Salzburg will see a special focus on segmental and other tunnel linings in one of the three major workshop sessions preceding this year’s Geomechanics Congress, before the main activities of the 74th Geomechanics Colloquium, both organised by the Austrian Society for Geomechanics (OGG).
WORKSHOPS: 8 OCT
Three workshops are planned to be held concurrently on 8 October for the 2025 Geotechnical Congress. The workshops are:
- Segmental Lining (a full day, looking at fundamentals; guidelines and fibre reinforcement; and, accessories, sealing and backfill);
- Sustainability in Infrastructure Construction: a full day, in four parts, covering different aspects of planning and construction (though exclusively in German); discussing circular economy, carbon emissions, reliability, standardisation, research, equipment, materials, and transport; and,
- Generating Knowledge from Data: a half day (afternoon), discussing how digital tools work together to plan for and gather data to achieve useful intelligence able to practical support decisionmaking for project planning, documentation and site management; real-world examples are to be discussed (instrumentation, grouting, water management, drilling, data management), and common pitfalls.
WORKSHOP: SEGMENTAL LINING
The full day workshop session on tunnel segmental lining is arranged in four parts, covering: Fundamentals of Segments; Accessories, Sealing and Backfill; Guideline and fibre Segments; and, Use of Fibre Segments.
Fundamentals of Segments:
With presentations being given by a consultant, a contractor and an equipment manufacturer, the lectures in the first section are to focus on design fundamentals of segmental lining, production casting, and formwork moulds, respectively.
Accessories, Sealing and Backfill:
Exactly as the section title suggests, these areas are to be covered by different manufacturers.
Fibre Reinforced Segments:
The entire afternoon of the workshop is being given over to fibre reinforcement of tunnel lining segments. There are to be two sections – including five lectures in total plus a discussion to round off the focus on fibres, but also the workshop.
The first of the two sections in the afternoon will consider the new Austrian Segment Guideline, steel fibres, and test results. The second section has invited views on fibre reinforce concrete segments (FRCS) to be shared by a design consultant and a contractor, respectively.
A very interesting workshop, indeed.
COLLOQUIUM: 9-10 OCT
The main lectures of the 2025 Geomechanics Colloquium will be held over 9-10 October, with a full day on the former and a half day on the latter.
Colloquium: 9 Oct
On the full, first day on the main Colloquium event, the lectures will be under two themes: Intergenerational Dialogue in Geotechnics; and, International Major Projects.
Intergenerational Dialogue in Geotechnics:
Lectures are to discuss conflict and dialogue; ways to learn from and work together; tradition versus future; and, interestingly, a spotlight on ‘Lack of Know-how Transfer’ in geotechnical works.
After time out for a breather, the theme continues for the rest of the morning, considering the profiles of different generations; how industry approaches to geotechnics has evolved; and, a ‘Transalpine perspective’ on the generation gap.
International Major Projects:
Looking at a range of transport and water projects from Asia as well as central Europe. Lots of speakers, and detail. The projects to be covered involve a wide variety of tunnelling and ground conditions, much dealing with groundwater in different scenarios, including using a pilot tunnel for drainage and urban excavations with compressed air, respectively.
Colloquium: 10 Oct
The morning of 10 October will round off the lectures of the Colloquium by covering two themes: Constructive Aspects of Tunnel Construction; and, Hydraulic Underground Structures.
Constructive Aspects of Tunnel Construction:
Under the theme Constructive Aspects of Tunnel Construction there are to be five presentations, considering: Pretensioned steel arches; resource efficiency in segmental lining systems with butt-jointed reinforcement of the longitudinal joint; steel fibre reinforced concrete segments on Grand Paris Express project; using fibre optics for monitoring of segmental lining on Brenner Base Tunnel; and, design and construction of pressure tunnels.
Hydraulic Underground Structures:
The theme on Hydraulic Underground Structures is to hear presentations on geotechnical aspects of the exploratory tunnel for Coire Glas pumped storage hydropower project, in Scotland; overview of EurCOLD information on underground conveyance structures (penstocks, pressure tunnels, and shafts); briefing on the Forbach pumped storage project under construction in Germany; discussion on pressure shaft optimisation for Limberg III pumped storage project, in Austria; and, a briefing on design and construction of the Ebensee pumped storage project, also in Austria (which is also the subject of a separate site visit, immediately after).
TECHNICAL VISITS
This year’s Geotechnical Congress also features a planned all-day excursion to Brenner Base Tunnel rail project (see box panel), on the first day, 8 October, as an alternative option to the workshops. On the last day of the event, 10 October, another major excursion is planned, this time to the underground works for the Ebensee pumped storage project.
SOME SEGMENT PRODUCTION ON BRENNER BASE TUNNEL
Brenner Base Tunnel is a huge, multi-year rail transport construction project being undertaken by Austria and Italy, mostly as bored tunnels under the Alps and passing below their border. It is being developed by the special owner-operator company BBT-SE.
The scale of construction called for the works to be split into multiple large lots, and the overall project is at an advanced stage of execution.
Preparations for setting up the equipment and materials to support the enormous tunnelling works had to begin early. These have been large-scale endeavours in their own right, lasting years. Two such major operations involved establishing factories to produce concrete segments for the bored tunnels on two separate lots – Lot H61 Mules 2-3 and Lot 41 Sillschlucht- Pfons, respectively
H61 Mules 2-3
The concrete casting factory for Lot H61 Mules 2-3 was built in Hinterrigger, near Brixen, and operated by Isocell Precompressi S.p.A. Segment production started in late 2017 and continued to late 2024. In total, the factory produced almost 218,250 concrete segments.
For the lot, each concrete ring is made up of seven segments plus one base segment on the two main rail tunnels and two base elements for the exploratory tunnel.
The factory manufactured nearly 26,000 concrete rings and more than 38,000 base segments for the lot’s main tunnels and the exploratory tunnel.
More specifically, there were 16,285 concrete rings and 16,298 base segments produced at Hinterrigger for the main tunnels, plus 9,456 rings and 21,762 base segments for the exploratory tunnel.
Each segment of the main tunnel weighs an average of nine tonnes, while a segment for the exploratory tunnel weighs half that. Approximately 30% of the excavated material from TBM boring on the lot was used in concrete segment production. The segments were transported to site by rail.
A consortium of Webuild, Ghella, Cogeis and PAC has operated three TBMs on the lot.
Lot 41 Sillschlucht-Pfons
Concrete ring production for Lot 41 Sillschlucht-Pfons finished in July this year after casting approx. 59,000 segments since early 2023.
The purpose-built concreting factory is located near Brenner’s Ahrental portal and BBT-SE noted that output averaged about 90 segments per day. With no rail transport locally, this arrangement on-site helped to avoid the large numbers of truck transportation runs that would have been required by road.
The factory has a storage area from where a dedicated local rail transport takes the segments to the tunnels.
Following the set-up of a circulation system for the segment manufacture, part of the factory is to be reused to make rebar cages.
