Abstract: Indoor modeling experiments are conducted to investigate the influence of quasirectangular shield tunneling on the confining pressure and deformation of adjacent existing tunnels in sandy soils. In this study, ground loss during 〖HJ3.8mm〗the construction as well as the relative positions of the new and existing tunnels are investigated. Different construction conditions, including overlapping underpass, pinch underpass, and orthogonal underpass with varying tunnel spacings are assessed. Results indicate that: first, among various construction conditions, the new quasirectangular shield tunnel has the most significant impact on the existing tunnel when it passes through in a constrained manner. Under this condition, quasirectangular shield tunneling beneath the existing tunnel leads to a sudden and notably remarkable change in the confining pressure at the bottom of the tunnel′s arch. Then, the spacing between tunnels remarkably affects the confining pressure, the strain at the arch bottom of the existing tunnel, and the displacement at the crown of the existing tunnel during the new quasirectangular shield tunneling. Therefore, a sufficiently safe distance between the new and existing tunnels must be maintained. Finally, the deformation of the existing tunnel crown is sharply increased in a certain stage during the new quasirectangular shield tunneling underneath. In actual engineering, considerable attention must be provided to control the deformation rate in this stage.

Key words: quasirectangular shield tunneling; existing tunnel, passing through below, shield tunneling, model experiment