The Floor Damage-fracture Mechanism Research On Mining Above Confined Water

Law of water-inrush before confined water analyzed systematically on the basis of extensive reading from home and abroad references. Mining underground pressure and confined water pressure jointly lead to the fracture of coal seam floor rock damage whose damage process is actually a micro-crack initiation, expansion, through until a macroscopic crack, leading to the floor rock instability and failure to form a water guide channel, resulting in influx of water to the work site, caused grave casualties and economic losses and threatened the safety production. Internal micro-cracks and even macro defects such as faults, caves and other geological formations distributed due to the complexity of floor rock. Floor rock strength, deformation and failure are related to the crack propagation. In this paper, damage and fracture mechanics theory are used to analysis the law of floor fracture and destruction depth; UDEC numerical simulation software used to simulate the floor impermeable ability on the conditions of different combination of coal seam floor strata; coal seam floor strata stress, displacement and crack propagation law analyzed under the process of mining. Innovation achievements are as follows:(1) The expansion of internal fissures and destruction depth under the mining rock pressure and hydrostatic pressure were analyzed based on the theory of elasticity and mining pressure, combined with damage and fracture mechanics.(2) The combination of floor strata divided into "soft, hard, soft, hard" according to the Plats rock classification and SUN TUAN Mine geological data. Law of variability of stress、displacement and fissures distribution of floor strata "three zones" through the simulation of UDEC software.(3) Along the stope dip direction, failure characteristics of single working face analyzed; and also the floor rock mass stress, displacement and fracture development under the interaction of the stress field of dual-face.(4) With the determination of seam depth and confined water pressure, the composition of floor strata divided into:①"soft, hard, soft, hard"②"hard, soft, hard, soft"③"soft, soft, hard, hard"④"hard, hard, soft, soft"⑤"soft, hard, hard, soft"⑥"hard, soft, soft, hard". The floor failure characteristics and water blocking ability of six cases were compared.