Centrifugal model tests on excavation of twin parallel tunnels

The excavation construction of twin parallel tunnels is simulated by using centrifugal model tests. The internal stress and deformation variation of shield structure of the existing tunnel and the ground surface settlement are studied owing to excavation of the new adjacent tunnel. The research results show that: (1) The ground surface settlement relates with the tunnel excavation process, and the settlement trough range is independent of the tunnel excavation process. (2) The shield structure side of the existing tunnel near to the new constructing tunnel is subjected to tension and the bending moment at the same side of the existing tunnel has a negative increment, the transverse diameter increases, and the lateral earth pressure decreases at the same side of the shield near to the new construction tunnel. However, the vertical diameter of the shield structure of the existing tunnel is not affected. (3) The crown earth pressure of the just completed shield firstly decreases and then increases during the sequent excavation process. (4) The proposed method for the stratigraphic structure by the authors can be used to analyze the internal stress and deformation of the shield structure for tunnel construction.