Study On The Stability Of Coal Pillar And The Water Inrush Mechanism In The Fault Zone Areas

This paper engineering background is Pingshuo Coal Industry Company the Anjialing II mine29213working face, the main coal seam is9#seam, the working face influenced by faults, dip angle75°, fault throw is about70meters, extends840meters. Because there is a big distance fault displacement, the footwall Ordovician aquifer was moved close to the seam on the hanging wall. When the working face advancing, the face will be affected by mining, water inrush channel may be formed between bottom plate and the fault. This is a serious threat to the safety of the stope production. In this paper uses laboratory experiments, theoretical analysis and numerical simulation method to study the working face strata behavior and predict the water inrush situation.Collecting the geological and hydrological data, through indoor rock permeability test, analyze the permeability of impermeable layer, the Ordovician aquifer rock and the fault zone rock. Waterproof pillar theoretical analysis based on the Mohr-Coulomb strength criterion, SMP strength criterion and Lade strength criterion. Coal pillar reasonable width mechanics formula were established and obtained the security impermeable coal pillar width range from30to33meters. Using FLAC-3D numerical simulation software, obtained security pillar width is30meters, analysis of the variation of the stress and displacement field, determine there is a15meters safe distance between the fault activation position and the greatest damage depth, verified the rationality of setting30meters width of coal pillar.Create a mechanical model of water inrush. When setting in the30meters coal pillar, calculate the damage depth near the side of the fault is18meters much smaller than the distance between peak stress propagation line and seam. So there is a certain distance between bottom plates fractured zone and fault, will not form a channel of water inrush, this result is consistent with the results of numerical simulation analysis. Through established a thin plate model, this paper analyzed the variation of extreme water pressure in the bottom plate impermeable layer under the affecting by mining. After theoretical calculation the variation of extreme resistance water pressure by the process of seam had advanced600meters can be obtained, the number is being close with about1.7MPa. According to the Coal Industry Taiyuan Desgn and Research Institute survey data, the maximum hydrostatic pressure Pw of the bottom plate impermeable layer (Benxi Formation Bottom boundary) is1.329MPa, smaller than the extreme resistance water pressure1.7MPa, prove the safety of the stope and provide a theoretical basis for the mine production safety.