[When the column is opened]
By the end of June this year, the Shenzhen China Channel will be completed and ready for traffic. As a major national project during the 13th Five Year Plan period, the Shenzhen China Channel is the only direct highway connection between the two major urban agglomerations of the Pearl River Delta, "Shenzhen Dongguan Hui" and "Pearl River Central". It has important strategic significance in promoting connectivity across the Pearl River and efficient allocation of various factors, helping to accelerate the construction of the Guangdong Hong Kong Macao Greater Bay Area, and promoting high-quality development in Guangdong. From now on, South+launched a series of reports on "Shenzhen China Connect the World Unlimited", comprehensively combing the construction process, project significance and development prospects of the Shenzhen China Channel. Please pay attention.
(10 world records! 120 seconds review of the 7-year construction of Shenzhen China Channel, 2 minutes in total)
Six years ago, Lin Ming, chief engineer of the Hong Kong Zhuhai Macao Bridge Island Tunnel Project, said, "If we win the Hong Kong Zhuhai Macao Bridge, there is no bridge in the world that the Chinese can't build".
Now, the Shenzhen China Channel, which took seven years of preliminary work and seven years of hard construction, completed the handover and acceptance on June 16 and passed the quality "big exam", is about to be officially opened to traffic. This 24km two-way 8-lane "super project" integrating bridges, islands, tunnels and underwater communication has once again "gone out of the loop" in world traffic.
With towering towers rising into the clouds, artificial islands standing on the sea, bridges like dragons, and the "domineering" deep and middle passage, why can "sigh and die" become "cross Lingding"? How can we create 10 "World's Most" at one fell swoop?
There is nothing in the sea
How to understand such a huge traffic cluster project? Think of the Western Rengong Island, a deep and middle passage with an area of about 137000 square meters, which is equivalent to 19 football fields, as a giant "kite" flying on the Lingdingyang Sea.
On December 28, 2016, the construction of the first project of Shenzhen China Channel West Man Island was started.
This "first child" of the deep and medium channel project in Lingdingyang plays a very critical role in the overall stability and progress of the deep and medium channel.
In order to ensure the navigation capacity of Lingding Channel of 300000 tons, the design scheme of East Tunnel and West Bridge is adopted for Shenzhen Middle Channel.
"There is an undersea tunnel in the east and a bridge across the sea in the west. If you want them to join hands, you must first build an artificial island in the sea," said Zhang Changliang, deputy director of the Shenzhen China Channel Management Center.
How to build an artificial island in the vast sea? The traditional technology of riprap reclamation and island building will have a long construction period and a great impact on the surrounding environment and channel.
The construction team uses steel cylinders to form an island. A total of 57 steel cylinders are used, each with a diameter of 28 meters, a height of 35-40 meters, and a weight of 650 tons.
At the same time, the western man-made island is located in the sand mining area, and the stratum is complex. The construction team has developed the core technology of steel cylinder foundation pretreatment, "grinding tofu" on the uneven and uneven construction sea foundation, reducing the strength of hard soil layer. In addition, the self-developed 12 hammer linkage hammer group vibrates at the same frequency, successfully driving one giant steel cylinder into the seabed rock stratum accurately and firmly.
On September 18, 2017, as the last steel cylinder vibrated and sank in place, the cofferdam at the outer circle of the West Rengong Island outlined a "sea kite" like a pearl.
It took only four and a half months to build an artificial island the size of 19 football fields in the middle of the vast Lingding Bay, setting a new world record for rapid island formation.
Today, this "sea kite" has become a new landmark in Lingdingyang. From here to the east, the Shenzhong Channel starts the 6845m long subsea tunnel. Soon, cars will drive from here to below the sea level, and the deepest place will drive in the immersed tube tunnel 39m below the sea level.
32 "deep sea kisses"
The "sea kite" dances with a firm and durable "traction line" - a 6.8 km long subsea tunnel.
