(1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. Huaneng Lancang River Hydropower Co.，Ltd.，Kunming，Yunnan 650214，China)
Abstract：The loading rate effect is an important property of rock materials. The research of the Brazilian splitting test at different loading rates on the hard brittle marble in depth in Jinping II hydropower station shows five characteristics：(1) The failure processes can be almost divided into four steps regarding the loading rates，i.e. stress concentration zones，expanding of the stress concentration zones，shaping of the failure and failure. (2) The peak stress in the Brazilian splitting test logarithmic increases with the increase of the loading rate. (3) The loading rate is higher，the average vertical strain is greater，but the average lateral strain is smaller. (4) According to the fractography，the analysis of the microcosmic fracture surfaces shows that the area of mirror district at the rate of 2.55 MPa/s is less than that a of 0.000 255 MPa/s and the shear failure is dominant；furthermore，the sawtooth district of the 0.000 255MPa/s is regular. (5) At the rate of 2.55 MPa/s，the sample breaks into more pieces and the failure is much more violent than that at a lower loading rate. The energy of sample failure at the rate of 2.55 MPa/s is greater than that at the rate of 0.000 255 MPa/s when calculation. The test result is analyzed in view of macroscopic and microscopic studies；and fractography is utilized to explain the mechanism of the rock failure at different loading rates. The analysis method is helpful for the understanding the loading rate effect and its mechanism.
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2013, Vol. 32 
