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Large-section special-shaped shield tunnels feature many advantages, such as versatility and a large space utilization rate in energy transmission and public transport; however, guaranteeing the quality of segments' assembly is difficult. Based on the quasi-rectangular shield tunnel project of Hangzhou Line 9 in China, this study investigated the formation mechanism and control measures of lining segment assembly defects. By quantifying the manufacturing error and positioning error, a simulation program for segment assembly is developed to calculate the error. Furthermore, considering the relative accumulative error between the upper and lower T blocks, the finite element model of key blocks (T-LZ block) is established to perform mechanical analysis, based on which the relative error control standard of the key block under the corresponding working conditions is proposed. The results show that the assembly quality can be effectively improved by assembling the LZ block first and applying corresponding error control measures, and the displacement of the segment along the rZ direction should be carefully controlled during the construction. The error caused by normal assembly will not damage the LZ block, and the corresponding control standard under the action of multi-degree-of-freedom error (extreme case) is 9.8 mm. Using this method to predict the assembly quality of segments can provide a basis for actual construction control of segment assembly. [ABSTRACT FROM AUTHOR]

The design of the lighting environment inside the tunnel has a profound impact on the long-term operation of the tunnel. The existing field studies, full-scale experiments and simulation methods, mostly focus on the luminance level inside the tunnel, ignoring the effect of the luminaires and decorations from the visual perspective. This paper proposed a novel digital-twin-based integral method, including virtual world design (the virtual reality (VR) experiment and the numerical simulation) and real-world validation (the tunnel mock-up experiment and the field experiment), to improve the design of the luminaires and decorations in the interior zone of the tunnel. The VR experiment and numerical simulation in lighting software were firstly conducted to determine the lighting parameters. Then the obtained lighting scheme was tested and validated in the real scenarios, where tunnel mock-up experiments and field experiments were conducted respectively. According to the results from the numerical simulations and VR experiments, the double-side luminance scheme is more conducive to driving safety and once the power of the luminaires is excessive low, the driver's attention variation rate is also unsatisfied. Moreover, the use of the anti-collision lower-side luminaires enhances the luminance level of the road surface and the sidewall to a certain level. The obtained lighting scheme was applied in a newly built tunnel in Hangzhou. The statistics of accidents data indicate that the installed luminaires and decorations, which are obtained from virtual simulation, can provide a considerably safe lighting environment. Ten months of accident statistics show that the breakdown rate in this tunnel was only 10% of the similar tunnels, and the accident rate was only 3%, thus the safety and environmental performance have been proved to be significantly improved. • A digital-twin-based integral method was proposed to optimize the tunnel lighting environment. • Numerical simulation and VR experiments were conducted to determine the scheme of luminaires. • Mock-up and field tests were conducted to validate results obtained from virtual simulations. • Valuable guidance and references are provided for the tunnel lighting design. [ABSTRACT FROM AUTHOR]