| Considering the asymmetry, nonuniformity and local characteristics of load in the near field, the expression of lateral load was derived by geometrical relation. According to the different bearing modes of structural section, the plastic failure criterion under the joint action of axial force and bending moment was given. Based on the four hinge failure mechanism, a simplified calculation method for the plastic damage of shallow buried arch structures was proposed. The bearing mode of circular arch plastic failure was calculated based on Matlab, then the distribution of structure plastic hinge was obtained. It is shown that plastic hinges are produced near two arches, at peak load, and at the shoulder of backside blast surface. When the bias angle is small, the plastic hinge firstly appears at the arch of backside blast surface and the position of projection point of explosion source. As the blast angle increases, the first plastic hinge appears at the arch of front blast surface. In practical engineering, large bias is an ideal failure mode.