According to the engineering design, 32 immersed tubes and one final joint should be placed in the deep soft soil layer more than 30 meters below the deep middle tunnel to realize two-way eight lane traffic on the seabed - this is also the longest and widest steel shell concrete immersed tube tunnel in the world at present.
The total steel consumption of the Shenzhong Tunnel exceeds 320000 tons, which is three times that of the National Stadium "Bird's Nest". The steel shell concrete immersed tube tunnel is about 5km long, which is divided into 32 pipe joints (26 standard pipe joints, 6 non-standard pipe joints) and one final joint. The standard pipe joint is 165m long, 46m wide and 10.6m high, which is a 55 storey building.
It is an unprecedented challenge to sink these 32 "big guys" into the sea bottom, head to tail, and tight fitting, so as to ensure that the whole project is "watertight" in its 100 year design life.
The first problem is to manufacture huge steel shell immersed tubes. According to the construction plan, the speed of delivering one steel shell per month must be reached to meet the needs of project construction.
To this end, Shenzhen Zhongdao Channel has created the first large-scale steel structure in China, "four lines and one system of intelligent manufacturing". "For the first time in China, we have realized intelligent welding and intelligent spraying of large steel structure blocks, greatly improving the quality and speed," said Song Shenyou, director and chief engineer of Shenzhen China Channel Management Center.
At 2:00 a.m. on June 16, 2020, the first 60000 ton immersed pipe joint was integrated with the integrated ship in the harbor basin of Niutou Island, Zhuhai.
They crossed the Hong Kong Zhuhai Macao Bridge and entered the Lingding Channel. After seven channel conversions, they overcame multiple challenges such as busy route conversion and shallow water channel grounding, and finally reached the installation point.
After a long journey, the first pipe joint starts the "kiss of the deep sea": the operator slowly lowers the immersed tube onto the seabed bed through the windlass, uses the retractor to make the immersed tube initially connect with the butt end, and then discharges the sea water in the junction chamber, and makes it "tightly embrace" with the butt end through hydraulic crimping.
At the depth of more than 30 meters, it is as difficult as docking a manned spacecraft with the "Tiangong" space station to make the 80000 ton standard immersed tube achieve millimeter level docking.
It took three years for 32 immersed tubes to be placed on the seabed from the successful "first show" of the first immersed tube to the successful installation of the last immersed tube.
In June 2023, the critical moment of E23 pipe joint and final joint sinking and docking will come. This is a floating installation with the longest time span and requires two docking operations.
The immersed tube transportation and installation integrated ship "Yihang Jin'an 1" is like a huge rectangular steel clamp, holding the last immersed tube and the final joint firmly on the bottom of the ship, with the final joint facing E24 in the east.
This is the world's first brand new structural device, which adopts the integral prefabricated underwater pipe push out final joint.
It manufactures the final joint together with the last section of immersed tube (E23), and the push out section is placed in the expanded end of the butt joint end of the pipe joint, floating and sinking together with the last section of immersed tube. After the standard section of the final pipe joint is docked with the installed pipe joint and confirmed to be in a proper posture, the push out section is like a giant drawer box, and the push out section is pushed out from one side by the force of jack and water pressure, Butt joint with the end steel shell of E24 pipe joint.
The push out section is only 2.2 meters away, but it took 6 hours for the final joint to connect with E24 pipe joint to achieve tunnel closure.
"This joint has the advantages of good safety, fast construction, no need for large-scale equipment, and good economy. We hope to form a safer, more efficient, and more accurate docking in the construction of offshore immersed tunnels, and at the same time achieve new breakthroughs in the world immersed tunnel construction field, expanding China's leading edge in this field." Song Shenyou introduced.
The strongest "China Core"
If the tunnel is a "hidden line" hidden under the water, the bridge is a "flying line" that soars with the "sea kite".
The total length of Shenzhong Channel Bridge Project is about 17 kilometers. With a main span of 1666 meters, Shenzhong Bridge has become the world's largest offshore steel box girder suspension bridge, with a navigation clearance of 76.5 meters, the world's highest navigation clearance sea bridge.
