基于分布式光纤测温技术的灌注桩完整性实时检测机理

The real-time detection method of bored pile integrity based on distributed optical fiber temperature measurement technology is presented based on some existing problems of pile foundation detection technology, such as undetected, error, susceptibility to interference and unable to real-time and long-term detection etc. Through a variety of methods and means, the optical fiber temperature change and the mathematical relationship are studied including the relations between temperature rise, thermal conductivity and pile defects, respectively, and the basic principle of this method is revealed. . Laboratory test and theory analyses are carried out to study the heat transfer substance of heating fiber and pile body, deduce the theoretical equation of this detection method. Through model test, field test, and numerical simulation, some influence on temperature rise of fiber including heating power, environment temperature, water content, laden silt, settled material and crack properties is studied. The quantitative relation of the fiber temperature rise with these factors is got. Then, the qualitative and quantitative formula between thermal conductivity, temperature rise and pile body integrity is given. The relationship about grade of pile with temperature rise and thermal conductivity is analyzed base on theoretical analysis, experimental results, and numerical simulation results. According to the difference of temperature rise and thermal conductivity, the evaluation system about pile body integrity is established. This project can lay solid theoretical foundation for engineering application of this detection method, promote detection technology development of bored pile, and achieve speedy, real-time and long-term detection of pile foundation.

针对灌注桩完整性检测技术中存在漏检错判、易受干扰、无法实时长期检测等问题，提出基于分布式光纤测温技术的灌注桩完整性实时检测方法。并通过多种方法与手段，深入研究光纤温升变化规律，以及温升、导热系数分别与桩身缺陷的数学关系，深入揭示该方法的机理。.采用室内试验与理论分析，研究加热光纤与桩身的传热实质，推导该方法的检测微宏观理论方程；采用模型试验、现场试验与数值模拟，研究加热功率、环境温度、含水量、夹泥量、沉渣、离析及裂缝特性等对光纤温升的影响规律，得到它们与光纤温升的定量关系，以此为基础，建立导热系数、温升与桩身完整性的定性定量判断关系式；综合理论分析、试验与数值模拟结果，分析桩的类别与光纤温升及导热系数之间的关系，建立以温升及导热系数差异为判断依据的桩身完整性评估体系。通过本项目的研究，为该检测方法的工程应用奠定坚实的理论基础，推进灌注桩完整性检测技术的发展，实现桩基快速、实时与长期检测。

针对灌注桩完整性检测技术中存在漏检错判、易受干扰、无法实时长期检测等问题，提出基于分布式光纤测温技术的灌注桩完整性实时检测方法。并通过多种方法与手段，深入研究光纤温升变化规律，以及温升、导热系数分别与桩身缺陷、光纤温升与桩土截面、桩土岩土介质性质数学关系，深入揭示了该方法的机理。通过理论研究，分析了水泥水化热、内置热源工况下，桩体热传导特征；分别研究了内置光纤热源光纤传感系统的布置优化，桩土界面、桩周岩土介质影响下桩体温度分布特征。通过多组物理模型试验和现场试验，研究了不同缺陷桩的模型制作及含不同缺陷工况下桩体温度分布特征；针对桩土结构面、桩周岩土介质环境对桩体温度特征的影响进行了研究；研究了DTS应用于桩基检测工程实践的可操作性及存在的问题。通过建立足尺完整桩、夹泥桩、缩颈桩、断桩的数值模型，分别研究了含不同缺陷桩的热传导规律，并与理论与物理模型试验进行对比，完善了DTS检测不同缺陷桩的参数设置及分析方法；通过建立光纤布置方式对桩体热传导影响的数值模型，进一步验证和完善了光纤检测系统的优化布置理论。通过本项目的研究，为该检测方法的工程应用奠定坚实的理论基础，推进灌注桩完整性检测技术的发展，实现桩基快速、实时与长期检测。