Effect of Roughness and Filling Materials on the Dynamic Strength and Failure Mechanisms of Filled Jointed Rocks under Strain Rate Effects

Tunnel engineering plays a critical role in modern infrastructure development. During its service life, tunnels are inevitably subjected to dynamic loads, such as earthquakes, Tunnel Boring Machine (TBM) excavation, and rockburst events. These forces can lead to mechanical property degradation of jointed rock mass, thereby affecting the safety of tunnel engineering. Grouting technology, a crucial method for enhancing the mechanical properties of jointed rock mass, has been widely utilized in tunnel engineering. Therefore, investigating the impact mechanisms of filled jointed rocks is of significant importance. This study examines the impact behavior of filled jointed rock specimens using a split Hopkinson pressure bar apparatus. The results indicate that the dynamic mechanical properties of filled jointed rocks exhibit significant strain-rate dependence. With an increase in the joint surface roughness coefficient of composite-filled specimens, higher dynamic compressive strength and lower failure rates are observed compared to specimens filled with portland cement materials. Specimens with higher joint surface roughness coefficients showed lower damage factors and greater stability under dynamic loading. The failure process and mechanical properties of filled jointed rock under dynamic loading were shown and analyzed specifically based on the numerical model built in this paper. At high strain rates, the relationship between the dynamic increase factor and strain rate for filled jointed rocks follows the Grady equation, which can be used to predict and analyze their dynamic compressive strength. This study provides valuable insights into the impact mechanisms of grouted jointed rocks.