Modeling of permeability and fracture-scale nonlinear response of coal body under multiple stresses
GUAN Shiju1,2, LIU Huihui1, 2*, YU Bin1, 2, LI Tingfang1, 2, WANG Zhiji1, 2, XU Chao3
(1. School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China; 2. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; 3. School of Emergency Management and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China)
Abstract：The evolution of coal permeability results from the interplay between external stress, pore pressure, and adsorption stress, with varying responses of the coal body′s fissure scale and permeability control under each stress condition. Therefore, establishing a coal permeability model that accounts for the individual stress factors and the nonlinear response of fissure scale is crucial for accurately and quantitatively characterizing permeability evolution. To this end, this paper first investigates the evolution characteristics of permeability and volumetric strain in the coal body under the influence of single stress factors: external stress, pore pressure, and adsorption stress. It then deduces the dynamic evolution model of the fracture compression coefficient corresponding to each stress and establishes a new model for coal permeability. The results indicate that: (1) Coal permeability exhibits a rapid initial decrease followed by a gradual decline as external stress and methane pressure increase, while under pore pressure influence, coal permeability shows a slow increasing trend. (2) The permeability models of coal mass under effect of external stress, pore pressure and adsorption stress respectively are established. Among them, fracture volume compressibility coefficient of coal mass under external stress follows an exponential decay relationship with external stress, fracture volume compressibility coefficient of coal mass under pore pressure exhibits an exponential growth relationship with pore pressure, and fracture volumetric strain of coal mass under adsorption stress conforms to a Langmuir-like equation with gas pressure. (3) A coal permeability model is developed that comprehensively considers the nonlinear response of fracture scale and individual stress factors. Compared to conventional permeability models, the newly established model demonstrates better alignment with experimental permeability data, providing a more accurate characterization of the influence of individual stress factors on coal permeability.
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2026, Vol. 45 
