Abstract: With the increase of crosssection size of mining tunnel in metro station by cutandcover and mining method, the structural risk multiplies. In order to reduce the mining crosssection size as far as possible under the premise of reasonable function and further reduce the structural risk, the architectural design optimization concept of returning to the standard requirements of architectural design standards, combing out the blind spots of electromechanical design standards, and promoting the adjustment of mechanical and electrical design schemes is proposed by incorporating the high risk of mining tunnel structure into the design evaluation system. According to project practice, three specific measures are summarized as follows: (1) Simplifying the partial functions of the mining tunnel, and simplifying or transferring the functions to the open excavation space. (2) Reorganizing the geometric relationship between the functions in the mining tunnel group, and effectively planning and reducing the scale. (3) Paying attention to the favorable stress characteristics of the circular and horseshoeshaped crosssection of the tunnel, and making the functional shape of the regular crosssection seamless with the tunnel. The measures mentioned above are applied to Qingxiushan Station in Nanning Metro Line No.3, which can effectively reduce the number and the crosssection size of tunnels, and expand the distance between tunnels. The comprehensive optimization crosssection area reaches about 30%, which can reduce the risk of mining structure.

Key words: metro station excavated by cutandcover and mining method, mining tunnel, crosssection optimization, metro architecture design standard, functional combination, engineering risk