Monitoring and analysis of overburden deformation and failure using distributed fiber optic sensing

BOTDR, a kind of distributed fiber optic sensing technology, is employed to monitor the overburden deformation and failure during the coal mining. As an example in Huainan mining area, the layout and the installation technique of the sensing cables for overburden monitoring are designed. The sensing cables are implanted into the overburden by drilling installation technique. The strain distribution of the sensing cables is collected regularly according to the mining schedule. The characteristics and variation of the strain distribution are studied to reveal the relationship between the strain distribution and strata. The strain distribution is not uniform, which is relatively larger in the soft strata, such as mudstone, than that in the hard strata, such as sandstone. The deformation and failure of the overburden are also obtained. Based on the strain distribution and the breakpoint position of the cables, the heights of the caving zone and fractured zone are 12.5 m and 40.0 m respectively with the consideration of the overburden lithology and stratum combination above 13-1 coal seam.