State methods of tunnel construction methods??

1. Cut-and-cover method: This method involves excavating a trench, constructing the tunnel structure within the trench, and then covering it back up. This method is commonly used for shallow tunnels in urban areas.

2. Bored tunneling method: This method involves using a tunnel boring machine (TBM) to excavate the tunnel in a continuous process. The TBM can bore through various types of soil and rock, allowing for the construction of tunnels at greater depths.

3. Sequential excavation method (SEM): This method involves excavating the tunnel in small sections, using temporary supports such as rock bolts and shotcrete to stabilize the tunnel walls as the excavation progresses. This method is commonly used for tunnels in unstable ground conditions.

4. Immersed tube method: This method involves constructing tunnel sections on land, floating them into position, and then sinking them into place on the seabed. This method is commonly used for underwater tunnels.

5. Drill and blast method: This method involves drilling holes into the rock or soil, filling them with explosives, and then blasting the material to create the tunnel. This method is commonly used for tunnels in hard rock.

6. New Austrian Tunneling Method (NATM): This method involves excavating the tunnel using a combination of drilling, blasting, and the use of rock bolts and shotcrete to stabilize the tunnel walls. This method is commonly used for tunnels in variable ground conditions.