Feasibility analysis of trenchless methods for subway stations in complex confined spaces within Suzhou soft soil areas

This study evaluates trenchless construction technologies for subway stations along Suzhou Metro Lines 9 and 10, where water-rich soft soil and heritage-protection requirements constrain construction. To quantitatively assess the feasibility of five distinct methods—pipe jacking, shield enlargement, large-diameter shield (LDS) tunneling, special-shaped shield tunneling, and the prefabricated cover-slab method—an Analytic Hierarchy Process (AHP) model was developed incorporating technical, economic, environmental, risk, and policy criteria. The AHP evaluation identifies LDS tunneling as the highest-ranked alternative under the proposed evaluation framework, with a comprehensive score of 8.43. Sensitivity analysis across four scenarios showed that LDS remained the highest-ranked option under safety-first and heritage-protection priorities, although its advantage decreased under cost-prioritized conditions. Furthermore, targeted adaptability improvements for LDS tunneling are proposed, integrating architectural optimization, fire safety enhancements, and intelligent construction modules to guide future engineering design. These findings support method selection for trenchless subway construction in Suzhou and other cities with comparable soft-soil and urban constraints.