Abstract: A threedimensional(3D) simulation calculation model of structural stress is established to analyze the damage evolution process of typical tunnel structures in silty clay and silty sand under two deformation modes of horizontally and vertically oval shapes, to provide a safety assessment for the Jiajiang tunnel operation in Nanjing, China. Based on the overall stress state of the concrete, bolt, steel bar, and structure, the control value of section convergence deformation in the operation period is discussed. The following conclusions are drawn: (1) Under the extreme scouring condition of 7 m in the middle river with strong permeability, the tunnel as a whole rises 2.85 mm. The bolt stress amplitude, which is the most sensitive, is reduced by 27.6%, and the concrete stress variation is the least. (2) When the longitudinal differential settlement is not considered, the structure changes to the mode of high axial compression due to water scouring, which is beneficial to bearing capacity. (3) As the water level increase, the vertical deformation of the tunnel increases by 0.22 mm, and the bolt stress decreases by 3.8 MPa. Furthermore, the vertical deformation decreases by 0.05 mm, and the bolt stress increases by 2 MPa. (4) The comparative analysis results of different geological sections show that 10‰ and 12‰ are considered the settlement control values for continental and middle river segments, respectively, under the horizontally oval shape mode; whereas 9‰ under the vertically oval shape mode. The results can be considered as reference points for inspection, data monitoring, and structural safety state determination during the operation of the Jiajiang tunnel.

Key words: underwater shield tunnel, structural damage evolution, deformation mode, diameter deformation ratio, control standards