Brittleness evaluation of gas-bearing coal based on statistical damage constitution model and energy evolution mechanism

• A novel statistical damage constitutive model for gas-bearing coal is developed by integrating effective stress and the Hoek-Brown criterion, validated against triaxial compression tests under varying gas pressures. • The post-peak stress drop and softening characteristics of gas-bearing coal are accurately captured, with shape and scale parameters reflecting brittleness and strength. • As gas pressure increases from 1 to 5 MPa, both brittleness and strength decrease (shape parameter -22.18%, scale parameter -60.45%). • The proposed brittleness index, integrating energy evolution and damage parameters, effectively reveals enhanced plastic deformation sensitivity under higher gas pressures.