Effects of gas adsorption on mechanical properties and erosion mechanism of coal

• Triaxial compression test of gas-bearing coal were carried out.
• The adsorbed gas erosion effects of coal was quantified.
• Cohesion softening model was established.

In order to study coal deformation and fractured mechanism under pore gas action, we chose gases N2 and CH4 as pore fluids, and carried out triaxial compression test of gas-bearing coal. To further explore the effects of gas erosion on coal deformation and failure, we tested the deformation and rapture process of coal during gas adsorption equilibrium under fixed axial load and confining pressure. The results showed that gas adsorption decreases coal's solid surface energy and lowers coal's compressive strength, leading to larger plastic deformation in coal and final rupture instability. From the physicochemical angle, we quantified the adsorbed gas erosion effects of coal based on both Griffith crack extension theory and Mohr–Columb strength criterion, explored the mechanical characteristics and erosion damage process of gas containing coals and put forwarded their mathematical models. These models can describe the experimental phenomena fairly.