Evaluation of new Austrian tunnelling method applied to Bolu tunnel's weak rocks

Since the development of the new Austrian tunnelling method (NATM) in the 1960s, this technique has been applied successfully in many tunnels. However, opinions of NATM principles emerged till 2000, i.e. NATM is not a tunnelling method, but an approach covering all general principles of tunnelling. To investigate the general principles of the NATM, this study focused on tunnelling practises in the Bolu tunnel, and evaluated the conditions under which the NATM practises could be effective. The Bolu tunnel project was designed following the NATM principles. It is evident that practises adopted in this tunnel are important with respect to the NATM. In addition, it shows that the solutions to the problems encountered in this tunnel are consistent with the NATM principles. Finally, the study determines the ground types of the NATM principles and proposes associated updates.