Abstract: Currently, studies on the construction control of overlapped tunnels passing through complex urban environments in China are mainly focused on demonstrating the effectiveness of construction measures in controlling the surface subsidence. There is relatively little research on the control of overlapped tunnel construction from the source system such as equipment improvement. This paper presents the construction of the overlapped shield tunnel section between the Huancheng South Road Station and the Kunming Railway Station of Kunming Metro Line No. 2. This case history introduces the experience of construction measures for small distance overlapped and shielded tunnel construction under complex geological conditions. The specific auxiliary construction measures include shielded shell thickness reduction, improvement of the shielded cutter-head and the support arm, optimization of the grouting mode behind the wall, strengthening of waterproof sealing at the shielded tail, setting up temporary support in the first construction tunnel. Improving the engineering properties of the soil within the influence range of two tunnels through grouting reinforcement measures. The implementation of the relevant auxiliary construction measures ensures the safety of overlapped shielded tunnel construction in this project. The relevant engineering measures and the implementation experience can provide references and guidelines for similar projects in complex geological conditions.

Key words: Submerged Sand and Gravel Strata, Shielded Tunnel Construction, Overlapped Tunnels, Construction Measures