DEFORMATION MONITORING OF OVERBURDEN BASED ON DIS-TRI-BUT-ED OPTICAL FIBER SENSING

As a kind of distributed fiber optic sensing technology based on Brillouin back-scattering, BOTDR was used to monitor the deformation of overburden during the coal mining. Taking a working face in Huainan mining area as an example, distributed optical sensing cables were implanted into the overburden of coal seam by drilling. By grouting the borehole with cement, it is assumed that the deformation of sensing cable and the overburden should be the same. During the mining, strain distribution of sensing cables was obtained periodically. By analyzing the strain distribution and its variation, the deformation and failure of overburden were investigated during the mining. The maximum tensile strain along the borehole is about 5m depth with the value of 8350με.The maximum compressive strain is -550με at the borehole depth of 37m. Strain distribution shows a good correlation with the structure of the strata. A relatively larger tensile strain can be observed in the soft strata, such as mudstone. However, the strain in the hard strata, such as sandstone, the cable strain is smaller and usually ompressive. The maximum deformation of the strata along the borehole is 34mm. The loosened circle of roadway is about 6m. The results show that distributed optical fiber sensing technology can obtain the deformation and its variation of the overburden, which can provide reliable data for the safe and efficient mining.