关于动力试桩问题

本文对动力试桩问题的几种方法,如波动方程法、凯司(CASE)法及凯普威普(CAPWAP)法作了较为详细的介绍和论述,并着重叙述了波动方程法及其计算结果。文中对动力试桩设备和各种类型的打桩分析仪,包括加速度及测力设备等也作了较为详细的介绍。文末对动力试桩方法的误差也进行了论述。     

基于径向不变假定的现浇大直径管桩纵向振动响应频域解

假定各物理量沿径向不变化,建立了低应变瞬态集中荷载作用下现浇大直径管桩振动响应的计算模型和波动方程。采用Laplace变换法,求得了波动方程的频域解析解,采用Fourier逆变换求得了时域响应。将文中解计算结果与三维频域解析解进行了对比分析,文中解的入射峰-反射峰时间差与三维频域解差别很小,说明对于PCC桩这种大直径薄壁管桩,采用径向不变假定对计算结果几乎没有影响。因此,在PCC桩低应变检测波形分析时,采用基于径向不变假定的二维解是完全合理的。将文中二维频域解的计算结果与二维时域解的结果进行了对比分析,结果表明,2种解在入射波、第一个桩底反射波、第二个桩底反射波峰值大小和到达时间非常吻合,这说明考虑环向位移与否对计算结果没有太大的影响,研究PCC桩低应变动力响应的问题时忽略水平方向的位移是完全可以的。     

Dynamic response of a pile embedded in a porous medium subjected to plane SH waves

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.     

低应变下变阻抗薄壁管桩动力响应频域解析解

管桩低应变完整性检测时,桩顶一点受到瞬态集中荷载的作用,其动力响应问题是一个三维波动问题。基于三维波动理论,建立了任意段变阻抗薄壁管桩动力响应的计算模型和波动方程,结合初边值条件,采用Laplace变换法求得了该波动方程的频域解析解,采用Fourier逆变换求得了时域响应。将计算结果与三维有限元结果进行了对比分析,解析解的计算结果和三维有限元结果较为接近,两者在入射波峰、缺陷反射峰和桩底反射峰处都较为吻合,两种方法位移响应曲线基本相同。给出了桩顶不同点的动力响应,并探讨了高频干扰问题。对变截面桩和变模量桩的动力响应特性进行了分析。     

基桩低应变动测中"短程多次反射波"的特征研究--兼论横波在检测中的应用前景

短程多次反射波对基桩动测资料解释常会形成干扰，并为人们所忽视。以往国内外文献对此未见详细讨论。这里通过对解析解的理论计算与物理解释，阐明了这种干扰波的波形与强度，取决于缺陷的性质、位置、尺寸以及桩周土的剪切波速，且其不能被频域滤波所消除。因此在一定的客观条件下，这种干扰波会对资料的定性与定量解释造成困难，在实际工作中应予以注意。通过计算与实例，说明了物探资料解释的多解性问题在基桩动测中同样存在，用实测资料与理论曲线拟合法解释，可提高对资料认识的全面性，从而减小这种困难。根据文献通过理论计算说明，若测量扭转波则这种干扰将会大大减小，仅从此角度亦能说明纵横波联合检测是基桩动测的发展方向之一。     

桥梁桩低应变反射波法检测及分析探讨

低应变反射波法检测技术作为一种成熟的桩身完整性检测方法,正在被广泛的应用到工程实践中。本文结合铜陵市沿新路互通立交工程桩低应变检测实例,简要介绍了低应变反射波法的基本原理,假定桩为一维线弹性直杆,建立了桩-土动力模型,结合现场测试数据对几个典型实测波形进行了分析,并且通过拟合计算,分析了桩的完整性。     

旋挖钻孔灌注桩低应变检测与分析

本文以水阳江特大桥的旋挖钻孔灌注桩低应变检测为例,分析了桩头浮浆及桩身扩径对低应变检测曲线的影响。桩头浮浆可以产生多次反射波或使波形畸变。桩身扩径产生扩径上界面的反相反射波和下界面的同相反射波;桩身扩径很大时,无桩底反射波及扩径下界面反射波,只有扩径上界面的多次反射波。     

