Under the circumstance of soft fractured surrounding rock with high geo-stress, the support technology of tunnel has become a major challenge. Traditional I-shaped steel and bar lattice girder, which cross-sections are often designed to be left-right symmetrical, may have insufficient strength and stiffness. Based on the concept of symmetry, a new support technology of spatial steel tubular grid (SSTG) arch is designed with high strength and large stiffness. In order to clarify the mechanical properties and failure mechanism of SSTG arch used as primary support, through laboratory and numerical experiments, this paper carries out the bending tests for the circumferential joint of SSTG arch components combined with the excavation tunnel project of Panyu Square Station in Guangzhou, and the analyses of the ultimate bearing capacity, deflection displacement, failure modes, and stress–strain evolution laws of joint components are conducted in detail. The results show that during the whole process of loading, the arch components have experienced elastic growth stage, plastic development stage, and final failure stage. The average ultimate bending capacity of SSTG arches is 340.5 kN·m, and the joint opening is 13.9 mm. The joint form of high-strength bolt + rigid flange plate proposed in the paper has reasonable stress state and high safety redundancy, which can bear the load of surrounding rock effectively, and ensure the safety in tunnel construction. The research results could provide a theoretical basis for the design and application of SSTG arch support in related projects.

Using RFPA software, the hydraulic pressure resistance and damage process of the grouted stone body of a tunnel in the high-pressure karst zone were analyzed, and the hydraulic pressure resistance of the composite surrounding rock and composite structure when the tunnel was expanded through the cavern under the effect of hydraulic coupling was investigated. Then, a new parallel heading expansion scheme for the New Yuanliang Mountain Tunnel was innovatively discussed, and the reliability of the results of the calculation model was verified by a field test. Lastly, the model calculation results guided the project to adopt a 5 m grouting range and advanced secondary lining to ensure that the composite structure’s water pressure resistance could reach 3 MPa; by adopting the improved technology of parallel heading expansion based on the CRD method, the safety of tunnel expansion through the cavity was effectively ensured, which can provide a reference for similar projects in the future.

In view of the problems of rapid construction and deformation control of large cross-section tunnels in complex urban environments, the concept of “timely high-strength support” was put forward to form strong support over time and bear the load of surrounding rock in real time, and innovatively developed the spatial reticulated grid bolt-shotcrete support structure (SRGB). The research in this paper focuses on the supporting principle, bearing mechanical properties, snatch simulation test, construction process, and engineering application effects. The components of the SRGB and their respective functions were expounded in detail. The failure modes and deformation characteristics of the tested components were revealed through the indoor loading test, and the performance characteristics of the spatial reticulated grid concrete components with high strength and high rigidity were displayed. With the help of the multi-functional operation trolley, the assembly process test of the spatial reticulated grid was carried out, which verified the feasibility of mechanized construction and the rationality of structural design. Relying on the underground tunnel project of Guangzhou Metro, the spatial reticulated grid structure was successfully used as the initial support of the tunnel for the first time, forming a complete set of mechanized rapid construction technology for a large cross-section tunnel, and constructing a timely high-strength support system suitable for the complex urban environment. The research results provide a new idea and new technology for the mechanized rapid construction and efficient support of large cross-section tunnels.

To solve the technical problems of slow construction progress, low mechanization and high risk of shallow buried large cross-section tunnels in a complex urban environment, a series of spatial reticulated shell (SRS) support structures are developed in this paper. Moreover, the equipment of a multifunctional operation trolley is developed to install the SRS arch, and the construction technology system of the prefabricated SRS structure is proposed for a large cross-section tunnel. Therefore, the deformation characteristics of the end-plate joint component and jointless component are clarified by laboratory experiments. The construction mechanics’ simulation of the SRS arch is performed to obtain the tunnel deformation and structure stress based on the tunnel project of Panyu Square Station of Guangzhou Metro. A field application of the prefabricated SRS arch is carried out to realize the mechanized construction operation. The obtained results reveal that the end-plate joint component has better ductility, and its ultimate bearing capacity is basically consistent with the jointless component. The SRS arch can effectively control the deformation of the surrounding rock, improve the stress state of the structure, and reduce the plastic zone of shotcrete by numerical simulations. The overall stress of the SRS arch by field measurement represents the characteristics of “bigger on the upside and smaller on the downside” and “uneven symmetry”. Additionally, the successful application of the prefabricated SRS arch provides a scientific reference for mechanized construction of large cross-section tunnels.

The factors leading to the collapse of tunnel face are diverse, and there is an interaction relationship between multiple influencing factors at the physical and mechanical level. By analyzing the coupling relationship between the factors affecting the instability of tunnel working face, this paper deduces the calculation method of the coupling effect of tunnel construction risk factors for a certain risk event based on conditional probability theory, and makes reasonable assumptions on the monitoring data and risk probability. Finally, it is verified by a model test. The results show that the tunnel construction risk factors have a coupling effect by affecting other risk factors or changing the physical and mechanical parameters of surrounding rock, in which the coupling amplification effect will significantly change the failure probability of the risk carrier, so it is unfavorable to the stability of the tunnel face. The coupling amplification effect of risk factors will cause the increase of tunnel face extrusion deformation. Even if it causes a small deformation increment, it can also make the transition of risk probability and grade of tunnel face unstable, and cause tunnel face instability collapse. The research results of this paper can quantitatively evaluate and predict the stability of the working face in the process of tunnel construction.