低应变反射波法检测大直径嵌岩桩的技术探讨与分析

根据低应变应力波反射法基本原理,分析了低应变反射波法检测大直径嵌岩桩的技术缺陷,结合几个工程检测实例,对反射波法检测大直径嵌岩桩的技术进行了探讨。     

应力波法桥梁桩基础无损检测简介

主要介绍应力波法对桥梁桩基础完整性的无损检测 ,简明阐述检测原理 ,通过对典型波形的分析 ,介绍应力波法波型的判读方法。     

桩基低应变检测技术及操作技巧

基本原理反射波法是根据应力波在一维弹性介质中传播时遇阻抗发生变化时,应力波在变化处发生反射和透射现象,根据这一原理进行分析阻抗的变化情况。当桩长远大于直径时,可视为一维杆弹性介质体     

应力波反射法在基桩检测中的应用

通过对应力波反射法在混凝土灌注桩检测上的应用效果．并且根据反射波曲线的不同形状，从理论上和施工中进行分析、判读。     

应力波反射法在基桩检测中的应用

通过对应力波反射法在混凝土灌注桩检测上的应用效果,并且根据反射波曲线的不同形状,从理论上和施工中进行分析、判读.     

低应变反射波法检测桩基的质量控制

成桩质量检测中反射波法(应力波法)以其基本原理简单、快速无损、判读直观、准确度较高、费用低等特点在桩基检测中推定缺陷类型及其位置、桩长校核、推定混凝土强度等得到了广泛应用。从检测的各个方面论述了低应变反射波法桩基检测的质量控制要点。     

低应变法检测嵌岩桩的几点认识

用低应变法检测嵌岩桩,若桩底出现明显同相反射,多数因桩底缺陷引起。而区分是桩还是持力层的缺陷,主要看反射的起跳时间在2L／C之前还是之后。当桩的变径及入岩反射对测试影响很大时,应进一步用钻芯法检验。     

PIT对公路桥梁桩基缺陷的判断与评价

本文根据ＰＩＴ的工作原理，结合我国公路现场桩基检测的工程实践，对桩身中应力波的传播、波速和桩长的计算，测试结果的分析与处理进行了探讨。在此基础上，对ＰＩＴ反射波进行桩身结构完整性测试的波形誊中的有关问题进行讨论，以供桩基检测技术人员参考。     

隧道典型衬砌缺陷的电磁波数值模拟及有效识别

隧道初期支护与二衬之间、初期支护与围岩交界之间是隧道衬砌最易出现缺陷的区域,衬砌脱空及脱空、渗水、砼混合体典型缺陷的波形响应特征是隧道工程试验检测的难点和重点。基于高频Ricker子波的探地雷达(GPR)能够有效地检测衬砌缺陷的位置,但对这些典型缺陷的严重程度无法定性,难以为设计加固与运营维护提供精确指导。从麦克斯韦方程组出发,建立了复杂典型的衬砌缺陷数值模型,改进衬砌缺陷模型的吸收边界条件,提出卷积完全匹配层吸收边界条件,以提高典型衬砌缺陷GPR探测的计算精度,更真实地模拟开放的问题空间,并分别从典型衬砌缺陷的电场分量波场快照、分量成像结果等方面开展数值试验。结果表明:单分量波场快照和成像结果,能有效地剔除探地雷达检测的虚假反射异常,提高了探地雷达探测图谱解释的准确性,为隧道衬砌的缺陷整治和维护加固提供更精确的指导。     

基于二维傅立叶变换的圆杆弹性波模式识别及分离

采用有限元模拟了声发射弹性波在高强钢丝内的传播过程,通过提取不同空间位置节点振动时程曲线组成二维幅值序列,由二维傅立叶变换获得了频率-波数域等值线图,并与理论频率-波数图进行了对比分析。结果表明:采用有限元方法能够精确地模拟弹性波在高强钢丝内的传播过程,不同时刻应力云图清晰反映了波在钢丝内的反射和叠加效应;基于二维傅立叶变换的频率-波数图与理论值吻合良好,可以有效地进行耦合波形模式识别和分离,从而实现复杂问题简单化。     

桥梁预应力孔道压浆质量检测现状及新技术研究

分析现有预应力孔道质量检测方法的优缺点及使用范围,结合弹性波全长法检测技术,提出全长法压浆质量普查、超声波缺陷专项检查相结合的检测方法,并经过缺陷处置,形成了完整的孔道检测及处理方法体系,弥补了孔道检测方面的不足。     

超声反射波法检测水泥混凝土板厚度的研究

为实现超声平测法反射波起跳点的识别,采用两阶段法予以实现.通过分析声波的传播特性,应用数学分析方法排除表面波、横波的干扰,通过预估检测结构面的厚度,判断反射纵波到达的大致范围,结合波形分析,确定反射纵波的到达时间点.在此基础上,考虑到尺寸效应,在实验室模拟研究进行了验证.应用该方法可以较好的实现水泥混凝土板厚度的检测.     

