Hong-Kong International Airport: Construction

This post is a part of Last post as Hong Kong International Airport: Brief View. In this post Construction of Hong Kong international airport is presented with few static details about project. The underwater tunnel, world’s Largest double Decker suspension bridge and land reclamation for highway construction on sea bed are given here. Terminal building of HKIA was the world’s largest terminal building when opened in 1998. Construction of terminal building was done taking typhoons in view. Further ahead…

As enlisted in last post the construction of this project involved two major parts -

• Construction of Airport site and Building.
• Connecting airport to the town.

CONSTRUCTION OF AIRPORT

The site construction of the airport included joining both islands and forming one bigger then both. So this work was started with blasting the rocks on the islands. Now the excavated earth was to be used as filling material. But before that a surface was required which was formed by using dredgers. These dredger ships picked up the 40 ft deep loose soil from seabed and formed a surface which was further followed by filling of excavated material. Now 12.48km² area was available, remaining was construction of terminal building and runway. This airport was equipped with two runways which routes the flights over the South China Sea. Half of the Airport construction and Improvement funds are consumed by runway, taxiways and aprons in any airport construction project.

After doing this all next was the Passenger terminal building. Terminal building of HKIA was the world’s largest terminal building when opened in 1998. Construction of terminal building had to be perfect against the most destructive force of nature “Typhoons”. For resisting the wind pressure of 200km/hour, it became necessary to provide pile foundation. Over these piles the mild steel trusses were resting covering the whole terminal building. The concrete piles were used for foundation purpose using massive hammer drivers. Each of these piles were 25000 tons in weight.

CONNECTING AIRPORT WITH POPULATED AREA

The distance between down town and airport was to be covered by providing -

• One Underwater Tunnel as western harbour crossing.
• Two Bridges as Lantau Link.
• and 8 Mile reclamation named as North Lantau Expressway.

UNDERWATER TUNNEL

From the side of town first obstruction was western harbour crossing which was eliminated by providing a underwater tunnel. Precast fabricated sections of steel and concrete were made for this construction. Each of these sections weighs 35000 tons while manufactured. It was not easy to take these sections to the site. Hence these sections are carried to the site by floating them to the location (having water tight seals on both faces). While on location, powerful hydraulic jacks connects them at joint providing a water tight connection.

DOUBLE DECKER SUSPENSION BRIDGE

At Lantau link it was not possible to construct a underwater structure because of heavy shipping traffic on the surface. Hence a bridge was needed but it must be so high that it allows the big ships to cross below it. A normal bridge on the site was not efficient to resist the high wind flow (typhoons). For eliminating the effect of high velocity air it was decided to increase the weight of bridge by making it double Decker. At these bridges a railway track with two lane road is provided below 3 lane road at top. As a suspension bridge was planned to be constructed it needed suspension wires for supporting the bridge deck.

 The load of deck was increased so wire must be enough strong to take it. Two 3ft diameter suspension wires were provided in this bridge each of them weighing 50000 tons. It was not possible to hang such a heavy weight wire on supporting columns after assembling it on ground. Thus section of wire was made by repeatedly laying small wires from one end to other on top of columns on their place.  

After this construction so linked bridge is designated as world’s longest double Decker suspension bridge. Finally after five years of the commencement of project the bridge was complete.

For connecting the bridge and tunnel, a highway is needed rather than existing highway. Hence this 6 miles distance was provided with an elevated highway and construction of this portion was carried out only at nights preventing the public from disturbances.

LAND RECLAMATION AT COASTAL LINE

Reclamation of Land for 8 miles North Lantau Expressway was a challenging work but to be completed at any cost for traffic interaction from town to airport. The route selected for construction of expressway was at the sea shore. The rocky ground surface available was difficult for construction and having steeper slope. So this rocky region was extended nearby half mile on seabed with the help of blasting the surface rocks and dredgers. So formed horizontal surface was taking the highway as well as the railway line. This last stretch of 8 miles allowed the connection between town and airport.

The Dead line of the project was so near when all this had completed. There was not enough time to establish remaining whole system of the airport as air traffic control system, flight display, Custom Screening and Security. Hence on 6^th July 1998 the lights of old airport was switched off and whole of the system was transferred to the new one in a night. At 7^th July 1998, first flight from Newyork landed on the new airport.

In 2010, a huge typhoon attacked on airport, but the largest enclosed structure was nailed to the seabed with massive concrete piles and just a minimal damage was caused. This project is a great example of extreme engineering. Lessons learned during this construction are valuable amd its likely to be impossible to create such a structure in such circumstances.  

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