Geosynthetics October/November 2023 - 31

On top of the world
In the mist-shrouded, lush green valleys
of the towering Himalayas, an airport
runway, terminal and apron are shielded
by an earth embankment soaring above it.
The Pakyong Airport took nine years
to build and is lauded as an engineering
marvel. Removing the side of a mountain
to create a flat platform for the runway
was just one of the challenges of building
one of the five highest airports in India.
Maccaferri, which provides solutions
for civil, geotechnical and environmental
construction markets, created a reinforced
soil structure to serve as a retention
embankment for the project's northsouth
runway.
The region's mountainous terrain,
heavy rainfall, high seismicity, balance of
cut and fill, and lack of land availability
were other challenges of building the
airport that stands at 4,500 feet.
The company's ParaMesh system,
made up of high-strength geogrid (ParaLink®)
along with fascia elements Terramesh®
system and Green Terramesh, was
used in constructing the airport that needs
to withstand earthquakes and monsoons.
The original plan to use a reinforced
concrete wall for the embankment was
abandoned in favor of geotextiles and
other geosynthetic products, which
provided a more flexible, earthquakeresistant
solution for the reinforced soil
embankments. A wraparound doubletwisted
hexagonal wire mesh facing was
used for less precipitous sections.
" Imagine importing the required
amount of select backfill material and
disposal of the excavated soil from the job
site, " says Sachin Mandavkar, technical
director at Maccaferri. " For this reason,
one of the critical project requirements
was to reuse the excavated soil from the
job site to build the [mechanically stabilized
earth] MSE structure. "
The team literally moved the mountain,
carving away soil from above the
FIGURE 3 Maccaferri created a reinforced soil structure to serve as a retention embankment
for Pakyong Airport's north-south runway. Photo courtesy of Maccaferri
runway and using it below. The base for
the airport and runway became walls up
to 72 meters (236 feet) high, reinforced
by a high-strength geogrid.
" Backfilling was done in a 200-mm
[8-inch] compacted lift thickness, and
five layers of compacted soil measuring
1 m [3.3 feet] high was installed
behind each Terramesh unit. It took
approximately five days to backfill each
Terramesh lift along the wall length and
ensure that geotextile would be held in
position, " says Ratnakar Mahajan, technical
manager at Maccaferri.
Geotextiles also addressed drainage.
Nine streams-known as jhoras-cross
the airport underground and impact
ground stability.
" A geotextile was used for separation
and filtration to replace graded filter, "
says Mahajan. " With Terramesh being
porous facia, there is possibility of soil
loss from the facia. Hence, conventional
graded filter could be an option behind
GeosyntheticsMagazine.com
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Geosynthetics October/November 2023

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