Abstract: To study the effect of temperature and loading rate on mechanical properties and failure modes of rock materials, experiments on granite were conducted under uniaxial compression at different loading rates and real-time high temperatures in the range of of 25-1 000 ℃ by the servo-controlled testing machine MTS810. The results show that: (1) Stress-strain curves of granite at real-time high temperature have the compaction, elasticity, yield and failure stages. Post-peak curves present stepped and segmented drop shape at loading rates from 0.001 to 0.01 mm/s, but present smooth and steeped continuous phenomena at loading rates from 0. 01 to 0.1mm/s. (2) The peak strength and elastic modulus are divided into four stages with increasing temperature, which is the slowly rising stage from 25 to 200 ℃, rapidly declining stage from 200 to 600 ℃, slowly rising stage from 600 to 800 ℃, and slowly declining stage from 800 to 1 000 ℃. The peak strength and elastic modulus at 1 000 ℃ decreases by 53.47% and 64.34% respectively, compared with that at 25 ℃. The peak strain presents cubic polynomial relationship with the temperature. (3) Both the peak strength and elastic modulus show a quadratic polynomial increased relationship with the logarithm of loading rates, the value of which increased by 38.82% and 37.22% respective at the loading rate of 0.1 mm/s to compare with that at 0.001 mm/s. The peak strain presents unobvious relationship with loading rates. (4) As the temperature increases under uniaxial compression state, the forms of deformation and failure of rock samples transfer from the tensile shear rupture to the cone fracture with fragmentation of liquidity; and the instability mode transfers from sudden instability to progressive failure. The fracture modes of rock sample are independent on the loading rate, but the instability patterns depends on loading rate.

Key words: granite, temperature, loading rates, mechanical properties, instability mode