Putting the NATM into perspective

A commentary on the features of the New Austrian Tunnelling Method (NATM) is intended to reconcile apparent misunderstandings concerning the tunnelling technique. Main elements of the NATM philosophy as they appear to the author, are tabulated. A description of the NATM by one of its originators states that the system incorporates surface stabilisation by a shotcrete lining. This necessary use of shotcrete was open to doubt according to the author. From a review of the central features of the NATM, such as conservation and mobilisation of rock strength, it is concluded that the NATM is a soundly based system of providing support in which instrumentation monitors the performance of the structure. The NATM is said to be open to conflicting interpretations, while its successful application requires a high degrees of understanding of support mechanics and geological interpretation. (TRRL) (TRRL)