Exfoliation Near Rock Surface

Many rock slope failures occurred recently in Hokkaido, Japan. Behavior of crack growth has to be clarified in order to investigate the mechanisms of the slope failures in detail. Examples of crack growth near rock surface can also be observed as burst like-rock failures in quarries and sheeting joints in V-shaped valleys.

Fig. 1. Example of sheeting joints.

It was clarified by 2-D Displacement Discontinuity Method that an inclined crack near rock surface can grow longer than that in an infinite medium. It is also possible that the buckling condition can be satisfied if the crack grows long enough. This would be one of the mechanisms of the rockbursts that were often observed in metal mines and tunnels beneath high mountains.

Fig. 2. Traces of tips of an inclined crack near rock surface under compression. Note that the scalings for x- and y-axes are different with each other.