Abstract: The thermal effects of rock in long-term varying low-temperature environment are mainly expressed by the mechanical parameters, thermal coefficients of rock and the pore ice expansion coefficient in the saturation state changing with the decreasing temperature. These changes have some significant influences on the deformation and strength characteristics of rock. The constitutive equation considering the thermal effects and the ice expansion coefficient is established according to the nonlinear thermo-elastic theory of varying properties, and the changing relationships of the thermal coefficients with temperature and their determining method are given under the uniaxial compressive condition. Then, the relationships of the thermal effects with low temperature for granite are obtained by means of the uniaxial compression test results of granite under the different dry low temperatures and the saturated frozen, and the influence of the different conditions on the compressive strength characteristics of granite is discussed. The analysis results show that the thermal coefficient and the ice expansion coefficient of granite decrease gradually with the increasing of the relative temperature difference under the varying low-temperature environment, and the reducing rate of thermal coefficient is lower than that of the ice expansion coefficient. The coefficient of the thermal expansion is greater than that of the ice expansion under the same temperature difference. The thermal stress and the ice expansion stress increase with the low temperature nonlinearly. The compressive strength values of granite in the two states are both increasing; but the thermal stress is the dominating, and the axial stress increment caused by the thermal coefficient is always larger than that caused by the ice expansion force. The proposed method and the obtained results can be supplied for the research on material deformation properties and engineering application under long-term varying low temperatures.

Key words: granite, varying low temperatures, thermal effects, expansion force of ice, compression test