【作者】 张志强；

【导师】 易南概；

【作者基本信息】 大连海事大学 ， 桥梁与隧道工程， 2012， 硕士

【摘要】 在基桩完整性检测中,利用低应变法准确的确定桩身缺陷位置、判断缺陷的种类和缺陷的严重程度是低应变法亟待解决的问题。为提高反射波法检测基桩完整性的准确性,有必要通过建立实验模型并结合数值分析,系统地研究桩身参数、地质条件对低应变反射规律的影响。本文主要做了以下几项工作：介绍了低应变反射波法一维波动理论,应力波的相互作用,应力波的三维效应,应力波受桩周土影响的拟合方程,用波阻抗法判断应力波传播规律的方法以及时域分析法判断缺陷位置。建立了完整桩、断桩、扩颈、缩颈、离析以及夹泥夹石六种模型桩；阐述了低应变法试验前需要注意的问题；通过研究桩周地质环境对完整桩反射波的影响,得到了桩周土与应力波衰减之间的规律；通过大量的实验研究,提出了较为准确的判断断桩位置的方法；通过研究孔底沉渣厚度不同时低应变反射规律的变化,总结了判断孔底沉渣时需要注意的问题；通过比较三种不同的局部扩颈桩低应变反射波曲线,获得了局部扩颈大小与低应变反射波之间的关系；通过三种局部缩颈桩波形图比较,获得了局部缩颈大小与低应变反射波之间的关系,并提出了判断局部扩颈和局部缩颈的方法；测得了三种不同离析层厚度的桩的波形图,确定了离析层厚度对低应变反射波的影响规律；提出了利用低应变反射法检测夹泥、夹石桩的方法。介绍了ANSYS/LS-DYNA动力显式分析方法的基本原理,并建立了此方法的有限元数值模型。对断桩、扩颈、缩颈、离析、桩周边界条件不同五种情况进行了模拟,通过与实验结果进行对比,提出了将现场试验和数值模拟结合起来,综合考虑准确的试验材料参数和桩周地质环境参数,利用数值模拟结果反推缺陷种类、缺陷位置以及缺陷程度的方法。更多还原

【Abstract】 In the Pile Integrity Testing, there is an important unresolved issue which is using Low Strain Method to fix the pile defect, judge the kind and level of the defect. To improve the accuracy of testing the pile integrity with Reflected Wave Method, it is necessary to build an experiment model with numerical analysis to systematically study the impact of pile parameter and geological conditions on the low strain reflection rule. Several aspects are made in this paper.One-dimension wave theory, the interaction of the stress wave, three-dimension effect of the stress wave and the fitting equation of the stress wave impacted by the pile in soil are introduced. Meanwhile the methods judging the stress wave propagation rule with the wave impedance and the defect location with time domain analysis are recommended.Six models of integrate pile, broken pile, expanding, necking, segregation, clod in pile and stone in pile are built. Besides some issues which should be pay more attention before the experiment with Low Strain Method are dedicated. Meanwhile the relationship between the pile in soil and the stress wave attenuation by studying the impact of the pile geological conditions on the reflected wave is proposed. According to amount of experiments, a more accurate method of judging the broken pile location has been got; Some issues have been summarized which should be paid more attention by studying the thickness of the sediment in the bottom of the hole; The relationship between the size of the local expanding and the low strain reflected wave has been got by comparing three kinds of low strain reflected wave curve of the local expanding; The relationship between the size of local necking and Low Strain Reflected Method has been got by comparing the oscillograms of three kinds of local necking, including the method to judge local expanding and necking. The pile oscillograms of three kinds of segregation thickness are reviewed and the rule of the impact about the segregation thickness on the low strain reflected wave is confirmed. The method to detect clod in pile and stone in pile with low strain reflected method is summarized.The limited numerical model of this method based on ANSYS/LS-DYNA dynamic explicit analysis is built. Meanwhile through the comparison of the experimental results with the models such as broken pile, expanding, necking, segregation, the conditions around the pile, a new method which combines with field test and numerical simulation, also including the exact experimental material parameter and the parameter of the geological conditions around the pile has been got. This method reversely judges the defect kind and location, as well as the defect level.更多还原