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Abstract Linear Coulomb criterion can not completely describe the strength features of rock；and various revisions have been developed. The Mohr criterion on shear failure，which manifests as the envelope of failure stress circles，is studied rarely for the inconvenient to determine its parameters from the results of conventional triaxial compression test. Strength criteria with principal stresses form can be divided into explicit and implicit criteria. Implicit criteria is usually constructed with maximum shear stress and average principal stress，and has high correlation coefficient and low fitting deviation for the evaluating index. Actually，the two criteria have the same mechanical background and can be alternated after the coordinate rotation. Strengths of rocks like sandstone and marble result from cohesion and friction among grains，and can be illustrated by the normal parabolic criterion with a single parameter，which is better than the Coulomb criterion and same as the Hoek-Brown criterion in fitting the relationship between strength and confining pressure. Ideal uniaxial compression strength of intact rock can be obtained by fitting the strength with normal parabolic criterion under high confining pressure，and may be used to evaluate the initial damage after comparing the real magnitude of uniaxial compression strength.
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Received: 16 April 2012
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2012, Vol. 31 
