Research On Dynamical Mechanism Of Shallow And Closed Distance Coal Seams Mining Locating At Sublevel Of Room And Pillars Goaf

With the Jurassic shallow seam mining in northern Shaanxi expanding, the shallow coal resource is gradually depleted and the coal seam mining has been transferred to the lower coal seam in the shallow coal seam. Since the short mining distance, the upper left coal seam coal pillar mining face produces a great impact on the lower portion of the lower coal seam mining of coal pillar working face.During the process of the lower coal seam mining the coal pillar,it often occurs dynamic pressure disasters, resulting in crushing accident.In this thesis, a close shallow coal seam longwall goaf by room and pillar coal pillar width in the process of dynamic pressure phenomena and particularity pressure frame of the accident, combined with the lower part of northern Shaanxi Coal Group Hanjiawan coal seam conditions, the use of Physical synthesis means similar simulation experiments, computer simulation and theoretical analysis, from the rock stress field changes and the perspective of migration out of the room and pillar mining face area hydrodynamic mechanism analyze the causes of accidents may lead to dynamic pressure. It reveals the dynamic pressure phenomena mechanism Lower Coal mining face crossing coal pillar. The lower part of the procedure room and pillar mining face in the region, under static loads Face Abutment pressure dynamic loads and pillar overprinted, and always in front of the face. Room and pillar mining area caused during the sinking floor, room and pillar region rock legacy coal columns at key swing instability, instability of key rock and coal pillar portion layer rock movement in the Z direction is no longer consistent with the upper part of overburden strata movement faster, its kinetic energy to the lower strata, coal pillar portion of the kinetic energy transmitted through the key rock pillar by pillar action to lower inner cover rock, these three superimposed in front of the working face, the formation energy parks. Pillar floor strata in high concentrated stress on rock bearing capacity is reduced. At the same time, due to the disturbance and the space provided during the face advance, so gather the sudden release of energy to the face, making Face dramatic dynamic pressure phenomena.Dynamic pressure occurs with a sudden, violent sex, and support for security protection face great dangers. The lower portion of mining face through its upper room and pillar area, must be pre-processed within legacy pillar. The key factor analysis by computer simulation of coal pillar width is under influence of dynamic pressure, and therefore the lower portion of mining technical measures put forward by means of the dynamic pressure ahead of the pre-split room and pillar area not controlled instability of coal pillar.