Numerical investigation of displacement pile installation in silica sand

The penetration of deep foundations into sand is a classic geotechnical engineering problem that carries not yet fully understood aspects of the soil-pile interaction. The complexity of rigorous numerical and experimental studies of these foundations is well-stated in the literature. Extensive measurements of the properties of the soil that surrounds the pile are difficult to obtain experimentally. In this paper, the analysis of the installation of closed-ended, displacement piles in two silica sands is undertaken. Centrifuge tests from the literature on loose and dense dry sand samples are employed for validation of the numerical models, based on the Arbitrary Lagrangian-Eulerian (ALE) method. To capture the constitutive behaviour of the sand, the hypoplastic constitutive law with intergranular strain is adopted. After successful validation, an investigation on the variation of the initial conditions of the soil mass surrounding the pile during its installation is undertaken, and their influence on the tip resistance, the radial stresses, and the void ratio at the target penetration depths are identified. This paper illustrates the effect of cone apex angle on the state of sand after installation. Flat-ended piles tend to create clear zones of dilated material around the shaft.