On New Year’s Day 2016, the Nanjing Yangzi River Tunnel (formerly known as Nanjing Weisan Road Crossing Tunnel), which was constructed and invested by China Communications Construction in a PPP mode, was officially opened to traffic. Known as "a world-class project at a depth of 70 meters at the bottom of the river".

Yangtze River Tunnel Project

The Yangtze River Tunnel is specifically constructed and invested by the China Communications Investment Corporation, the Second Public Court and the Public Planning Institute are designed, the Tunnel Bureau and the Second Aviation Bureau are responsible for the construction of civil works, the Electrical and Mechanical Bureau and the Tunnel Bureau are responsible for the mechanical and electrical engineering, and the Fourth Public Bureau is responsible for the housing construction project. And is responsible for providing shield equipment. The tunnel is divided into two lines, north and south. The north line connects with Yangzijiang Avenue, with a total length of 7 kilometers, and the shield section is 3557 meters in length; the south line passes through Yangzijiang Avenue and connects with Dinghuaimen Street, with a total length of 7.3 kilometers, with a shield section. It is 4135 meters long.

Among similar tunnels, the Yangtze River Tunnel has the highest water pressure in the world. The water pressure of the Channel Tunnel is only 0.6 MPa, and all the rock formations that the Channel Tunnel pass through are weak in water permeability, and the tunnel diameter is only more than 8 meters. The Yangtze River Tunnel has a diameter of 15 meters, a maximum water pressure of 0.72 MPa, and complex geological conditions. It has to pass through soft soil, hard rock, sand and pebbles. There is no precedent at home and abroad. A suitable shield machine became a tunnel. The key to construction.

In August 2010, CCCC Tianhe took over the equipment manufacturing task to provide the Yangtze River Tunnel with two super-large muddy water pressure balance composite shield machines with a length of about 133 meters and a diameter of 14.93 meters. Through integrated innovation, CCCC Tianhe broke the monopoly of foreign super large shield machines, and developed and produced super large muddy water pressure balance compound shield machines with completely independent intellectual property rights-"Tianhe No. 1" and "Tianhe No. 1" "The world's first saturated hot-pressure tool change technology, the first domestic use of the ring-shaped frozen Yangtze River water replacement shield tail brush technology and many other research results have filled the gap in this field at home and abroad. The two shield machines have the most complex cutter heads in the world at that time. There are 717 knives on the giant multicolored cutter heads. The types of knives are distinguished by different colors. The total weight of the machine is nearly 5,000 tons. The super large shield machine was created in the specific construction. 3 A new domestic record of 620 meters in a month.

At a depth of 63 meters under the Yangtze River, the shield machine encountered a 500-meter-long rock formation. The rock with the highest strength of 120 MPa caused severe wear of the shield machine's cutters. It was necessary to manually enter the cutter head of the shield machine to change the knife. At this time, the shield machine was subjected to water pressure of 0.72 MPa, which was the largest water pressure encountered in shield engineering in the world at that time. According to the traditional operation method, special operators need to pressurize into the working surface to change tools, but even at 0.6 MPa air pressure, the working time cannot exceed 50 minutes. In order to improve efficiency, CCCC engineers innovatively applied the "space capsule" to the Yangtze River Tunnel. Under the helium-oxygen saturated gas, a high-pressure living cabin is set up, and the operator lives under high pressure for a long time, so that the body gradually adapts to the environment. During operation, the living cabin is hoisted to the tunnel at the bottom of the Yangtze River to connect with the high-pressure mud tank. When the operator enters the muddy water tank with the same pressure from the living cabin, the working time can be increased from 50 minutes to more than 4 hours, and the tool change efficiency is increased by more than 8 times compared with the traditional method.

The shield tail brush is the main tool to block the river water from entering the tunnel through the side seam of the shield machine. It is a very common operation to replace the shield tail brush of the shield machine. Generally, polyurethane material is used to block the shield tail, which is safe, fast and low in cost. This requires that the water pressure cannot be too high. Although the shield machine uses five shield tail brushes for waterproofing, after a certain period of use, the shield tail brushes will still wear and be prone to unexpected accidents. In order to smoothly replace the shield tail brushes, the engineers came up with a ring-shaped freezing method, using liquid nitrogen to freeze a certain volume of Yangtze River water to form a fixed ice circle to extend the time for replacing the shield tail brushes. Once, the project department frozen the Yangtze River water five times the volume of the shield machine for 10 days at a water depth of nearly 70 meters at the bottom of the Yangtze River, and successfully completed the replacement of the shield tail brush.

Keywords: engineering construction, engineering news, engineering construction information

The Yangtze River Tunnel pioneered the world’s first double-layer, multiple-exit X-shaped overall design. It adopted a double-tube, double-layer, X-shaped 8-lane shield tunnel scheme. The design speed was 80 kilometers per hour. Each tunnel can independently undertake the two-way traffic between the north and south of the Yangtze River. , Make full use of the tunnel space and effectively improve the traffic efficiency. Starting from the entrance of the tunnel on Yangtze River Avenue, the car travels through the tunnel at a speed of 60 kilometers per hour to reach Jiangbei in just 5 minutes. As the sixth highway crossing the river in Nanjing, the Yangtze River Tunnel has become the most convenient and fast channel connecting Nanjing's main urban area, Hexi area and Jiangbei New District.Editor/Xing Wentao