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Abstract Three groups of conventional triaxial tests，square triaxial tests and plane strain tests of rockfill material are conducted to study its strength in plan strain stress state. Significant differences between conventional triaxial tests and square triaxial tests show that peak strength of latter is higher than the that of former. Especially when its density is large，the stress-strain curve shows softening characteristics and obvious peak deviatoric stress. Each Mohr circle of square triaxial tests has a common tangent，and so do plane strain tests. Thus，Mohr-Coulomb strength criterion is reasonable to reflect its strength characteristics. Lode parameter of same kind of rockfill material approximately keeps constant in its failure state and their values are close to the sine internal friction angle of square triaxial tests. Based on experiment results，the relationship between strength parameters of rockfill material in plane strain state and square triaxial tests is established using the unified strength theory. Through the analysis of influence parameter in plane strain state，it is shown that the internal friction angle of plane strain state is only related with the friction angle of triaxial state；and its cohesion mainly depends on the corresponding parameter of triaxial state and the friction effect is minor. Finally，the results of theoretical formula are compared with test results. It is shown that the formula of strength parameter proposed in this paper can mainly describe the strength characteristic of rockfill material in plane strain test under constant minor principal stress.
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Received: 04 May 2011
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2011, Vol. 30 
