Mechanical behavior analysis of station construction by the tunnel-before-station pile method

In the current metro construction of urban core areas, shield tunneling frequently faces the challenge of passing through stations, especially when mined stations are incomplete, resulting in pronounced mutual interference between shield tunneling and station construction. The “group tunnel effect” commonly arises in urban underground construction employing the pile-tunnel method, intensifying the complex changes in surface settlement and structural stress. Based on the Memorial Hall Station of the Guangzhou Metro, this study employs model testing and numerical simulation to systematically explore how the “group tunnel effect” influences settlement deformation during pile-tunnel method station construction, and how shield tunneling through stations at various construction stages affects structural stress. The results indicate: (1) Ground settlement is primarily caused by pilot tunnel excavation and the installation of initial support with invert arches. The intersecting works of cross-passages with pilot tunnels and invert arches markedly intensify the structural interaction, and notable stress concentration occurs at the cross-passage’s initial support following the removal of the headwall.(2) If shield tunneling occurs before the invert arch construction is completed, it will lead to a significant increase in the segmental stress and a change in the stress distribution of the soil between the shield and the surrounding ground.