Overview
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When and Why choose NATM over TBM and Cut and Cover tunnelling techniques? For shorter tunnel sections (generally less than 2 km), tunnels with variable geometry and tunnels in mixed ground conditions, NATM provides for more cost effective, flexible and safe tunnelling without the long mobilization process associated with TBM procurement. Compared to the Cut & Cover construction method, it minimizes the impact on the environment by avoiding surface disruption. Today, NATM works in any ground with minimal overburden and is therefore well suited for tunneling in urban environments. Therefore, because of its flexibility and because of its highly reliable construction schedule, NATM has become widely accepted by both clients and contractors. This is also demonstrated in the pie chart extract from 'Tunnel' magazine (edition 8/2003) which shows over 64% of transportation tunnel construction in Germany is now procured using this method.
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