When and why choose NATM over TBM and Cut & Cover tunnelling techniques

For shorter tunnel sections (generally less than 2 km), tunnels with variable geometry and tunnels in mixed ground conditions, NATM provides more cost effective, flexible and safe tunnelling without the long and costly mobilisation process associated with TBM tunnelling. When compared to the Cut & Cover construction method, it minimises the impact on the environment by avoiding surface disruption.

Today, NATM works in any ground with minimal overburden and is therefore well suited for tunnelling in urban environments.  Because of its flexibility and highly reliable construction schedule, NATM has become widely accepted by clients and contractors alike.