Influence of Groundwater Fluctuation on Differential Settlement in Arid Foundations

Abstract

Purpose: The aim of this study is to examine the effect of variations in groundwater table height on foundation settlement behaviour in arid-zone soils, where evaporation, restricted recharge and anthropogenic groundwater extraction are the dominant hydrologic conditions. Design/Methodology/Approach: This research integrates field monitoring, laboratory testing, and numerical modelling to quantify settlement behaviour in response to changing groundwater levels. At an actual site, seasonal groundwater table depths between 1.2 m and 2.8 m BGL have been measured and implemented in hydro-mechanical simulations with PLAXIS 2D for the three common arid-region soil types (fine-grained, expansive soils and silty sands). Research Limitation: The research focuses only on general desert soil types and the level of groundwater fluctuation present at the chosen site. Long-term climatic variations and extreme pumping scenarios seeded into the models, as well as three-dimensional groundwater flow effects, were not considered explicitly and potentially alter settlement behaviour under different field conditions. Findings: The results show that groundwater depletion decreases effective stress and increases consolidation settlements, whereas fine-grained and expansive soils exhibit settlement up to ~38 mm for a groundwater drawdown of 2–3 m, and silty sands respond rapidly with lower settlement magnitudes. At footing edges, maximum differential footing settlement was near the footing edges and increased with depth due to the localised pumping hydraulic gradient. Deep foundations produced the highest reduction in differential settlement among all mitigation measures (up to 65%); lime–cement stabilisation was the next best alternative (reduction of 42%); and groundwater control systems provided only moderate improvement at relatively lower incremental costs. Practical Implication: The results have immediate implications for foundation design in arid regions, highlighting the leading role of groundwater oscillations in settlement behaviour. Social Implication: Better detection and tracking of groundwater-induced settlements can avoid damage to buildings and infrastructure in arid areas, increasing public safety, decreasing maintenance costs, and supporting reliable groundwater management practices. Originality / Value: The combination of field data with hydro-mechanical numerical modelling offers a unifying approach for improving the outcome of large foundation designs and a useful input to researchers and practitioners alike.