The University of Southampton
University of Southampton Institutional Repository

Internal fluidisation of granular material

Internal fluidisation of granular material
Internal fluidisation of granular material
Uncontrolled seepage flow due to defects or imperfect joints in civil engineering structures (such as dams, levees, dry-dock, seepage barriers, and sheet piles interlocking) or from fractured underground pipes is a major concern. The result of such leakage is increased water pressure and hydraulic gradients at the source of leakage making the behaviour of the surrounding material complex. This is because of the interaction of particles with the source of flow, turbulent flow in the surrounding bedding and the potential of developing additional mechanisms at the source of flow. Evidence of the occurrence of internal fluidisation has been reported in a number of fields, and yet not much is known about it.
In this fundamental study experimental apparatus and techniques have been developed to investigate the mechanism of internal fluidisation of granular material due to localised flow. A two-dimensional experimental model was created for the study, in which a machined box with variable orifice openings was designed and built to simulate an idealised crack for a localised leak. The box was fitted inside a modified seepage tank to fluidise a bed of granular material. Various parameters were investigated: flow rate, excess pore water pressure in the bed, pressure upstream of the orifice, particle size, particle shape, height of the bed, and orifice size on the observed mechanism. Image analysis techniques based on the Particle Image Velocimetry (PIV) have been developed in this study to monitor the behaviour of the fluidised zone.
Results and observations of this study suggest that the mechanism of internal fluidisation in a bed of granular materials is associated with an uplift mechanism of the grains in the active region of the bed. This is attributed to the drag force exerted by seepage flow overcoming the downward bulk weight of the bed. From the results and observations of this study a mathematical model based on the concept of force equilibrium has been proposed to predict the pore pressure at the onset of internal fluidisation. The results show that high pressure heads can be sustained upstream of the orifice without the internally fluidised zone breaking through to the bed surface. They also show that the onset of this mechanism in a bed of granular material is highly dependent on packing properties (grain size, grain shape, height of the bed), seepage velocity and orifice size.
internal fluidisation, hydraulics gradient, excess pore water pressure, granular, localised flow, particle image velocimetry (PIV)
University of Southampton
Alsaydalani, Majed
2ee4d5ea-8543-4f4e-92bf-018de6a5dce5
Alsaydalani, Majed
2ee4d5ea-8543-4f4e-92bf-018de6a5dce5
Clayton, Christopher
8397d691-b35b-4d3f-a6d8-40678f233869

Alsaydalani, Majed (2010) Internal fluidisation of granular material. University of Southampton, School of Civil Engineering and the Environment, Doctoral Thesis, 236pp.

Record type: Thesis (Doctoral)

Abstract

Uncontrolled seepage flow due to defects or imperfect joints in civil engineering structures (such as dams, levees, dry-dock, seepage barriers, and sheet piles interlocking) or from fractured underground pipes is a major concern. The result of such leakage is increased water pressure and hydraulic gradients at the source of leakage making the behaviour of the surrounding material complex. This is because of the interaction of particles with the source of flow, turbulent flow in the surrounding bedding and the potential of developing additional mechanisms at the source of flow. Evidence of the occurrence of internal fluidisation has been reported in a number of fields, and yet not much is known about it.
In this fundamental study experimental apparatus and techniques have been developed to investigate the mechanism of internal fluidisation of granular material due to localised flow. A two-dimensional experimental model was created for the study, in which a machined box with variable orifice openings was designed and built to simulate an idealised crack for a localised leak. The box was fitted inside a modified seepage tank to fluidise a bed of granular material. Various parameters were investigated: flow rate, excess pore water pressure in the bed, pressure upstream of the orifice, particle size, particle shape, height of the bed, and orifice size on the observed mechanism. Image analysis techniques based on the Particle Image Velocimetry (PIV) have been developed in this study to monitor the behaviour of the fluidised zone.
Results and observations of this study suggest that the mechanism of internal fluidisation in a bed of granular materials is associated with an uplift mechanism of the grains in the active region of the bed. This is attributed to the drag force exerted by seepage flow overcoming the downward bulk weight of the bed. From the results and observations of this study a mathematical model based on the concept of force equilibrium has been proposed to predict the pore pressure at the onset of internal fluidisation. The results show that high pressure heads can be sustained upstream of the orifice without the internally fluidised zone breaking through to the bed surface. They also show that the onset of this mechanism in a bed of granular material is highly dependent on packing properties (grain size, grain shape, height of the bed), seepage velocity and orifice size.

Text
00491700.pdf - Version of Record
Available under License University of Southampton Thesis Licence.
Download (77MB)
Video
height of fluidised zone 0.33mm orifice _ 220mm bed of LBS_B.mpg - Other
Download (21MB)
Video
intenral fluidisation in a 150 mm bed of LBS-B.mpg - Other
Download (12MB)
Video
0.62mm orifice_ 220mm bed of GB_ Q 1150 to 1200 lph .mpg - Other
Download (21MB)
Video
0.62mm orifice_ 220mm bed of GB_Q 1300 lph to 1350 lph.mpg - Other
Download (38MB)
Video
0.62mm_220mm bed of GB_Q 1250 lph to 1300 lph.mpg - Other
Download (18MB)

Show all 6 downloads.

More information

Published date: August 2010
Keywords: internal fluidisation, hydraulics gradient, excess pore water pressure, granular, localised flow, particle image velocimetry (PIV)
Organisations: University of Southampton, Centre for Environmental Science

Identifiers

Local EPrints ID: 385439
URI: http://eprints.soton.ac.uk/id/eprint/385439
PURE UUID: 2ed3cc82-a1d2-4891-aa74-13a8a1f21361
ORCID for Christopher Clayton: ORCID iD orcid.org/0000-0003-0071-8437

Catalogue record

Date deposited: 04 Jan 2016 13:00
Last modified: 01 Jun 2022 01:36

Export record

Contributors

Author: Majed Alsaydalani
Thesis advisor: Christopher Clayton ORCID iD

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×