路面雷达检测技术初步研究

路用探地雷达的基本原理是向地下发送脉冲形式的高频电磁波。电磁波在地下介质传播过程中．当遇到存在电性差异的地下目标体,如空洞、路面结构层分接口等时,电磁波便发生反射,返回到地面时由天线接收。在对接收到的雷达波进行处理和分析的基础上,根据接收到的雷达波形、强度和双程走时等参数可推断地下目标体的空间位置、几何形态。采用地质雷达对路面脱空缺陷雷达检测进行初步研究,得到了路面脱空缺陷识别方法。     

Separation method of bi-directional reflected waves and oblique incident regular waves

Wave reflection is one of the key problems affecting wave simulation quality in ocean engineering basin. The deep ocean engineering basin is equipped with two-sided segmented wavemakers and two wave absorbing beaches, which are located opposite to wave generators to reduce wave reflection effects. When an oblique longcrested wave is made by two-sided segmented wavemakers in a wave basin, two bi-directional reflected waves with the same azimuth but opposite propagation directions are generated. According to this feature, based on the two-point approach developed by Goda, a method to separate an incident regular wave from two bi-directional reflected waves using three wave gauges is proposed. The validity of this method is proved by numerical composite waves. The results indicate that the method can separate incident wave from reflected waves effectively. The method can be used to determine the reflection coefficient and verify the capacity of wave absorbing beaches in deep ocean engineering basin.     

基于模糊综合评判法和有限元法的超声波测桩评定方法

在建立评价集的隶属函数的基础上,采用加权平均法对超声波测桩进行模糊综合评价;再用有限元法计算桩身不同位置在相同缺陷的情况下的桩基竖向承载力,计算出不同位置的缺陷影响系数;将模糊综合评价的结果与相应的缺陷影响系数相乘,并将所有的乘积结果值相加,得到一个考虑桩基缺陷位置的综合评定。与其他超声波测桩评定方法相比,该方法以桩基的竖向承载力为依据,并考虑了缺陷位置,是一个更全面、更准确的评定方法。     

Influences on the spatial directivity of acoustic vector sensor by finite cylinder baffle and future prospects about eliminating the effects

The directivity of acoustic vector sensor can be distorted by the sound diffraction wave of baffle. According to Helmholtz integral equation, the directivity of acoustic vector sensor under the condition of finite cylinder baffle is calculated by using boundary element method (BEM). Considering the problem of nearly singular integrals of BEM, the exponent parts of fundamental solutions are expanded in trigonometric functions. The singular and the nonsingular parts are separated: the nonsingular parts are calculated by Gaussian integral method; the singular parts are regularized by subsection integral method. Then the surface integrals are reduced into line integrals along the elements?? contour which can be calculated by Gaussian integral method. The sound diffraction field of a plane wave under the condition of finite cylinder baffle at different frequencies and incident angles is calculated, and the characteristics of directivity of pressure and vibration velocity at different frequencies are analyzed. The experimental data are treated and the errors between the experimental and theoretical results are analyzed. Finally, according to the research results about the influences on the directivity of acoustic vector sensor by baffle at present, some future prospects about eliminating the effects of sound diffraction field by baffle are presented.     

沥青混合料最大密度测试方法的试验研究

沥青混合料最大密度是沥青混合料配合比设计中至关重要的参数.其获得的准确性直接影响体积参数真实性,进而影响到最佳沥青用量甚至是施工质量的控制.文中通过对国内外现有测试最大理论密度方法的总结与分析,给出一种测试沥青混合料最大理论密度比较可靠的测定条件.此外,综合分析不同计算法和实测法所得结果的关系,认为按我国2004版规范所述的计算公式,并利用合成集料有效密度得到的最大理论相对密度的计算方法与真空实测法较为接近.     

低应变反射波法在基桩完整性检测中的应用

桩基的质量具有高度的隐蔽性,低应变反射波法作为基桩完整性无损检测方法之一,具有数据采集快速、方便,结果分析简单及费用较低等优点,被检测单位所采纳。简要介绍低应变反射波法的原理、桩身缺陷位置的确定、桩身完整性的判定以及一些典型波形的分析。     

锚杆无损检测技术在梅大隧道的应用研究

锚杆无损检测技术是基于一维弹性波反射原理,推断出锚固工程中锚杆的长度和检测锚杆施工质量的方法。通过对无损检测技术的理论研究,归纳出常见的锚杆波形特征,并结合工程抗拔试验进行论证,为无损检测技术在公路隧道的应用推广提供了一定的理论和实践依据。     

Full waveform inversion method for horizontally inhomogeneous stratified media

Full waveform inversion method is an approach to grasp the physical property parameters of underground media in geotechnical nondestructive detection and testing field. Using finite-difference time domain （FDTD） method for elastic wave equations, the full-wave field in horizontally inhomogeneous stratified media for elastic wave logging was calculated. A numerical 2D model with three layers was computed for elastic wave propagation in horizontally inhomogeneous media. The full waveform inversion method was verified to be feasible for evaluating elastic parameters in lateral inhomogeneous stratified media and showed well accuracy and conver- gence. It was shown that the time cost of inversion had certain dependence on the choice of starting initial model. Furthermore, this method was used in the detection of nonuniform grouting in the construction of immersed tube tunnel. The distribution of nonuniform grouting was clearly evaluated by the S-wave velocity profile of grouted mortar base below the tunnel floor.