Abstract
To study the effects of compression rate and weight ratio of sandstone to mudstone on permeability, water flow tests were performed on crushed rocks using an in‐house designed and built water flow apparatus. Seepage properties of sandstone and mudstone were tested on specimens under six axial displacement levels. The weight ratios of the six specimens of sandstone to mudstone were set to 1 : 0, 4 : 1, 3 : 2, 2 : 3, 1 : 4, and 0 : 1. A non‐Darcy law was adopted to calculate the permeability in the experiments based on verification of the Reynolds number. Non‐Darcy flow is found to be most significant when the axial displacement or mudstone content increases. The permeability in the experiments is found to be in the range of 9.1 × 10−15–9.492 × 10−13 m2, which is calculated from a quadratic polynomial fit between the flow velocity and pressure gradient. A compression rate of 28.6% and weight ratio of sandstone to mudstone of 60% are found to be key values affecting permeability. When the axial displacement of specimen A (1 : 0) increases from 10 mm to 30 mm, the compression rate (ratio of axial displacement to original specimen height) increases from 9.5% to 28.6%, and the permeability decreases by 83.8% to 1.534 × 10−13 m2. When the axial displacement is 10 mm and the content of mudstone is increased from 0% to 60%, the permeability decreases by 77.1% to 2.172 × 10−13 m2.
Highlights
Underground mining can lead to strata movement and loss of equilibrium of the stress state, causing deterioration in the mechanical behavior of surrounding rocks [1,2,3]
It was found that a piston velocity of 10 mm/ min corresponds to the first axial displacement level in the water flow test, and the 10 mm/min curves show more significant changes than other curves as time increases
E positions and distributions of the constituent grains changed as the tests continued, leading to the unstable state of the curves. e 10 mm/min curve in Figure 4(a) and the 20 mm/min curve in Figure 4(c) both show a significant decrease before the water flow stabilized. is resulted from the evolution of water flow channels
Summary
Underground mining can lead to strata movement and loss of equilibrium of the stress state, causing deterioration in the mechanical behavior of surrounding rocks [1,2,3]. E method considers factors such as flow intensity, condition of waterbearing formations, suspended materials contained in the water, and protective coal pillars. Advances in Civil Engineering of mine water inrush accidents [17], and the study of permeability of rocks is the foundation of such. Benavente et al [19] studied the water permeability of 15 sedimentary rock types and proposed a model for calculating permeability that considers factors such as flow velocity, water properties (density and viscosity), porosity, interfacial tension, and contact angle. E experimental results provide an improved understanding of the mechanism of water inrush through such preferential pathway materials and serve as a reference for prediction and control of water inrush accidents Water flow tests were performed on crushed rocks containing sandstone and mudstone. e experimental results provide an improved understanding of the mechanism of water inrush through such preferential pathway materials and serve as a reference for prediction and control of water inrush accidents
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