基于BOTDR的基坑变形分布式监测实验研究

Experimental study of foundation pit monitoring using BOTDR-based on distributed optical fiber sensor

在基坑开挖和支护过程中深部土体的水平位移监测是一项十分重要的工作。布里渊光时域反射计(BOTDR)是近年来国际上研发成功的一项新型的分布式光电传感技术。通过该技术,将传感光纤按照一定的工艺粘贴在埋置于土体中的测斜管上,由传感光纤实测的应变分布,可以实现深部土体水平位移的在线监测。通过室内的模型模拟试验,由实测的光纤应变可以准确地得到测斜管上任意一点的水平位移。结合南京市某深基坑进行的现场试验,探讨了基于BOTDR的分布式光纤传感器应用于基坑深部土体水平位移监测的具体施工工艺,验证了该技术在实际工程中应用的可行性。

Deep soil movement monitoring is a very important task during the excavation and sustainment of large foundation pit. Brillouin optical time domain reflectometry （BOTDR） is a newly developed distributed measurement technique with characteristic of distribution, long distance and duration. It has been used to monitor the structure deformation and temperature. In this paper, the principle of the BOTDR was introduced firstly; and then an experiment was given to study the feasibility of applying BOTDR to foundation pit monitoring. In laboratory the deformation of inclinometer tube was measured by BOTDR through the sensing optical fiber bonded on it; and the measured results were contrasted with ones measured by strain gauges. It＇s shown from the comparison results that the strain measured by BOTDR is consistent with that by strain gauges. The successful application of the method introduced here into practical foundation pit monitoring demonstrates the feasibility and effectiveness of the method.