Damage around a cylindrical opening in a brittle rock mass

Abstract This paper presents an application of the sliding/wing crack model to the problem of a cylindrical opening in a brittle rock mass subjected to a hydrostatic stress field. The rock mass is assumed to contain a uniform initial distribution of microcracks. These microcracks serve as sources of stress concentration, and can propagate tensile wing cracks at their tips in a compressive stress field. It is shown that the sliding/wing crack model can essentially reproduce the complex stress–strain response obtained in laboratory experiments. The stress and displacement field induced by excavation of a tunnel in such a brittle rock mass is determined using the Biot Hodograph Method. The condition for instability of the tunnel can be inferred from the wing crack density, which characterizes the degree of rock damage around the tunnel.

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