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An engineering marvel in the Himalayas

At a height of over 1,370 metres, India’s new Pakyong Airport has opened following a nine-year construction project that was not without its challenges.

Described by the BBC as “an engineering marvel”, it is the latest in a series of impressive projects – from the world’s largest artificial island off Dubai to the biggest-ever land reclamation project in Hong Kong – that have been built on foundations of nonwoven geotextiles.

In such global infrastructure projects, permeable geotextiles – typically made from needlepunched or spunbonded polypropylene or polyester – have a range of vital functions to perform in respect of the separation, filtration, reinforcement, protection or drainage of built-up ground structures.

Isolation

Pakyong is in Sikkim, a fairly isolated and landlocked Indian state located in the Himalayas and well-known for its lush green topography. It is connected to the neighbouring countries of Tibet, Bhutan and Nepal through eight mountain passes and in addition to its remote location, is subject to heavy rainfall – including a four-month Monsoon period – with heavily-weathered ground conditions and a susceptibility to earthquakes, all of which posed challenges. There were also constraints on the availability of land that was suitable for cutting and filling for the site.

Once the site had been selected, the mountainside slope had to be excavated up to around 110 metres and the valley side slope required retention structures up to 74 metres high in order to first make the ground level for the airport to be constructed.

The materials for the retention structures were supplied by global engineering firm Maccaferri, headquartered in Zola Predosa, Italy, and consisted of the company’s modular and patented Terramesh system for the formation of rock-faced and reinforced soil walls. It consists of pre-assembled units of double-twisted wire mesh and polymer-coated steel wire, employing geogrids for primary reinforcement and layers of nonwoven geotextiles to provide drainage, secondary reinforcement layers and pipe protection.

The facing section of a Terramesh unit is formed by connecting a back panel and diaphragms to the main fascia unit, creating rectangular-shaped cells used for the stone confinement. The geogrid reinforcement, fascia and lid are all a continuous panel of mesh and the complete units are supplied in standard lengths, in order to require no cuts at the construction site.

One of the demands set by the Airport Authority of India (AAI) was that construction should not have an adverse impact on the environment and local habitat, especially since the cutting side area had direct visibility from the runway and terminal building. 

Terramesh, with its geogrid soil reinforcement and integral nonwoven fascia system is engineered to ensure slope stability, allowing slopes to stand steeper, accommodate greater loads and settle less.

At the same time, the nonwoven geotextiles ensure the ground does not “choke”, providing layers with the permeability and breathability to allow such steep, stable slope faces to rapidly revegetate.

All of this, while remaining cost competitive.

Tourism boost

For projects such as the Pakyong Airport, Maccaferri leaves nothing to chance, being involved from the initial planning stage and employing powerful software for perfectly sizing and customizing infrastructure in terms of the technical performance, environmental compatibility and architectural harmony of its products.

As India’s 100th airport, Pakyong was inaugurated by India’s Prime Minister Narendra Modi on September 24th this year, and its first flight took place on October 3rd.

The airport has a 1.75km-long runway, two parking bays and a terminal building which can handle about 100 passengers at a time. It is expected to boost tourism to Sikkim, which is home to a number of notable and beautiful peaks, glaciers and high altitude lakes.