The salvage of a 800-year-old wooden ship off south China coast may help ravel three prominent puzzles surrounding the sunken boat of Southern Song Dynasty (1127-1279), Chinese experts say.
The three puzzles include whether the submerging of the Southern Song Dynasty ship was caused by overloading, where the ill-fated ship departed from, and what was inside the subsistence cabin.
The salvage operation, scheduled to start on Tuesday, is claimed to be first of its kind in the world. The sunken ship will be hoisted out of the seawater in July, according to Wu Jiancheng, who is in charge of the salvage operation.
Early on Sunday, a tug boat set sail from a dock in Guangzhou, a city on the Pearl River, for South China Sea waters 30 nautical miles off Hailing Isle near Yangjiang, south China's Guangdong Province, shipping a huge, double-box steel structure specially made for the salvage operation.
The tug boat will reach the destination on Tuesday. Finding of Nanhai No.1 wooden ship
The sunken ship was found accidentally in 1987 by Guangzhou Salvage Bureau and an underwater salvage company of Britain. It was the first ancient vessel discovered on the "Marine Silk Road" in the South China Sea and was named "Nanhai No.1", meaning South China Sea No.1.
The ship is located some 30 nautical miles west of Hailing Island of Yangjiang City in south China's Guangdong Province, and more than 20 meters deep in the sea. With a length of more than 25 meters, the ship is the largest cargo ship from the Song Dynasty so far discovered. Reasons for the salvage of the sunken ship
Though the reports about the real reasons behind the salvage have remained few apart from tourism development purpose, it is believed that a successful salvage of the sunken ship will offer important material evidence for restoring the "Silk road on the Sea", studying China's history in sea-faring, ship-building and ceramics making.
Altogether eight rounds of exploration have been made since the sunken ship was discovered in 1987.
According to Wu Jiancheng, workers have cleared away 25 tons of silt around the sunken ship and have brought out of the seawater 390 items of cultural relics. They include green glazed porcelain plates, tin pots, shadowy blue porcelains.
Archaeologists estimate that there are probably 50,000 to 70,000 relics on the sunken ship.
How to salvage the sunken ship
Experts spent three years making a plan for the salvage, considered to be the first for underwater archaeology both at home and abroad. In accordance with the plan, a huge, double-box steel structure has been envisioned in order to salvage the ship together with its silt.
Traditionally archaeologists would excavate the relics on the sunken boat first and then salvage the boat.
Zhang Bai, deputy director of the State Administration of Cultural Heritage, said: "in order to better protect the precious relics on Nanhai No.1, and gain essential information, we plan to salvage the ship together with the silt that covers it and move it into a specially built facility to carry out the excavation as carefully as possible."
With a weight of 530 tons, the steel structure is rectangle, featuring 35.7 meters in length, 14.4 meters in width and 12 meters in height. It took engineers from Guangzhou Salvage Bureau more than one month's time in making.
The engineers have filled the interlayers between the two boxes of the steel structure with sand, a move designed to increase the weight of the steel structure and meet the demand of gravity under static pressure.
According to the salvage plan, the upper part of the steel structure will be brought out of the seawater together with the sunken ship, while the lower part will be left to stay at the seabed forever, said Wu Jiancheng. Where to keep the sunken ship upon completion of salvage
The salvage operation will be undertaken by Guangdong Provincial Bureau of Culture, Underwater Archaeological Team of the National Museum and Guangzhou Salvage Bureau affiliated with the Ministry of Communications.
Two meters of silt have helped protect the treasures and the ship for 800 years, but are also creating excavation difficulties for archaeologists.
"We could see nothing in the water, and could only work by touch in the silt," Zhang Wanxing, a member of China's underwater archaeological team of the National museum, was quoted as saying.
Guangdong Province has lavished 150 million yuan for building a "Marine Silk Road Museum", to preserve the salvaged ancient ship on land.
To ensure that environmental and pressure changes do not damage the relics, the ancient ship, wrapped in silt, will be put in a huge glass pool, where water temperature, pressure and other environmental conditions will be kept the same as on the sea bed where the ship has slept for centuries.
At present, the underground infrastructure for the glass vat has been finished, but the structure above the ground is required to be completed before the sunken ship is brought out of seawater in July.
Archaeologists will conduct thorough excavations of the ship in the pool.
"We also intend to turn the glass pool into a tourist attraction which will be opened to the public later in the year," said Wu Jiancheng, "Looking through the glass wall of the pool, visitors will be able to observe the archaeologists at work." Conclusion
It is learned that the Chinese Ministry of Finance has decided to shed 90 million yuan for the salvage operation. (One US dollar equals to 7.73 yuan)