Interactive effects of crossing tunnel construction on existing tunnel: Three-dimensional centrifugal test and numerical analyses

Abstract

To study the influence mechanism of a new crossing tunnel on an existing tunnel, centrifugal tests and three-dimensional numerical analysis were performed considering the different excavation sequences of the new tunnel, formation loss, and the clearance between the old and new tunnels. The results indicate that a vertical stretching phenomenon occurs in the existing tunnel, regardless of the sequence in which new tunnel crosses it (above or below). Compared to the new tunnel excavation above the existing tunnel, the manner of under-pass has a more significant impact on the additional internal force and deformation of the existing tunnel. The maximum vertical displacement and longitudinal bending moment typically occur at the symmetry plane at the center. An increase in the clearance between the old and new tunnels leads to an increase in the minimum vertical stress ratio, which is conducive to the formation of load-bearing arches. However, this leads to an increase in the range of collapsed arch, which decreases the maximum values of the vertical displacement and induced bending moment of the tunnel as well as increases the range of deformation. When the construction of the new tunnel leads to a higher loss of formation, there is a significant increase in minimum vertical stress ratio and a clear reduction in the maximum vertical stress ratio, which cause a more marked structural response from the existing tunnel.