00:18In the turbid depths of the Yangtze River estuary, a Qing Dynasty merchant ship was discovered.
00:24It had rested there for more than a century. Confronted with such a massive and ancient wooden vessel, experts carefully
00:33considered which underwater archaeological and conservation plans to adopt.
00:38Underwater archaeology generally employs four methods.
00:42In-situ conservation is ideal for sites with stable environments, such as the Shengbei Yu Yuan Dynasty shipwreck.
00:50A cofferdam excavation method was successfully carried out at the Jiangkochenyin historic site in Sichuan province.
00:59Sectional recovery is often used for severely damaged shipwrecks, for example, the Huaguang Reef No. 1 Southern Song Dynasty shipwreck.
01:08However, these three approaches would still face major challenges in the Yangtze River estuary, leaving one final option.
01:20After much evaluation, it was decided that overall salvage would best preserve the historical information held within this ancient ship.
01:29The successful salvage of the Song Dynasty shipwreck, Nanhai-1, back in 2007, offered valuable experience and insight for the
01:38salvage project.
01:39However, the Yangtze River estuary No. 2 was larger and its environment more complex.
02:06After more than a year of comparative evaluation, a solution was found.
02:10Non-contact overall relocation of cultural relics using arched beams.
02:18How to make all the engineers and all the scientists believe that this project is possible.
02:27I think this is the most difficult thing, because its development is too big.
02:31The pioneering scheme employed a new generation of salvage technology.
02:37Engineers first sank an end plate and the longitudinal beam down to the riverbed.
02:43A launching frame was then installed, driving 22 giant arched beams to rotate and pass beneath the wreck.
02:51This technology innovatively drew on the tunneling shield excavation techniques,
02:57resolving the difficulties of threading steel beams encountered during the Nanhai-1 project.
03:03After the ancient ship and surrounding silt were fully encapsulated, the entire structure was lifted out of the water.
03:11Could this solution, embodying Chinese ingenuity, really overcome the formidable waters of the Yangtze River estuary?
03:40Hu Jian, diving team leader at Shanghai Salvage, also oversaw the Yangtze River estuary No. 2 salvage project.
03:48The approaching typhoon season only added to his stress.
03:54An assistant, Wang Yu, is the first female engineer from Shanghai Salvage to participate in an offshore construction project.
04:04After more than 50 consecutive days of effort from the team, side end plates and four longitudinal beams were successfully
04:12completed.
04:14Standing by was the main force behind this salvage operation, the Dali.
04:22This self-propelled floating crane has a lifting capacity of up to 2,500 tons.
04:30With a boom force reaching 6,000 tons, it can achieve remarkable feats in major engineering projects, as well as
04:38emergency salvage missions.
04:39From the
05:06However, with all preparations complete and offshore operations about to commence,
05:11a typhoon struck the region at the end of August.
05:15Work was brought to a halt as all personnel remained on standby, waiting for the storm to pass.
05:22Mid-autumn astronomical high tide arrived after the typhoon,
05:26causing the optimal window for offshore operations during this minor flood season to be missed.
05:33Typhoons are frequent in Shanghai during this season,
05:36so the large construction team couldn't afford to wait any longer.
05:44On September 6, 2022, after four hours in transit,
05:50the Dali arrived at the ancient shipwreck site, ready to drop anchor for positioning.
05:56Let's go.
06:02Engineer Yu Xiaogang from the Tianjin Research Institute for Water Transport Engineering
06:08utilized a differential global positioning system.
06:12It was capable of monitoring the relative position between the Dali and the ancient ship in real time,
06:18with an error margin of less than 10 centimeters.
06:31The primary task during this offshore operation was to place the end plates and longitudinal beams in their designated positions,
06:39a process that took more than seven continuous days.
06:44Yu Xiaogang and his colleagues also utilized pressure sensors and fiber optic technology
06:49to monitor the structure's underwater position and its depth in the sediment.
06:54This formed the core framework of the arched beam system.
06:59It had to be precisely positioned to ensure the smooth execution of subsequent operational stages.
07:07The Dali performed fine adjustments by altering the lengths of its anchor cables.
07:13The giant crane carefully lowered parts while ensuring that the four guide sleeves were aligned with the positioning piles.
07:25Technicians carefully monitored the entire process from start to finish.
07:34As the end plates neared the seabed, the chain bucket mud removal device was activated.
07:40This excavated silt and lifted it above the end plates.
07:44After being pulverized by a high-pressure water pump spray, silt was carried away by the water flow.
07:51The end plates sank naturally under their own weight.
08:00Zhuang Xianwei, deputy chief engineer of the mechanical manufacturing branch of Shanghai Tunnel Engineering,
08:07was responsible for the design and construction of this arched beam system.
08:12All automated equipment operations were centralized in this control room.
08:22Inside the control room, spirits were high.
08:26Monitoring data indicated that everything was proceeding smoothly, putting the project ahead of schedule.
08:33The forecast was 24 hours.
08:36But in the actual operation, the speed was quite fast.
08:41The forecast was about 5-6 hours.
08:46With everyone welcoming the smooth progress, monitoring data began exhibiting anomalies.
08:54The structure s depth in the sediment showed increasing deviations.
08:59Its inclination angle quickly exceeded the design parameters.
09:17No one could predict the underwater conditions for certain.
09:22A diver needed to be sent down to confirm the specifics.
09:26Everyone was anxiously awaiting the arrival of slack tide.
09:50Finally, a diver could enter the water.
10:11On site investigation revealed that the positioning piles on the north side were pressed tightly against the stiffened plates in
10:19the inner walls of the pile casings.
