Coal excavations performed in areas of shallow, thick sand can overburden the strata layers of the excavation site, resulting in fractures in the strata layers. Surface water, groundwater and sand layers can flow into mine goaf through the fractured rock and thus often lead to inrush of water and collapsing of sand. It is important to study the mechanical properties of water and sand in excavations sites under different conditions and the influencing factors of the water and sand seepage system. The viscosity of water-sand mixtures of various particle sizes were tested based on the relationship between the shear strain rate and the surface viscosity. A seepage system test was designed to analyze the permeability of water and sand in fractured rock. According to the seepage test, effective fluidity is in 10~(-8)～10~(-5)m~(n+2)·s~(2-n)/kg, while the non-Darcy coefficient ranges from 10~5 to 10~8 m~(-1) with the change of particle size of sand. Effective fluidity decreased as the particle size of sand increased. The non-Darcy coefficient ranged from 10~5 to 10~8 m~(-1) depending on particle size and showed contrary results.
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