Influence of particle size on non-Darcy seepage of water and sediment in fractured rock

Surface water, groundwater and sand can flow into mine goaf through the fractured rock, which often leads to water inrush and quicksand movement. 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 under different particle sizes, different concentration was tested based on the relationship between the shear strain rate and the surface viscosity. Using the self-designed seepage circuit, we tested permeability of water and sand in fractured rock. The results showed that (1) 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; (2) effective fluidity decreases as the particle size of sand increased; (3) the non-Darcy coefficient ranges from 10(5) to 10(8) m(−1) depending on particle size and showed contrary results. Moreover, the relationship between effective fluidity and the particle size of sand is fitted by the exponential function. The relationship between the non-Darcy coefficient and the particle size of sand is also fitted by the exponential function.