10:21The entire combination has shifted slightly to the south.
10:26Analysis indicated that this resulted from the two northern positioning piles slightly tilting southeast during placement.
10:35Although this deviation was within the design's tolerance, the gap between the northern positioning piles and the casings progressively narrowed
10:44as the end plates were lowered.
10:45Unable to push away the thick and sticky silt nearby, the end plates jammed.
10:54In response to this emergency, Hu Jian promptly gathered the team to discuss possible solutions.
11:00The
11:01Now we're planning to take the machine to cut the machine out of the machine.
11:05It's just three or four.
11:07It's only two.
11:09I'll ask you, if I cut it out after I put it, it will not be able to cut it
11:12again.
11:13It's not going to be able to cut it again.
11:17We'll have some new problems.
11:18Together, we'll have a lot of problems.
11:25We'll have a lot of problems.
11:27We'll have a lot of problems.
11:38The generous gap inside the pile casings created by the stiffened plate structure during an initial
11:44stage was put to good use. The structure was hoisted out of the water. Workers promptly
11:54cut off the stiffened plates inside the four pile casings to enlarge the openings. Hoping
12:00to prevent the end plates from shifting southward again, two sets of guide rollers were installed
12:05inside the pile casings on the south side. This forced the end plates to move northward.
12:12On the exterior of each pile casing, three temporary L-shaped stiffened plates were installed
12:18to ensure precise positioning. If necessary, underwater trimming could later be carried
12:24out. Intense alterations continued throughout the night.
12:32On the afternoon of September 9th, 2022, the structure was lowered for the second time.
13:15before long, the structure had successfully been lowered to a suitable depth.
13:26However, the additional task of cutting the stiffened plates underwater still added to the
13:32diver's workload. Their already tight operation schedule was becoming even tighter.
13:40water needed to change. The air is a huge impact of the air. If we're too fast, then we couldn't
13:44land. If the air is too fast, then we can't land until we land. It can't land until it
13:50in place. The air is to land, if it is at the에요. The air is empty, then we don't land
13:53until
13:53there. Then we have to have a quick week until we start to develop. Then we have to wait until
13:54the
13:54sea of wind is slow. As we're early in the day, there's 4-day Nico Bodet.
13:56We have four cases. Every second counted. Missing slack tide would mean waiting hours more.
14:17To enhance underwater operational efficiency and ensure diver safety, Shanghai Salvage
14:24urgently dispatched the workboat to support the Dali.
14:27In doing so, the number of divers working rose to four.
15:15The jamming issue between the positioning piles and their casings was resolved, yet Hu Jian still grew increasingly worried.
15:36The 12th powerful typhoon of 2022, Meihua, formed over the northwest Pacific Ocean on September 8th.
15:45It was expected to approach the Zhejiang coast on September 12th and continue moving northward.
15:52This meant that the Dali had to be withdrawn from the site by September 13th, at the very latest.
15:59With less than 96 hours remaining, could the Dali complete its mission before the typhoon struck?
16:07Offshore operations continued around the clock.
16:10There was absolutely no time for delay.
16:13Within one metre of the structure's target depth, another problem emerged.
16:21...
16:22...
16:22.
16:51This sandbar at the Yangtze
16:54River estuary is a submerged shoal, notorious among local fishermen. It's also known as the
17:00iron plate bar. The hardened underwater shoal was formed by the unique mix of brackish and
17:06fresh water along with continual sediment deposits in the estuary.
17:26Sinking the end plate was facing unprecedented challenges. Hu Jian decided to implement a
17:32backup plan. To address situations like this, eight sets of suction pipes were pre-installed
17:38inside each end plate. Divers carrying water sprays entered the end plate cavity to disperse sediment,
17:45helping it sink. Inevitably, the mid-autumn tide soon arrived. This made diving conditions
17:58even more challenging.
18:16Sinking.
18:44Sinking twenties in the dangerous
18:47Go ahead.
18:48Right.
18:49Right.
18:50What's the case?
18:51Go ahead.
18:52Go ahead.
18:53Go ahead.
18:54Go ahead.
18:56Go ahead.
18:57Go ahead.
18:57Go ahead.
18:59I'm going to move over.
19:00I'm going to go ahead.
19:01I'm going to move over.
19:05I've got the back-up plan to show you success.
19:09The south end plate was practically settled into the desired position, but the north end
19:14plate wasn't quite there yet.
19:39The typhoon was closing in, time was running out.
20:07After accounting for necessary withdrawal time, less than 24 hours remained to lower the end plate.
20:38To overcome this final hurdle, Hu Jian's team made a bold decision.
20:44Suspending mud removal operations on the south side while unloading the lifting hook of crane number one, they added nearly
20:52200 tons of weight to the end plate.
20:55By harnessing the force of natural subsidence, they aimed to remove their final obstacle.
21:18At 3am, on September 12th, 2022, underwater probing finally delivered some good news.
21:27The structure was successfully positioned at the designed depth.
21:31The requirements for the launching frame installation and arched beam threading had been met.
21:48In the face of nature, the mind of the world is the most important part of the world.
21:49The world is the most important part of the world.
22:00in the face of nature the marvels of human engineering often appear insignificant it is
22:11precisely this pressure this race against time and struggle against the elements that brings
22:17greater significance to each breakthrough successfully sinking the end plate was not
22:24only a technical triumph but also a testament to the strength of this team in extreme conditions
22:31after typhoon mehua swept through the area the waters soon calmed once again the next chapter
22:39of this legend was ready to be written in the depths of these waters as other questions waited to be
22:45answered
