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Date of Publication:2009-01-01

Journal:煤炭学报

Volume:34

Issue:9

Page Number:1203-1207

ISSN No.:0253-9993

Abstract:The disadvantage of existing gob porosity or permeability models was
   analyzed,which generally simplify porosity or permeability as
   discontinuous distributed or one-dimensional continuous parameter.Based
   on the theory of roof strata collapse,the distribution model of
   continuous and heterogeneous porosity and permeability was deduced.By
   incorporating the Brinkman-Forchheimer-extended-Darcy model especially
   for air flow in permeable gobs,and applying the stream
   function-vorticity approach of porous/fluid composite system,the
   mathematic model of seepage filed involve the mining face and the gob
   was established.The simulation of a "U" ventilation retreating longwall
   face shows that the porosity have a two dimension distribution rule both
   on the gob incline direction and face working direction.Within 10 m away
   from the coal mining face,the gob porosity reaches about 0.4 due to the
   supporting of coal pillar and supports.For reason of roof strata
   collapse,the porosity decreases quickly along the gob direction,finally
   to about 0.1 in the gob boundary.On the other hand,the leakage filed
   show an asymmetric airflow pattern perpendicular to the face centerline
   in the gob.The leakage airflow returns back in the front of the middle
   of the working face.Moreover,the leakage intensity reduces gradually
   along gob depth direction,and the intensity almost unchanged in the
   place of 40 m away from working face.

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