Abstract: To address the challenges of multicriterion decision-making involving safety, reliability, durability, and economy when selecting an appropriate immersed tube tunnel element strategy, the authors introduce a comprehensive evaluation model that integrates the entropy weight method (EWM) and the technique for order preference by similarity to an ideal solution (TOPSIS). The model establishes a technical and economic comparison framework for multidimensional structural element plans, incorporating technological, construction-related, economic, and environmental factors. Ten key indicators are systematically identified and quantified: structural technique maturity, prefabrication difficulty of tunnel elements, construction site requirements, floating transportation difficulty, masonry structure durability, environmental protection impact, structural reliability, structural waterproofing performance, construction duration, and engineering cost. EWM is used to objectively determine the indicator weights, and TOPSIS is subsequently applied to calculate the relative closeness of each alternative strategy to the ideal solution, enabling systematic ranking. Using the immersed tube tunnel project of the Shenzhen-Zhongshan link as a case study, an empirical analysis evaluates three strategies: a steel-shell concrete element strategy, a reinforced concrete element strategy, and a combined steel-shell-reinforced-concrete strategy. The results show that the steel-shell concrete element strategy achieves the best overall performance, with a comprehensive score of 0.72, ranking first. The combined and reinforced concrete strategies rank second and third, respectively. The proposed model effectively integrates multidimensional information—including technical feasibility, construction complexity, economic cost, and environmental impact—thereby providing a systematic and objective quantitative decision-making tool for selecting immersed tube tunnel element structures. It supports the optimization of structural strategies and aids decision-making under complex engineering conditions.

Key words: immersed tube tunnel, tunnel element structure selection, technical and economic comparison, entropy weight method-TOPSIS model, Shenzhen-Zhongshan link