Continuum (PFEM) and discrete (DEM) modelling of pile installation in rocks

Recent advancements in computational efficiency have enabled the application of advanced numerical models to solve challenging large-displacement soil structure interaction problems such as pile installation in non­linear irreversible materials prone to softening type of behaviour. Such challenging problems however require specialized approaches due to material and geometrical non linearities combined to the large deformation soil­-structure interaction. This paper presents a comparison of two approaches for modelling open ended (OE) pile installation in soft, crushable and collapsible rocks. The first approach employs the Discrete Element Method (DEM), which represents the rock as separate particles bonded together, and introduces a new contact model for highly porous rocks. The second approach uses the Geotechnical Particle Finite Element Method (GPFEM) and investigates the coupled hydromechanical effects during pile installation using a robust and mesh-­independent implementation of an elastic-plastic constitutive model at large strains. The DEM approach explores the micromechanical features of pile plugging and unveils the mechanisms behind radial stress distributions inside and outside the plug. The study highlights the strengths and limitations of each modelling technique, providing insights into the behaviour of OE piles installed in soft rocks.