Solid progress in the construction of the Shenzhen Zhongshan Corridor (Industry and Economic Observation · Entering the Front Line of Major Projects ③)
Scenery of the Lingdingyang Bridge in the Shenzhong Passage.
Photo by Du Cailiang
The Pearl River estuary, Lingdingyang, flying clouds and rippling blue waves.
Standing on Ma'an Island in Zhongshan City, Guangdong Province, the under construction Shenzhong Passage winds over the deep blue sea, sometimes jumping into the air and sometimes escaping into the sea, traveling 24 kilometers to reach Qianhai in Shenzhen. After the Hong Kong Zhuhai Macao Bridge, this super large cross sea passage that integrates tunnels, islands, bridges, and underwater interchanges will once again break multiple world records.
From a higher perspective, the Shenzhong Passage is 30 kilometers north of the Humen Bridge and 31 kilometers south of the Hong Kong Zhuhai Macao Bridge, making it a crucial "horizontal" part of the A-shaped transportation backbone in the Guangdong Hong Kong Macao Greater Bay Area. When it is completed and opened to traffic next year, the drive from Zhongshan to Shenzhen will be shortened from 2 hours to 20 minutes, becoming the main traffic artery connecting the urban agglomeration on both sides of the the Pearl River Estuary. How to build a super project? How can the "most of the world" be created? Recently, the reporter rushed to the construction site to investigate the situation.
Sea Kite
In just 4 and a half months, a man-made island equivalent to 19 football fields was built in the vast open sea
In the early summer morning, when viewed from a high altitude, the sea shimmered with ripples, and the deep middle passage was like a huge "sea kite" flapping its wings and ready to fly.
The "kite face" of this kite is the Xiren Island in the Deep Middle Passage. To ensure the navigation capacity of 300000 tons in the Lingdingyang waters, the design scheme of the East Tunnel and West Bridge has been adopted for the Shenzhong Channel. "To the east is the underwater tunnel, and to the west is the cross sea bridge. To make the two work hand in hand, we need to first build an artificial island in the sea," said Zhang Changliang, Director of the Island Tunnel Engineering Management Department of the Shenzhen China Channel Management Center.
How did the "first son" fall in the vast sea?
"The water depth in the open sea is over 10 meters, and the soft soil layer is several tens of meters thick. It's like building an island on a 'water tofu'. Traditional stone throwing caissons are prone to slipping and difficult to fix. Zheng Weitao, Deputy Chief Engineer of the Deep Middle Channel Project Department of China Communications First Navigation Bureau, said that the team fully drew on the construction experience of the Hong Kong Zhuhai Macao Bridge and proposed a new large-scale deep insertion steel cylinder enclosure plan. 57 giant steel cylinders with a single diameter equivalent to the length of an international standard basketball court and 13 floors high were driven into the seabed, and then filled with sand to form an island.".
However, the sea will not easily comply with people's wishes. After underwater exploration, the problem lies ahead. "The seabed structure here not only has thick silt, but also is covered with hard interlayers of varying depths, and the geological conditions are worse than the construction conditions of the artificial island of the Hong Kong Zhuhai Macao Bridge." Zheng Weitao told reporters that construction on this uneven "water tofu" is prone to positional deviation.
"If geological problems are not solved, everything is just talk on paper." Zheng Weitao pointed to the underwater deep mixing ship not far away and said that it was the "hero" who solved the problem. Originally, this ship was like a huge mixer, with three drill pipes attached that could penetrate deep into the sand layer, inject mud, and soften the geology, making it easier for the steel cylinder to penetrate the hard sand layer and accurately reach the design position.
The experiment went smoothly and the steel cylinder was ready. On May 1, 2017, the construction curtain of the island was officially opened - a 10000 ton ship carrying the first large steel cylinder slowly sailed into the Lingding Ocean, and hundreds of construction workers lined up at sea to welcome it. The 4000 ton crane ship "Yihang Jintai" extended a long sling and steadily lifted the hydraulic vibration hammer group and the large steel cylinder together. Guided by the independently developed positioning system, it was accurately placed in the water.
With a "sinking start" sound, the ocean suddenly boiled. The world's largest twelve hammer linkage hydraulic vibration hammer group simultaneously exerts force, with a sound like a ding and a momentum like a rainbow. After more than 3 hours, a steel cylinder weighing over 600 tons was steadily inserted into the seabed for more than 10 meters, and the settling accuracy reached 100%.
"Compared to the Hong Kong Zhuhai Macao Bridge, the diameter and weight of the steel cylinder in the deep middle channel are longer and heavier, and the power required for vibration sinking operation is also stronger." Zheng Weitao proudly said, and the team optimized and transformed the original eight hammer linkage hammer group, designing and manufacturing a twelve hammer linkage hammer group, with a maximum applied gravity of 5900 tons, leading the industry in level. In the months following the successful sinking of the first steel cylinder, this technology was replicated 57 times. "After the passage of Typhoon 'Tiange', we measured each tube and found that the position remained almost unchanged. Both the structure and stability were tested," Zheng Weitao said.
