Laboratory model tests and three-dimensional numerical analyses to investigate the behavior of floating granular piles in soft clay

In geotechnical construction, floating granular piles (FGPs) are employed to increase the bearing capacity and decrease the settlement of soft and highly compressive silt materials. FGPs have been installed more quickly and cost effectively than full depth piles, thereby shortening the construction period and saving on materials. Therefore, the present paper investigates the behavior of FGPs under short-term, displacement-controlled conditions through laboratory testing and numerical simulations using Plaxis 3D. Granular piles (GPs) with diameters of 60, 75, and 90 mm corresponding to the respective spacing (s) of 3.1d, 2.5d, and 2d were installed in soft clay employing the unit cell concept. The piles with lengths of 4d, 5d, and 6d were chosen as multiples of the pile diameter (d), alongside end-bearing piles with a length of 7d for comparative analysis. Lengths (4d–7d) and diameters (60–90 mm) of the GPs, area replacement ratios (9.43%–22.67%), angles of internal friction of the granular material (35°–45°), undrained shear strength of the surrounding clay (10–30 kPa), and pile spacings (2d–3.1d) were investigated. The outcomes of laboratory experiments were analyzed against the results obtained from the numerical simulations performed using Plaxis 3D. Results suggest that the load carrying capacity (LCC) of GPs considerably increased, by a factor of 2.6 to 3.1 in comparison with the untreated ground, as the length of the piles increased from 4d to 7d. Larger diameters and higher friction angles also significantly improved the LCC. Failures observed were mainly due to the bulging of the FGPs. The findings support a more cost-effective and friendly alternative to traditional foundation approaches, helping to promote more sustainable and resilient construction practices in geotechnically demanding regions.