Discrete-continuum analysis of monotonic pile penetration in crushable sands

This paper presents numerical results from a two-dimensional discrete element method (DEM) simulation study on the monotonic pile installation in crushable sands. The particle breakage was included in the model by setting a crushable zone around a pile that was filled with parallel-bonded agglomerates. In the other part of the model, rigid, unbreakable particles are used to minimize the computational cost. Parametric studies were carried out to examine the effects of initial in situ vertical stress, soil void ratio, and particle crushability on the penetration resistance behavior. The validity of the DEM model was examined by comparing the simulation data with published results from laboratory centrifuge and calibration chamber tests on model pile installation. A variety of DEM analysis techniques were employed to make a detailed discrete-continuum study on the pile penetration mechanisms, particularly on the particle breakage-related soil mechanics incurred during the penetration process. Simulation results show that the in situ stress and particle breakage are the two competing factors dominating the tip resistance behavior. The underlying mechanism was elucidated through the analysis of stress and strain paths derived from pre-assigned sampling windows and their full-field distributions.