What is a shield tunnel boring machine? A shield tunneling machine is an advanced engineering machine for tunneling in rock or soil. Its core feature is that it is equipped with a sturdy shield structure, which can protect the machine and the operator from the collapse of rock or soil during the tunneling process. This machine is usually used in underground engineering projects such as subways, highway tunnels, railway tunnels, water conservancy projects, and mining.
Shield tunnel boring machine are mainly divided into single shield tunnel boring machine and double shield tunnel boring machine.
Single shield tunnel boring machine are similar to shield machines. Their main feature is that they do not require a pressure chamber to balance the excavation surface, and the thrust is provided by jacking the installed ring-shaped segment lining. After excavating a segment ring distance, it is necessary to stop the excavation for segment installation, and continuous construction cannot be carried out.
Double shield tunnel boring machine have two sets of shield shells. Its main feature is that the front shield located in the front part of the equipment can be extended, so that the cutterhead can also be extended. During the excavation process, the reaction forces (torque and axial and longitudinal forces) are dispersed and applied to the surrounding rock through the grippers extending from the shield area of the TBM. Since these reaction forces have been dispersed, the segment installer can install the lining segments during the excavation process, thus ensuring efficient tunnel excavation operations, which is not possible with the traditional excavation mode. After a stroke, the grippers are retracted and the rear part of the TBM is pushed forward by the auxiliary propulsion cylinder. This conversion process only lasts a few minutes, after which the next excavation cycle begins.
The double shield TBM can carry out propulsion and segment assembly operations in double shield mode, improving construction efficiency. For example, the "Iron Soldiers Guanghua No. 6" that rolled off the production line on April 26, 2023 is a large-diameter double-shield earth pressure combined tunnel boring machine. It solves the problem that the previous double-shield tunnel boring machine only has open excavation and is only suitable for excavation under a single stable geological condition. It realizes the effective combination of double shield and earth pressure excavation mode, filling the global design gap of large-diameter tunnel boring machines under the interaction of soft soil and extremely hard rock. This equipment has a diameter of 8.9 meters, a total length of 131 meters, and a total weight of about 1,500 tons. After rolling off the production line, it will participate in the construction of the section from Jingxi Road Station to Baiyun Dongping Station of the Guangzhou East to Huadu Tiangui Intercity Project.
Shield tunnel boring machines are suitable for a variety of geological conditions and play an important role in tunnel construction. It has the advantages of safe, reliable, and fast excavation construction, and little interference with surrounding ground buildings. Compared with traditional tunnel construction methods, shield tunnel boring machines have a higher degree of mechanization, which can improve construction efficiency and reduce construction risks to a certain extent. However, the equipment cost of shield tunneling machines is relatively high, and in some complex geological conditions, it may be necessary to combine other construction methods to operate. In practical applications, it is necessary to select the appropriate type of shield tunneling machine or other tunneling equipment according to the specific engineering geological conditions and construction requirements.