Abstract: Applying closedcavity thinwalled components is crucial for the lightweight design of large prefabricated components for underground structures. The closedcavity thinwalled components were first used in prefabricated metro stations′ lining structures in Changchun, Qingdao, and Shenzhen. Presently, no applicable codes and standards exist for underground structures′ closedcavity thinwalled components. Based on theoretical research and practical engineering application, the principal technologies for designing closedcavity thinwalled components of underground structures are discussed. First, from mechanical characteristics, joint structures, joint waterproof, and durability of prefabricated underground structure viewpoints, the lightweight design method of prefabricated components is analyzed, and the advantages of lightweight closedcavity thinwalled components. Second, a comparative analysis with Tshaped, Ishaped, and boxshaped section components with ribs revealed that closedcavity thinwalled components have similar mechanical properties regarding the shear lag effect and shear stress distribution. A typical shear lag effect occurs in closedcavity thinwalled components, but the influence degree is low. Furthermore, the primary influencing factors are analyzed, and the shear lag coefficient is proposed for closedcavity thinwalled components. The longitudinal rib plate shows section shear stress. Finally, the primary structural characteristics of closedcavity thinwalled components and their influence on the mechanical properties of the components are discussed. Structural indices such as flange plate, longitudinal rib plate, diaphragm, endplate, and internal cavity rate are put forward. The critical points of the structural design of closedcavity thinwalled components are developed from calculation analysis and design methods.

Key words: prefabricated metro station, lightweight design, closedcavity thinwalled component, boxsection components, section shear lag effect, cavity rate