关键词: 预制临时仰拱, 大断面隧道施工, 支护结构, 三台阶七步工法, 现场测试, 变形控制

Abstract: In tunnel construction, it often takes long time to build temporary support structure, and the teporary structure cannot be reused easily after demolition. A design and construction scheme of reuseable precast temporary invert arch is put forward, and application tests are carried out in loess tunnel with threebench sevenstep method. By comparing the field data of fiber Bragg grating sensors and numerical simulation results, the implementation effect of precast temporary inverted arch is studied. The results show that: (1) Precast temporary inverted arch is simple, and reuseable and can be assembled fast,  which helps to quickly form temporary inverted arch and close primary support structure after middle bench excavation in largesection tunnel construction with threebench seven steps method. (2) Compared with traditional threebench sevenstep excavation construction scheme, the "threebench sevenstep excavation + precast temporary inverted arch" method proposed can effectively decrease the stress and deformation of primary support structure, in which the maximum principal strain of the primary support is reduced by 72%, and the vault settlement is reduced by 78%. (3) With precast temporary inverted arch, middle bench can be sealed quickly, which improve the interaction between primary structure and surrounding rock, effectively reduce the plastic deformation range of the surrounding rock after tunnel excavation, and ensure the safety of tunnel construction.

Key words: precast temporary inverted arch, construction of largesection tunnel, supporting structure, threebench sevenstep method, field test, deformation control