Two-tier Mining Ground Deformation Simulation

As an important underpinning industry of nation’s economy, mining plays animportant role in supporting the sustainable development of our country. But theenvironmental problems with mining industry are severely concerned. The instabilityof goaf area will largely change the landform and contribute to the surface depressions,which are potential threats to ground buildings. Therefore scholars pay much attentionto the goaf stability, especially the ground subsidence in goaf area.Based on monitoring data from Dongyuan mining area, the surface subsidence inmultiple coal seam conditions has been studied, and the influences from exploitationto the strata deformation are also discussed. The major contents and results are asfollowings:(1) On the premise of fully study on the engineering geological conditions, theprobability calculus method is utilized in the evaluation of surface subsidence, and thefigure of influence scope in gob area is drawn. The results shows that, with theexploitation of19b and21coal seams, the maximum ground depression value reachesto3.05m, which has a certain gap comparing with the monitoring data,2.215m. Therehas a theoretical uncertainty in the calculation of probability calculus method inmultiple coal bed area.(2) Numerical simulation method has been taken with FLAC3D software in theevaluation of Dongyuan gob area. The results indicating that in terms of the maximumsurface subsidence and the regularities of strata deformation, numerical simulationresult has a high similarity with the actual situation, demonstrating the effectivenessin the evaluation of gob area’s depression with numerical simulation method.(3) On the basis of the above research, with chosen physical and mechanicalparameters, effective factors, such as the length and width of exploitation, dip angle ofcoal seam, thickness of coal seams, buried depth, etc. have been considered in theinfluence of surface subsidence study. Finally a expression formula has been given tocalculate the maximum ground depression with the several factors, which will have asignificant influence on the evaluation of ground depression in the multiple coal seam regions.The research of surface subsidence in gob area still has some flaws, and in thecondition of multiple coal seam areas, theoretical calculation method is largely limited.Based on the monitoring data of Dongyuan mining area, the mechanism of surfacedeformation is discussed, and the results may contribute to the evaluation ofgeological hazard in mining area.