Study on dynamic compression characteristics of coal containing gas under different strain rates

To investigate the dynamic compression properties and crushing features of gas-containing coal under complex geological environments, a dynamic and static combined loading test system was independently developed for conducting triaxial dynamic compression tests. The dynamic stress-strain curves under different strain rates were analyzed to study the effects of strain rate and gas pressure on the dynamic mechanical characteristics. Crushed coal samples were sieved and analyzed using a standard sieve and fractal theory. The study reveals that strain rate and gas pressure significantly influence the plastic deformation stage of the dynamic stress-strain curve of gas-containing coal. Under high strain rates, low gas pressure lengthens the plastic deformation stage, while high gas pressure shortens this stage and enhances brittleness. Increased strain rates lead to higher peak stress and peak strain in gas-containing coal samples. As gas pressure increases, the dynamic peak stress decreases, and the peak strain initially increases and then decreases. The damage form of gas-containing coal is primarily tensile-shear, accompanied by crushing damage. The fractal dimension increases at higher gas pressures and strain rates but stabilizes at gas pressures greater than 0.7 MPa. These findings enhance the understanding of the dynamic behavior of gas-containing coal under triaxial loading and provide valuable insights for the prevention and control of dynamic hazards in gas-containing coal bodies under complex stress environments.