Abstract: The aim of this study is to investigate the effects of construction sequences of twin tunneling at different depths on the adjacent pipeline. A three-dimensional (3D) centrifuge model test was conducted by considering both the volume loss effect and the weight loss effect during the tunnel excavation. Moreover, the corresponding numerical simulation of this centrifuge model test was carried out, which further considered a displacement controlled method based on ground loss and an advanced hypoplastic constitutive model based on nonlinear small strain characteristics of soil. It reveals that twin tunnels at different depths with various construction sequences greatly affects the greenfield surface settlements, the pipeline settlements and the pipeline bending strain. After the twin tunneling, the sagging regions are located within the range of -2.5DT－1.5DT and the maximum bending strain within the sagging regions is around two times that within the hogging regions. The results indicate that the superposition principle cannot be simply applied to predict the surface settlements, the pipeline settlements and the pipeline bending strain caused by twin tunneling at different depths with various construction sequences. The effects of the accumulated shear strain and the relative pipe-soil rigidity should be reasonably considered.

Key words: 3D centrifuge modeling, 3D numerical analysis, twin tunnels, construction sequences, tunnel-pipeline-soil interaction