Optimum design calculation method for the reasonable buried depth: A case study from Hong Kong-Zhuhai-Macao immersed tunnel

摘要

Immersed tunnels are built on the seabed, which is washed and unloaded by seawater, resulting in a thinner covering layer when compared to drilling blast tunnels. If the overburden layer is too thin, it increases the tunnel's buoyancy and the shear stress of the joints; if the overburden layer is too thick, the external pressure increases and reducing structural stability. To limit the impacts of stress, instability, and costs, the buried depth of a tunnel is an important variable. In this study, a calculation of the reasonable buried depth for an immersed tunnel is presented. Using the Delphi method and fuzzy set theory, the weights associated with an engineering analogy, foundation settlement, structural internal force, and seismic load methods each method were obtained for a set of proposed buried depths. These weights were used to construct an optimization calculation model for optimal buried depth, which was then applied to the Hong Kong-Zhuhai-Macao immersed tunnel. Based on the model results a buried depth of 14.25 m was selected. The results provide a reference point and guide for future research on calculating a reasonable depth for immersed tunnels.