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Hydrogeology in Tunnelling – Beyond Prediction Prognosis

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Geoconsult ZT GmbH

Abstract: At first glance, hydrogeology in tunnels and underground works looks simple, ephemeral and unscientific. The groundwater normally flows into the excavation, evidently by gravitation, leaves the tunnel in “its” drainage or - in descending tunnels or in mines - by artificial pumping.

For deep questions about environmental impact or proper design of drainage works, it is worth going deeply into the contexts of groundwater flow in the rock mass, its hydraulic limitations, its physical properties, its gas content, its dissolved elements, and isotopic composition.

Looking at these details, things quickly get significantly complicated. Almost all the water parameters are changed in the vicinity of the excavation work, and the test or the sample obtained near the front or the side walls of the excavation, gives a result of waters that present rather a process of equilibrium than a certain property.

The changes not only affect groundwater: The hydraulic properties of the rock massif, flow regimes, recharge zones and even the surface of the landscape, kilometers away from the work, are also changed.

All these evidences have to be recognized in the hydrogeological design, considering all the theoretical effects to the environment. They contain not only nature, protected flora and fauna, direct and secondary consequences to the hydric environment, but also to the human being and its facilities.

In civil works with extended life cycle such as railway tunnels, underground stations, metropolitan or highway tunnels, the management of groundwater in the drainage system has a significant impact on maintenance costs. The properties of the waters affect drainage facilities by precipitation or dissolution and not rarely in the same tunnel the seeping water differs in its properties along the alignment.

As a last aspect, waters and its properties provide opportunities. To give examples: Not infrequently, underground “springs” are captured for the supply of drinking, irrigation or industrial water, and geothermal energy is used for heating civil works, greenhouses or de-icing a section of access to the portal.

Bio: Dr. Giorgio Höfer-Öllinger studied geology at University of Salzburg, Austria from 1993 to 2000 and tunnelling at Mining University of Leoben (Austria) and Technical University of Graz from 2009 to 2011. Since 2005, he is Chartered Engineer, since 2020 Court Expert. He defended the doctor thesis at Freie Universität Berlin, Germany.

He worked as freelance geologist for different companies until he joined Geoconsult in 2002. Since 2005, he is head of Geological Department of Geoconsult and Managing Director.

His main focuses are investigation campaigns for tunnel projects, tunnel prediction, hydrogeological modelling and consulting during excavation works.

He worked for tunnel projects in South and Central America, Europe and Asia, among them Pir Panjal Railway Tunnel, Brenner Base Tunnel, Agua Negra Tunnel and Koralm Base Tunnel; and for large scale HEPP like GKI and SKW Kühtai.

Since 2008, he regularly gives lectures at Freie Universität Berlin, Germany and spontaneously at different universities.

Mr. Höfer-Öllinger is based at main office of Geoconsult in Salzburg but travels frequently to South America and other destinations. In parallel to more than 20 years of consulting in more than 20 nations, he participated with about 110 publications, oral or poster presentations. He attends to the yearly WTC and other conferences. He takes part with different working groups at ITA and Austrian Association of Geomechanics and frequently leads sessions at geological conferences.