Abstract：To accurately determine the deformation of coal during the CO2 adsorption process, the pressurization experiments using non-adsorptive helium were employed to analyze the volumetric deformation caused by free gas effects. By integrating this with swelling deformation during CO2 adsorption, a decoupled computational method that accounts for the tripartite coupling effects involving swelling deformation due to adsorbed gas, as well as the compression and expansion deformation of the coal matrix caused by free gas was proposed. The results indicate that: (1) The relationship between apparent volumetric deformation (the compression deformation of the matrix) and gas pressure for both reconstituted and raw coals during the increase in helium pressure can be divided into two distinct stages: pore compaction and linear elastic deformation. Additionally, the overall volumetric deformation-pressure curve exhibits a rapid reduction followed by a gradual reduction phase. (2) The difference between the overall volumetric deformation and the apparent volumetric deformation in coals under the pressure of free gas is quantified by the coefficient of difference in volumetric deformation, VK. As helium pressure increases, VK initially increases and then decreases. The overall volumetric deformation is found to be 14.29 to 39.54 times the apparent volumetric deformation, indicating that the deformation in pores and fractures due to pressure from free gas is significant. (3) The proposed method for calculating coal deformation accurately determines the overall volumetric deformation during CO2 adsorption processes. The calculations reveal that the relationship between overall volumetric deformation and adsorption pressure follows the Langmuir function, with the maximum overall volumetric deformation ranging from 2.39 to 3.14 cm3 under the experimental pressure range, representing an increase of 3.54% to 4.22% compared to the initial volume. The maximum deformation is 1.31 to 2.06 times greater than the apparent volumetric deformation measured by the strain gauge.
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2025, Vol. 44 
