Abstract
Coal permeability plays an important role in the simultaneous exploitation of coal and coal-bed methane (CBM). The stress of mining-disturbed coal changes significantly during coal mining activities, causing damage and destruction of the coal mass, ultimately resulting in a sharp increase in permeability. Conventional triaxial compression and permeability tests were conducted on a triaxial creep-seepage-adsorption and desorption experimental device to investigate the permeability evolution of mining-disturbed coal. The permeability evolution models considering the influence of the stress state and stress path on the fracture propagation characteristics were established based on the permeability difference in the deformation stages of the coal mass. The stress-strain curve of the coal was divided into an elastic stage, yield stage, and plastic flow stage. As the axial stress increased, the permeability decreased and then increased, and the curve’s inflection point corresponded to the yield point. The permeability models exhibited a good agreement with the experimental data and accurately reflected the overall trends of the test results. The results of this study provide a theoretical basis for coal mine disaster prevention and the simultaneous exploitation of coal and CBM.
Highlights
Coal-bed methane that is called gas is an unconventional natural gas generated during coalification and accumulates in coal seams
The results of this study provide a theoretical basis for coal mine disaster prevention and the simultaneous exploitation of coal and coal-bed methane (CBM)
The stress state of mining-disturbed coal is changed by mining activities, causing elastic deformation and even damage and changing the coal permeability [14,15,16]
Summary
Coal-bed methane that is called gas is an unconventional natural gas generated during coalification and accumulates in coal seams. CBM is a clean and efficient energy source, it is a disaster factor and greenhouse gas in coal mining. The exploitation of CBM can reduce the occurrence of coal mine accidents and greenhouse gas emissions and minimize energy shortages. The permeability of coal seams is the decisive parameter affecting CBM exploitation. In China, coal seams are characterized by high in situ stress, strong adsorption features, and low permeability, making the extraction of CBM relatively difficult [1, 2]. Improving the permeability of coal seams is crucial for the efficient extraction of CBM. When coal seams are mined, the stress of mining-disturbed coal undergoes complex changes, resulting in the deformation, damage, and permeability enhancement of the coal. The simultaneous exploitation of coal and CBM has been widely promoted and applied in China
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