Study of Downward Crack Closing of Clay Aquiclude in Shallowly Buried Coal Seam
According to the mechanical experiment on soil samples from an aquifuge,the stress and strain curve and permeability as well as expansibility of Lishi loess and Hipparion red clay have been obtained.Based on similar simulation of solid and liquid coupling and the similarity of whole stress and stain curve and water reaction feature of clay aquifuge,the law of long wall mining the crackd zones in overburden strata of the shallowly buried seam is revealed.The result shows thatupward crackand crackare the main factors affecting the aquifuge stability,and the downward crack is the main channel of the subsurface ground water flowing.And the expansibility of clay and loess with water will cause crack closing,which will slow down the development of downward cracks.The mechanical model of downward crack is set up and the criterion of its closing is presented,which have provided a theoretical basis for further studying the stability of the aquifuge and water preserved mining.