Based on the first successful application of new prefabricated technology in underground metro stations on line 2 of the Changchun Metro in China, a comprehensive analysis and discussion on research strategies for new prefabricated technology for large underground structures is provided. This paper introduces the application status of prefabricated technology in underground engineering worldwide, illustrates the different characteristics of prefabricated technology applied to ground buildings and underground structures, puts forward the key technologies, and compares the major technical, economic, and social benefits achieved. The successful application of prefabricated technology for underground structures in Changchun Metro demonstrates the feasibility and great advantages of the new prefabricated technology for underground engineering.

Prefabricated underground structures were first researched in China to address the serious social and environmental issues associated with underground construction. Five metro stations have been built on Line 2 of the Changchun Metro in China using this new prefabrication technology. The joints connecting prefabricated elements are the most critical components in such prefabricated structures. In this study, experiments and numerical simulations investigating the influences of different grouted mortise and tenon joint geometrical parameters were conducted to determine the optimal parameters and ensure proper performance. To do so, a finite element model was built with the appropriate characteristics using the experimental results, and an analysis of the influence of different geometrical parameters was conducted. The results indicate that increasing the dip angle of the tenon could improve the flexural rigidity of the joint, but its effect was relatively small compared to that of the other parameters. Increasing the width of the tenon only had a positive effect on the flexural rigidity of the joint when the width was relatively small and under small axial loads. Increasing the length of the tenon helped to enhance the flexural performance of the joint; however, this advantage was not obvious when the tenon length was relatively long. Proper indentation of the joint improved the flexural capacity under a small axial load, but was not beneficial under a high axial load. The findings of this study are of value to help researchers and engineers more effectively design prefabricated underground structures.

The grouted mortise‐tenon joint, invented as the connection between the large prefabricated components, is the key to the prefabricated underground structures, and the double‐tenon joint is most widely used in the prefabricated metro station structure. This paper conducts characteristic analysis of bending stiffness with a 1 : 1 prototype test in key working direction of different joint types for grouted double mortise‐tenon joint. The results show that the double‐tenon joint is characteristic of variable stiffness under different loads. Change laws of double‐tenon joint bending stiffness without and with auxiliary pretightening device in tension side and compression side are also discussed. The correlations for calculating double‐tenon joint bending stiffness with various axial loads and bending moments are derived at last, which offers the theory foreshadowing of similar joints.

The MT·G-Joint (grouted mortise-tenon joint), invented as the connection between the large prefabricated elements, is the most important component in the prefabricated underground structures. Its shear performance is critical to the overall mechanical performance of the prefabricated structure. This paper carries out four-point pure shear experiment to investigate the shear performance of the MT·G-Joint. The shear key method is then proved to be suitable for MT·G-Joint when the axial load is 0 kN based on the experimental results. In addition, combining the shear key method and experimental results, the calculation method of the shear capacity, improved shear key method (ISKM), is proposed on account of the mechanical model of the failure plane. ISKM is appropriate for different load conditions. Finally, every kind of joints used in the prefabricated metro station structures on Changchun Metro Line 2 is calculated by using ISKM. The results indicate that the shear capacity of the MT·G-Joint is good, and the used joints still have large safety margin even under the worst working condition. The findings of this study are of value to help researchers and engineers more effectively design prefabricated underground structures.

The grouted mortise‐tenon joint, invented as the connection between the large prefabricated elements, is the most important component in the prefabricated underground structures. This paper conducts analysis of load‐carrying capacity performance and failure mode with 1 : 1 prototype test in key working direction of different double mortise‐tenon joint types for the prefabricated metro station. The resistance moment is developed and used to analyze the bending bearing characteristic curve, and the corresponding test results of each stage of the characteristic curve are described in detail. In addition, the bending bearing performance of different types of double‐tenon joints under different load conditions is compared. The test results clarify the ultimate failure mode of double‐tenon joint and the variable bearing capacity characteristics of the joint with the increase in axial load and explain the bearing performance of each stage. It is also found the auxiliary pretightening device is helpful to delay the appearance of cracks and improve the bearing capacity, especially when it is set on the tension side. The research results have important application value for the joint design of prefabricated metro station structures.

This paper analyzes the law of joint deformation of grouted mortise‐tenon joint with 1 : 1 prototype test in key working direction types under 38 working conditions of different joint types, tenon lengths, grouting ranges, grouting materials, and loading combinations for the prefabricated metro station. The deformation performance of the joint has also been compared. In addition, finite element models have been built, and the joint deformation stages are discussed. The influences on the law of joint deformation of different influencing factors have been discovered. The deformation development stages and the main deformation laws of each stage of the joints have also been obtained. Moreover, this paper also compares and analyzes the field test results and experimental results. The monitoring results show that the safety margin of joint deformation is sufficient during the whole construction process from the assembly to the completion of the station. The research results have great values for the joint design and calculation for the prefabricated metro station structure.