Some laboratory studies of anisotropy of permeability of kaolin

Hamidon, AbuBakar (1994) Some laboratory studies of anisotropy of permeability of kaolin. PhD thesis, University of Glasgow.

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Abstract

This thesis is concerned with an investigation into some aspects of the permeability
measurement and permeability characteristics of reconstituted saturated supreme
kaolin clay. Development of permeability anisotropy is investigated when the sample
has experienced: (1) anisotropic consolidation, and (2) undrained shear.
Conventional step-loaded consolidation tests, constant flow rate and some constant
head permeability tests were conducted on the kaolin slurry and block samples. For
every conduct of testing, a pair of identical samples were tested: one underwent
vertical drainage and the other radial drainage conditions. Both, however, were
subjected to one dimensional deformation in the vertical direction.
Permeability of the clay was evaluated both directly and indirectly, from results of
the permeability tests and consolidation tests, respectively. Data from the constant
flow rate and constant head permeability tests yield the same values of permeability
for both cases of vertical or radial flow (kv not necessarily equal to Kh). Theoretical
considerations of the transient phase of the experimental record of the constant flow
rate permeability test are found to be applicable to form the basis of evaluation of
permeability, coefficient of consolidation, and coefficient of volume compressibility of
the clay sample.
Experimental results showed that during the progress of anisotropic consolidation
of the kaolin slurry, the clay's vertical and horizontal permeability exhibited unique
relationships with the void ratio which are linear on the logarithmic-linear scale [linear
(lg k vs e) plot ]. These relationships were found to be independent of the
overconsolidation ratio. A lack of permeability anisotropy was observed in the early
part of compression or at the initial void ratio, e = 3.1, but as the compression
proceeds, development of permeability anisotropy was observed to reach a value of up
to 2.1 which correspond to a void ratio of 1.30, where the corresponding vertical
effective stress was 530kPa.
Experimental results for the block samples that had experienced undrained shear
also showed the unique relationships of the clay's vertical and horizontal permeability
with void ratio. Development of permeability anisotropy, however, was somewhat in
opposition with that of the slurry sample observed during anisotropic consolidation.
For samples sheared to vertical strains of 7.9 to 11.5%, an initial permeability
anisotropy of 1.3 at a void ratio of 1.66 was observed to decrease with compression
and developed into isotropic condition at a void ratio of 1.50, where the corresponding
vertical effective stress was 120kPa. For samples sheared to vertical strains of 2.0 to
5.0%, an initial permeability anisotropy of 2.5 at a void ratio of 1.30 was observed to
decrease very little with compression and the degree of anisotropy remained to a value
xiv
of 2.3 at a void ratio 1.05, where the corresponding vertical effective stress was
480kPa.
Solutions from both the Terzaghi's and Biot's consolidation theories were used to
evaluate the experimental data of the axisymmetric problem of consolidation with
radial drainage to inner and outer fixed boundaries. Compared with measured values,
permeabilities of the samples calculated from both the Terzaghi's and the Biot's
solutions and using the Taylor'S square root of time method, are underestimated by a
factor of 10 to 100 (ie. kcal/km = 1110 to 11100). Furthermore, the calculated
permeabilities are less orderly in the l9.k vs e plot while the variation is more ordered
and linear for the measured values.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Colleges/Schools: College of Science and Engineering > School of Engineering
Supervisor's Name: Wood, Prof. D Muir
Date of Award: 1994
Depositing User: Ms Anikó Szilágyi
Unique ID: glathesis:1994-6338
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 May 2015 10:27
Last Modified: 11 May 2015 10:28
URI: http://theses.gla.ac.uk/id/eprint/6338

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