## 1 Introduction  
In recent years, with the acceleration of urbanization and the rapid increase in the urban population, urban traffic congestion has become increasingly serious, which has become a major bottleneck restricting urban development to a great extent. In consideration of the limited resources of urban aboveground space, scientific and reasonable development of underground space is an important means to alleviate traffic congestion and expand urban functions. For the construction of large cross-section and superlarge cross-section tunnels, most tunnel faces are divided either horizontally or vertically into several drifts, and the drifts are excavated in a predetermined sequence [1], such as the center diaphragm method, cross diaphragm method and double side heading method [2, 3, 4]. The main advantage of dividing a large cross section into small parts is that the support can be carried out in time after each excavation step, which makes it easier to control the overall settlement and horizontal convergence of the tunnel. However, the total construction sequence will increase significantly, and large mechanized equipment is difficult to operate in limited space, which may reduce the excavation efficiency and eventually increase the construction cost [5, 6]. There are many kinds of tunnel primary support methods; among them, grid arch/steel arch and rock-bolt mesh shotcrete are widely used [7; 8; 9; 10]. A large cross-section tunnel with complex soft surrounding rock has poor self-stability after excavation; once the bearing capacity of the supporting structure is insufficient and it cannot be quickly closed into a ring, large deformation easily occurs. If the excavation exposure time is longer, the risk of loosening and collapse accidents will increase significantly [11; 12; 13]. Furthermore, arch installation is still mainly a manual process, and there are problems, such as low construction efficiency, high labor intensity, and difficulty in ensuring the quality of installation operation [14; 15]. Therefore, it is of great significance to determine the appropriate construction method and reasonable support structure to improve the stability of the working face, construction efficiency, and economic benefits. [PERSON] and [PERSON] [16] designed a new type of three-leg grid arch with an 8-shaped web reinforcement, and proved the rationality of the structural design by carrying out a series of field application tests. [PERSON] et al. [17] carried out the flexural mechanical performance test of the three-leg grid arch and conducted research on the structural design and parameter optimization of different forms of connecting web bars. [PERSON] et al. [18] designed a lattice type of four-leg grid arch. Through the four-point bending test and numerical simulation, and compared with three-leg grid arch, the differences in ultimate bearing capacity and structural stability were analyzed. [PERSON] et al. [19] carried out research on the mechanical properties of a high-strength grid arch, obtained reasonable structural design parameters, and verified that it has good stability and economy. The reinforced reticulated shell structure has the advantages of reasonable stress, large overall rigidity, and various forms, which has been widely applied in supporting projects, such as mine roadways and traffic tunnels [20]. The concrete reticulated shell structure gives full play to the performance of steel and concrete materials. After construction, the whole tunnel support system presents a continuous hyperbolic arch structure, which gives the support advantages of being three-dimensional, continuous and light weight, and has the dual characteristics of active support and passive support [21]. [PERSON] et al. [22] designed a new structure of reticulated shell bolting and shotcrete according to the mechanical principle of a large-span reticulated shell structure on the ground and successfully carried out industrial tests in soft rock roadways with high ground stress in the Huianian mining area.