Our reporter Jiao Yang
On the morning of June 28, the “Yongxing” shield machine of the Zhanjiang Bay Subsea Tunnel of the Guangzhou-Zhanjiang High-speed Railway began shield tunneling and entered the main construction of the shield section.
The Guangzhou-Zhanjiang high-speed rail crossed the seabed of Zhanjiang Bay for the first time in the form of a single-hole double-track high-speed rail subsea tunnel.
"The Zhanjiang Bay Subsea Tunnel has a total length of 9640 meters, of which the open cut section is 1148 meters, the U-shaped groove section is 1140 meters, the shield section is 7352 meters, the sea section is about 2500 meters, the excavation diameter is 14.33 meters, the outer diameter of the segment is 13.8 meters, and the inner diameter is 13.8 meters. 12.6 meters." Chang Yong, the project leader of the China Railway 14th Bureau Shield Company, said that the project is a full-line controlled project for the Guangzhou-Zhanjiang high-speed railway. It is also the first large-diameter shield machine to pass through Zhanjiang Bay into the central city of Zhanjiang. It will challenge the domestic dominance. The submarine tunnel with the longest excavation distance is another representative project of China's high-speed railway.
"The Zhanjiang Bay Subsea Tunnel has the characteristics of large excavation section, poor geological conditions, a lot of waste mud, easy formation of mud cakes, high construction standards, and many key technologies." Project shield manager Wang Hao said that the shield machine started from the well. In the beginning, it mainly traverses silty clay and sand layers.
The excavation diameter is large, the excavation distance is long, the underground pipe network is dense, and the construction is difficult. The requirements for the operation of the shield machine, parameter control, and equipment performance are very strict.
The construction drawings of the Zhanjiang Bay Subsea Tunnel show that the tunnel along the line passes through Dongwang Avenue, Dongcheng West Road, Zhanjiang Olympic Sports Center in turn, and goes under Longwangwan Road into the sea area parallel to the Zhanjiang Bay Bridge, and passes through Zhanjiang Bay at the China-Australia Friendship Garden on the west side of the sea. Later, the long distance passes through Leshan Road, the main road of Zhanjiang City, with densely constructed buildings on both sides and dense underground pipe network.
Among them, there are 2 pier pile foundations that cross the ramp of Zhanjiang Gulf Bridge, and the minimum clear distance is only 1.20 meters and 1.3 meters.
In view of the geological conditions of the Zhanjiang Bay Subsea Tunnel, the China Railway 14th Bureau combined with the rich experience in the construction of the cross-river and cross-sea shields for many years, and the cutter head structure, tool types, ring outflow slag, pressure and corrosion resistance of the cross-sea shield Targeted research and design have been carried out in all aspects.
The "Yongxing" shield machine has been manufactured since September 2020, and it took more than 8 months to efficiently complete the production and commissioning.
The total length of the shield machine is 147 meters, the total weight is 3,600 tons, the minimum curve radius of the shield tunnel line is 3000 meters, the maximum longitudinal slope is 13.18‰, the total installed power is 7,800 kilowatts, the maximum buried depth is 50 meters, and the maximum water pressure is 6 bar.
The cutter head is equipped with 112 fixed scrapers, 59 normal pressure replaceable scrapers, 32 fixed advance knives and 12 peripheral blades, totaling 227 knives. It adopts a telescopic main drive with a maximum torque of 43,156 kN and enhanced design. Reach the best configuration and improve the tunneling efficiency.
"In view of the characteristics of the long-distance single-head tunneling of the shield machine of this project, the cutter head of the'Yongxing' shield machine adopts an atmospheric cutter head. In order to adapt to the high-efficiency excavation in the silty clay layer, a larger shield machine is selected. At the same time, in view of the difficulty in the construction of the shield cutter head that is easy to form mud cakes, the center scour system has been optimized and strengthened to prevent the accumulation of muck in the center area of the cutter head and the bottom of the excavation cabin." Wang Hao said in The slag outlet under the air cushion is equipped with the "agitator + roller crusher" device used for the first time in China, which can more effectively crush the block clay cut by the cutter head, which is conducive to the removal of the slag and the efficiency of the ring out of the slag.
Technicians said that in the next shield tunneling process, managers will implement 24-hour uninterrupted construction operations, comprehensive management and control through the smart command center, real-time intelligent monitoring of shield machine parameters, monitoring and measuring ground subsidence, and inspection staff Conditions, etc., strictly control the tunneling parameters, and grasp relevant data in real time to ensure the safe and stable progress of the shield machine.
The main line of the Guangzhou-Zhanjiang high-speed rail is about 401 kilometers long, and construction has started on June 30, 2020.
Designed to travel at 350 kilometers per hour, it is the high-speed rail project with the longest mileage and the largest investment in Guangdong Province.
After the opening of the Guangzhou-Zhanjiang high-speed rail, the 90-minute interchange between downtown Guangzhou and the downtown area of Zhanjiang will enable the Zhanjiang Expressway to be integrated into the Guangdong-Hong Kong-Macao Greater Bay Area for joint development and enhance the regional economic status of Western Guangdong.
??