On September 18, 2017, as the last steel cylinder sank into place, the outer cofferdam of Xiren Island outlined a "sea kite" like pearls and jade. In just 4 and a half months, a man-made island equivalent to 19 football fields was built out of thin air in the vast open sea dozens of miles offshore, breaking the world record for rapid island formation.
Underwater embroidery
32 sections of sunken tubes are connected and placed on the seabed, with a 6.8 kilometer long underwater tunnel holding hands under the ocean surface
The sea kite dances gracefully, requiring a sturdy and durable "traction line" - a 6.8 kilometer long underwater tunnel.
According to the channel engineering design, 32 immersed tubes should be installed in the deep sea soft soil layer below 30 meters in the tunnel section to achieve bidirectional eight lane traffic on the seabed. This is also currently the longest and widest steel shell concrete immersed tube tunnel in the world.
Regardless of the intricate internal structure of each immersed tube, looking solely at its shape, each standard tube segment is 165 meters long and weighs approximately 80000 tons. To sink these 32 "big guys" into the seabed, with their heads and tails tightly connected, ensuring that the entire project is "leak proof" throughout its 100 year design life, posing an unprecedented challenge.
Manufacturing giant steel shell sunken pipes was the first tough battle.
Outside the the Pearl River Estuary, Niutou Island, Zhuhai, has experienced the construction of the Hong Kong Zhuhai Macao Bridge, where the world's largest tunnel sinking prefabrication factory has been built. "According to the project requirements, we need to ensure the production of one sunken tube per month. In this way, the longitudinal movement of the steel shell sunken tube in the factory must be completed within one day. To achieve this, intelligence is the only way out," said Luo Bing, Deputy Production Manager of the Deep Middle Channel Project of China Communications Fourth Navigation Bureau.
Over 80 discussions, over 300 drawings, and 23 breakthroughs have led to the release of a complete set of intelligent manufacturing solutions: 200 independently developed intelligent trolleys operate synchronously and transport the steel shells to the pouring area within 4 hours. Subsequently, the intelligent pouring robot emerged, intelligently calculating the pouring speed and controlling the concrete cutting height in real time to ensure that each compartment was fully poured, ultimately completing a section of steel shell sinking pipe.
Creating a sunken tube is just the first step. How to float and transport the sunken pipes into place, which is nearly 50 kilometers from the prefabrication plant to the docking area of Xiren Island, has become a new challenge.
The project team first proposed to widen the two installation ships originally used for the construction of the immersed tubes of the Hong Kong Zhuhai Macao Bridge, to match the width of the immersed tubes in the deep middle channel. However, due to the inability of the two ships to navigate independently, the widened hull needs to be towed by tugboats on both sides, and the existing channel width cannot meet the navigation needs of installation ships and tugboat formations. If a new self-propelled semi submersible is built, the cycle is long and the operational risk is also high.
What should we do? At an expert seminar in 2016, Li Yiyong, then Deputy General Manager and Chief Engineer of China Communications First Navigation Bureau, led his team to come up with an inspiration: can two installation ships be transformed into a single integral structure and equipped with towing power through main and side thrust devices?
The mind changes and the world becomes wider. After more than a year of refinement, construction, and debugging, the world's first sunken tube floating installation integrated ship "Yihang Jin'an 1" has been conceptualized as a physical object: with a length of 190 meters, a width of 75 meters, and a depth of nearly 15 meters, even carrying 80000 tons of sunken tubes, it can achieve precise sinking and docking of sunken tubes underwater for 50 meters.
The next step is the most severe test: place the first immersed tube at the designated location deep in the sea.
At 2am on June 16, 2020, an 80000 ton sunken tube was pulled out of the Niutou Island slot dock and merged with a 20000 ton integrated ship. Accompanied by 8 tugboats and maritime vessels, they crossed the Hong Kong Zhuhai Macao Bridge and entered the Lingdingyang Channel. After 7 channel transitions, they overcame numerous challenges such as shallow water channel stranding and strong siltation, and finally arrived at the installation site.
After a long journey, the sunken tube began to "kiss the deep sea": the operator slowly lowered the sunken tube onto the seabed through an anchor machine, and discharged excess water through hydraulic pressure connection. The sunken tube and the fixed pipe joint tightly embraced each other.
From the successful debut of the first section of the immersed tube to the successful installation of the last section, 32 immersed tubes were placed on the seabed, which took a full 3 years.
At noon on June 9th this year, more than 150 technical personnel were on standby in the command hall of the integrated ship. Through the Beidou navigation system, the underwater operation is clearly visible: the last section of the sunken tube is securely placed in the designated position, and then the final joint is slowly pushed out through the jack system, followed by pressing, aligning, and sealing.
