Home Engineering World’s longest bridge and its man-made islands open for use in China

World’s longest bridge and its man-made islands open for use in China

505
0
dav

 

Report and photos By IKENNA EMEWU

China recently rolled out another wonder to stamp her authority as outstanding. The new stride stands over the Lingdingyang Bay, the sea that sits between Guangdong Province in mainland China and the island outlets of Macau and Hong Kong at the Pearl River Delta Estuary.

The structure is designed with a life time of 120 years.

“In the Chinese history of bridge engineering, the Hong Kong-Zhuhai-Macau Bridge (HZMB) has become the bridge of the largest scale involving the most complex technologies and facing the most difficult construction challenges,” said the builders in a booklet it distributed to journalists and officials that attended the opening on June 9.

After series of concept development that started in 1983 and policy fine-tuning, work started on the project in December 2009 when Chinese Premier Li Keqiang did the commissioning; and it was exactly two years later that work at the Hong Kong end commenced. The opening to traffic and use was actually what we attended that morning.

A reference about the project on Wikipedia narrated the economic benefits and reasoned that: “By slashing travel times between the eastern and western banks of the Pearl River Delta, parts of less-developed southern China will gain improved access to global markets through Hong Kong. In addition, it is said that Hong Kong will benefit from this project in the long term, through the enhanced flow of labour and goods between China and the rest of the world.”

The ferry journey between the points linked by the bridge that used to last 90 minutes is cut down to 30 minutes using the bridge. The implication is that people can commute through the bridge to work in Hong Kong or Zhuhai over the Pearl River Delta and back everyday.

dav

Scenic Zhuhai

The Zhuhai harbour overlooking the sea to the left as you drive into the coastal beautiful city from Shenzhen has a shopping mall that has within it a ferry port and also the boarding point for passengers booked on flights from Hong Kong.

Looking towards the sea at night, the light on the long bridge forms a beautiful and amazing arc of illumination far into the night and over the vast waters of the Lingdingyang.

At the upper floor of the mall, a sign screams: Welcome to Hong Kong Airport boarding gate. Passengers at this side of the vast sea that is some 90 minutes by ferry ride check in and board the flight by first boarding the ferry to cross the sea into the Hong Kong Airport.

And over this sea, China has completed the world’s longest sea bridge of 55km linking Zhuhai, Macau and Hong Kong. The windy architecture over water like a huge snake is the latest wonder of the world’s second largest economy and now hub of developmental wonders.

That Saturday morning, June 9, a team of journalists from China of various nationalities, including six from Nigeria had arrived the bridge in buses. There were also government officials and those of the company that built the bridge to unveil the wonder to the world. It is an amazing sight and the warm sun graced the occasion as the team made several stops to see, feel and take photos of the bridge.

dav

Work commenced on the project in December 2009 and in bits and pieces the builders kept momentum until the finishing point. The chief engineer that handled the project, Luo Dong at a point during the stops approached a huge billboard and started lecturing the team on how the project was actualized. He had a drawing of the bridge hung on the pavement dividing the lanes of the bridge and gave details of the work.

As the journey advanced, Engr. Luo unfolded more wonders especially when the team got to the man-made island on the bridge.

Man-made island

It is an egg-shaped giant island linking the two ends of the snaky structure over water, and the structure on it where Engr. Luo at the last floor unfolded the details of the ingenious creation is exactly like a huge cruise ship, even with a mast jutting skyward.

On the islands the engineers created to provide the tourism aspect of the project, is a vast space built into a full land environment with grass lawns, trees, structures, streets lights stands and parking spaces for vehicles.

A booklet on the project from the company that built it noted that the islands are actually two and fitted next to each other. Each is 100,000 sq/m in area with the 6.7km subsea tunnel form the critical component of the HZMB.

dav

However, under the man-made island is an underwater road or bridge also intentionally built into the giant project. On the third floor of the building on the island that would later provide tourists with recreation including restaurant, offices, lounges and lodging spaces, the visitors were ushered into a hall big enough for up to a hundred persons seated.

Luo stepped forward to the large LED display board and took on lecturing his guests on how the work started and later ended in success. First was a computer simulation of the work from the minutest start to completion. Bit by bit he explained the details and how the slabs, platforms, the components that later made the bridge were made at an island nearby and transported to location, fitted together into the bridge. After about 70% of the bridge had been completed, less 12.1km from the Zhuhai end towards Hong Kong (HK), Luo said the team reasoned that the spans as partitioned would not favour the remaining stretch and decided to create the islands that is 6000.7m or approximately 6.7km.

They therefore took the project about 6km from the HK end and stopped somewhere. With the work progressed from Zhuhai, the structure then had a gap in between the two and that gap was later put into place as the man-made islands and underwater tunnel – 6.7km in length and slightly wider than the two bridges making the two lanes with the side extensions.

He said the construction team considered the closeness of the HK airport and its take-off and landing tracks and deduced that if the spans of the bridge continued at lengths not more than 200m apiece, they would have construction and technical challenges at the HK end. That was what made the island so necessary. They also limited the height of the structure on it.

dav

True to his word, within about 20 minutes on the bridge at the last stop, at the HK end, there was an unbroken succession of flights taking off from the HK airport and overflying the bridge.

Engineering ingenuity

Work started on the island by first dredging and creating a deeper trough at the seabed followed by the fixing of columns, ramps, base foundations and later vertical slabs to form two walls which later isolated the water within that was drained to expose a dry long region in the middle of the sea with high concrete slab walls warding off the water of the sea. This was sustained to the desired height and the enforcement and raft base with phalanx of complex concrete works, iron works etc before it was decked and buildings and other structures put fast on the new island that the engineers created. On this island, visitors would converge and have fun and a feel of the engineering creation. As they have their time relaxing, feasting, celebrating, vehicles are cruising by underneath in the underwater tunnels.

The construction booklet explained that the builders adopted “innovative composite foundation, combined gravel bed. The composite foundation consists of rigid columns, high pressure jet grouting piles and sand compaction piles for reinforcement; while the combined gravel bed is composed of tamped rock fill and paved ravel layer.”

dav

Prefabrication of the immersed tunnel element

“In an industrialized production process, immersed tunnel elements were prefabricated in the world’s largest immersed tunnel precast yard, which was built within 14 months. All 33 tunnel elements, including five curving elements were successfully prefabricated in six years. The weight of each standard tunnel element is about 80,000 tons. To solve the challenge brought by the semi buried depth, a new semi grid tunnel was innovatively developed. The innovatively developed ‘memory’ joint has resolved the risk of damage to the joint structure.”

Lost in awe

Coming down from the building on the island, we proceeded to drive through the underwater tunnels.

It is a wonder for every meaning of the word, and but for the explanation, no one that gets in there would imagine he or she is standing in a space from creation occupied by water and evacuated months ago to create the road. The tunnel highways are heavily lined at the roofs with bright daylight electric lamps.

dav

You see sign of the water nearby or under you when you step on the wet road that is very cold and looks or feels almost like there is seapage from the sea under. You would just be marveled being here, feeling the sea under your feet and behind the high walls that carry the man-made island but not reaching you.

 

 

 

 

LEAVE A REPLY

Please enter your comment!
Please enter your name here