Mechanism Research On Dynamic Destabilization Of Interlayer Rock-pillar Induced Disasters In Extremely Steep Coal Seam

Dynamic disasters emerged frequently due to special geological settings in extremely steep coal seam. Hugely interlayer pillar has occurred between the steep coal seams in Wudong Colliery. Failure and destabilization of the rock-pillar would be one of mechanical source induced the dynamic disasters in the mining spaces, which seriously affects safety operation in the colliery. The difference and complication on instability of interlayer pillars are determined by two reasons including storage conditions and high levels of segmentation stage pillar mining method. In order to achieve the safe mining, the research on dynamic instability of interlayer pillar between extremely steep seams induced the relevant disaster should be paid more concern.Taken interlayer pillar between extremely steep seams in Wudong colliery into consideration, factors of dynamic disasters could be analyized and achieved through geology investigation. Based on the structure of extremely steep coal-rock mass, mechanical model was built up. With the numerical calculation software of FLAC3 D, reasonablility of mechanical model has been validated. With acoustic emission, ground penetrating radar and other monitoring techniques, disaster-prone regions were predicted in the interlayer pillar, and valid measures for disaster prevention were proposed.Geological survey showed that thickness of coal seam and roof were large in such a ―hard floor-seam-roof‖ setting and integrity of the interlayer pillar was well. All these factors provided basic emerging setting for dynamic disasters. Mining depth of South panel in Wudong Colliery has reached 350 m which was critical mining depth for frequently emerging disaster. The mechanical model on stress leverage rotation-effect(SLRE) was built based on structure of extremely steep coal-rock masses. SLRE provided power source for dynamic disasters. Numerical computation showed that activation occured in the bottom of interlayer pillar, and the sporting trends of interlayer pillar was significant. The deformation characteristics and leverage rotation of interlayer pillar is consistent. According to field monitoring data analysis, energy release of coal-rock masses dispalyed an overall "flat-raised-gently" variation characterisitcs, and a certain periodicity(23-30 days) was shown simulateously. Stages of dynamic destabilization for interlayer pillar would be fallen into disturbance burst, stress squeezing, damage destabilization and stress redistribution. Combining monitoring results and the mechanism on dynamic destabilization induced the disasters, the scope of induced hazard-prone region under SLRE has been established, respectively, the scopes were the region from +500 m to +510 m being excavated coal seam in B1-2 and from +475 m to +485 m neighboring pillar in B3-6. With all above mentioned prediction results, dynamic disasters prevention measures were proposed like watering in coal seam, watering in interlayer pillar, deeply-hole blasting in the pillar, and determining the relevant parameters. After Evaluation, the prevention of dynamic disasters was scientific and effective.The research results provide reference for prevention and treatment of dynamic disasters under similar mining settings.