What is the difference between Natm & conventional method?

Question

Accepted Answer

NATM (New Austrian Tunneling Method) is a flexible method of tunneling while conventional method is a rigid method.

NATM involves excavation and support in small sections while conventional method involves excavation of the entire tunnel and then support is provided.
NATM uses shotcrete and rock bolts for support while conventional method uses steel ribs and wooden supports.
NATM is more adaptable to changing ground conditions while conventional method is more suitable for stable ground conditions.
NATM is more expensive than conventional method due to the need for specialized equipment and skilled labor.
Examples of NATM projects include the Channel Tunnel and the Gotthard Base Tunnel while examples of conventional method projects include the Eisenhower Tunnel and the Mont Blanc Tunnel.

What is the difference between Natm &amp; conventional method?