"Shenjiang No.1" has an average daily excavation of 4.5 meters.
In Section 1 of the Pearl River Mouth Tunnel of Shenzhen-Jiangmen High-speed Railway, the shield machine "Shenjiang No.1", a pioneer tool for tunnel excavation, excavates 4.5 meters per day, with a maximum excavation of 12 meters per day. From the gravel sandstone formation where it is located, it will enter the granite area with hard geology 30 rings further.
To this end, construction workers are recently replacing the "teeth" of this "dragon"-the blade. After the replacement, it will continue to be put into construction and complete the final attack.
Shenjiang high-speed railway is an important part of the coastal passage of China’s "eight vertical and eight horizontal" high-speed railway network. The line starts from the newly-built Shenzhen Xili Station, passes through Dongguan City, Guangzhou City, Zhongshan City and Jiangmen City in the west, and connects to Jiangmen Station. The main line is 116 kilometers long, with a bridge-tunnel ratio of 98%.
The line needs to cross the Lion Ocean in the Pearl River Estuary. The Pearl River Mouth Tunnel, one of the control projects in the whole line, has a total length of about 13.7 kilometers, a maximum depth of 106 meters and a maximum water pressure of about 1 MPa. It is the deepest subsea tunnel in China at present.
The tunnel is designed as a single-hole double-track high-speed railway tunnel. The diameter of shield machine excavation is about 13.4 meters. The shield segments are designed with nine equally divided structures, and the capping blocks are also larger than the conventional design size. It is a large-diameter shield tunnel.
Moreover, the geological conditions it crosses are very complicated, and it needs to cross 13 kinds of strata, 5 kinds of composite geology and 17 fault zones, such as silt, soft sand and extremely hard bedrock uplift. The full-face hard rock excavation is about 2.8 kilometers long, and the maximum strength of granite is 124.6 MPa.
According to the characteristics of the project, the Pearl River Mouth Tunnel of Shenjiang High-speed Railway adopts the combined construction method of "shield at both ends+middle mine". The starting shafts of shield at both ends are located in Humen Town, Dongguan City, on the east side of the estuary, and Wanqingsha Town, Guangzhou City, on the west side. Two tailor-made domestic shield machines-"Shenjiang No.1" and "Shenjiang No.2" came into being, heading in opposite directions. In Nansha District, Guangzhou, an inclined shaft is set up, which is constructed from the middle to both sides by mining method to connect the tunnels dug by shield machines.
Shield construction is safe and controllable in quality.
Shield tunneling, synchronous grouting, segment assembly and box culvert assembly are the four main processes of shield construction. Each working procedure should follow the corresponding standardized operation flow to ensure the safety and quality control of shield construction.
The pipe wall of the Pearl River Mouth Tunnel is composed of precast segments made of reinforced concrete.
In the face of high water pressure and high corrosion environment, the segment adopts gasket and anti-corrosion technology, which greatly improves the waterproof, anti-corrosion and anti-seepage performance of the tunnel. At the same time, the synchronous grouting process is strictly controlled, and the connection between the formed tunnel and the external water system is isolated, so that the tunnel is impermeable and leakproof.
The front end of "Shenjiang No.1" shield machine is where its main drive and central cone are located, and the central cone is connected with the cutter head.
Among them, the main drive is the core and most precise component of the shield machine, and it is also the key of the whole pressure-resistant system. "Shenjiang No.1" shield machine is equipped with the main drive seal automatic pressure maintaining system, which can effectively cope with the excavation in high water pressure environment. It is also equipped with an on-line oil detection system to realize the on-line inspection of the "blood index" of the main drive and ensure that the core components of the main drive are normal.
Technological innovation runs through the whole process of shield tunneling.
In order to adapt to the seabed conditions, "Shenjiang No.1" has adopted a number of technologies with independent intellectual property rights-high-precision gas-liquid pressure balance control technology of the excavation bin to ensure the stability of the excavation bin in the subsea shield construction.
Informatization and intellectualization always run through the process of shield tunneling. "Digital Deep River" information platform realizes BIM visual application platform and remote control of shield machine. On the screen of the cab, real-time monitoring system of shield tunneling parameters, advanced geological prediction system of shield tunnel, cutter head and cutter wear monitoring system of shield machine, main drive seal monitoring system, shield equipment maintenance management system and grouting density detection system behind segment wall are displayed respectively.
The data of these systems will be transmitted back to the digital shield module of BIM visualization application platform, and the excavation of large shield projects can be monitored remotely through digital shield.
Around shield construction, technicians provide a series of support services from data collection, application analysis to decision optimization, so as to guide shield tunneling construction quickly and accurately and ensure construction safety.
