Abstract
The Center Diaphragm Method (CDM) fits shallow tunnels with unsymmetrical pressure, large cross-section and adverse geological conditions. However, the curvature of the center diaphragm, as the key parameter, is currently determined empirically. This paper explored the interaction between the support system and the surroundings in CDM-constructed tunnels under different curvatures of the center diaphragm. The theoretical analysis was conducted by establishing a mechanical model of the primary lining-upper center diaphragm double-arch support structure, which takes covering depth, unsymmetrical pressure angle, and temporary support location as variable parameters. Therefore, the relationship between the curvature of the center diaphragm and the internal forces of the support structure was obtained, and the validity of this model was verified. Moreover, three-dimensional numerical models were established with Midas GTX NX to investigate construction performance under various curvatures. The results showed that as the curvature of the center diaphragm increased, the crown settlement of the leading pilot tunnel increased and the growth in the compressive stress of the primary support caused by the dismantling of the center diaphragm was weakened, and the straight center diaphragm bore less stress than the curved ones. These results provide reference for similar projects and assist in improving tunnel CDM application.