Abstract: To improve the structural design theory of the secondary lining trolley, numerical simulations and field measuring are conducted to analyze the structural stress and formwork deformation of the secondary lining trolley under various concrete pouring conditions, and the stress distribution and variation patterns of the trolley are summarized by taking the Fangshan tunnel of the Linyi-Tengzhou expressway as a example. Results show that: (1) The trolley stress primarily concentrates on arch springing jacks, portal frames, and load-bearing columns, with a maximum reaching 585.8 MPa. The maximum formwork deformation occurs at the crown when asymmetrically concreting at sidewalls, reaching 10.97 mm. (2) The end columns tensioned and the central one compressed along the walking direction of the trolley when concreting sidewalls, whereas the end columns compressed and the central one tensioned after crown concreting. When the outer columns are concreted to the crossbeam with a height difference, the stress difference reaches an extreme. The left column′s tensile stress reaches 12.2 MPa and the right column′s compressive stress reaches 23.6 MPa. (3) When there is a concreting height difference, the left compressed and the right tensioned. After crown concreting, the compressive stress on the crossbeam decreases from both ends to the center. Taking the front end section of trolley waking direction as an example, the stress changes little when sidewalls have not yet been concreted to the crossbeam height; when concreting to the crossbeam height, the stress on both sides changes from tensile to compressive, with the left and right reaching 19.2 MPa and 4.4 MPa, respectively.

Key words: tunnel lining, secondary lining trolley, structural stress, formwork deformation, stress distribution pattern, stress variation pattern