Mesoscopic deformation based plastic constitutive model of salt rock

The existing phenomenological constitutive model is hard to describe how the impurity content, temperature and strain rate affect the mechanical behavior of the salt rock. It is more difficult to explain its deformation mechanism. Salt rock mainly consists of halite crystal. The deformation mechanism of salt rock is controlled by the polycrystalline structure. Therefore, it is more appropriate to build the plastic constitutive model using solid dislocation theory for the description of the deformation of the rock salt. The mesoscopic mechanism of the plastic-creep is the coupling of dislocation sliding of inner crystal grains and dislocation climbing-sliding of boundaries and their interference surfaces of inner crystal grains. According to the above hypothesis, the relationship between the average scale of the subgrain (or grain) and flow stress, the mean density of dislocation of inner grains and evolution model of microscopic parameters (including dislocation, subgrain diameter and boundary width between subgrains) are obtained sequentially. Finally the meso-macroscopic deformation and then plastic constitutive equation of salt rock are established using Orowan's law. The obtained equation can reflect the physical mechanism of plastic-creep deformation of salt rock and has an improved physical significance, comparing with traditional plastic constitutive model. This constitutive model could only be obtained through observation and research on mesoscopic structure of rock salt.