Index of Loading-Rate Dependency of Rock Strength
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To estimate long-term deformation and stability of underground structures, knowledge of the time-dependent behavior of rock is essential. It is well known that rock strength increases with an increase in loading rate (loading-rate dependency), strain increases under constant stress (creep) and stress decreases under constant strain (relaxation). It has been reported that such time-dependent behaviors under different loading conditions are closely related to each other. The constant n, which represents slow crack growth due to stress corrosion, has been used to formulate the loading-rate dependency of strength (Sano et al. 1981) and the relation between creep stress and lifetime (Wilkins 1981). Lajtai et al. (1991) stated that rock strength is proportional to the 1/(n + 1)-th power of loading rate and that creep lifetime is inversely proportional to the n-th power of creep stress. Hashiba et al. (2006) presented the results of strength and creep tests which demonstrated...
KeywordsTime-dependent behavior Loading-rate dependency Creep Variability of strength Size effect
The authors are grateful to Mr. Masaki Hatakeyama and Mr. Yuta Oishi of the University of Tokyo for their assistance in conducting the tests.
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