Seismic response of shallow circular tunnels in two-layered ground

• The effect of ground stratification on the tunnel׳s seismic response is investigated.
• A 2D model of a circular tunnel in two-layered ground is used.
• The layers interface was placed at the crown, centre and invert level.
• Ground stratification has an important role on the lining seismic forces.
• Analytical solutions cannot be used when large layers׳ stiffness contrast exists.

The effect of ground stratification on the seismic response of circular tunnels is investigated, as most practice-oriented studies consider homogeneous ground. A finite element plain-strain model of a circular tunnel cross-section embedded in a two-layered ground is used to highlight the influence of stratification on the tunnel׳s seismic response. The layers interface was placed at the crown, centre and invert level.It is proved that ground stratification has an important role in the lining seismic forces. When the tunnel is fully embedded in one of the layers, the seismic lining forces may vary significantly in comparison with the single-layer case. If the tunnel intercepts both layers, maximum lining forces aggravation occurs when the lower layer is very stiff.