Modelling the micro-structure and hydraulic properties of sands
Author(s)
Garcia Teijeiro, Xavier
Type
Thesis
Abstract
The main objective of this work is to model granular materials comprising particles of as
pherical shape and investigate the effect of the grain shape on the hydraulic properties of
the material. For this purpose, a Discrete Element Method code for clustered spheres was
developed during the course of this work to simulate aspherical particles. The shape of
the particles modelled mimics the morphology of real grains obtained from a shape library
of real scanned particles for which development this thesis also contributed. The simulation tools are then used to construct models of real sands by simulating the settling under
gravity and compaction of the grains. The hydraulic properties of the sand moels are then
investigated via numerical simulations using two different approaches. First, we simulate
low Reynolds numbers flow in granular packs using a Finite Element method within the
Stokes flow approximation. Then we explore the applicability of the two-fluids approach
to simulate fluid flow in the presence of solid obstacles and complex microstructures.
By integrating the technologies developed during this work, it was possible to simulate
the single phase flow in a wide range of Reynolds number in models of sand. The results
obtained closely agree with available experimental data and empirical correlations for relatively clean and homogeneous sands. These results show that the hydraulic permeability
can vary within a factor of two as a consequence of the particle shape. This indicates that
for unconsolidated media the most important parameter with regards to fluid flow conductivity is the porosity.
pherical shape and investigate the effect of the grain shape on the hydraulic properties of
the material. For this purpose, a Discrete Element Method code for clustered spheres was
developed during the course of this work to simulate aspherical particles. The shape of
the particles modelled mimics the morphology of real grains obtained from a shape library
of real scanned particles for which development this thesis also contributed. The simulation tools are then used to construct models of real sands by simulating the settling under
gravity and compaction of the grains. The hydraulic properties of the sand moels are then
investigated via numerical simulations using two different approaches. First, we simulate
low Reynolds numbers flow in granular packs using a Finite Element method within the
Stokes flow approximation. Then we explore the applicability of the two-fluids approach
to simulate fluid flow in the presence of solid obstacles and complex microstructures.
By integrating the technologies developed during this work, it was possible to simulate
the single phase flow in a wide range of Reynolds number in models of sand. The results
obtained closely agree with available experimental data and empirical correlations for relatively clean and homogeneous sands. These results show that the hydraulic permeability
can vary within a factor of two as a consequence of the particle shape. This indicates that
for unconsolidated media the most important parameter with regards to fluid flow conductivity is the porosity.
Date Issued
2007-12
Date Awarded
2010-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Latham, John-Paul
Sponsor
Rio Tinto ; Department of Earth Sciences and Engineering
Creator
Garcia Teijeiro, Xavier
Publisher Department
Earth Science and Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)