"In order to ensure the smooth passage of ships, the Shenzhong Bridge has a deck of 91 meters, which is equivalent to a height of 30 floors, and is the highest sea crossing bridge in the world. In addition, the bridge is located in the open waters of the Pearl River Estuary, and strong typhoons frequently occur. Famous foreign bridge companies believe that 'wind resistance safety requirements cannot be met'." Fan Chuanbin, executive deputy director of the Shenzhong Channel Management Center, said.
"Where can we defeat?" Fan Chuanbin recalled that, under the leadership of Shenzhen China Channel Management Center, several units jointly tackled key problems. It took more than three years to develop new combined pneumatic control technology, overcome the disaster control technology of super large span integral steel box girder suspension bridge in typhoon prone areas, and broke the authoritative judgment of foreign countries at one fell swoop.
In addition, fatigue of orthotropic steel deck and anti-corrosion of main cables of suspension bridges in the sea are also worldwide problems.
Suspension bridge refers to a bridge whose superstructure is mainly composed of cables suspended by cable towers and anchored on both banks or at both ends of the bridge.
"The cable is one of the key components of the suspension bridge, and also the 'lifeline' of the suspension bridge." Fan Chuanbin introduced that the Shenzhong Bridge has a large span, and has been in a high temperature, high salt, and high humidity marine environment for a long time. The corrosion fatigue problem is prominent, and the cable can not be replaced in the whole life cycle, so the requirements for cable strength and corrosion resistance are very high.
For this reason, the main cable steel wire used for Shenzhen Zhonghai Bridge is very special: the zinc aluminum multi alloy coated steel wire with a diameter of 6 mm and 2060 MPa has at least one time the salt spray corrosion resistance of the existing hot-dip galvanized steel wire and two times the zinc aluminum coated steel wire.
"Both the strength and corrosion resistance have reached the world's leading level. This is also the first time in the world that the 2060 MPa steel wire 'Chinese core' independently developed by China has been used in the construction of suspension bridge main cables on a large scale." Fan Chuanbin introduced.
There are two main cables at the upstream and downstream of the Shenzhong Bridge. A single main cable is about 3000 meters long and weighs about 17000 tons. It is composed of 199 strands, and each strand is composed of 127 high-strength steel wires. The single wire bearing capacity can lift three cars, which is the strongest "Chinese core".
A bridge flies over Lingding. In five years, the construction team overcame many unfavorable conditions, such as all offshore operations, complex construction conditions, frequent strong typhoons, and finally made the Shenzhong Bridge stand between the sea and the sky.
Major nodes and amazing data cannot form the whole picture of super engineering. During the construction of the Shenzhen China Channel, the stories about innovation and breakthrough, such as the sun and sea breeze, were carved into the "body" of this "super project" and became its inherent strength.
Shenzhen China Channel Top 10 in the World
[Shenzhong Bridge]
1. The world's largest span offshore steel box girder suspension bridge (main span 1666m).
2. The world's highest bridge deck, the highest navigation clearance sea bridge (deck height 91 meters).
3. Anchorage of suspension bridge in the world's largest sea (the concrete volume of a single anchorage is about 344000 m3)
4. The world's highest wind speed for suspension bridge wind resistance test (the highest flutter test wind speed is 83.7m ／ s)
5. The world's largest volume of steel deck hot mixed epoxy asphalt pavement (with an area of 378800 square meters).
[Deep and Medium Tunnel]
6. The world's longest two-way eight lane subsea immersed tunnel (5035m long, 32 pipe joints+1 final joint).
7. The widest submarine steel shell in the world - concrete immersed tube tunnel [standard pipe section is 165 meters long, 46 meters wide (the widest 55.6 meters), and 10.6 meters high].
8. The world's largest single volume pouring of steel shell sinking self compacting concrete pouring (the concrete pouring volume of a single pipe joint has reached 29000 m3, with a total of 910000 m3).
9. The world's first underwater expressway hub interchange airport interchange.
10. The world's widest (3m) collapsible M-type waterstop shall be used for the final joint of immersed pipe.
