Fractal geometry study on uniaxial compression fracture characteristics of sandstone subjected to freeze-thaw cycles

The mechanical properties of rocks in cold regions are often affected by freeze-thaw cycles and loads. The uniaxial compression fractures of rocks subjected to freeze-thaw cycles contain damage evolution information related to freeze-thaw cycles and loads. It is of great value to study the uniaxial compression fracture of freeze-thaw rocks for the rock fracture failure mechanism after freeze-thaw degradation. To study the uniaxial compression fracture morphology of freeze-thaw rock and its correlation with the macro mechanical parameters, in this paper, fractures of sandstone under the uniaxial compression and different freeze-thaw cycles are observed by photography. The fracture fractal dimension is calculated by the pixel covering method, and the relationship between the fractal dimension and the macro-mechanical parameters is discussed. The results indicate that as the number of freeze-thaw cycles increases, the uniaxial compressive strength, elastic modulus, fracture fractal dimension, and energy dissipation density decrease gradually, and the peak strain increases. There are exponential relationships between the three parameters (uniaxial compressive strength, elastic modulus and dissipated energy density) and the fracture fractal dimension. The larger the fracture fractal dimension is, the greater the three parameters are. The fractal dimension of the freeze-thaw rock fracture under the uniaxial compression can be used as an effective parameter for the mechanism analysis of rock failure in cold regions.