Accurate monitoring of coal pillar deformation based on distributed optical fiber

Abstract

In many structural deformation monitoring applications, determination of the response length of embedded optical fibers is difficult due to the use of strain integration method, which increases the measurement errors. For systematic investigation of the deformation law of coal pillars under mining action, distributed fiber optic technology was used herein to analyze its response length. This study discusses how non-uniform strain distribution can increase the accuracy error of fiber optic displacement measurement, and verifies the effectiveness of theoretical analysis by using coupled FEM–DEM numerical simulation method. Furthermore, the relationship between the Brillouin gain spectrum characteristics of different sampling points and the non-uniformity of strain distribution was explained. To reduce accuracy errors, a new method was proposed herein for determining the response length of optical fibers. The feasibility of this method was verified through indoor experiments. Next, this method was applied to the deformation monitoring of coal pillars in a section of Huojitu Well. By using the proposed method, the deformation of coal pillars can be accurately monitored.