Sutdy On Development Law Of Coal Seam Mining"Infiltration Zone" Of Qidong Coalmine The Unconsolidated Layer

The unconsolidated layer of Qidong coalmine on a mine field scale are thick commonly, its bottom hosting a layer of aquifer, called generally "the fourth aquifer" or "bottom aquifer". The aquifer mainly consists of non-consolidated sand soil with a better permeability and sand gravel and so on, which directly occur on coal measure bedrock top, and the aquifer water has a very high confined property when water head is superior. Since the mine went into operation,17times accidents that unconsolidated confined aquifer water inrush into working face through the roof has successively occurred. By analyzing the working face, where these cases’water inrush accident ocurred, leaved enough waterproof pillar according to the relevant regulations, combined with water-burst face exploitation hydro-engineering geological conditions study, the paper studied hydro-engineering geological conditions and development law of bedrock roof cracks propagation seepage zone(simply called " infiltration zone")under high confined loose layer water, also discussed the applicability and selectivity of water flowing fractured zone height calculation formula of "buildings, water, railway and coal pillar and coal mining regulations" according to "infiltration zone" development law.Taking7131working face as an example, the unconsolidated layer and bedrock hydro-geological and engineering geological conditions were analyzed, working face overburden bedrock weathering zone preexisting fissures development law were studied, and lithology composition features were analyzed statistically. By simulating the test results of similar hydro-engineering geological condition’s Zhangji coalmine infiltration zone height test site,7131working face"infiltration zone" height were calculated9.21m. Based on Elastic Mechanics and Fluid Mechanics theory, the extension mechanism of high confined water to bedrock weathering zone were studied under the circumstances that high confined loose aquifer covered directly bedrock weathering zone, and "infiltration zone" height composed by bedrock preexisting fissures and extension height influenced by water pressure were calculated10.35m.According to "infiltration zone" development law research result, the paper took "infiltration zone" bottom as "the fourth aquifer" bottom and water flowing fractured zone roof, calculated and leaved waterproof pillar for7131working face according to the correlation formula of "buildings, water, railway and coa pillar and coal mining regulations" according to "infiltration zone". Meanwhile, taking inrush7114working face as an example, waterproof pillar height were calculated according to "infiltration zone" principle, by comparing with working face water inrush’s coal and rock pillar height, waterproof pillar height of mining working face calculated according to "buildings, water, railway and coal pillar and coal mining regulations" under high confined loose aquifer were proved smaller than the actual value. Waterproof pillar height calculated by "infiltration zone" principle is scientific and reasonable.