Permeability and seepage stability of coal-reject and clay mix

This paper presents an experimental investigation into the permeability and seepage stability of the granular coal-reject mixed with clay, which is affected by clay content, axial pressure, and the use of geotextile. Laboratory seepage tests were performed to determine the coefficients of permeability under both Darcy’s and non-Darcy’s flow conditions. The critical hydraulic gradients of coal-reject with different percentages of clay, axial pressures and geotextile were also tested. The results indicate that the coefficients of permeability, k, and global permeability, K, decrease while the critical hydraulic gradient increases with increasing clay content and axial pressure. The permeability and the critical hydraulic gradient start their radical changes when the clay content exceeds 10% of the total dry weight of the sample. The placing of a layer of geotextile on the bottom of specimen can decrease the permeability and significantly improve the seepage stability of the coal-reject and clay mixture.