Accurately predicting the long-term evolution of coal permeability is crucial for the safety of coalbed methane extraction. This study aims to develop and validate a coupled damage–creep–seepage model, while critically examining its theoretical underpinnings and practical limitations. A novel constitutive model was developed based on continuum damage mechanics and the Nishihara model, establishing a rigorous link between microscopic damage, macroscopic creep, and permeability evolution. The model’s theoretical framework was then tested against a series of meticulously designed multi-path creep–seepage experiments. The experiments revealed that permeability evolution is governed by a dynamic competition between confinement-induced compaction and deviatoric-stress-induced shear dilation. The model successfully captured these phenomena, and a multi-round cross-validation confirmed its high predictive accuracy within specific stress domains. More profoundly, the analysis uncovered two critical characteristics of the model: 1) the key damage parameters, Fm and mm, are not intrinsic material constants but highly stress-dependent coefficients, serving as macroscopic representations of the underlying micro-mechanics. 2) The model, in its current form, represents an effective phenomenological framework for a complex, fully coupled strain–damage process. This research provides a robust model for predicting coal’s creep–seepage behavior, supported by profound mechanistic insights from targeted experiments. It critically identifies the stress-dependent nature of the model’s parameters, which not only defines the model’s application boundaries but also paves the way for its future evolution from a phenomenological tool to a physically based predictive framework. The findings underscore that for reliable engineering applications, parameters must be calibrated for the target stress environment, while also highlighting a clear pathway for future algorithmic and theoretical refinements.Highlights<UnorderedList Mark="Bullet"> <ItemContent> Develops a fully coupled damage–creep–seepage model for coal, rigorously linking microscopic damage to macroscopic hydromechanical behavior. </ItemContent> <ItemContent> Reveals that permeability evolution is governed by the dynamic competition between confinement-induced compaction and deviatoric-stress-induced shear dilation. </ItemContent> <ItemContent> Identifies that the model’s key damage parameters are not intrinsic material constants but are highly stress dependent. </ItemContent> <ItemContent> Validates the model’s high predictive accuracy (R2 > 0.94) within specific stress domains, underscoring the necessity of stress-specific calibration. </ItemContent> </UnorderedList>

Stress-State Dependency of Damage Evolution During Coal Creep and Its Impact on Permeability: A Coupled Constitutive Modeling Approach

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发表日期：

2026年1月6日

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Shijie Jing,
Hongbao Zhao,
Zuoquan Li

摘要

Accurately predicting the long-term evolution of coal permeability is crucial for the safety of coalbed methane extraction. This study aims to develop and validate a coupled damage–creep–seepage model, while critically examining its theoretical underpinnings and practical limitations. A novel constitutive model was developed based on continuum damage mechanics and the Nishihara model, establishing a rigorous link between microscopic damage, macroscopic creep, and permeability evolution. The model’s theoretical framework was then tested against a series of meticulously designed multi-path creep–seepage experiments. The experiments revealed that permeability evolution is governed by a dynamic competition between confinement-induced compaction and deviatoric-stress-induced shear dilation. The model successfully captured these phenomena, and a multi-round cross-validation confirmed its high predictive accuracy within specific stress domains. More profoundly, the analysis uncovered two critical characteristics of the model: 1) the key damage parameters, Fm and mm, are not intrinsic material constants but highly stress-dependent coefficients, serving as macroscopic representations of the underlying micro-mechanics. 2) The model, in its current form, represents an effective phenomenological framework for a complex, fully coupled strain–damage process. This research provides a robust model for predicting coal’s creep–seepage behavior, supported by profound mechanistic insights from targeted experiments. It critically identifies the stress-dependent nature of the model’s parameters, which not only defines the model’s application boundaries but also paves the way for its future evolution from a phenomenological tool to a physically based predictive framework. The findings underscore that for reliable engineering applications, parameters must be calibrated for the target stress environment, while also highlighting a clear pathway for future algorithmic and theoretical refinements.

Highlights

Develops a fully coupled damage–creep–seepage model for coal, rigorously linking microscopic damage to macroscopic hydromechanical behavior.

Reveals that permeability evolution is governed by the dynamic competition between confinement-induced compaction and deviatoric-stress-induced shear dilation.

Identifies that the model’s key damage parameters are not intrinsic material constants but are highly stress dependent.

Validates the model’s high predictive accuracy (R² > 0.94) within specific stress domains, underscoring the necessity of stress-specific calibration.