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Abstract The progressive failure of rock can be divided into five stages，including crack closure stage，elastic stage，crack initiation and stable growth stage，and accelerated crack growth and post-peak stage. The characteristic stresses in the progressive failure process of rock under different strain rates were studied by using the dynamic mechanical system of rock with changing frequencies. The results show that：(1) When the strain rate 5×10－4 s－1，rock strength is slightly dependent on the strain rate；when 5×10－4 s－1，the rock strength is significantly dependent on strain rate. (2) The ratios of crack initial stress and dilatancy stress to the peak strength and the ratio of crack initial stress to dilatancy stress are 50%–60%，70%–80% and 80%–90%，respectively，showing no evident dependence of strain rate. Based on the energy conservation law，the energy characteristics and energy mechanism in the process of rock failure were analyzed. Some conclusions are dram as follows. (1) Both of the total absorbed strain energy and the elastic strain energy increase with the growth of strain rate；but the damage strain energy increases firstly and then decreases. (2) When 5×10－4 s－1，the absorbed energy and the elastic energy are slightly dependent on strain rate；when 5×10－4 s－1，the absorbed energy and the elastic energy are significantly dependent on strain rate. (3) If the strain rate is fixed，the strain energy absorbed by rock is stored mainly in the form of elastic strain energy，but the damage strain energy remains nearly unchanged，which only increases near the peak strength. Once the peak strength is reached，the strain energy stored in the rock is quickly released.
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2012, Vol. 31 
