Damage and Permeability Evolution Law of Coal Mass During Confining Pressure Relief
Authors
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Jiangsu Key Laboratory of Fire Safety in Urban Underground Space, China University of Mining and Technology, Xuzhou, Jiangsu 221116 ,CN
Qingying Cheng -
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou, Jiangsu 221116 ,CNBingxiang Huang
Keywords:
Coal mass; fluid-solid coupling; transient pressure pulse method; confining pressure relief; damage; permeability coefficient; radial expansion deformation; plastic deformation 1Abstract
In order to research the damage and permeability evolution law of coal mass under fluid-solid coupling during confining pressure relief, the permeability coefficient determination test on coal samples with transient pressure pulse method has been conducted under the condition of false triaxial and constant axial pressure. The experiment results indicated that the deformation of coal sample is mainly radial expansion deformation during confining pressure relief. When axial pressure is between uniaxial compressive strength and triaxial compressive strength, the typical curve of “confining pressure relief-volume strain” contains three stages: elastic deformation recovery, plastic deformation and failure stage. The damage and permeability coefficient variation has a confining pressure relief threshold. Below this threshold, permeability coefficient increases slowly and steady; above this threshold, it rises rapidly. It also has a inflection point for confining pressure relief. When confining pressure relief exceeds inflection point, coal sample gets macro rupture and permeability coefficient increases sharply.
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