Great country project stunning the world, showing the strong strength of China engineering construction

CCTV News:Today (November 28th) morning, the main line of the deep-middle passage of Guangdong-Hong Kong-Macao Greater Bay Area core transportation hub, a major national project, was officially completed. The Shenzhen-China Passage spans the east and west banks of the Pearl River Estuary, connects Shenzhen, Guangzhou and Zhongshan, and integrates "bridge, island, tunnel and underwater communication", with a total length of about 24 kilometers. It is planned to be open to traffic in June next year.

The deep middle passage is one of the most difficult cross-sea cluster projects in the world at present. The construction scheme of "West Bridge and East Tunnel" is adopted. The length of the submarine tunnel in the east is about 6.8 kilometers, and it is designed as a two-way eight-lane tunnel, which is the longest and widest submarine steel-shell concrete immersed tube tunnel in the world. The cross-harbour tunnel is connected with two artificial islands, the east artificial island realizes the conversion between the cross-harbour tunnel and various highways on the road surface, while the west artificial island undertakes the conversion function between the tunnel and the offshore bridge.

West Artificial Island: A New Landmark on Lingdingyang, a "Kunpeng at Sea"

Driving in the deep middle passage with a total length of 24 kilometers, how can vehicles safely and smoothly enter the cross-harbour tunnel from a bridge tens of meters high on the sea? The artificial island in the west of the deep middle passage has solved this problem.

Viewed from the air, the West Artificial Island, which covers an area of about 137,000 square meters and is equivalent to 19 football fields, is like a Kunpeng, spreading its wings on the sea of Lingdingyang.

The most important function of the West Artificial Island is to realize the bridge-tunnel conversion. Construction started in December 2016, and it is the earliest project in the whole line. The "first son" of this deep-middle channel falling on the Lingdingyang plays a very key role in the overall stability and progress of the deep-middle channel. The position and function are irreplaceable, but where should we start to build such an artificial island on the vast sea?

Each of the 57 steel cylinders has a diameter of 28 meters and a height of 35-mdash; 40 meters, weighing 650 tons. The west artificial island of the deep middle passage is located in the sand mining area, and the stratum is complex. The construction team developed the core technology of steel cylinder foundation pretreatment, which "grinding bean curd" on the uneven and uneven foundation of the construction sea area, reduced the strength of the hard soil layer, and combined with the self-developed 12-hammer linkage hammer group with the same frequency vibration, successfully drove giant steel cylinders into the seabed rock stratum accurately and firmly, creating a world record for the rapid island formation of the west artificial island in four and a half months.

In addition to realizing the function of bridge-tunnel conversion, the West Artificial Island will also be an important place for the maintenance and management of tunnels and bridges, and this artificial island with the shape of "Kunpeng on the sea" will also become a new landmark on the Lingdingyang.

East artificial island: realizing underwater intercommunication

In order to realize the underwater intercommunication function, the deep-middle passage cannot be separated from the East Artificial Island. So how to switch between island tunnels? How to connect with the adjacent road network on the ground and realize multi-site interconnection? Follow the reporter to the East Artificial Island to continue to understand.

The artificial island in the east of the deep middle passage is located in the south of Shenzhen Baoan Airport, and connected to the submarine immersed tunnel in the west, which is the gateway project of the Shenzhen end of the deep middle passage.

Seen from the air, the T-shaped main tunnel of the East Artificial Island and the ramp tunnel bridge on both sides are like a seabird flying on the sea with its wings. Before construction started in 2017, it was still a shallow sea. The island body filled with sea sand covers an area of nearly 350,000 square meters, which is equivalent to 48 standard football fields.

CCTV reporter Li Weidai:This is a diversion point of the underwater interchange hub of the East Artificial Island of the Shenzhen-China Passage. We are now 15 meters below the sea surface. In front of me is the submarine immersed tube tunnel of the Shenzhen-China Passage. The tunnel divides into two forks here. In the future, vehicles from Zhongshan to Shenzhen will be smoothly connected with the ground road network through this Y-shaped fork.

There are four off-ramp and confluence points like this in the underwater hub of East Artificial Island, which together with the main tunnel on the island realize the diversion and confluence of vehicles.

