The "Greater Bay Area Code" shield machine rolled off the assembly line, challenging the 115-meter seabed to build a high-speed rail
Recently, the "Greater Bay Area" (also known as "Shenjiang No. 2") super-large-diameter slurry balance shield machine rolled off the assembly line in Shunde, Guangdong.
The "Greater Bay Area Code" was jointly developed by China Railway Tunnel Bureau Group and China Railway Equipment. It is a national weapon tailored for the construction of the Pearl River Mouth Tunnel of the Shenzhen (Shenzhen) Jiang (Men) Railway with the world's largest buried depth and highest water pressure.
What are the characteristics of the Pearl River Estuary tunnel construction?
What difficulties may be encountered during construction?
What new technologies need to be adopted?
Reporter conducted an interview.
Ultra-long-distance sea-crossing shield tunnel
The main line of the Shenjiang Railway is 116 kilometers long and passes through 5 cities such as Shenzhen, Dongguan, Guangzhou, Zhongshan and Jiangmen.
The Pearl River Mouth Tunnel is located at the estuary of the Pearl River between Dongguan and Guangzhou. It is a single-hole double-track high-speed railway tunnel.
The total length of the tunnel is 13.69 kilometers and the designed speed is 250 kilometers per hour. After completion, it will only take 4 minutes by car from Nansha to Dongguan.
The China Railway Tunnel Bureau Group undertook the construction of the most difficult section 2 of the Pearl River Mouth Tunnel. The construction of this section includes a 9.1 km subsea tunnel and an emergency passage for the inclined shaft in the Nansha work area.
The "Shield + Mine" combined construction method is adopted. The "Great Bay Area" shield machine starts from Wanqingsha in Nansha and enters the seabed of the Pearl River estuary, and digs towards Dongguan.
The maximum buried depth of the sea area of the Pearl River Mouth Tunnel is 115 meters, which is the deepest record of an underwater tunnel in my country. The hydrological and geological conditions are extremely complicated, and the surrounding environment water is corrosive. The maximum water pressure is 1.06 MPa, and the strength exceeds 10 standard atmospheres. , The best in the world.
The Pearl River Mouth Tunnel of the Shenjiang Railway is also a key control project for the entire line.
The deep river railway needs to cross the Pearl River Estuary Lion Ocean waters. Due to the complex geographical environment, the construction scheme adopted is the key factor restricting the construction of the project.
After a long period of repeated scientific comparison and selection, the scheme of the Shenzhen High-speed Railway crossing the Pearl River Estuary was finally changed from the Humen Highway-Rail Bridge to the tunnel form.
Chen Huichao, deputy general manager and chief engineer of China Railway Tunnel Co., Ltd., introduced that compared with road-rail dual-use bridges and single bridge solutions, the submarine tunnel has less impact on urban planning, navigation, flood control, and the marine environment. The resilience is stronger, and it has obvious advantages in terms of operation and maintenance costs.
The country's heavy weapon challenges the world's most
The excavation diameter of the "Greater Bay Area Code" shield machine is 13.32 meters, the total length is 133 meters, and the total weight is about 3900 tons. The design pressure of the whole machine is up to 12 bar (bar, 1 bar is approximately equal to 1 standard atmosphere).
Chen Huichao introduced that after the shield machine is launched, it will encounter complex geological problems such as liquefied sand zone, uneven soft and hard sections, short-distance side crossing of the Fuzhou Bridge, and broken zone. Long-distance hard rock excavation will extremely test the cutter head. Strength and wear resistance.
Especially in the Pearl River Estuary, there are 3 groups of fractured zones and 6 secondary fracture zones. The unevenness of the rock mass is unusually significant. Tunnel tunneling to the fracture zone is prone to collapse of the tunnel face, roof fall on the river surface, and mud water silo. Risks such as internal stagnation and drainage put extremely high requirements on the performance of shield machine, the control of tunneling parameters, the production of tunnel prefabricated components, and the quality of assembly.
