The deformation modulus of rock is affected by the strain rate. It is an important behavior in predicting the long-term stability of rock mass. In this paper, the conventional compression tests and multi-stage creep tests were conducted and the isostrain-rate curves were plotted based on the test results. Meanwhile, a method for investigating the strain-rate dependent behavior of rock's deformation modulus based on the isostrain-rate curve was proposed. It's demonstrated that the modulus has a

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... ogarithmic relationship with strain rate, and an empirical formula was obtained. Furthermore, we found there was a threshold of strain rate, when the strain rate was lower than this threshold, the modulus was sensitive to strain rate.