Improved Nonlinear Burgers Shear-Creep Model for Rock Masses Disturbed by Dynamic Loading

Abstract The mechanical properties of engineering rocks and the long-term stability of tunnels and stopes are mainly controlled by weak structural surfaces, which are prone to shear creep under geostress. Dynamic disturbances induced by drilling and blasting during excavation exacerbate shear-creep failure. It is of great significance to study the shear-creep damage mechanism of rock induced by dynamic disturbance to reveal the activation mechanism of weak structural surfaces. In this work, the shear-creep impact test is carried out using a creep-impact test machine to study the effect of dynamic disturbance on rock shear creep. Based on the Riemann–Liouville fractional-order theory, the viscoplastic element in the Burgers body is improved to characterize the shear-creep deformation induced by dynamic disturbance. To describe damage to rock masses subjected to dynamic disturbances and shear creep, a damage factor is defined based on Norton’s power law and Kachanov’s creep damage law. By coupling the effects of dynamic disturbance with shear creep, an improved nonlinear Burgers shear-creep model for rock disturbed by dynamic loading is proposed. The shear-creep deformation of sandstone under different stresses and impact energies was investigated using the nonlinear least-squares method to verify the accuracy of the improved theoretical model. The model can effectively characterize the nonlinear characteristics of sandstone in the accelerated creep stage and the deformation behavior under dynamic loading. The influence factors of the time to apply dynamic disturbance, uniaxial critical stress, friction angle, sawtooth inclination, and cohesion on the shear-creep deformation behavior of sandstone are analyzed and discussed using the improved theoretical model. This study is of great significance for clarifying the shear-creep impact damage and failure mechanism of jointed rocks during tunnel excavation and deep mining.