3D liquefaction assessment of soils surrounding circular tunnels

• Seismic behavior and liquefaction response of underground structures is determined numerically.
• Important parameters are the diameter, support thickness and depth of the tunnel.
• The most important parameter in defining the liquefaction potential is the depth of the tunnel.
• Diameters and support thickness do not have much effect on the liquefaction potential.
• The maximum acceleration values of free field are nearly equal to tunneled sites.

The aim of this paper is to investigate the effect of underground circular tunnels on cyclic behavior and liquefaction potential of soils surrounding them. For this purpose, an intensive numerical analyses scheme which includes three-dimensional, finite difference based total stress analyses on generic soil, tunnel and earthquake combinations has been performed. The effect of tunnel diameters, depth of tunnel center, support thickness of tunnels and the strength of soils have been discussed in detail. It is concluded that changing the diameter and support thickness of the tunnels does not make a remarkable change on surface acceleration. Similarly, the liquefaction potential of the soils considered does not depend on the diameter and support thickness. However, it was shown that the most important parameter defining the liquefaction potential is the depth of the tunnel from the ground surface. If the tunnels are deeper, they are less vulnerable to liquefaction compared to shallow tunnels.