Abstract: The study on the influence of structural lateral stiffness reduction induced by ignorance of shield shaft opening in calculation of opencut metro foundation pit on the stress and deformation of the foundation pit is of great significance. A loadstructure model for the standard twolayer shield shaft foundation pit of Weilaisanlu Station of Wuhan Metro Line 11 is established, and the equivalent lateral stiffness of the shield shaft ring frame beam structure is calculated by the formula of k=F/l, which is used as the foundation pit reverse support condition. And then the soilstructure model is established based on finite element software Plaxis, and the comparison is made between the equivalent lateral stiffness of the ring frame beam and the whole plate stiffness in the reverse construction of the foundation pit. The results show that the maximum displacement difference of the retaining structure between the two kinds of stiffness is 4.8%, the maximum bending moment difference is 2.7%, and the maximum shearing force difference is 1.3%, which are small differences.

Key words: metro, opencut foundation pit, shield shaft, ring frame beam, equivalent lateral stiffness