Abstract: The key problems encountered during the construction of Qingxiushan Station on Nanning Metro Line No. 3 in semi-diagenetic stratum by cut-and-cover and mining method are analyzed based on numerical analysis and site monitoring; and some corresponding countermeasures are put forward. The research results show that: (1) The multiple well dewatering method can be used to consolidate the stratum in water-rich semi-diagenetic stratum; the cohesion of the surrounding rock is improved greatly after dewatering, which can provide favorable conditions for tunnel excavation. (2) When excavating tunnel group in the platform layer, the construction procedure should be reasonably arranged; the horizontal channel can only be excavated when the distance between the excavation face of the main tunnel and the horizontal channel is greater than 1 times of the tunnel diameter; and the ramp passage should be excavated after the cross passage lining reaches the strength. (3) The intersection of the tunnel should be strengthened according to the engineering conditions, especially the longitudinal direction. (4) Under certain conditions, it is feasible to construct the open-cut structure on the station floor before the tunnel group is excavated on the platform floor.

Key words: semi-diagenetic stratum, metro station excavated by cut-and-cover and mining method, multiple tunnels, multiple well dewatering, numerical simulation analysis