Abstract: A statistical constitutive damage model was developed within the elastic theory frame of porous materials to investigate rock damage characteristics under water pressure. By incorporating continuum damage mechanics and statistical theory with the principle of effective stress, the Hoek-Brown criterion was regarded as a microbody strength failure criterion. According to the relationship between residual strength and peak strength, the damage variable of the model was modified for fully reflecting the softening characteristics in the post-peak stage. The model was validated using indoor experimental data. Results evinced the established model could well reflect the stress-strain relationship of rock under water pressure. As water pressure increased, the value of model parameter n exhibited a rising trend and the brittleness of rock also increased, but the value of F₀ and the strength of rock both declined. In addition, peak point method is better than curve fitting method in determining model parameters.

Key words: rock mechanics, water pressure, Hoek-Brown criterion, statistical damage model, residual strength, peak point, curve fitting