Title page for ETD etd-06032004-155123


Type of Document Master's Thesis
Author Alramahi, Bashar Adeeb
Author's Email Address balram1@lsu.edu
URN etd-06032004-155123
Title Assessment of Shearing Phenomenon and Porosity of Porous Media Using Microfocus Computed Tomography
Degree Master of Science in Civil Engineering (M.S.C.E.)
Department Civil & Environmental Engineering
Advisory Committee
Advisor Name Title
Khalid Alshibli Committee Chair
Dante Fratta Committee Member
Emir Macari Committee Member
Keywords
  • computed tomography
  • porosity
  • triaxial
  • shearing
  • grain size distribution
  • alramahi
  • compaction
  • consolidation
  • rotation
  • imaging
  • strain
  • rocks
  • soils
  • non destructive testing
  • granular materials
  • dilatancy
  • tomography
  • x-ray
  • bashar
Date of Defense 2004-05-19
Availability unrestricted
Abstract
Microfocus x-ray computed tomography (μCT) is a powerful non-destructive scanning technique to study the internal fabric of granular materials. In this thesis, μCT was applied to two cases. The first case involves studying the behavior of particles in a triaxial specimen during shearing. Three-dimensional translation and rotation of the particles were tracked throughout the shearing process, and they were used to calculate the local strain distributions. Moreover, the local dilatancy angle distribution was calculated throughout experiment. These distributions were compared to study the changes in the behavior of the particles at different stages of the test.

It was noticed that the radial strains εx and εy showed a similarity due to the axisymmetric conditions. It was also found that high rotation angles took place, where the vertical rotation component reached up to 30 degrees and the horizontal rotation reached up to 60 degrees. Furthermore, the rotation strain component reached up to about 50% at the end of the test. On the other hand, a wide range of local dilatancy angles was observed, where the values varied between -50 degrees and 70 degrees.

The second part of this thesis aims at determining the effect of grain size distribution and consolidation pressure on the spatial porosity distribution of synthetic rock cores. Twelve rock cores were prepared with different grain size distributions and consolidation pressures, and scanned using a high resolution μCT system. Density calibration was conducted to correlate the CT numbers to the bulk density, and the porosity of the cores. 15 million porosity values were calculated for each core. μCT showed an excellent ability to track the changes in the local porosity distribution of the cores. It was found that grain size distribution has a larger effect on the porosity values, where a noticeable decrease in the porosity values was observed when using well graded grains. On the other hand, increasing the consolidation pressure did not always decrease the porosity values. This could be due to the crushing of the particles at very high consolidation pressures.

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