【作者】 胡新发；

【导师】 何继善； 柳建新；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2012， 博士

【摘要】 桩的检测包括桩身完整性和承载力。对大直径端承型桩而言,当桩身完整、沉渣厚度满足规范要求、桩端持力层的性质满足设计要求的前提下,桩的承载力可认为合格。本文围绕如何采用轻便、快速、有效的方法对大直径端承型桩这三个方面的检测进行研究,摸索总结出了一整套针对大直径端承型桩的检测方法组合,取得了以下创新性的研究成果：(1)针对大直径灌注桩反射波波速测不准的问题,通过现场实验与理论分析,建立了考虑时间滞后的完整桩纵波波速计算公式、缺陷位置计算公式以及有助于判断桩身下部缺陷段缺陷的严重程度的平均波速计算公式。(2)利用小波分析的时频分析特点,将其用于基桩的低应变检测,在识别桩身下部缺陷、桩底沉渣、桩端持力层性质中有明显的优越性,取得了很好的效果。(3)针对反射波法检测嵌岩桩时,在一定条件下桩身下部缺陷、沉渣、桩端持力层缺陷等存在检测盲区,对桩身下部存在缺陷、沉渣的情况进行了数值模拟,了解反射波曲线特征,得到的结果能指导实际检测资料的分析；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进行组合检测的方法,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。(4)针对嵌岩桩加固后是否达到要求的问题,提出通过比对加固前后的反射波及其小波分解各频带的波形和动刚度的变化,并将它们与正常桩的波形和动刚度对比,必要时用静载荷试验或钻芯法验证的方法检测加固效果。结合工程实例,证实本方法的可行性,并能取得很好的效果。研究表明,加固后,原缺陷在反射波及其小波分解各频带的波形上无反映,动刚度值在正常范围时,可认为加固效果良好。(5)针对目前声波透射法检测桩身混凝土质量缺陷所采用分析方法的不足,提出了一种采用多参量信息反映桩身混凝土质量缺陷的新方法—多参量综合分析法。该方法假定混凝土的缺陷信息量是与缺陷有关的表征量的线性组合,将突出混凝土缺陷的问题,归结为计算表征量的相关矩阵的最大特征值和相应的特征向量；通过趋势分析,除去缺陷信息量背景值,得到缺陷信息量的异常值。结合工程实例,证实本方法的可行性,并能取得很好的效果。研究表明：采用不同参量间的权系数计算混凝土缺陷信息量,得到的异常曲线比单因素分析法和多因数概率分析法能更合理地反映桩身混凝土质量情况；避免单因素分析法引起的误判、漏判；缺陷信息量异常值越大,混凝土的缺陷越严重。更多还原

【Abstract】 Pile testing includes integrity and bearing capability of pile. For large diameter end-bearing pile, it is agreed that good integrity and bottom sediment meeting standard specification and normal characters of pile bearing stratum are the key factors ensuring bearing capability of pile. The research of the three aspects of large diameter end-bearing pile testing is discussed, and the combination of multi-method is formed. The following creative achievements have been obtained through this research:1. In order to solve the uncertainty of P-wave velocity, three formulas for the velocity of perfect pile and for the site of defect and for the average velocity of defect in the lower section of the pile are deducd, with which the severity of the defect can be estimated.2. Wavelet analysis, as the typical represent of time-frequency analysis, has been applied to low-strain reflected wave, which has obvious advantages in recognition of the abnormalities of defect in the lower section of the pile and bottom sediment and characters of pile bearing stratum.3. With the help of numerical simulation of defect in the lower section of the pile and of bottom sediment, reflected wave curve characteristics and the size of non-detection zone are understood. In practical engineering testing, the combination of low-strain reflected wave method, frequency-initial velocity method and core drilling method should be used to do the end-bearing piles and reinforcement effect testing so that they can verify mutually and the reliability of the testing can be enhanced. The abnormalities of the reflected curve of pile bottom or of obvious low dynamic stiffness would be considered too thick bottom sediment or abnormal characters of pile bearing stratum, and then which would be validated with core drilling method.4. In order to study the reinforcement effect of the rock-socketed piles,through deeply investigating the changes of the reflected curve and its independent wavelet decomposition frequency bands and the dynamic stiffness before and after reinforcement and comparing the reflected curve and its independent frequency bands and the dynamic stiffness after reinforcement with those of the perfect piles under the same conditions, validating with static load testing or core drilling method if necessary, the analysis and qualitative evaluation on the reinforcement effect of rock-socketed piles are carried out. Based on the practical examples, the feasibility of this method was proved and very good results can be achieved. The results show that the reflection of the original defects in the reflected wave was disappeared with the dynamic stiffness in the normal range, can be considered a good reinforcement effect.5. In view of the disadvantages of the present analysis methods of cross-hole sonic logging to detect extent and location of pile defects, A new method called comprehensive analysis of multi-parameter was put forward to assess the concrete quality using several parameters associated with defects. Assume that the defect information is linear combination of the parameters, emphasizing defects boils down to calculating the largest eigenvalue and corresponding eigenvectors of the correlation matrix of the parameters. After the trend analysis, the background values were removed from the defect information to get abnormal values of the defect information. Based on the practical examples, the feasibility of this method was proved and very good results can be achieved. As a result, the abnormal curves of the information of concrete defects, which calculated with different weights of the parameters, can be more reasonable to assess the concrete quality than single factor analysis and numerous factor probability method,and avoid misjudgment caused by single factor analysis.In addition, the greater the abnormal value, the more serious the concrete defect is.更多还原