Experimental Research on the Tensile Strength of Saturated and Dry Rocks at Ultra-Low Temperatures

To explore the tensile mechanical properties of saturated and dry granite and marble at ultra-low temperatures， this study employed a specifically designed mechanical loading apparatus in an ultra-low temperature environment. Brazilian split tests were conducted on granite and marble at temperatures of -90 ℃， -120 ℃， and -165 ℃. The results indicated that the tensile strength of coarse-grained granite continuously increased as the temperature decreased under ultra-low temperature conditions， albeit at a decelerating rate. Fine-grained granite exhibited a weakening trend at -165 ℃ but remained higher than at ambient temperature. Compared with ambient conditions， rock fractures in ultra-low temperature environments not only demonstrated through-going cracks but also featured persistent cracks. Moreover， water-saturated specimens exhibited triangular zone failure at the base. The peak energy dissipation rate during the process of rock tensile failure showed a similar trend to the peak strength， with a strong correlation between the two. This study aims to examine the tensile failure performance of rocks in ultra-low temperature environments and the changes in patterns of rock properties under the coupling of force and temperature， offering engineering insights for the design of cavern-type liquefied natural gas （LNG） storage tanks.