Abstract: 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.

Key words: BOTDR, optical fiber, distributed monitoring, foundation pit, inclinometer tube