What geological conditions can NATM be applied in?

The flexibility of NATM approach as illustrated by the Dr. Sauer Group's "NATM Tool Box"  means that it can be adapted in all geotechnical conditions. Ground conditioning/improvements such as jet grouting, ground freezing, grouted pipe spiling or Barrel Vault Methods are also available to stabilize the face. The application of the Doorframe Slab Method, a semi cut-and-cover construction method also allows very shallow tunnel alignments. The Caisson Method, for example  provides a safe and cost effective alternative to Immersed Tube tunnels.