Geosynthetics June/July 2020 - 21

Case Study

High-strength
geocell and geogrid
hybrid reinforcement
Compressor station gravel pad on soft subgrade

PROJECT HIGHLIGHTS

By Sanat Pokharel, Timothy Yii, Marc Breault and Meisam Norouzi

COMPRESSOR STATION GRAVEL
PAD ON SOFT SUBGRADE

I

nfrastructure development in natural resources rich Alberta, Canada, often
encounters very soft ground conditions that pose several construction and sustainability challenges to transportation infrastructure, such as roads, rails and pipelines. As the conventional construction practices may not always prove suslainable,
developers look for cost-effective and environmentally friendly innovative options.
In this region, it is important to minimize the use of scarce and expensive virgin
aggregates in construction. Situated in a cold northern climate, this region faces
short construction periods and frozen soil for considerable time; outdoor construction activities come to a halt during winter. This makes the tight project time lines
difficult to manage, and both cost and time overruns can happen.
The conventional practice in this region for unpaved roads and load-bearing
soil structures, such as compressor station pads, is to remove the existing soft
soil and backfill with competent imported fill. For good-quality gravel, haul distance can be as long as 62 miles (100 km). In a similar setting the authors were
approached to recommend a cost-effective, innovative design for a compressor
station pad near Otter Lake in Northern Sunrise County of Alberta. The pad,
intended to support heavy operating traffic and a crane, was conventionally
designed to remove the soft soil and build a gravel structure with multiple layers of
planar geosynthetics reinforcement. An adjacent pad that was recently built using
the conventional design had met with several problems during construction. This
experience indicated that building the same type of structure on this pad was going
to be expensive and the construction schedule would be overrun. Since the work
had to be completed in time for project commissioning, it did not seem practical to
use a conventional design. In addition, winter construction would be necessary to
meet the tight construction schedule. In lieu of the conventional design, a hybrid
geogrid and high-strength novel-polymeric alloy (NPA) geocell-reinforced gravel
structure was designed that saved both a huge amount of crushed gravel and cost
and construction time.
This article discusses hybrid geosynthetics reinforcement design to support
a heavy-loaded gravel pad for the compressor station and compares it with the

LOCATION

North Sunrise County, Alb., Canada
GENERAL CONTRACTOR

Strike Group Limited Partnership
SUBCONTRACTOR

Paradox Access Solutions Inc.
DESIGN ENGINEER

Stratum Logics Inc. (Sanat Pokharel/
Timothy Yii)
GEOSYNTHETICS PRODUCTS

NPA Geocell, Biaxial Geogrid, Woven
and Nonwoven Geotextile
GEOSYNTHETICS
MANUFACTURER/SUPPLIER

PRS Mediterranean Ltd. (Geocell)/
Geogrid and Geotextiles Supplied
by Paradox Access Solutions Inc.

Sanat Pokharel, Ph.D., P.Eng., is principal
engineer at Stratum Logics Inc. in
Acheson, Alb., Canada.
Timothy Yii, P.Eng., is project engineer at
Stratum Logics Inc. in Acheson, Alb., Canada.
Meisam Norouzi, MSc., P.Eng., PMP, is
project engineer at Stantec Consulting
Ltd. in Vancouver, B.C., Canada.
Marc Breault is president of Paradox Access
Solutions Inc. in Acheson, Alb., Canada.
All figures courtesy of the authors unless otherwise noted

www.GeosyntheticsMagazine.com

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Geosynthetics June/July 2020

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