Abstract：Numerical research on the interaction between the jointed rock mass and the support structure of a tunnel of large section and the mechanical state of the whole tunnel system in the sequential process of the excavation and construction is carried out by adopting the discrete element method(DEM). By using the universal distinct element code(UDEC) built-in structure model and a new developed method—de- and reactivating method，simply D-R method，the support structure which is sequentially constructed in steps and sections is simulated. The interaction and mechanical state of the surrounding rock and the support structure in a sequential construction process for a tunnel of large section are systematically studied，and the numerical results conform very well to the reality.
