Overcome the problem of high water pressure and large diameter, and my country's self-developed shield machine smoothly crosses the Yangtze River

　　◎Reporter Zhang Ye

　　【Results broadcast】

　　A few days ago, the reporter came to the Jiangyin Jingjiang River Crossing Tunnel located in the lower reaches of the Yangtze River.

Deep in the bottom of the river, a mud-water balance shield machine with the largest diameter and the most advanced performance in my country is striving to cross the Yangtze River.

　　Along the left tunnel of the Jiangyin Jingjiang River Crossing Channel that has been formed, the reporter of Science and Technology Daily walked about 1,500 meters from north to south. Accompanied by a slight low-pitched roar, a machine with a diameter of 16.09 meters, a length of about 170 meters, a weight of about 5,000 tons, The "steel behemoth" with a height of about 6 floors came into our eyes. This is the "Juli No. 1" shield machine independently developed by CCCC Tianhe.

　　Engineering and technical personnel told reporters that this "steel behemoth" can dig up to 20 meters per day, and the error is extremely small. In the nearly 1,500-meter-long tunnel that has been formed, the misalignment of the segment does not exceed 3 mm, and the float of the segment is controlled. Within 5 mm, it is far lower than the tunneling data of 5-10 mm in the industry.

　　Super strong shield machine makes crossing the Yangtze River easy

　　It is by no means an easy task to let the "steel beast"-like shield machine easily cross the Yangtze River.

Long distance, high water pressure and complex geological environment will bring extremely severe tests to the design, development, manufacturing and tunneling technology of shield tunneling machines.

　　The Jiangyin Jingjiang River Crossing Channel Tunnel is 6,445 meters long, of which the shield section is 4,937 meters long, ranking second among the Yangtze River tunnels.

During the excavation process of the shield machine, it needs to pass through sensitive structures and harmful gas accumulation areas many times, and the unfavorable geological excavation distance is long, which requires extremely high system and reliability of the shield machine.

In order to ensure the speed, safety and environmental protection of tunnel excavation, a composite mud-water balance shield machine is used in the Jiangyin Jingjiang River Crossing Channel Tunnel.

　　The maximum total thrust of "Juli No. 1" is 268,800 kilonewtons (kN), which optimizes the cutter head flushing device to the greatest extent, and effectively avoids the problem of coalescence of mud cakes during the tunneling process of the shield machine under the same geological conditions. Even faster than designed.

Taking August 2022 as an example, the maximum daily excavation speed of "Juli No. 1" is 10 rings (20 meters), and the monthly total excavation is 215 rings (430 meters).

　　The maximum water pressure of "Juli No. 1" crossing the Yangtze River is 0.87 MPa, which is equivalent to 8.7 kilograms of pressure per fingernail size. It is the highway shield tunnel under construction with the highest water pressure in China.

The complex tunneling operation environment puts forward higher requirements on the shielding system and the pressure resistance of the body.

To this end, the R&D personnel have equipped a special air cushion cabin for the shield machine to precisely control the face pressure within ±0.02 MPa, control the mud water pressure during the excavation process at any time, prevent the subsidence of the stratum, and ensure the tunneling attitude of the shield machine. Smooth and beautiful.

　　"Juli No. 1" needs to penetrate complex strata such as silty-fine sand, medium-coarse sand, and high quartz content rich in cement, and the bottom section of the river is a fault fracture zone. The thinnest part of the covering soil is only 11 meters, and the water permeability is strong. , The construction is difficult, and the wear of the cutter head is 3 times that of the same type of soft soil.

But by adopting unique technology, it can realize long distance without tool change.

　　"Juli No. 1" is also equipped with intelligent guidance, intelligent geological advance prediction, optical fiber monitoring of tool wear, automatic measurement of shield tail gap, automatic monitoring of segment floating and convergence, high-precision harmful gas monitoring and synchronous dual-liquid grouting, etc. The system ensures that the tunneling is "visible, measurable, controllable and accessible", so that the high-strength, high-risk and high-polluting tunneling operations can be transformed into a safe, efficient, energy-saving and environmentally friendly green driving mode.

　　"Steel Beast" and "Smile Angel" coexist in harmony

　　In addition to the hard side of the "steel behemoth", "Juli No. 1" also has a gentle side.

Its blade is painted with a finless porpoise pattern.

The finless porpoise is a national first-class protected animal, known as the "water giant panda", and also known as the "smiling angel" because of its friendly smiling image.

The finless porpoise, which has been home to the Yangtze River for generations, is extremely sensitive to water quality and noise.

The "smile angel" pattern on the knife plate not only highlights the regional cultural characteristics of Jiangsu, but also contains high standards and strict requirements for the ecological protection of the Yangtze River.

From design and development, production and manufacturing to excavation operations, CCCC Tianhe has always placed the protection of finless porpoises and the ecology of the Yangtze River in the most prominent position, infiltrated the concept of big protection into all links, and always integrated green research and development, green design, green manufacturing and green excavation. as the original mission.

　　CCCC Tianhe's design and development team has revised and improved the plan countless times around the ecological protection of the Yangtze River to minimize the impact on the survival and continuity of the finless porpoise family, and actively seek the optimal parameters to protect the finless porpoise and rare fish, so as to provide them with a healthy, Safe and high-quality living environment.

Based on the underwater noise monitoring technology, the relationship model between the cutter head speed, the driving speed and the operation noise is established, and the noise generated during the driving process is monitored in real time to ensure that it is controlled within the design threshold (80 decibels). The overflow of mud and water in the tunnel pollutes the operating environment, and consciously maintains the surrounding environment and biodiversity.

　　Jiangyin Jingjiang River Crossing Channel starts from Jingjiang Gongxin Highway in the north and ends at Jiangyin Furong Avenue in the south. It is constructed in accordance with the standard of two-way six-lane expressway, with a design speed of 80 km/h, which is helpful for alleviating the traffic pressure of Jiangyin Yangtze River Bridge and enhancing the passage of the Yangtze River Trunk Line crossing the river. It is of great significance to promote high-quality integrated development of the Yangtze River Delta.

　　According to Yang Hui, assistant general manager of CCCC Tianhe, the Jiangyin-Jingjiang River Crossing Channel Project, as a landmark project for the construction of Jiangsu’s model in the construction of a powerful transportation country, and an innovative project for the construction of large-diameter shield tunnels with high water pressure in China, is expected to be completed by the end of 2023.