Study On The Hazard-Formation Mechanism Of Key Strata Compound Breaking Mining Under Unconsolidated Confined Aquifer With High Water Pressure

There is a layer of unconsolidated confined aquifer with high water pressure which form with unconsolidated sand and grit at the bottom of thick quaternary topsoil in some east china north china coalmine.It exists at the top of bedrock.In recent years,some coalmine have happened several accident as supports crushing and water inrushing when mined the under unconsolidated confined aquifer with high water pressure.It has caused significant economic losses and a serious threat to coal mine production safety. According to the traditional theory the pathogenesis of these supports crushing and water inrushing accidents can't be properly explained. According to a large number of field measurements and laboratory simulation this paper revealed the movement law of above strata and the pathogenesis of the workface supports crushing and water inrushing accidents under unconsolidated confined aquifer with high water pressure.The study found:for the liquidity and flow recharge of confined water,while excaving coal the load acting on the top interface of the overlying rock do not performance significantly lower like usual but remained constant, the unconsolidated confined aquifer could transfer the the load acting on the top interface of the overlying rock. Due to the effect of load transfer of the unconsolidated confined aquifer, on condition of unconsolidated confined aquifer, the adjacent key strata are prone to compound breakage when mining under the unconsolidated confined aquifer with high water pressure, which leading to the bedrock broken as a whole and sliding instability of the overlying structure and bring about supports crushing and water inrushing. The height of water flowing fractured zone developing to the unconsolidated aquifers is much larger than the value of"coal mining order for buildings, water, rail and major roadway pillar leaving and coal of holding down".This is the root causes of the supports crushing and water inrushing accidents when mining under unconsolidated confined aquifer with high water pressure in some minecoal.Based on the pathogenesis of these supports crushing and water inrushing accidents when mining under unconsolidated confined aquifer with high water pressure, risk assessment methods and countermeasures under unconsolidated confined aquifer with high water pressure was proposed and hazardous area was projectioned when mining under unconsolidated confined aquifer with high water pressure on QiDong mine which avoid a similar disaster from happening again. It completely reversed the situation of supports crushing and water inrushing accidents continuously when mining under unconsolidated confined aquifer with high water pressure on QiDong mine and ensure safety in production and recovery workface after supports crushing and water inrushing accidents in 7₁14 working face.It has achieved remarkable economic benefit.