Experimental study on non-Darcy seepage of water and sediment in fractured rock

Due to the excavation of coal seam with shallow depth,large seam thickness,thin bedrock and thick sand layer,the failure of overburden strata can usually induce the connected crack. Owing to the movement of surface water or groundwater,the sand layer flows to mine goaf through the fractured rock,which often leads to the disaster of water inrush and sand collapse. In order to study the permeability law of water and sand flows in the fractured rock,the set test system of water-sand seepage in fractured rock was designed. The result shows that the mixture of water and sand can be regarded as power-law fluid as particle size is less than 0. 180 mm and the concentration of sand is less than 80 kg / m3 . Along with the enlargement of particle size of sand and mass concentration,the consistency coefficient be- comes greater. The relationship between velocity and pressure gradient can be described by binomial relation. Effective fluidity Ie -mass concentration ρs and non-Darcy β-mass concentration ρs belong to power-exponent function, which means the increase of mass concentration will result in the increase of effective fluidity Ie and the decrease of non-Darcy factor β. Mass concentration of sand has more influence on the permeability parameters compared to the particle size of sand.