Project title: Multi-scale analysis of liquefaction phenomena in soil
Supervisors: Dr. Catherine O’Sullivan Dr. Daniele Dini, Dr. Berend van Wachem
Soil is a complex, multiphase system consisting of a particle 'skeleton' held in a metastable configuration by a network of interparticle forces permeated by interstitial pore fluid. Loading saturated soil sufficiently quickly generates large pore fluid pressures due to the incompressibility of water at typically encountered stress levels. Liquefaction occurs when an applied load is resisted entirely by the pore fluid pressure. At this point the effective stress in the soil skeleton vanishes and shear failure occurs. Extensive damage was caused by liquefaction during the 2010 and 2011 earthquakes in Canterbury, New Zealand and the 1989 Loma Prieta earthquake in California, USA.
A coupled Discrete Element Method – Computational Fluid Dynamics (DEM-CFD) method will be employed to further the understanding of liquefaction phenomena through numerical investigation of the micro and meso-scale properties of soil. A critical evaluation of fluid-particle drag expressions commonly used in geomechanics DEM simulations at the coarse grid scale will be carried out to determine their validity for systems with a high degree of size polydispersity. An attempt will be made to improve on these drag expressions by incorporating the effects of size polydispersity and configuration in a parametric form in the fluid-particle drag force calculation. Results obtained from micro-scale fluid flow simulations using the Immersed Boundary Method (IBM) will inform the choice of equations and parameters to be used at the coarse grid scale.