Viscosity of rock mass at different structural levels

This paper examines viscosity of rock mass at different structural hierarchies. The study shows that viscosity and characteristic strain rate of rock mass vary at different structural levels. There exists one-to-one correspondence between characteristic scale level and strain rate. High viscosity with low characteristic strain rate occurs under macro-level, while meso- and micro-levels are characterized by low viscosity with high characteristic strain rate. Generally, with the increase in strain rate, deformation and fracture take place at decreasing scale levels, and viscosity gradually decreases. With high characteristic strain rate at meso- and micro-levels, viscosity is inversely proportional to strain rate at these levels. Based on the analysis on viscosity at different structural levels, a unified description of viscosity is suggested and applied to the description of the strength–strain rate sensitivity of rock mass.