The current macro-mechanical models of salt rock are usually phenomenological models

which cannot fully explain the true physical mechanism of mechanical deformation and failure of salt rock. Salt rock is a polycrystalline aggregate

which mainly consists of NaCl and a few amounts of impurities formed in the geological lithification process. Its deformation mechanism is largely controlled by mechanical properties of the grain and grain boundary. The microstructure of the grain in salt rock was obtained by scanning electron microscopy (SEM)

and the micro/meso mechanical parameters of the grain and grain boundary were determined by molecular dynamics (MD) and nanoindentation technologies. Based on the numerical Voronoi polygon technology

a microscopic numerical model of salt rock was established by regarding grains of salt rock as deformable blocks. The discrete element method (DEM) was adopted to perform numerical simulation on the macroscopic behaviour of salt rock specimens under uniaxial compression and direct shear. Numerical results are in good agreement with macro-mechanical experimental results

which indicates that the method proposed on the micro/meso grains of salt rock and the DEM can describe macroscopic mechanical properties well based on physical microstructure of salt rock.