Research on the physical and mechanic properties of carbonaceous phyllite subjected to freezing-thawing cycles

The Sichuan-Tibet Railway passes the high-altitude metamorphic rock areas in western Sichuan, where rocks freeze-thaw and weather intensely, and geological disasters occur frequently. It is of great theoretical significance and engineering value to carry out freezing-thawing cycle tests on typical rocks. Specimens collected at a bridge over the Jinsha River were divided into five groups, and each group experienced 4 h for freezing and 4 h for thawing with a wide temperature range in which the freezing and thawing temperature was -40 ℃ and 50 ℃, respectively. During the experiment, loss of quality, change in P-wave velocity of the carbonaceous phyllite were counted with observing deterioration in the appearance of rock specimens every five freezing-thawing cycles, combining with the uniaxial compression tests after 22, 42, 65, 85, and 105 times of freezing-thawing cycles, respectively. Comparison and analyses of the calculated physical and mechanical parameters show that with the increasing cycles of freezing and thawing, there is no obvious change in the appearance of the rock specimens, the quality decreases slightly and the rate of decline decreases gradually. There is no obvious law of the P-wave velocity with large shock after freezing, but the P-wave velocity shows a decreasing trend after thawing. The uniaxial compressive strength decreases gradually and tends to be steady at last. The carbonaceous phyllite exhibits the characteristics of weakened brittleness and enhanced ductility. The rock properties have an important effect on the experiment. For this reason, more research should be carried out on the three aspects of microfracture, rock structure and rock texture.