"The unloading, floating, and installation of E23 pipe joints have all been completed, and the final joint has been pushed out. The measurement tower and diving exploration display accuracy meet the requirements!" Ning Jinjin, Executive Deputy Chief Engineer of the Deep Middle Channel Project Department of China Communications First Navigation Bureau, excitedly reported on site.
Nearly 70 hours of tension suddenly turned into a scene of joy. Everyone knows that this means that the Shenzhen Zhongshan Channel underwater tunnel has successfully closed, and Shenzhen and Zhongshan have achieved "hand in hand" at the bottom of the Lingdingyang Sea.
On the early morning of June 11th, celebratory fireworks rose on the Lingdingyang, rising into the sky and cutting through the night sky, reflecting the smiling faces of onlookers at sea.
Needle piercing in the wind
The world's largest sea anchor lifts the world's highest navigation clearance sea bridge, and a main cable consisting of 199 steel wire strands is erected at an altitude of 270 meters
If a tunnel is a hidden line hidden underwater, then a bridge is a flying line holding a kite from the sea.
This is a very simple thread. It has a total length of about 17 kilometers, starting from the Zhongshan Ma'an Island approach bridge, passing through the Zhongshan Bridge, passing through the Lingdingyang Bridge, and finally connecting to the West Artificial Island. The Lingdingyang Bridge, with a main span of 1666 meters, has become the world's largest offshore steel box girder suspension bridge, and also the world's highest navigation clearance sea bridge due to its 270 meter main tower.
To ensure navigation capacity, the Lingdingyang Bridge has a net height of 76.5 meters for ship navigation, which is the highest in the world. To achieve such a clear navigation height, two higher main towers of the bridge need to be built on the Lingdingyang.
A large-span suspension bridge requires a stronger anchorage as the load-bearing structure. Following the direction of Liao Wenlong, Deputy Manager of the Deep Middle Channel Project Department of China Communications Second Navigation Bureau, a huge "weighing weight" is firmly anchored in the sea at the junction of the main cable and the sea surface. "The single anchor of the Lingdingyang Bridge weighs 1.7 million tons and is the largest anchor in the world. It is like the person at the end of a tug of war, having to rely on its weight to grab the main cable of the bridge and bear the weight of the entire bridge and vehicles."
The vast ocean is unsupported, where should we start? Build artificial islands to transform offshore construction into onshore construction. Next to the artificial island, there is a living platform that is half the size of a football field. A "small town" formed by 130 containers has become what workers call a "sea view house", and it has been there for over four years. "The longest time I've been on the island for three months, listening to the waves during the day and watching the stars at night." Liao Wenlong vividly remembers the day I went down to the island - April 28th this year. "That was the day when the bridge closed, and everything was worth sticking to."
The anchor is embedded in the deep sea, and the main tower stands tall. Two suspended ropes tightly connect the two. This rope is the main cable of the bridge and also the lifeline of the suspension bridge.
"If you want to install a suspension cable, take the catwalk first," said Zhang Ping, Deputy Manager of the Shenzhong Channel Project Department of China Communications Second Navigation Bureau. As an aerial construction channel for laying the main cable of the bridge, the catwalk runs through the entire upper structure construction process of the suspension bridge.
Entering the elevator built close to the main tower and measuring five feet square, moving the construction platform and climbing two levels of stairs, the reporter arrived at the top of the tower, which is 270 meters above the sea and about 90 floors high. A completely aerial catwalk came into view: two 3-kilometer long, 4-meter wide air corridors flew over the waterway, with bottom steel wires tied into a mesh and waist high railings on both sides. Muster up courage, take small steps forward, white clouds flying over your head and waves rolling under your feet, making your legs and feet feel weak.
For over two months, construction workers were shuttling back and forth at such a height of 100 meters, threading the bridge with needles and wires. They moved 199 steel wire strands one by one, pulling the anchor head horizontally from one end to the other, and finally formed a main cable with a diameter of 1 meter and strength enough to withstand a weight of 150000 tons.
"We are all 'tightrope walkers', and we walk the tallest and longest' tightrope 'in the world's oceans. Starting from 2007, this is the seventh suspension bridge that Zhang Ping participated in the construction.' We must build a world-class bridge with the highest construction standards, and every person, every day, and every process must not have any slack. This is the requirement of the Lingdingyang Bridge for us bridge builders. '"
At present, all bridges along the Shenzhen Zhongshan Expressway have been completed and construction of bridge deck ancillary facilities is underway in full swing. Along the bridge to the east, the follow-up construction of artificial island and undersea tunnel is in full swing, and a huge "sea kite" connecting the city groups on both sides of the the Pearl River Estuary leaps to the sea, becoming a spectacular scenery on the Lingding Ocean.
