Incorporating the impact of floating piles in estimation of large-scale subsidence

Journal article, 2026

The current methods to predict subsidence due to underdrainage on a large-scale, and the consequent damage, tend to neglect the soil–structure interaction, potentially overestimating damage to piled buildings. This paper investigates the settlements of floating piles caused by underdrainage and proposes time-dependent modification factors for greenfield settlements for building damage predictions at large scale. The modification factors are derived from a series of finite element analyses that consider a floating pile in soft clay in which the thickness of the clay layer, the drawdown scenarios, and the load of the pile head are systematically varied. The results are compiled in normalised graphs of the interaction levels evaluated and the settlement modification factors derived for use in models to predict building damage at large-scale. In contrast to greenfield predictions, the long-term subsidence of piled buildings is significantly reduced (approximately 20%). Additionally, long-term interaction levels are shown to be well-approximated by the simple methods more commonly used in industry (2/3-depth and α-methods). The magnitude of pile head displacements is significantly influenced by the drawdown and the clay thickness. Finally, the viability of the method is demonstrated for the assessment of building damage in central Gothenburg. The new time-dependent modification factors for piled buildings are shown to be more significant for low-level damage predictions, where for one scenario, the new damage classification led to a reduction in assessed damage for ca. 23% of the piled buildings.