Analysis of surface cracks growth and damage in salt rock under uniaxial compression

The surface cracks growth and dispersion of salt rock, mudstone and salt-mudstones under uniaxial loading condition were studied with fluorescent approach. For salt rock, the surface cracks are mainly grain boundary micro cracks controlled by the grain scale and the uniformity distribution of salt grains. For mudstone, cracks are mostly oriented parallel to the uniaxial stress direction. The micro cracks firstly form in the mixture of several mineral deposits, and then develop until they fail. For salt-mudstones with serrated interface, the micro cracks grow in salt grains at the beginning, after that the flaws extend to mudstone. While in the interface with a thin layer of clay, the inconsistent lithology makes more cracks in clay layer than other samples. The inversions of P-wave velocities are used to define the damage variable of salt rock, which reflects the processing of the cracking.