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Influence of end effect on rock strength in true triaxial compression test
The influence of the end effect on rock strength in true triaxial compression testing was studied using a numerical approach. The influence of the intermediate principal stress (σ 2 ) on rock strength was isolated by using the two-dimensional Mohr–Coulomb failure criterion that depends only on the major principal stress (σ 1 ) and minor principal stress (σ 3 ). Thus, any enhancement to the rock strength with the increase of σ 2 can be attributed to the end effect. It was shown that the end effect can result in an apparent σ 2 effect, as long as the coefficient of friction (μ) at the rock specimen – steel platen contacts is not zero and the specimen in the σ 2 loading direction is squat. When the strengthening due to the increase of σ 2 predicted by a theoretical failure criterion was added to the strengthening due to the end effect, the results were in good agreement with the observed σ 2 effect from some previous laboratory tests, indicating that the observed σ 2 effect in true triaxial compression testing could be partially influenced by the end effect, particularly when σ 3 was low. It is suggested to decrease the end effect to a level where the apparent σ 2 effect is very small so that the obtained test results are more meaningful to characterize the actual σ 2 effect.
Influence of end effect on rock strength in true triaxial compression test
The influence of the end effect on rock strength in true triaxial compression testing was studied using a numerical approach. The influence of the intermediate principal stress (σ 2 ) on rock strength was isolated by using the two-dimensional Mohr–Coulomb failure criterion that depends only on the major principal stress (σ 1 ) and minor principal stress (σ 3 ). Thus, any enhancement to the rock strength with the increase of σ 2 can be attributed to the end effect. It was shown that the end effect can result in an apparent σ 2 effect, as long as the coefficient of friction (μ) at the rock specimen – steel platen contacts is not zero and the specimen in the σ 2 loading direction is squat. When the strengthening due to the increase of σ 2 predicted by a theoretical failure criterion was added to the strengthening due to the end effect, the results were in good agreement with the observed σ 2 effect from some previous laboratory tests, indicating that the observed σ 2 effect in true triaxial compression testing could be partially influenced by the end effect, particularly when σ 3 was low. It is suggested to decrease the end effect to a level where the apparent σ 2 effect is very small so that the obtained test results are more meaningful to characterize the actual σ 2 effect.
Influence of end effect on rock strength in true triaxial compression test
Cai, M (author) / Zhang, X.W / Xu, Y.H / Feng, X.T
2017
Article (Journal)
English
Rocks , end effect, three-dimensional empirical failure criterion, numerical modeling , Stress analysis (Engineering) , résistance de la roche , Mechanical properties , true triaxial compression test, intermediate principal stress, rock strength , essai réel en compression triaxiale , effet de bout , modélisation numérique , critère de rupture empirique en trois dimensions , Methods , contrainte principale intermédiaire
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