The Development of a New Air Permeability Testing Apparatus
Date
1997
Authors
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Publisher
ORCID
Type
Degree Level
Masters
Abstract
This thesis presents the development of a new laboratory testing apparatus for the
measurement of the coefficient of air permeability of soil specimens using steady state
methods. The apparatus was designed to measure coefficients of air permeability with in a
range of 1*10-5 to 1 * 10-9 cm/s at a standard pressure and temperature of 101.3 kPa and
20°C respectively. The apparatus design allows for duplicate, independent measurements
of air volume flow rates and the air pressure differential. The apparatus features the use of
a large lucite testing cell which can accommodate specimens up to four inches in diameter
and eight inches in height. The apparatus was originally developed to determine the
coefficient of air permeability of undisturbed specimens of a highly plastic, fractured clay
(i.e., Regina clay).
A laboratory testing program was conducted on specimens of a sandy till (i.e., Floral till)
to verify the performance of the new air permeability testing apparatus. The apparatus
was confirmed to be capable of measuring the coefficient of air permeability of soil
specimens with in a range of 8.7*10-6 to 2.6*10-8 cm/s; nearly three orders of magnitude
(at standard atmospheric pressure and a temperature of 20°C). The coefficient of air
permeability of Floral till was shown to be highly dependent on the degree of saturation of
the soil specimens, and dependent to a lesser degree on the void ratio (i.e., density) of the
soil.
A second laboratory testing program was conducted on undisturbed specimens of Regina
clay. The results of the laboratory testing program indicate that the coefficient of air
permeability of Regina clay is relatively low; approximately 1*1 0 -7 cm/s near the surface of
the deposit and decreases rapidly with depth. The soil matrix of Regina clay is essentially
saturated through out the entire depth of the in-situ deposit and is relatively impermeable
to the advective flow of air. The advective flow of air through the bulk soil deposit is
therefore controlled by the characteristics of the unsaturated fracture network. The
fracture network was shown to significantly increase the bulk coefficient of air
permeability of Regina clay in the upper two to three meters of the deposit. The influence
of the fractures is not as significant at greater depths. This is attributed to the decrease in
fracture density and the increase in confining pressure which occurs with increasing depth
in the deposit.
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Citation
Degree
Master of Science (M.Sc.)
Department
Civil Engineering
Program
Civil Engineering