Abstract：Loading rate has an important influence on rock mechanical properties and failure modes. Experiments on uniaxial compression and acoustic emission of different loading rates on granite were conducted by MTS810 servo-controlled testing machine and PCI-2 acoustic emission instrument. The results show that: (1) Stress-strain curves of granite under uniaxial compression have experienced compaction, elasticity, yield and failure four stages. Post-peak curves of the rock sample present stepped and segmented drop shape at loading rates from 0.001 mm/s to 0.01mm/s, and present a smooth, steeper continuous curve at loading rates from 0. 01 mm/s to 0. 1mm/s. (2)Peak strength and elastic modulus of rock increases with increasing loading rate, both present cubic polynomial relations with the logarithm of the loading rate. Peak strain decreases with increasing loading rate,which shows linear regression relationship with the logarithm of the loading rate. (3)As the loading rate increased from 0.001mm / s to 0. 1mm / s, the total strain energy was volatile, releasable elastic strain energy increased 60.42%, dissipated strain energy decreased 66.38%, the ratio of releasable elastic strain energy of the total strain energy increased 43.33%, the ratio of dissipated strain energy of the total strain energy decreased 66.67%, rock fracture mode changes from tensile shear failure to tensile splitting failure gradually, the number of broken pieces also increased. (4)When the loading rate from 0.001 mm / s to 0.1 mm / s, the failure process of rock sample is the same kind of damage although the failure mode is different. The energy dissipation makes rock damage and the strength loss, but the energy release makes the macrofracture surface be run-through, which towards the direction of the energy released by rifting or catapult destruction.
2015, Vol. 36 
