FAILURE OF CAVITIES IN HOMOGENEOUS ROCK UNDER DYNAMIC LOADING FROM NUCLEAR EXPLOSIONS,
Y George B.
MISSOURI SCHOOL OF MINES AND METALLURGY ROLLA
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Stress concentration about an underground opening and strength of rock, per se, do not constitute adequate criteria to define failure of openings in homogeneous rocks. The Griffith theory of failure and its application to the failure of materials in tension and shear are reviewed. There appear to be analogous criteria for crack propagation and failure for materials in compressive uniaxial, biaxial and triaxial stress fields, although no investigations are reported in this area. Existing rock strength data for uniaxial fields, unconfined, may be utilized to determine the conditions for initiation of cracks at the periphery of an opening. Crack propagation phenomena then become the determining factors, in combination with stress field parameters, in limiting the extent or degree of failure. Such parameters include crack velocity, confinement effects, energy flow, duration and magnitude of stress field and rock properties themselves. Author