To evaluate the accuracy in the results of the proposed method, they are compared with the results of finite element method and Coulomb methods (Table 1). By changing the angle of the retaining wall and soil friction angle, a stress is obtained which acts on the wall in a certain depth in three methods. Fig. 5a–c shows the geometry of the constructed models in Plaxis 3D Tunnel [34]. If the numerical answers are considered accurate, the errors presented in Table 1 belong to Coulomb and the proposed method as compared to the numerical method. It can be seen that the error of Coulomb׳s method increases with reducing the angle of the retaining wall. Instead, the error of the proposed theory remains in the acceptable range.