Basic HTML Version
www.geotechnicalnews.com
Geotechnical News • June 2013
45
THESIS ABSTRACTS
hydrate was performed and the results analyzed within the
proposed framework of modeling and evaluating theoretical
permeability predictions.
Sponsoring Professor: Dr. Jocelyn Grozic, University of Calgary,
Department of Civil Engineering, 2500 University Drive NW,
Calgary, Canada T2N 1N4
Hydraulic Conductivity Measurements for a
Champlain Clay Deposit in Lachenaie,
Quebec: Theory and Applications
François Duhaime
François Duhaime, Department CGM, École Polytechnique de
Montréal, P.O. Box 6079, Station CV, Montreal, QC, Canada,
H3C 3A7, E: francois.duhaime@polymtl.ca
Precise hydraulic conductivity (K) measurements in
aquitards are needed for several types of civil engineering
projects. In situ permeability tests are known to produce K
values that are more representative of field-scale seepage.
Variable-head tests conducted in monitoring wells (MWs)
are the most commonly encountered in situ test setting.
These tests unfortunately have a long duration (more than a
month in Champlain clays). Pulse tests were developed to
circumvent this issue. To initiate a pulse test, a small volume
of water is injected in the screened portion of a MW while
it is isolated by a packer. Typically, a pulse test can be com-
pleted in two hours in Champlain clays.
The thesis presents a new interpretation method for pulse
tests conducted in saturated soft clays. This new method is
based on a joint analysis of cavity expansion and clay vol-
ume changes. The new method is based on the superposition
of theoretical and experimental non-dimensional velocity
graphs. The theoretical type curves were obtained from
analytical and finite element solutions (COMSOL) to the
Biot equations for the case of 1D axisymmetric flow and for
the more general case of partially penetrating wells (2D axi-
symmetric flow). Compared to existing methods, this new
interpretation procedure has the advantages of constraining
the range of type curves available for the interpretation of
test data, and of being based on a more realistic treatment of
deformations.
The new interpretation method was applied to the Lachenaie
clay deposit. A strong correlation was observed between
the K values obtained from pulse tests and variable-head
tests conducted in the same MWs. The large number of in
situ and laboratory tests conducted in this deposit allowed a
detailed analysis of other issues associated with permeabil-
ity measurements in Champlain clays to be studied (seasonal
head variations, scale effects and hydraulic conductivity
predictions).
Sponsored by Professor Robert P. Chapuis, Department CGM,
École Polytechnique de Montréal, P.O. Box 6079, Station CV,
Montreal, QC, Canada, H3C 3A7, T: 514-340-4711 ext. 4427
F: 514-340-4477, E: robert.chapuis@polymtl.ca
A Field Scale Evaluation of Wrinkles in
Exposed HDPE Geomembranes
Melissa Jill Chappel
Melissa Jill Chappel, CTT Group, 3000 avenue Boullé,
St-Hyacinthe, QC J2S 1H9, T: 450-778-1870,
E:
Intact geomembranes are barriers to advective aqueous flow
and are often a key component in the design of composite
liner and cover systems. During installation, the combina-
tion of solar heating, a high coefficient of expansion, and
the stiffness of high density polyethylene (HDPE) causes
the geomembrane to expand and buckle, forming wrinkles
(waves). Up to 20-30% of the area of the geomembrane
may be under hydraulically connected wrinkles, which
could substantially increase leakage through the composite
liner if there is a hole on or near a wrinkle in the connected
network. To quantify wrinkles at the field scale, a technique
for low altitude aerial photography and photogrammetric
correction was developed.
The technique was used to quantify the geometry of indi-
vidual wrinkles and the length of the longest hydraulically
connected wrinkle at each time for nine field cases. Hand
measurements of height and width were conducted at five of
the cases. Solar radiation, air and geomembrane temperature
was recorded as permitted by site conditions and instrumen-
tation.
The longest measured connected wrinkle was 5330m on a
0.61ha slope. For a 1.5-mm thick geomembrane, the average
wrinkle width over a GCL was 0.20-0.23m and 0.24-0.32m
over a CCL. The average wrinkle height was 0.06m, and the
tallest wrinkle measured was 0.18m. The longest connected
wrinkle length was <200m when the sum of the wrinkle
lengths was <580m (<8% of the area of the geomembrane
was wrinkles). The reported connected wrinkle lengths are
significantly longer than previously reported. When input
into an existing theoretical leakage solution, these very long
wrinkles can explain previous large field measurements of
leakage. Results also suggest that limiting the time of day
when cover soil is placed and/or reducing the area in which
wrinkles can form may greatly reduce the length of con-
nected wrinkles after covering.
Supervisors: R. Kerry Rowe,
T: (613) 533-3113, E: kerry@civil.queensu.ca
Richard W.I. Brachman,
T: (613) 533-3096, E: brachman@civil.queensu.ca
W. Andy Take, T: (613) 533-3124, E: andy.take@civil.queensu.ca
Department of Civil Engineering, Queen’s University, Ellis Hall,
58 University Avenue, Kingston Ontario. Canada K7L 3N6,
F: (613) 533-2128