What is the primary purpose of a Tunnel Boring Machine (TBM)?

Explanation:

A Tunnel Boring Machine (TBM) is a specialized construction machine used primarily for mechanized excavation of tunnels through soil or rock. Its function is to excavate with precision, reduce ground disturbance, and provide continuous support during tunneling.

Key Features of TBM:

• Controlled Excavation: TBMs cut through ground with a rotating cutterhead, removing material safely and efficiently.

• Minimized Surface Disruption: Ideal for urban tunneling, where minimizing surface settlement is critical.

• Simultaneous Lining: Many TBMs install precast concrete segments to form the tunnel lining as they progress.

• Applications: Used in subways, water tunnels, sewer tunnels, rail tunnels, and hydropower projects.

 Additional InformationNew Austrian Tunnelling Method (NATM)

• NATM is based on the principle of utilizing the in-situ ground (rock or soil) as a structural component to support the tunnel.

• Instead of resisting ground pressure completely, the method allows some controlled deformation, which helps mobilize the strength of the surrounding ground mass.

• It emphasizes monitoring and adapting construction based on actual ground behavior.

• The tunnel is excavated in small sections, usually using conventional methods like drilling and blasting or mechanical excavation.

• After excavation, immediate temporary support such as shotcrete (sprayed concrete), rock bolts, and sometimes wire mesh is applied.

• Final lining (usually cast-in-place concrete) is added later, only after stability is confirmed.