Underwater interchange is in a relatively closed environment, which has certain influence on driving sight distance. As early as the preliminary study of the project, the professional team simulated driving in various states through professional software system, optimized the continuous partition wall at the confluence of the main line tunnel and the ramp tunnel as a column to increase the permeability, and adopted intelligent electronic safety auxiliary facilities to improve the driving safety.

Reporter’s visit: immersed tube floating installation integrated ship

The submarine tunnel part of the deep middle passage has a total length of about 6.8 kilometers and eight lanes in both directions. The immersed pipe section of the tunnel is connected by 32 pipe sections and a final joint, each of which is 165 meters long, 46 meters wide, 10.6 meters high and weighs about 80,000 tons. How can we float these "Big Macs" in place in the vast sea and install them accurately? It all depends on one core equipment, which is the world’s first immersed tube floating installation integrated ship independently developed by China.

This submerged floating installation integrated ship tailored for the deep middle passage is 190.4 meters long, 75 meters wide and 14.7 meters deep, and its deck area is equivalent to two football fields. It is a special ship for submerged construction of submarine tunnels with the strongest installation capacity, the highest sinking accuracy, the most efficient construction operation and the most advanced performance in the world. Seen from a height, it looks like a huge rectangular steel clip, holding the immersed tube firmly in the center of the ship.

The biggest highlight of the floating and installing integrated ship is that it is equipped with an automatic driving system, which perfectly solves all kinds of difficulties in floating and transporting immersed tubes out of the dock. All immersed tubes of the Deep-Middle Passage need to be docked from Guishan Island Immersed Tube Prefabrication Factory and floated to the immersed tube installation area near the West Artificial Island, which is nearly 50 kilometers long. After seven channel changes, the channel width is only 200 meters, and it passes through the busiest Lingdingyang channel in China, which will face many safety risks in the whole process.

Compared with the traditional pipe joint floating installation method, the integrated ship greatly reduces the dredging amount of the floating channel, which is more environmentally friendly and economical. Through the intelligent driving system, the installation system on the integrated ship will show its talents after the immersed tube is transported to the designated sea area.

Through the display screen, the commander accurately grasps the specific position of the immersed tube on the seabed; At the same time, the attitude of immersed tube is monitored in real time by using dynamic signal acquisition information system. With the close cooperation of several systems, the immersed tube is lowered to the foundation bed to realize the initial docking. Then, with the help of the pressure of seawater, hydraulic pressure welding is carried out, so that the immersed tube butt joint can be seamless. At present, the deep middle channel submarine immersed tube tunnel has achieved the docking accuracy of all pipe joints within five centimeters, with seven pipe joints in a row, achieving millimeter-level accuracy.

"Beidou" Helps Seamlessly Dock 80,000-ton Submerged Pipes with Needles

The immersed tube section of the deep middle passage subsea tunnel is composed of 32 pipe joints weighing about 80,000 tons and a final joint. How to ensure that these pipes can be accurately installed in place at one time on the seabed? Beidou navigation system contributed greatly.

This is the world’s first super-long, super-wide two-way eight-lane steel-shell concrete immersed tunnel. 6.8km long, it is divided into 32 pipe joints and final joints, which are installed step by step, and each immersed pipe weighs 80,000 tons.

First of all, the giant immersed tube should be transported by cable, accurately placed in the foundation groove of the seabed, and then it should be seamlessly connected with the front pipe joint from end to end, and it should be used safely for 100 years.

Under the invisible water, the installation error of 5 cm can be said to be "embroidery with needles" for immersed tubes with a length of more than 160 meters, a width of 46 meters and a height of 10 meters. If the positioning is inaccurate or the accuracy is insufficient, resulting in excessive deviation of pipe joint installation, the project will have to be completely suspended for "fine adjustment".

When the project started, it coincided with the Beidou system being put into use. In order to introduce the power of Beidou, the team repeatedly made thousands of tests and verifications on land, sea and immersed pipes, and finally formed a scheme. The Beidou satellite antenna on board and the nearby reference station cooperated to differentially locate the immersed pipes, with an accuracy of up to millimeter level.

After entering the water, the position and posture of the immersed tunnel under water are clearly displayed on the screen. Beidou’s positioning performance is stable and reliable, which makes the project progress high-quality and efficient.