Abstract
In this research, the particle size distribution and permeability of saturated crushed sandstone under variable axial stresses (0, 2, 4, 8, 12, and 16 MPa) were studied. X-ray Computed Tomography results revealed that particle crushing is likely to occur considerably as the axial stress is approaching 4 MPa, which results in the change of pore structure greatly. During compression, the particle size distribution satisfies the fractal condition well, and the fractal dimension of particle size distribution is an effective method for describing the particle crushing state of saturated crushed sandstone. When the axial stress increases from 0 MPa to 4 MPa, the fractal dimension of the particle size distribution increases rapidly by over 60% of the total increase (0–16 MPa), and the permeability decreases sharply by about 85% of the total decrease. These results indicate that 4 MPa is a key value in controlling the particle size distribution and the permeability of the saturated crushed sandstone under axial compression. The permeability is influenced by the initial gradation of the specimens, and a larger Talbot exponent corresponds to a larger permeability.
Highlights
Due to the large permeability of crushed rocks, flow catastrophes and water inrush accidents can be triggered in the discontinuous zones of aquifers in underground coal mines [1, 2]
The permeability of crushed rock is determined by the pore structure, which has a close relationship with the particle size distribution [3]
The results show that particle size distribution is mainly affected by the applied stress, particle size, particle mixture, and other environmental factors
Summary
Due to the large permeability of crushed rocks, flow catastrophes and water inrush accidents can be triggered in the discontinuous zones of aquifers in underground coal mines [1, 2]. Miao et al [1] analyzed the seepage properties of broken sandstone with different porosities; Ma et al [2, 3] obtained the relationship between the permeability and variable grain diameters under variable axial displacements They investigated the effect of particle size mixture on the seepage properties and compaction behaviors of crushed mudstones. These studies show that the seepage properties of the fractured rocks are mainly affected by rock type, porosity, permeability, and other factors. These previous studies did not take into account the quantitative relationships among the particle size distribution, the porosity, and the permeability. The results can provide a scientific basis for the prevention of water inrush accidents in coal mining
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