Failure phenomena and determination of damaged zone of concrete in softening regime under triaxial compression

Abstract

To elucidate the failure phenomena of plane concrete under triaxial compressive stresses with low lateral pressure after the maximum strength has been passed, a triaxial compression test device, with which a two-dimensional failure pattern can be obtained, has been developed. The maximum size of the coarse aggregate, concrete strength and shape of the specimen were made experimental variables and triaxial compression tests on 193 specimens were carried out. It was shown that the Mohr–Coulomb failure criterion could be explained by using the model of the stress transfer mechanism resulting from the ‘bridge action’ occurring between the coarse aggregates. The residual strength criterion was formulated and it was observed that the load-carrying mechanism was different between the maximum strength and the residual strength. The cracking angle was measured, and it was experimentally shown that it could be approximated by the friction coefficient of the strength criterion. In addition, by making the cracking visual, and by carrying out graphical image processing of it, the crack density near the discontinuous plane was quantitatively measured, and at the same time the damaged zone could be determined.