Simulation of failure around a circular tunnel using a bonded particle model

At low in-situ stress magnitudes, the continuity and distribution of natural fractures in a rock mass control failure processes. However, at highly stressed levels, the failure process is affected and eventually dominated by stress-induced fractures growing preferentially parallel to the excavation boundary. And in these geological environments, brittle failure is the dominant failure mode. Brittle failure results from the growth and accumulation of tensile cracks around tunnels. This failure is usually described as “spalling” or “slabbing,” and the shape of the failure zone is commonly called the “breakout” or “V-shaped notch.”