The New Austrian Tunneling Method (NATM), also known as sequential excavation method (SEM) or advance and smash,[1]​ is a modern tunnel design and construction method. The excavation is carried out in two phases, first the upper excavation is carried out (advance) and then the ground below is removed to the level of the tunnel (destroy). The method is based on using the geological stress of the surrounding rock mass so that the tunnel stabilizes itself using the arch effect "Arch (architecture)"). To achieve this, they are based on geotechnical measurements to draw an optimal section. The excavation is immediately protected with a thin layer of shotcrete. This creates a natural discharge ring that minimizes rock deformation.

This technique gained notoriety in the 1960s based on the works of Ladislaus von Rabcewicz"), Leopold Müller and Franz Pacher") between 1957 and 1965 in Austria. Its name was intended to distinguish it from the former Austrian tunnel approach. The fundamental difference between this new tunneling method, as opposed to previous methods, comes from the economic advantages available by harnessing the inherent geological strength available in the surrounding rock mass to stabilize the tunnel.[2]​.

NATM/SEM is generally believed to have helped revolutionize the modern tunneling industry as many have used this excavation technique.

The NATM integrates the principles of the behavior of rock masses subjected to loads and the monitoring of the efficiency of underground construction. NATM is often cited as a "design-on-the-fly" approach, providing optimized support based on observed ground conditions. More correctly, it can be described as a "design as you monitor" approach, based on the convergences and/or divergences observed in the coating and on the study of the prevailing rock conditions. The NATM is not a set of specific excavation and support techniques.

The NATM consists of seven elements: