane strain theory is performed. The selected numerical results are obtained to analyze the influence of the major parameters on the torsional impedance at the level of the pile head. Finally, the dynamic torsional impedance of this study is compared with that for floating pile in elastic soil. 相似文献
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桩基础对邻近场地冲击荷载的响应分析 总被引：1，自引：0，他引：1
桩基础对邻近场地作用冲击荷载的响应本质上是桩-土组成的体系在冲击荷载下的整体动力相互作用问题。为了研究该问题,采用有限元法模拟冲击荷载引起桩基础的振动。利用通用有限元分析软件ABAQUS建立了有限元-无限元（FE-IFE）耦合分析模型,分析了冲击荷载作用时桩基础动力响应的规律,并对影响桩基础响应的因素进行了探讨。计算结果表明,桩的振动程度取决于冲击荷载作用间距和冲击荷载能量,而冲击荷载作用间距越远,桩的振动波长越长。 相似文献
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以西安地铁工程为背景,设计了穿越地裂缝隧道——地层动力响应试验模型,开展了地铁振动作用下穿越地裂缝隧道——地层相互作用的动力模型试验,揭示了地裂缝活动及地铁列车振动时对位于地裂缝处地层的动力响应规律。试验结果表明:在地裂缝未活动时,隧道拱顶位置的加速度响应与拱底相比,其值相对较小,表明地铁列车振动引发拱底部的振动加速度,通过衬砌传递至上覆岩土体时,加速度发生了显著的衰减;当地裂缝上盘下降时,隧道拱底及拱顶测点产生的振动响应比地裂缝未活动时明显更为强烈。表明地裂缝的活动对隧道结构振动特性具有显著影响;受地铁列车运行位置变化和地裂缝上盘下降的双重影响,地裂缝两侧土体振动加速度幅值有明显的差异,这会对隧道结构的振动特性造成不利影响,在设计中应采取适当措施,防止造成隧道衬砌的局部损伤或破坏。 相似文献
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为研究免共振沉桩过程对地表振动影响,采用密度放大法以消除模型桩弹性模量过大对计算效率的影响,在有限差分软件FLAC3D中建立了相应的连续振动沉桩模型,并和文献中的现场测试结果进行了比较,分析了激振力幅值和振动频率这两个施工参数对地表振动响应的影响。结果表明：密度放大法可有效提高数值模拟的计算效率,模拟沉桩7.0倍桩径（4.9 m）所需计算时间约为12.0 h,数值结果较好地模拟了现场测试中免共振沉桩的地表振动影响;激振力幅值和振动频率均主要对近场（水平距离为5.0倍桩径范围内）的地表振动有明显影响;临界沉桩深度与地表振动影响峰值相对应,该深度随水平距离先增大后趋于稳定;激振力幅值对临界沉桩深度的改变不明显,振动频率对远场临界沉桩深度则有较明显影响。 相似文献
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A new dynamic interaction factor for the analysis of pile groups subjected to vertical dynamic loads
Luan Lubao Zheng Changjie Kouretzis George Ding Xuanming Poulos Harry 《Acta Geotechnica》2020,15(12):3545-3558
Τhis paper presents an analytical method for calculating the steady-state impedance factors of pile groups of arbitrary configuration subjected to harmonic vertical loads. The derived solution allows considering the effect of the actual pile geometry on the contribution of pile-soil-pile interaction to the response of the group, via the introduction of a new dynamic interaction factor, defined on the basis of soil resistance instead of pile displacements. The solution is first validated against a published solution for single piles that accounts for the effect of pile geometry on the generated ground vibrations. Accordingly, we show that the derived soil attenuation factor agrees well with existing solutions for pile groups in the high frequency range, but considerable differences are observed in both the stiffness and damping components of the computed impedance when the relative spacing between piles decreases. Numerical results obtained for typical problem parameters suggest that ignoring pile geometry effects while estimating the contribution of pile-soil-pile interaction in the response may lead to inaccurate results, even for relative large pile group spacings.
相似文献20.
基于Abaqus软件64CPU并行计算集群平台,建立了车辆-轨道-高架桥-基础-地基耦合的三维有限元分析模型。得到了不同工况下列车运行时引起的地表振动特征,对地表振动振级随着与桥墩距离增大而衰减的规律进行了参数化分析,结果表明,随着列车车速的增大,地表振动振级明显增大;与空载时相比,列车乘客满载时仅靠近桥墩处的地表振级略微增大,对远处几乎无影响;列车车厢数量对地表振动振级的影响不明显;列车双线运行时引起的地表振动振级比单线运行时有明显的增大。扣件刚度的增大会略微减小地表振动振级。随着桩长的增加,地表振动振级有较大幅度的减小;增加桥墩的跨度能减小地表振动振级,但增加到一定值时再增加也不会有明显的减振效果;桥墩高度对地表振动振级无明显影响。随着场地土层剪切波速的增加,地表振动振级呈逐渐减小的趋势。 相似文献