Experimental study on the displacement sensor of coal roadways roof settlement based on distributed fiber optic sensing

Roof displacement monitoring is an important means to ensure roof stability and prevent roof accidents of Coal Roadways (CRs). In this paper a new sensor of roof settlement displacement (RSD) monitoring of CRs’ roof by the pre-stretched optical fiber (PSOF) laid out horizontally at fixed points was proposed. The principle of the sensor is to qualitively and quantitively characterize the RSD by the Fiber Optic Strain (FOS) which is measured based on distributed fiber optic strain measurement. Through theoretical analysis, the mathematical expression for quantifying RSD is derived. The correctness of the sensor is verified by the indoors FOS experiments and the field monitoring of CRs’ roof in Yinying Coal Mine. This new sensor can be applied not only to the roof of CRs, but also to the displacement monitoring of other structures with the similar settlement presentation.