Study on the mechanical performance of lightweight arched prefabricated structures in large-span cut-and-cover tunnels

An innovative composite-jointed arch structure is proposed to address construction challenges such as slow progress, high precision requirements, and elevated costs encountered in the large-span prefabricated cut-and-cover tunnel project of Xinsen Avenue in Chongqing. The study incorporates theoretical analyses, field tests, and nonlinear numerical simulations to examine the mechanical properties, deformation characteristics, load-bearing mechanisms, and failure modes of prefabricated hollow structures compared to solid structures. Results indicate the newly developed composite-jointed arch structure exhibits excellent load-bearing capacity. The structure forms a two-hinged arch system, where grout-keyed joints at the inverted arch and rubble-concrete sidewall backfills collectively ensure horizontal and vertical stability, maintaining overall structural integrity. Composite joints efficiently transfer internal forces, ensuring coordinated deformation of components. Although hollow structures experience increased stress and deformation due to reduced stiffness and sectional discontinuity-induced stress concentration, both solid and hollow structures exhibit typical four-hinged failure mechanisms under ultimate loading conditions without significant degradation of ultimate load-bearing capacity. Current thin-walled hollow components effectively balance weight reduction with structural safety, significantly enhance concrete temperature control efficiency, shorten lifting periods, optimize construction efficiency and economic indicators, and promote broader application and development of prefabricated techniques in underground engineering.