Abstract To study the threshold value of strain rates between static loading and quasi-dynamic loading of rock materials,uniaxial compression tests of several hard-rock samples were conducted with various strain rates. Then,the correlation between the ratio of rock dynamic compressive strength to static compressive strength,?,and strain rate was quantitatively analyzed using statistic theories and methods. The relationships between strength parameters of hard-rock samples and strain rate were obtained. Further,the threshold value of the strain rates of rock materials under static and quasi-dynamic loading tests were found. The results show that:(1) When the strain rate <5×10-4 s-1,the tests are static with around 1.00. It means that rock strength is independent of strain rates. (2) When 5×10-4 s-1< <102 s-1,the tests are quasi-dynamic with a power relationship between and strain rates. It indicates that rock strength is significantly dependent of strain rates.
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Received: 27 December 2011
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