Nonlinear Creep Damage Model For Rock Salt

The nonlinear creep damage mechanism of rock salt is investigated with triaxial creep tests, theoretical analysis and numerical simulation in the study.The creep behavior of rock salt is studied with triaxial creep tests under different deviatoric stresses. Laboratory creep tests indicate that the creep deformation rates during the second stage are equipped with nonlinear characteristics and accumulated creep deformation has effect on the rates. Hereby, a 3D creep damage model for rock salt is suggested with the modified Burgers creep model. The creep mechanical parameters of Jintan rock salt are obtained with fitting tests data into the model. The fitting contrast of the suggested damage model with other models is illustrated and the results show that the creep damage model is better than other creep models in fitting the experimental data.The stability analysis on Jintan underground gas storage caverns has been carried out with plugging the model in FORTRAN into FEM code ABAQUS. The deformation process and deformation distribution characteristics are obtained. The reference heights of casing shoes are proposed with the evolution process of damage zone. Furthermore, the numerical studies show that, the creep of storage caverns in last ten years is small with the present of inner brine pressure; the creep in gas injection period is small with the increasing pressure and the creep in gas extraction period increases with the decreasing inner pressure. However, the deformation and plastic zones of caves are large comparatively with the small spacing among the caves. And the collapse of rock pillars will be expectant if there are sharp increments or reductions in inner pressure.