Tunnels and underground spaces

Since the establishment of our company the leading area in which we participate is the design of tunnels and large underground spaces where we can combine our expertise in geotechnics, geotechnology and mining.

According to modern definition, a tunnel can be any underground passageway with a cross-section larger than 20m2 and any length. In the past, tunnels mostly served as transport routes, which are also their main purpose today. The construction of the tunnels was conducted by manual labour until 1680, when a 160 m long tunnel »Canal du Midi« was constructed in France using a tunnel blasting method. Mechanical tunnel excavation techniques were only established after 1930, while the TBM (Tunnel Boring Machine) technology, where a whole cross-section is excavated at once, was first used in 1954 for the construction of tunnel routing dams in South Dakota, USA.

With the development of today’s different excavation techniques, new theoretical basis and methods of design are developed in parallel, which can relatively accurately predict the behaviour of the rock surrounding the tunnel excavation. The precision of the predictions greatly depend on the evaluation of geologic and geotechnical conditions in the surrounding area. It is this fact which separates the underground facilities from other construction sites, buildings, because the rock media is unpredictable many cases and its behaviour, in construction, is different from that assumed.

In recent years, among the conventional methods of planning the construction of the underground spaces, here and in the world the most established technique is a new Austrian method of tunnel construction -NATM (New Austrian Tunneling Method), which some also know by the Shot concrete lining (SCL) method. It combines modern technology of excavation and support and other technological processes of construction including the geological-geotehnical observation before, during and after the completion of the construction of the underground facility. NATM is incorporated in two important documents, namely the Austrian standard ÖNORM 2203-1 and guidelines for the geomechanical design subterranean part of cyclical progression of excavation and primary support, which is issued by the Austrian society for geomehanics – ÖGG. In our company we successfully use NATM in the design of underground structures in all projects and implementation stages..