Failure modes and energy evolution of basalt in uniaxial compression tests after cryogenic freeze-thaw cycles

With the gradual deepening of human extraterrestrial exploration, the extreme temperatures in the environment of celestial bodies have become key research focuses. In environments of celestial bodies such as the Moon, the huge difference and frequent change in the surface temperature have exposed rocks to the freeze-thaw (F-T) cycles. Meanwhile, F-T damage is also a non-negligible natural disaster in cold-region engineering. Uniaxial compression mechanical tests were conducted on basalt specimens subjected to cryogenic F-T cycles (-80 ℃ ~ 100 ℃), during which acoustic emission (AE) monitoring was used to record the damage evolution process in the specimens. Test results show that after experiencing multiple F-T cycles, the P-wave velocity of basalt specimens decreases by 12%, the uniaxial compressive strength declines by 26% ~ 33%, and the volume with F-T damage accounts for 31.6% ~ 46.7% of the total. In addition, for basalt specimens subjected to 15 and 25 F-T cycles, the damage areas show radial distances of 7.9 mm and 11.7 mm from the surface. The proportion of tensile failure in the specimens increases from 10.3 to 28.8% (25 cycles). The scanning electron microscopy (SEM) was utilized for microscopic analysis of fracture planes of the tested basalt. New fractures showing the characteristics of intergranular failure are observed on the fracture planes of specimens undergoing F-T cycling, which causes more tensile failure in the specimens. The test results provide not only basic data for research into mechanical behaviors of rocks with F-T damage but also offer theoretical guidance for building construction and slope design and construction in alpine regions.