Geosynthetics June/July 2020 - 27

fill costs. The reduction in the volume of
aggregate contributed to environmental
benefits; the reduced number of trips to
haul material and construction duration all contributed toward lower CO2
emissions, as suggested by Norouzi et
al. (2017).

Conclusion
A hybrid geosynthetic structure was
designed to support a 237-ton (215tonne) crane load and regular and
construction traffic on a compressor
station pad. The design was based on
mechanisms of combination of planar
geosynthetic (geogrid and geotextile)
and three-dimensional NPA geocell
reinforcement to improve the modulus of
the structure, create a slab effect, and distribute the loads to a wider area to meet
bearing capacity requirements of the subgrade and rut criteria at the surface for
moving wheel traffic. The hybrid design
eliminated the need to excavate existing
soft subgrade soil, reduced the thickness
of the structure by 42.3% and enabled the
construction activities to be completed in
freezing conditions. Overall, this design
saved 22.8% of the project costs and
potentially reduced maintenance cost
during the pad operation. The structure
performed well under the design loads
and fulfilled its design requirements. In
conclusion, this design paved the path
and directed a future course for combining different geosynthetic material for
the design and construction of a heavily
loaded gravel pad on very soft subgrade
soil in a sustainable way.

Acknowledgments
The authors would like to thank Anthony
Ramos from TransCanada Pipeline Ltd.
and Mark Bonnell and Cord Roberts
from Strike Group for feedback on the
project performance.

References
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The design had
anticipated that the
mechanisms of cellular
confinement and gravel
interlocking would
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of the entire structure
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stress applied to the
subgrade during spring
thaw. The pad held
firm under the applied
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the designed structure
and construction
methodology.

Qian, Y., Han, J., Pokharel, S. K., and Parsons, R. L. (2013).
"Performance of triangular aperture geogrid-reinforced
base courses over weak subgrade under cyclic loading."
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