Failure of fractured rock

Abstract It is shown that knowledge of the strength and deformation behaviour of fractured rock is essential for determining the ultimate stability of underground excavations in rock. Special experimental techniques and equipment for polyaxial rock testing, developed for studies of failure characteristics of fractured rock are described. Results of tests on both soft (sandstone) and hard (quartzite and norite) rock are given. Failure behaviour of fractured rock under multiaxial stress conditions is discussed and its significance outlined.