Experimental study on uniaxial compression of granite under real-time loading at designated low temperatures conditions

The effect of low temperature and degree of saturation has important influences on the surrounding rock mechanical properties of cave-type Liquefied natural gas underground storage. Uniaxial compression tests were carried out on dry and saturated granite under different real-time loading at designated low temperatures (25, 0, −20, −40, −50 and −60 °C) conditions. The porosity and microstructure were then observed by nuclear magnetic resonance and scanning electron microscopy. The results show that with the decrease of temperature, the uniaxial compressive strength (UCS) and porosity of both the dry and saturated granite monotonously increases, while the elastic modulus undergoes increase-decrease transition, and finally stabilizes. At the same temperature, the UCS and elastic modulus of the dry granite are generally greater than those of the saturated granite. The reinforcement in the UCS and elastic modulus is caused by cold shrinkage, while the degradation in the elastic modulus, especially for the saturated granite, is attributed to freezing damage below 0°C. The results of this study can provide technical support for the long-term stability analysis and evaluation of underground cavernous Liquefied natural gas storage reservoirs.