Numerical assessment of groundwater-table effects on building-floor displacement under seismic surface waves

Groundwater-table depth alters the saturated and unsaturated zones of a soil profile and can influence seismic surface-wave transmission to building foundations. This study evaluated the floor-by-floor displacement response of a multi-storey building subjected to Rayleigh-type excitation for groundwater levels of 20 m and 4 m below the ground surface. A three-dimensional PLAXIS 3D soil-foundation-building model was developed using a 200 × 100 × 50 m domain, 44,836 tetrahedral elements, and a 24 × 24 m, 27 m high building with a 3 m basement. Drained linear-elastic loam and gravel layers, viscous absorbing boundaries, Newmark time integration, and a 10 Hz harmonic displacement applied for 5 s were used. The 4 m groundwater table reduced peak horizontal displacement at all monitoring levels. Basement displacement decreased from 2.59 to 2.11 mm, the first-floor response from 2.59 to 2.03 mm, and roof displacement from 1.28 to 1.02 mm, corresponding to reductions of 18.53%, 21.62%, and 20.31%, respectively. The average reduction was approximately 19-20%. These results show that groundwater conditions can significantly affect computed soil-structure interaction, although the findings remain specific to the adopted material model, excitation frequency, and boundary conditions.

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