"Shield tunneling to cross the Peizhou Bridge at close range requires strict control of various parameters of the tunneling, and real-time monitoring must be done in the process to ensure the safety of the Peizhou Bridge." Chen Huichao also said that the saturated silt and sandy soil layer may produce sand. For the phenomenon of soil liquefaction, it is necessary to strengthen the geological pre-exploration before the excavation of the shield machine, and to improve the geology through reinforcement measures.
In the design and manufacture stage of the “Greater Bay Area Code” super-large diameter mud-water balance shield machine, China Railway Tunnel Bureau and China Railway Equipment Group carried out construction requirements for the ultra-high water pressure, complex geology and long-distance penetration of the Pearl River Mouth Tunnel in the sea area. A series of adaptive designs have greatly strengthened the performance of the equipment.
Among them, it is specially equipped with a small tool spacing and atmospheric pressure composite cutter head, which improves the cutting ability of the tool in the high-strength full-face stratum; the telescopic main drive can feed back the reaction force data received by the cutter head in real time, improve the tunneling control ability, and replace it. When cutting tools, the cutter head can be retracted, and the space between the cutter head and the face of the face can be opened, thereby ensuring the tool replacement space; the main bearing sealing system with a maximum pressure of 12bar is equipped with an ultra-high pressure automatic compensation system, which can meet the requirements of 12bar Under ultra-high pressure construction, the drive box is automatically pressurized; the four-circuit pressure holding system uses the principle of constant pressure segmented parallel control to achieve precise and rapid pressure control; an air cushion direct discharge system is reserved, and it also has a direct discharge mud shield. The advantages of the precise pressure control of the stagnant discharge and the air-cushioned mud water shield further improve the applicability of the equipment.
Deep-sea tunnel technology "test site"
The Pearl River Mouth Tunnel has problems such as ultra-high water pressure, complex geology, and long-distance sea crossing. There is no engineering experience, shield equipment and design standards with equivalent conditions in China for reference.
Experts in the industry believe that the Pearl River Mouth Tunnel is “in the super-long subsea tunnel construction method, the outer water pressure value of the ultra-high water pressure sea area shield method tunnel, and the joint waterproofing, the large-diameter shield under-pressure initiation in the deep silt formation, and the mining method tunnel. A number of breakthroughs will be made in technologies such as large-diameter shield reception and overall dismantling.”
At present, the China Railway Tunnel Bureau Group is actively deploying a series of technical breakthroughs for the construction of the Pearl River Mouth Tunnel.
Including the world-class key technologies that the project is focused on exploring and cracking, such as the joint control of initial reinforcement and construction settlement of shield tunneling in sea water-rich stratum, advanced geological prediction in tunnel tunnels with ultra-high water pressure and deep-buried sea environments, and sea environment Optimized configuration and predictable tool change of shield cutter head cutters in high water pressure soil and rock composite formations, ultra-high water pressure and complex geological large-diameter shield tunneling parameter setting and dynamic optimization matching, sea environment large-diameter shield long-distance construction tunnel Energy-saving ventilation, cooling and noise reduction, advanced treatment of complex geological conditions such as the outcropping of boulder group fracture zone in the base rock of the shield tunnel in the sea environment, and a complete set of key technologies for the mechanization of the submarine high-speed railway tunnel mining method.
The Shenjiang Railway runs through the core urban agglomerations of the Guangdong-Hong Kong-Macao Greater Bay Area and is an important part of the coastal passage of the national "eight vertical and eight horizontal" high-speed rail network.
After the completion of the Shenjiang Railway, it will further open up coastal high-speed rail channels, help create a half-hour living circle and economic circle in the Guangdong-Hong Kong-Macao Greater Bay Area, and radiate to drive the coordinated development of eastern Guangdong and western Guangdong and the Pearl River Delta.