When the coal mining conducts under the overlying strata with thick aeolian sand,the connected fractures were formed by the failure of overlying strata.Then the accident is always caused by the unstable flow of water and sand in the fractures.Therefore,the study of two-phase flow of water and sand in the fractures becomes the basic task to prevent the disaster of water and sand inrush.In this paper,the permeability experiment system was designed based on the seepage behavior of two-phase fluids of water and...