AUTHOR=Dong Lei , Yao Aijun , Zhou Daxing , Zhang Pengfei 

TITLE=Characterizing the bending behavior of underground utility tunnel roofs in a fabricated composite shell system

JOURNAL=Frontiers in Materials

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2023.1201752

DOI=10.3389/fmats.2023.1201752

ISSN=2296-8016

ABSTRACT=This study proposes a new fabricated underground utility tunnel system — underground utility 
tunnels in the fabricated composite shell system. As the permanent formwork, 20 mm thick high-performance 
cement-based material is used, and the framework of steel reinforcement is located in the cavity between the 
formwork shells on both sides. After the on-site hoisting is performed in place, concrete is poured to form 
integral tunnels. This research investigates the system design, clarifies the system's component structure and 
connection structure, and evaluates the mechanical properties of high-performance cement-based material 
used in the formwork shells. A bending test is conducted on the roof specimen of utility tunnels in the 
composite shell system. The test results indicated that the roof specimen of the composite shell system presents 
the same failure phenomenon as the cast-in-place roof specimen, and their bearing capacity, stiffness, and 
others are identical to those of the cast-in-place structures. Based on the analysis of the experimental 
phenomena and results, the characteristics of the formwork material, and the bending test outcomes, a formula 
for calculating the roof's bearing capacity in a composite shell system is proposed. The calculated results agree 
well with the experimental values.