Abstract
The rise of groundwater levels above the ground surface represents a serious risk to infrastructure, as it can undermine the stability of foundations supporting buildings, bridges, roads, and other essential systems. This challenge is intensifying due to the growing occurrence of extreme weather events and land-use changes that accelerate groundwater depletion and alter natural recharge patterns. Consequently, understanding groundwater inundation processes, their effects on soil–structure interaction, and establishing reliable approaches for vulnerability assessment and damage mitigation have become critical research priorities. In this study, a laboratory-scale physical model was developed to simulate groundwater seepage conditions and replicate field-like scenarios. The experimental program focused on monitoring seepage behavior through sandy soil mixed with varying proportions of gypsum under elevated groundwater table conditions. The principal aim was to establish a mathematical expression describing the phreatic line within this homogeneous soil system. A dimensionless parabolic function was derived and validated through statistical analysis, demonstrating strong predictive capability for estimating the phreatic surface. The investigation considered two main influencing factors: soil type (sandy soil with gypsum content) and groundwater table height. The proposed equation showed excellent agreement with experimentally measured phreatic lines, confirming its reliability and applicability.