Comparison of continuum (PFEM) and discrete (DEM) approaches for large insertion BVPs in soft rocks

In recent years, significant advancements in computational efficiency have enabled the application of advanced numerical models to solve boundary value problems (BVPs) in geotechnics, including those related to large-displacement problems. However, challenging problems, such as those involving open-ended piles (OEs) in soft rocks, 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 modeling OE pile installation in soft 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 modeling approach, providing insights into the behavior of OE piles in soft rocks.