DEM [Discrete Element Method] simulations of drained and undrained behaviour

Abstract

This thesis reports the results of DEM (Discrete Element Method) simulations of the behaviour of granular material for axisymmetric compression and plane strain deformation under both drained and undrained conditions. The aim is to study the behaviour of saturated granular material using DEM and the objectives of this thesis are: • to explore the drained behaviour of granular material using DEM • to explore the undrained behaviour of loose samples of granular material with and without preshearing history, using DEM • to compare axisymmetric compression and plane strain behaviour of a granular material under both drained and undrained conditions, using DEM A servo-control mode with constant mean stress is used to model drained simulations, and a strain-control model with constant volume is used to model undrained simulations. A periodic cell is used for all the simulations. For the drained simulations, the results of both dense and loose systems are presented, and all the systems reach a unique critical state at large strains. For the undrained simulations, mainly the results of loose systems are presented. The influence of preshearing history is also examined for a loose system under undrained axisymmetric compression conditions. The concept of liquefaction is shown to strongly correlate with mechanical coordination number, and liquefaction is shown to be related to structural mechanism. An attempt has been made to compare the axisymmetric compression and plane strain deformation for the drained and undrained conditions respectively. Shear strength criteria are examined and the Lade criterion is shown to be the most appropriate failure criterion.