山地和岩溶地区端承桩质量检测与加固技术研究

针对嵌岩桩桩底存在沉渣时,采用常规的低应变反射波法可能观测不到其同相反射信号,桩底软弱夹层（或溶洞）的顶面倾角接近或不小于45º时,反射法检测不到桩底软弱夹层（或溶洞）的反射信号。为弥补以上不足,提出了用低应变反射波法、频率-初速度法和钻芯法对端承桩质量及缺陷桩的加固效果进行组合检测。当反射波波形曲线异常或动刚度明显偏低时,可认为桩底沉渣较厚或桩端持力层性状异常,再用钻芯法验证;建立了桩身下部缺陷段的平均波速计算公式,有助于判断缺陷的严重程度;通过对比缺陷桩加固前后的反射波曲线和动刚度值,并将它们与其他同条件下正常桩对比,检验缺陷桩的加固效果     

A new analytical model to study the influence of weld on the vertical dynamic response of prestressed pipe pile

This investigation is concerned with the mathematical analysis of a viscoelastic prestressed pipe pile embedded in multilayered soil under vertical dynamic excitation. The pile surrounding soil is governed by the plane strain model, and the soil plug is assumed to be an additional mass connected to the pipe pile shaft by applying the distributed Voigt model. Meanwhile, the prestressed pipe pile is assumed to be a vertical, viscoelastic, and hollow cylinder governed by the one‐dimensional wave equation. Then, analytical solutions of the dynamic response of the pipe pile in the frequency domain are derived by means of the Laplace transform and impedance function transfer method. Subsequently, the corresponding quasi‐analytical solution in the time domain for the case of the prestressed pipe pile undergoing a vertical semi‐sinusoidal exciting force applied at the pile top is obtained by employing the inverse Fourier transform. Utilizing these solutions, selected results for the velocity admittance curve and the reflected wave curve are presented for different heights of the soil plug to examine the influence of weld properties on the vertical dynamic response of prestressed pipe pile. The reasonableness of the theoretical model is verified by comparing the calculated results based on the presented solutions with measured results. Copyright © 2017 John Wiley & Sons, Ltd.     

An analytical solution for wave propagation in a square pile due to transient point load

This paper presents an analytical solution for wave propagation in a square pile due to transient point load. The differential equation of dynamic equilibrium is established considering propagation of waves in both vertical and transverse directions. The soil resistance is simulated by Voigt model. The three-dimensional analytical solution is deduced by using Fourier transform and the separation of variable method. The arithmetical results of the proposed solution show that the velocity responses along the radial direction at the pile top are highly non-uniform. In addition, Young’s modulus and the pile side length exert undisputable influences on the velocity responses.     

灌注桩超声波跨孔法检测技术探讨

超声波中专孔法是以纯纵波声速在无限介质内的传播规律为理论基础,发展起来的一门灌注桩质量检测技术。超声波检测的原理、现场检测、检测过程中应该注意的问题、对检测数据的分析研究和桩身质量判定方法,是章文讨论的重点。     

现浇薄壁管桩低应变动力检测适应性探讨

现浇薄壁管桩是一种大直径的管桩,在低应变检测时必然存在平截面假定不满足以及桩头三维效应的问题。无桩帽管桩低应变检测时由于激发了非轴对称的弯曲模态,并不是达到一定的深度平截面假定就会满足,各截面不同的点会受到不同程度的高频干扰,桩顶90°点受到了较小的高频干扰,低应变检测时激振点与传感器夹角为90°时更容易得到清晰的反射波信号。解析解和有限元解的结果均表明,带帽桩在桩帽的动力响应信号能看到明显的桩底反射和缺陷反射时距离桩心不同点上所感受的高频干扰的频率一样,速度振幅不同,距桩心0.50 （ 为桩半径）的点受到最小的干扰。     

动力打桩一维波动方程的改进及其工程应用

对桩的可打入性进行准确的分析和预测是打桩施工的关键环节,同时也关系到整个工程的进度与成败.近年来,在海洋工程和港口工程中都出现了大直径、超长桩,由于这种桩的重量大对桩的可打入性有显著影响,考虑桩身自重和桩周土阻力,对打桩分析的一维应力波动方程进行改进、推导.采用有限差分法求解波动方程,编制计算程序结合实际工程进行打桩分析,分析结果与实测数据吻合较好,表明经改进的动力打桩一维波动方程能很好的预测桩的可打入性及打桩过程中桩身应力分布情况.     

