Abstract
Water inrush disasters in mining frequently occur under the influence of confined water-bearing fault zones. Therefore, investigating the fault water inrush mechanism is necessary to reduce the number of occurrences of this type of disaster. In fault zones, the rock is highly fractured, and the mechanism of water conduction is complex. In this research, the seepage mechanism of fractured sandstone in fault zones is studied through experiments, and the results indicate that the permeability coefficient of fractured sandstone depends on the axial stress and particle size. The relationship between the permeability coefficient and axial stress was an exponential relationship. Then, a water-rock coupled model is proposed based on the experimental results, which considers the different water flow patterns during water inrush disasters. Finally, a numerical simulation combined with the water-rock coupled model is conducted to investigate the fault water inrush mechanism of a case study, and the results reveal that when water inrush disasters occur during mining, two types of conditions are required. One is that the connection among the fractured zone of the coal seam roof, fault fracture zone, and aquifer fails, and the other is that the connection among the fractured zone of the water inrush prevention pillar, fault fracture zone, and aquifer fails. This study contributes to an increased understanding of the mechanism of water inrush disasters and the design of water inrush prevention pillars.
Highlights
Fault zones are the outcome of active tectonic movement that occurs for a long period of time; fault zones have the following characteristics: (1) there are a large number of fracture surfaces in the fault fracture zone; (2) there is a lack of integrity and association between the structural fracture surfaces and rock mass that can result in flow deformation; (3) highly developed fractures are present, and the rock is highly fragmented in the fracture zone
The aforementioned fault zones can act as water inrush channels between the confined water-bearing strata and adjacent working faces in the mine [1, 2]; the latter can result in water inrush accidents if no preventative measures are implemented
Li et al [3] proposed that an excessive amount of fracture displacement and fault seepage erosion, which is caused by confined water in key layers of fault zones, constitute the floor water inrush mechanism of fault zones based on a structural layer model
Summary
Fault zones are the outcome of active tectonic movement that occurs for a long period of time; fault zones have the following characteristics: (1) there are a large number of fracture surfaces in the fault fracture zone; (2) there is a lack of integrity and association between the structural fracture surfaces and rock mass that can result in flow deformation; (3) highly developed fractures are present, and the rock is highly fragmented in the fracture zone. Certain experiments and studies have been conducted to investigate the seepage properties of fractured rocks [25,26,27,28,29,30]; the seepage properties were not associated with the fault water inrush mechanism These investigations were mainly focused on continuous and quasi-continuous media and neglected the presence of a water-bearing fault in the mining zone; the physical and mechanical properties of rocks and rock masses are greatly affected and different from those of rocks and rock masses without faults. The water-rock coupled model is extended based on the experimental results, and the water-rock coupled process is proposed, as shown in Figure 2(b). ird, numerical simulation is conducted to analyze the fault water inrush process, and the calculation process is shown in Figure 2(c). e research methods are introduced
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