• Terratec

Austria centre for realistic underground research May 2020

Robert Galler, Chair of Subsurface Engineering, Montanuniversität Leoben, and
Head of the ZaB-Zentrum am Berg project, Austria

ZaB-Zentrum am Berg, the new, cutting-edge testing facility opened in Austria, has been designed and developed to provide a realistic environment for research and education in the underground sector. Research topics at the facility are diverse and include fire safety; geology and geophysics; geothermal energy; NATM and TBM technology; underground mining techniques; sustainability and the environment; concrete technology; ICT applications; measurement and analysis technology; and numerical simulation.

Location within Erzberg mine
Location within Erzberg mine

The centre is situated in a disused part of the Erzberg iron ore mine in the Styria region, proved to be an ideal location for the facility due to its existing tunnel system and its connections to regional road and rail networks. The facility comprises almost 3km of tunnels with different cross sections and varying overburden to facilitate research projects under various conditions.

The €30 million construction cost of ZaB-Zentrum am Berg was shared with €6 milllion contributions from the BMVIT, the Austrian Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology; the BMWFW, Austrian Federal Ministry for Digital and Economic Affairs; and the Montanuniversität Leoben, with the remaining €12 million allocated by the Province of Styria.

Excavation of the new areas of the centre using NATM to create twin tube, two-lane motorway sections, and a twin tube single-track railway line, began in 2016. The tunnels are each connected with cross-passages. Parts of the existing Pressler and Kerpely tunnels of the mine were also repaired to be incorporated into the ZaB facility.

Railway tunnel Portals
Railway tunnel Portals
Portal of the motorway tunnels
Portal of the motorway tunnels

Geology

The Erzberg mine site is located at the north edge of the northern greywacke zone with the lithology comprising essentially limestone; siderite, rohwand dolomite and ankerite; Blasseneck porphyroid; and Eisenerzer beds of shale, phyllite. The Blasseneck porphyroid and the Eisenerzer beds had been categorised as problematic during construction of the old northern tunnels and had been supported, whereas the Sauberger limestone and the ore-bearing limestones were stable without further support and only showed rupturing due to jointing.

Challenging geotechnical conditions

The existing tunnels are predominantly damp with some dripping and isolated running water ingress, which was drained through the west tube of the rail tunnel toward the south portal. Starting at the south portal, the west tube of the rail tunnel joins the south tube of the road tunnel. The cover above the centre tunnels ranges from 217m to a maximum of 235m.

Reopening the old galleries

The rail and motorway portals are both situated on level Dreikönig, but they are in distinct geotechnical conditions. Preparation of the slopes at both locations was therefore quite different. In the area of the railway portal, long bolts had to be used to avoid slope stability problems. As this portal is situated in a wooded area, rock fall was not an issue. In the area of the motorway portal, it was necessary to construct an intermediate level to minimise rock fall.

Location within Erzberg mine
Rescue training underground

Although geological strata were available for observation in the open cut mine levels of the 1960s, the construction team encountered a number of challenges in the new mined headings. These included fault zones, containing completely sheared materials, and open fault zones presenting an open width of about 1m. In the old galleries of the former underground iron ore mine, six challenging sections had to be reopened to connect them to the four new motorway and railway tunnels. This involved a substantial amount of manual work using small units of equipment.

Fire safety research

Several tragic tunnel fires that occurred around the turn of the millennium revealed that a lot more research was needed in the area of fire safety. Fires in enclosed spaces are characterised by rapid propagation and the sudden development of smoke gases. Air currents create an additional negative effect on fire behaviour. The efforts of emergency services are made extremely difficult and often seriously dangerous by the incandescent flame front, poisonous clouds of smoke and poor visibility conditions.

Research and education underground

Fire safety investigations that take place in laboratories are of limited reliability and even tests that take place in existing tunnels cannot emulate a real catastrophe. Tests in existing tunnels are also laborious and expensive since the tunnel has to be closed and traffic has to be diverted. Also, in existing tunnels it is only possible to carry out tests with a restricted fire load in order to avoid damage to the structure.

The test tunnels are equipped with extensive ventilation equipment that can realistically represent the function of various ventilation systems. Extraction fans for the removal of exhaust gases and jet fans to influence the longitudinal air flow in the tunnel are also installed. This means that both longitudinal ventilation and semi-transverse ventilation can be simulated in the test tunnels.

References

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