Study on Factors Affected to Stability of Water Prevention Coal Pillar in Steep Inclined Seam Mining

In order to have a safety mining in the steep inclined seam under a water body, based on the geological condition of the hydrological project in the steep inclined seam of the South No.2 Mining Block in Longhu Mine, a discrete element UDEC2D numerical calculation was applied to analyze the factors affected to the stabi lity of the water prevention coal pillars for the mining operation in the steep inclined seam. The results showed that with the mining thickness of the steep inclined seam i ncreased and the coal strength decreased, the falling down scope of the water prevention coal pillar would be increased in tendency.The key stratum existed in the over burden strata and the broken and rotary of the rock beam in the immediate roof both caused the falling down scope increased of the water prevention coal pillar.When t he elastic modulus of the backfill mass reached at 0.5 GPa, the falling down and failure scope of the water prevention coal pillar would be reduced by 54.3%.Therefore, according to the data calculation results of the site, a roof control technology with coal rejects self sliding backfill and grouting bound backill mass was determined for t he mining goaf in the steep inclined seam.Meanwhile the reinforcement measures of the water prevention coal pillar would effectively ensure the stability of the water pr evention coal pillar during the mining period of the steep inclined seam.