Shield boring machines, also known as boring machines, are key equipment in modern tunnel engineering and are widely used in tunnel construction projects such as subways, highways, railways, water diversion, and sewage drainage. According to the number of shield shells, shield boring machines can be divided into single-shield boring machines, double-shield boring machines and triple-shield boring machines. Each type of shield machine plays a different role in the construction process and is suitable for different geological conditions and construction needs.

　　1. Single shield boring machine

　　The single-shield tunnel boring machine is the most basic type of shield tunneling machine and is suitable for areas with relatively stable geological conditions. Its main feature is that it has only one shield, which is used to support the tunnel wall during excavation and prevent tunnel collapse. The single-shield boring machine has a simple structure, easy operation, and relatively low cost. It is often used in short-distance or shallow-depth tunnel projects.

　　2. Double-shield boring machine

　　The double-shield boring machine adds a shield to the single shield to enhance the safety and stability of tunnel construction. The double-shield tunnel boring machine is suitable for areas with complex geological conditions, especially in unstable geology such as soft soil and sand. It has significant advantages. The double shield design can provide stronger support during the excavation process, effectively reduce the risk of deformation and collapse of the tunnel wall, and improve construction efficiency and safety.

　　3. Three-shield boring machine

　　The three-shield boring machine is a high-end equipment among shield boring machines and has the strongest support capacity and adaptability. Three-shield boring machines are usually used in tunnel projects with extremely complex geological conditions and extremely difficult construction, such as deep tunnels, high-pressure water layers, etc. Its triple shield design not only provides stronger support, but also better handles geological changes and external pressure during the excavation process, ensuring the continuity and safety of construction.

　　With the continuous development of shield machine technology, the types and functions of shield machine are also constantly improved and enriched. Single-shield, double-shield and triple-shield tunnel boring machines have their own characteristics and are suitable for different geological conditions and construction needs. In practical applications, engineers will select the appropriate shield machine type based on specific project requirements and geological conditions to ensure the smooth progress of tunnel construction and improvement of project quality. The wide application of shield machines not only improves the efficiency and safety of tunnel construction, but also promotes the progress and development of underground engineering technology.