Research on Cracks Zone of Clay Aquiclude in Overburden

Abstract

The mining induced cracks in aquiclude are major factor of water resisting property and mining safety under water. The aquiclude is composed by loess layer and red clay layer in Yushuwan coal mine. The water reaction property of clay and loess of aquiclude is tested by soil mechanics method. The permeability coefficient of loess will be 0.856 m/d and clay will be 0.434 m/d in Yushuwan mining condition. The dilatability coefficient of loess is 16.1% and the clay is 14.6%. Through physical solid-liquid simulation with whole stress-stain similarity for Yushuwan shallow coal seam mining, the distribution of “downward crack zone” and “upward crack zone” is found to be the major factors of aquiclude stability and the “downward crack” is the main channel of the subsurface ground water flowing down. Furthermore, the downward crack closing in wet clay is revealed and the closing length is about 30% of the downward crack length. The expanding of clay and loess with water are principal factors of downward crack closing. This work will provide the theoretical base for aquiclude stability research.