For stability analysis of underground oil/gas storages in laminated salt rocks

it is of paramount importance how to select the appropriate constitutive model for the characteristics of laminated salt rocks. In consideration of the laminative geological structural character of most salt mines in China

a new user-defined FLAC3D interface program is developed using the Visual C++ flat on the basis of 3-D expanded Cosserat medium constitutive model that takes the mesotropic bending effect into account in the sense of macro average; and in the meantime

a dynamic link library(DLL) is compiled in connection with the main calculation methods of FLAC3D software. A simple tunnel example shows that the calculating results using the present model are reliable. Furthermore

the new model can describe the progressive damage failure of compound element composited by two layers with different mechanical characters

and can also reduce greatly the number of element meshes through introducing some statistic parameters such as volume percent. The present model embedded in FLAC3D is expected to lay a foundation for stability analysis of the underground openings in layered rocks.