The movement of shallow rectangular tunnels in soft clays under earthquake loading

Publication Title
The movement of shallow rectangular tunnels in soft clays under earthquake loading

Abstract

Earthquake-induced ground failure can cause uplift in buoyant underground structures, including shallow tunnels. While much research has looked at the seismic response of tunnels in liquefiable soils, less attention has been given to their response in soft clays. This is of interest as structural and ground failure has also been observed in fine-grained soils in the field, owing to the degradation of their strength and stiffness with cyclic loading. As such, it is important to understand the effects of this cyclic softening on a buried structures ability to resist uplift during an earthquake. In this study, dynamic centrifuge experiments were conducted to investigate the effects of seismic loading on a shallow rectangular tunnel buried in a soft clay. With each test, the undrained shear strength of the clay was varied, yielding differing dynamic responses. Particle image velocimetry analysis showed that the seismic response of a tunnel in soft clay is distinct from its well-investigated counterpart in sandy soils, even when tunnel uplift does occur. While similar displacement mechanisms occurred, as the clay retains some stiffness, clay above the tunnel heaved together with the tunnel, resulting in similar vertical displacements between the surface and the tunnel. Lateral movements were also significant due to the high compressibility of clay, even when uplift was minimal. These findings highlight the value in studying the seismic response of tunnels in clay, even if less critical than liquefaction in terms of uplift.

Authors
N. G. Lee; P. Gopal MADABHUSHIS

Published In

11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)

Theme

Session 3: Resilient geotechnical infrastructure