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Geotechnical News • June 2014
45
THESIS ABSTRACTS
zones. This approach was found to be most sensitive to the
input tensile strength. Back analysis of the Niagara Tunnel
Project, forward prediction of damage around a shaft in the
Queenston Formation, and cut-off dimension and place-
ment modelling are used to illustrate the importance of this
research. This research has enhanced the understanding of
excavation damage in sedimentary rocks and provided a
methodology to predict the depth of the damage zones using
a continuum approach.
Sponsoring Professor:
Dr. Mark S Diederichs, Department of
Geological Sciences and Geological Engineering, 36 Union
Street, Queen’s University, Kingston, Ontario, Canada, K7L 3N6,
Tel. (direct): +1 613 533 6594, email: mdiederi@geol.queensu.ca
Durability of HDPE Geomembranes for
Municipal Solid Waste Landfill Applications
Fady Badran Abdelaal
Fady Badran Abdelaal, 58 University Avenue, Ellis Hall, Kingston,
ON, Canada, K7L 3N6, Tel: 343-333-2675,
email: fady.badran@ce.queensu.ca
A series of laboratory accelerated immersion tests are
used to examine the effects of different chemicals found in
municipal solid waste leachate, geomembrane thickness,
and incubation temperatures on the degradation of differ-
ent high density polyethylene geomembranes. It was found
that surfactant was the key leachate constituent affecting
antioxidant depletion while salts accelerated degradation of
the mechanical properties, especially stress crack resis-
tance. Immersed in synthetic leachate, the time to nominal
failure at 35
o
C was predicted to be 62% longer for the 2.5
mm, and 12% longer for the 2.0 mm, than for the 1.5 mm
geomembrane tested. The antioxidant depletion in synthetic
leachate and air at temperatures > 85
o
C was consistent with
what would be expected from Arrhenius modeling based
on data from lower temperatures (≤ 85
o
C). However, the
early depletion rates in water incubation decreased with the
increase of the temperature above 100
o
C. It was also found
that at temperatures above 100
o
C, there was significant
change in the polymer morphology that affected the stress
crack resistance at early incubation times prior to polymer
degradation.
Large-scale geosynthetic liner longevity simulators (GLLSs)
which simulated field conditions were used to investigate
the susceptibility of pre-aged high density polyethylene
geomembranes to stress cracking and to evaluate the perfor-
mance of geomembranes under a 150 mm sand protection
layer. A pre-aged geomembrane with a 560 g/m
2
geotextile
protection layer experienced brittle rupture at local gravel
indentations. The time to failure was correlated to the
incubation temperatures. The use of a sand protection layer
not only delayed antioxidant depletion compared to that
with a traditional geotextile protection but also substantially
reduced the long-term tensile strains in the geomembrane
below the allowable strain limits.
Supervisor:
R. Kerry Rowe, Queen’s University, 58 University Av-
enue, Ellis Hall, Rm 229b, Kingston, ON, Canada, K7L 3N6, email:
kerry@civil.queensu.ca
Performance of Geosynthetic Clay Liners in
Cover, Subsurface Barrier, and Basal Liner
Applications
Mohamed Said Hussein Hosney
Mohamed Said Hussein Hosney
,
Graduate Student,
GeoEngineering Centre at Queen’s-RMC, Queen’s University,
Ellis Hall, Kingston, ON, Canada, K7L 3N6. Tel: (613) 583-8054.
Fax: (613) 533-2128, email: Mohamed.hosney@ce.queensu.ca.
The use of geosynthetic clay liners (GCLs) as (i) covers for
arsenic-rich gold mine tailings and landfills, (ii) subsurface
barrier for migration of hydrocarbons in the Arctic, and (iii)
basal liner for sewage treatment lagoons were examined.
After 4 years in field and laboratory experiments, it was
found that best cover configuration above gold mine tail-
ings might include a layer of GCL with polymer-enhanced
bentonite and a geofilm-coated carrier geotextile under ≥
0.5 m of cover soil above the GCL. However, acceptable
performance could be achieved with using a standard GCL
with untreated bentonite provided that there is ≥ 0.7 m of
cover soil.
When GCL samples were exhumed from an experimental
landfill test cover after complete replacement of sodium
in bentonite with divalent cations, it was observed that the
higher the hydraulic head across the GCL and the larger
the size of the needle-punched bundles, the higher the
likelihood of preferential flow for liquids to occur though
bundles. A key practical implication was that GCLs can
perform effectively as a single hydraulic barrier in covers
provided that the water head above the GCL kept low.
The hydraulic performance of a GCL in the Arctic was
most affected by the location within the soil profile relative
to the typical groundwater level with the highest increase
in the hydraulic conductivity (by 1-4 orders of magnitude)
for GCL below the water table. However, because the head
required for jet fuel to pass through the GCL was higher
than that present under field conditions, there was no evi-
dence of jet fuel leakage through the barrier system.
The leakage through GCLs below concrete lined sewage
treatment lagoons was within acceptable limits, in large
part, due to the low interface transmissivity (in order of
10
-11
to 10
-13
m
2
/s) between GCLs and the overlying poured
concrete.
Supervisor:
R. Kerry Rowe, Queen’s University, 58 University
Avenue, Ellis Hall, Rm 229b, Kingston, ON, Canada, K7L 3N6,
email; kerry@civil.queensu.ca