Study on mechanical characteristics of support system for Shallow-buried Single-Arch subway station in rock stratum

摘要

During the construction of shallow-buried single-arch subway station, because of unstable surrounding rock and lack of design experience, failure and hazard phenomena, such as large deformation, collapse and instability of soils/rocks often occur, substantially affecting the safety of tunnel structure and construction. In the case of the Xinggongjie Station subway tunnel, Dalian, Liaoning Province, Northeast China, mechanical and deformation characteristics of support system are analyzed by numerical simulations and in-situ monitoring data. Additionally, comparative analyses are conducted for internal force of arch support in different surrounding rock pressure and in-situ monitoring result. It is concluded that the single-arch subway station usually cannot form a pressure arch characterized by shallow-buried tunnel properties; the double initial support of stacked loaded arch bear full load together in construction process, and the outer initial support bear the main load; the up-step excavation of middle pilot and dismantling temporary support are key processes in the construction control. It is found that the structure will stabilize upon the completion of the stacked loaded arch. The stacked loaded arch structure can control the stratum deformation to an acceptable range; meanwhile, it has certain safety margin and stratum adaptability. The study method and conclusions can provide references for support in-site construction and similar projects and can enrich and improve design method of the large-span single-arch station.