///In this paper, by using nonlinear finite element numerical method, the authors studied the mechanical characteristics, the interference patterns of superposed folds and the feature of the united arc-shaped structures in Daba Mountain Foreland. The evolution of a series of arc-shaped structures has been demonstrated, and a group of boundary conditions adapted to the superposed deformation in this region has been obtained. The study shows that 1) the creep materials selected in our model were deformed greatly with time even under very small and slow variation of stress field, which made us possible to study the tectonic deformation through principal stress trajectory; 2) the interference patterns of superposed folds in Daba Mountain Foreland are mostly perpendicular intersection, inclined intersection and in parallel roughly; and 3) the formation of Daba arc-shaped structures is thought due to the action of northeastern boundary forces with two tectonic convergences at east and west part, but another arc-shaped structure in Eastern Sichuan Basin assembled with Daba Mountain forming a convergent double arc is thought due to the action of the boundary forces from southeastern direction.
