Abstract:A new expanded Cosserat medium constitutive model,in which the influence of bending was taken into account,was proposed for bilaminate-layered salt rock. In this model,a new unit cell,namely,the material point containing two alternate layers,was employed to simulate the coordination of the meso-displacement between two layers with mismatch mechanical properties. It was validated primarily by an experiment on laminated salt rock samples under uniaxial compression. This model provides a new way for the analysis of layered salt rock. Having the Cosserat stresses,namely,the macro-average ones,which have been determined,the conventional stresses of the different layers in a unit cell can be obtained in sequence. Then the conventional stresses can be utilized through a routine way for the strength and failure analysis. The proposed model can be expanded to solve three-dimensional and nonlinear problems directly,and is expected to provide a key theoretical frame for the stability analysis of the underground openings in laminated salt rock.