Mesoscopic analysis of creep characteristics of hard tuff considering damage

This article employs a nonlinear creep constitutive model and explores the microscopic deformation features of hard tuff during the creep process, incorporating damage effects. Utilizing the particle flow program (PFC2D), a creep contact model is developed to simulate hard tuff under triaxial compression conditions. The study analyzes the creep mechanism of hard tuff under varying confining pressures, focusing on microscopic evolutions. Triaxial compression tests, conducted with confining pressures ranging from 10 to 30 MPa and axial pressures from 50 to 80% of peak strength, reveal significant influences of the confining pressure on the strength, deformation, and failure mode of hard rock. The results reveal that higher confining pressures enhance peak strength and peak strain, while the elastic modulus reduces continuously with increasing deviatoric stress, accompanied by pronounced attenuation creep features and cumulative deformation. The numerical results indicate that the mixed model accurately represents creep behavior in hard rocks. The meso-crack propagation pattern reveals that tensile fracture is the predominant mode of particle failure under triaxial compression. At low axial pressure, micro-crack propagation in attenuation creep and steady-state creep is limited, although internal damage accumulates continuously. As axial pressure increases, the rate of fracture formation rises, making creep failure more apparent. The numerical results align with the experimental data, with the mixing ratio of the mixed model effectively representing the creep characteristics of various rock types. The developed approach has significant implications for ensuring the enduring stability and structural integrity of rock masses in challenging sedimentary rock formations.