A study of granite damage in the macro and microscopic scales under freezing-thawing cycles

Freezing-thawing damage to rocks is one of the natural disasters that cannot be ignored in engineering construction in plateau regions. Under the action of freezing and thawing, uneven shrinkage of rock minerals and freezing of pore water lead to rock damage caused by pore expansion in rocks, which poses a great threat to engineering stability. In recent years, many researchers have conducted a lot of researches on rock properties under freezing-thawing conditions through theoretical and experimental methods. However, most of the previous studies focused mainly on sedimentary rocks such as sandstones, and very few studies were involved in freezing-thawing of granites in highland alpine regions. In this study, the granite on the landslide area was subjected to uniaxial compression, resistivity and electron microscope scanning (SEM) tests to discuss the damage of granite after multiple freezing-thawing cycles by simulating the cold climate changes on the plateau under freezing-thawing cycles. From the macro and micro multi-scale studies it can be found that: (1) the change of granite quality during freezing-thawing cycles tends to decrease, then increase and finally decrease, which is related to the dual effect of particle drop on the surface of the specimen and the expansion of internal fissures caused by freezing-thawing cycles. (2) As the freezing-thawing cycles increase, the uniaxial compressive strength, elastic modulus and cohesion of granite all show a non-linear decay, while the internal friction angle only fluctuates slightly around the mean value. (3) When the number of freezing-thawing cycles increases, both the freezing-thawing damage factor and the total damage factor under the coupling of freezing-thawing and load increase, which indicates that the number of freezing-thawing cycles has a greater influence on the strength of granite. The results of the study can provide a reference basis for measuring the freezing-thawing strength characteristics of granite in engineering construction in the plateau region.