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Abstract The degradation law of the damaged rock sample is an important task in the field of rock mechanics. A new method to precast the damaged samples was used. The uniaxial compression tests and triaxial compression tests were made on the samples and the test results were compared with that of intact rock samples which were nearly homogeneous. Under the uniaxial compression，splitting failure was accompanied with slant fracture failure. With the increase of the confining pressure，a new nearly horizontal failure was likely to appear at the cementation area. The strength degradation of the damaged sample to the slant sample increased with the increasing confining pressure，but the increasing range gradually fell. Based on the laboratory test and particle flow code(PFC) numerical software，the size effect of the strength degradation under uniaxial compression on the damaged sample was studied. The research shows that the strength degradation of the uniaxial compression fell with the increase of the height-diameter ratio but had a trend to become gentle. The theoretical model of strength degradation under uniaxial compression was proposed as ，where is the strength degradation value under uniaxial compression of any damaged sample； is the strength degradation value under uniaxial compression of the standard damaged sample； is the height-diameter ratio of the column sample；a and b are the parameters of the material. The theoretical curve is consistent with values from the tests. The calculation result shows that when the size is infinitely indefinitely large，the strength degradation value under uniaxial compression is closer to .
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Received: 18 July 2011
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2012, Vol. 31 
