Climate Driven Water Table Changes and Their Influence on Liquefaction Response of Integral Bridges

Abstract

Integral abutment bridges (IABs) eliminate bearings and joints but transfer seismic demand directly into the surrounding soil, making their response highly sensitive to groundwater conditions and soil–structure interaction. This study presents a 60 g centrifuge testing programme on single-span IABs designed to isolate the influence of water-table elevation on seismic behaviour.

Water-table elevation was found to be a dominant control on system response. With a saturated foundation and dry backfill, spread-footing IABs experienced the largest settlements, approaching 0.30 m, accompanied by co-seismic ratcheting and minor global rotation. When both foundation and backfill were saturated, early backfill liquefaction shifted the response from kinematic to inertial control. Although settlements reduced to approximately 0.09 m, structural demand increased. Across all spread-footing tests, shallow saturated backfill zones liquefied while soil beneath the footings remained partially liquefied but significantly softened, explaining large settlements without complete loss of support. Piled abutments effectively limited settlements and suppressed liquefaction near the abutments; however, under saturated foundations they developed higher peak and residual bending moments, indicating redistribution rather than reduction of seismic demand.

These results demonstrate that elevated water tables can induce settlement ratcheting in spread-footing IABs and amplify structural demand in fully saturated systems, highlighting the need for explicit groundwater load cases and SSI-consistent design in seismic and flood-prone regions.