Dynamic monitoring the deformation and failure of extra-thick coal seam floor in deep mining

Abstract

With the increasing depth of mining, the disasters of water inrush above confined aquifers tends to increase annually, which seriously threatens the safe mining of coal seam, especially the extra-thick coal seam floor in deep mining. This research is to study the characteristics of deformation and failure of extra-thick coal seam floor in deep mining, the field measurement is carried out by the distributed fiber optic sensing technology (BOTDR) and the 3D resistivity method of studying coal field in China. The axial strain curves and resistivity distribution characteristics of the mining face at different depth under the coal seam floor are obtained by extending the working face. Through the comprehensive comparison and analysis of monitoring data in the monitoring boreholes, the characteristics of deformation and failure of extra-thick coal seam floor in deep mining can be ascertained. The results indicate that the comprehensive monitoring technology can effectively distinguish the characteristics of stress excess, distortion and failure of rock during the process of the working face mining. The influence range of mining advance stress is about 36 m, the failure depth of coal seam floor is about 12 m and the depth of mining disturbance deformation is about 26 m. The formation of the deformation and failure of the coal seam floor have obvious stratification, which are mainly influenced by the formation structure and the lithology of the rock strata. The comprehensive monitoring technology can effectively capture the fine features of the deformation and failure of the coal seam floor, which is valuable for extra-thick coal seam floor in deep mining.