Poroelastic model for pile–soil interaction in a half‐space porous medium due to seismic waves

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.     

Dynamic characteristics of a large‐diameter pile in saturated soil and its application

This study theoretically investigates the dynamic response of an end‐bearing pile embedded in saturated soil considering the transverse inertial effect of the pile. The saturated soil surrounding the pile is described by Biot poroelastic theory, and the pile is represented by a Rayleigh‐Love rod because both the vertical and radial displacements at the soil‐pile interface are considered. The potential function decomposition method and variable separation method are introduced to solve the governing equations of the soil, in which the vertical and radial displacement components are coupled. The governing equation of the pile is solved using the continuity conditions at the pile‐soil interface. Next, the velocity admittance in the frequency domain and the velocity response in the time domain at the pile top are presented based on the Laplace transform and inverse Fourier transform, respectively. Subsequently, the reduced solution is compared with a 1‐dimensional model solution to verify the validity, and the influences of the slenderness ratio of the pile on the transverse inertial effect of the pile are analyzed. Moreover, Poisson ratio, the slenderness ratio of the pile, and the pile‐soil modulus ratio are studied. Finally, the theoretical and measured curves in the engineering project are compared, and the results demonstrate the good application prospects of the solution presented in this article.     

表面波法确定卵石土地基承载力模型研究

利用统计学的原理,对卵石土地基动力触探击数和剪切波速的关系进行了研究,推导了它们之间的二次多项式、幂函数和指数函数回归方程。通过对比研究发现,二者之间具有良好的指数函数相关关系。为了验证该指数函数回归模型的可行性,选择了相似场地进行面波检测试验,试验结果与勘探结果完全吻合。研究结果表明,应用表面波法不但可以进行卵石土地基分层,而且还可以定量地评价其地基承载力。     

桩基质量分析及动力检测方法研究

本文分析了两类常见的沉管灌注桩和人工挖孔灌注桩的工艺特点，桩基质量问题的产生原因及动力检测方法，同要准确地判断两类桩基质量问题，必须准确计算缺陷的位置，对桩基的工艺特点和施工过程有深刻的认识，对动力检测理论有透彻的理解。同时，对人工挖孔灌注桩动力检测的特殊性进行了专门分析。     

高应变动力试桩法对端承管桩检测的分析研究

针对高应变动力试桩法对端承管桩检测准确性低的问题,结合多年实际检测经验,归纳总结出端承管桩在土中的各种受力特点及其实测曲线特征,进行对比分类及分析,提出对该类桩的测试要点以及分析解释方法。     

跨孔超声波在混凝土灌注桩质量检测中的应用

文章阐述超声波检测混凝土缺陷的原理，结合工程实例介绍跨孔超声波检测混凝土灌注桩质量的具体操作技术、资料的综合分析和对桩基质量的评价方法，以及对跨孔超声波检测结果的验证。     

Analytical solution for distributed torsional low strain integrity test for pipe pile

Low strain integrity tests (LSITs) are the most popular non-destructive methods for pile testing. However, traditional LSITs have encountered unprecedented challenges as the need for long pile and existing pile testing keeps multiplying. Compared to traditional longitudinal excitations, the torsional wave is less influenced by the velocity attenuation effect and can be subjected at the pile shaft for existing piles. Distributed torsional LSIT is proposed in this article with the presentation of the corresponding analytical solutions that exhibiting the velocity responses along the pile shaft. The solution is verified with previous simplified theoretical and rigorous finite element method (FEM) answers. At the end, the application of this method is exhibited through the identification of necking and concrete segregation defects on pipe piles, which shows the advantage of this method on long pile testing.