Investigation of geometric effects on three-dimensional tunnel deformation mechanisms due to basement excavation

Numerical parametric study is conducted to investigate geometric effects of basement excavation on existing tunnels. Centrifuge test results are adopted to validate numerical models. If basements with a same excavation area are constructed above a tunnel, the most preferable excavation geometry is short-rectangular basement, followed by cylindrical, square, and long-rectangular basements. When excavation diameter of cylindrical basement reaches eight times of the final excavation depth, three-dimensional effects of basement-tunnel interaction at basement centerline are negligible. If three-dimensional effects in a small basement are ignored, the heave and transverse tensile strain of tunnels are overestimated by up to 160% and 50%, respectively.