Anisotropy and Hysteresis of Coal Dynamic Deformation During Adsorption and Desorption

Abstract

Coal deformation-induced by adsorption/desorption is dynamic and anisotropic, influenced by various factors, such as pressure, temperature, and gas type. This paper investigates the dynamic deformation of coal during the adsorption–desorption process and analyzes the anisotropic and hysteretic characteristics. Results show that maximum deformation is reduced by approximately half with every 10 °C increase above 40 °C, and nearly doubles with each 1 MPa pressure increase. The swelling of CO₂ at adsorption equilibrium is twice that of CH₄, and almost 4 × that of N₂. During desorption, shrinkage and desorption gas are approximately linear. Anisotropy coefficients increase initially, then decrease with adsorption, stabilizing around 2. During desorption, anisotropy coefficients generally decrease. The anisotropy coefficient of CO₂ is higher than that of CH₄ and N₂, and all show a tendency to increase with equilibrium pressure. Cumulative hysteresis deformation decreases with the increasing temperature, even reversing at higher temperatures. CO₂ exhibits significantly higher hysteresis than CH₄ and N₂. These findings offer valuable insights for engineering applications.