GENERAL INFORMATION ON THE CONSTRUCTION LOT

The ongoing works on the construction lot H21 "Sill gorge" - scheduled to run from August 2020 to the end of 2024 - will provide the link between the Brenner Base Tunnel and the central station in Innsbruck.
A stretch of approx. 600 metres and several different works will be built within this lot. River engineering works will be also carried out. The estimated construction costs for this stretch are 59.5 million Euro and Porr Bau GmbH Kematen will be in charge of the works.

Compared to other construction sites in Austria, whose works are mostly underground, the works in this construction lot are largely performed above ground.
The "Sill Gorge" stretch basically includes the following construction works: a supporting wall (200 metres long), a cut-and-cover tunnel (130 metres long), 2 railway bridges over the Sill, the northern portal of the BBT, as well as a subsequent tunnel stretch (approx. 140 metres long). In spite of the relatively short stretch, this construction lot comprises very complex construction activities.

The stretch leads through the narrow and thus logistically challenging Sill Gorge. The area is characterized by several infrastructural facilities such as the A12 Inntal highway, the A13 Brenner highway, the "Tirol Panorama" museum, the "Untere Sill" power plant of the municipal undertakings "Innsbrucker Kommunalbetriebe", as well as the existing ÖBB railway line with the Berg Isel tunnel.

The narrow brook gorge - which is mostly in its natural state - is an important recreational area for the people of Innsbruck and can be reached via several hiking trails. In order to ensure the access to the Sill gorge while construction works are ongoing, an alternative hiking trail will be built. In addition, for easier orientation, a system showing the various trails will be installed and interesting spots near the construction site will be provided with information boards.

CURRENT CONSTRUCTION WORK

• Slope removal works in preparation for the Silltal tunnel at the Berg Isel mountain
• Scarp stabilisation for the construction of the Silltal tunnel
• Scarp stabilisation at mount Viller Berg for the northern portal
• River engineering works – Pre- and post consolidation of the bed
• Access road on the left bank of the Sill for the construction of the retaining wall
• Scarp stabilisation for the construction of the retaining wall

Planned works

From north to south, the planned works for this construction section include:

• A supporting wall, roughly 200 metres long and 9 metres high, built on drilled piles
• the “Silltal” tunnel through the Bergisel mountain (approx. 130 metres long), partly constructed using the cut-and-cover method and with a pile foundation
• Two railway bridges (both 50 metres long) over the Sill for the east and west tracks: one will be built as an open steel trellis bridge and the other one will be enclosed.
• Northern portal of the BBT, including slope stabilization with over 80 prestressed anchors up to 80 metres long
• Two tubes of the “Viller Berg” tunnel stretch, both 140 m long.
• Stressed ribbon bridge over the Sill (55 metres with long) as part of the hiking trail network of the Sill Gorge
• New access bridge over the Sill (lenght: 42 metres)
• River engineering works 

An important part of the “Sill Gorge” construction lot is the restoration of upstream fish passage in the Sill. The AGA weir, located at the entrance to the Sill gorge with a drop height of approx. 8 metres, will be therefore removed and replaced by a roughly 350-m long fish ladder with an in-set low-lying meandering channel. As part of these river engineering works, the riverbed will be moved about 8 metres eastwards in order to have enough room for the supporting wall and the two-track line on the western side. Flood-proof and long-lasting embankments will be constructed.

At the end of the works, revegetation measures will bring about an upgrade and improvement of the popular recreational area.

GENERAL INFORMATION ON THE CONSTRUCTION LOT

This construction lot was awarded to the Strabag SE / Webuild S.p.A. (ex Salini-Impregilo) bidding consortium in Summer of 2014.

construction time: 2014 - 2021
section of the tunnel to be driven: 43.3 km
contactual amount: € 491 million

It consists of several structures:

• Tulfes emergency tunnel
• Innsbruck emergency stop
• Main tunnel tubes
• Connecting tunnels
• Ahrental-Pfons exploratory tunnel

CURRENTLY ONGOING CONSTRUCTION WORK

Emergency tunnel

The emergency tunnel was being driven parallel to the existing Innsbruck railway bypass. It is 9.7 km long and the excavation cross-section is 35 m². The drill-and-blast excavation work on this tunnel started from three points at the same time: from Tulfes westwards, from the Ampass access tunnel eastwards and again westwards. The emergency tunnel was completed in Summer of 2017.

Main tunnel tubes

The main tubes have been excavated by blasting according to the so-called New Austrian Tunnel Construction Method. The ceremonial first volley was set off on 19/03/2015 in the presence of EU Commissar Violeta Bulc and the Ministers of Transportation of the 7 Alpine countries (Austria, Italy, Germany, Switzerland, France, Liechtenstein and Slovenia. This stretch includes about 6 km of main tunnels with an excavated cross-section of about 70 m2 .

Connecting tunnel between the BBT and the Innsbruck bypass

Construction has been under way since summer of 2015 on the two connecting tunnels between the Brenner Base Tunnel and the existing Innsbruck bypass. The connecting tunnels were also excavated by blasting, with a cross-section of about 115 m². Excavation work was completed in Spring of 2017.

Exploratory Tunnel

The construction lot Tulfes-Pfons included the construction of the stretch of exploratory tunnel between the Ahrental junction point and the town of Steinach am Brenner. The gripper TBM, 200 m long, started work on September 26th, 2015 and excavated about 16.7 km southwards, completing its work on July 6th, 2019. Since the breakthrough, the construction lot has been connected to the Pfons-Brenner lot.

CURRENT CONSTRUCTION WORK

Restoration of the collapse "Iris"

This collapse is a cavity that formed in a fault zone during the excavation of the exploratory tunnel. This must now be backfilled by means of cement mortar injections from an injection tunnel in order to rule out any effects on the overall tunnel system. As part of these repair works, the main tunnel tubes in the fault zone will be excavated in advance by blasting using an auxiliary drivage from the exploratory tunnel. This allows to reduce interferences when the subsequent TBM arrives.

CONSTRUCTION LOT PFONS-BRENNER

Construction work in the construction lot H51 was suspended on October 27th, 2020. Only measures to avoid danger ahead and/or measures to avoid danger to the established structures are carried out. The remaining stretches of this construction lot will be reassessed and optimised during the revision of the construction programme. To ensure that works in this area can be resumed as quickly as possible, these works will be carried out in two construction lots in the future. The corresponding tenders will both take place with the aim of resuming construction works in the Pfons-Brenner stretch in autumn 2021.


GENERAL INFORMATION ON THE PFONS-BRENNER CONSTRUCTION LOT

The construction lot consists of several works:

• Main tunnel
• Exploratory Tunnel
• The St. Jodok emergency stop
• St. Jodok cross-over

In close proximity to the Pfons-Brenner construction lot, the largest disposal site in Europe, with an accommodation capacity of about 7.5 million m³, is located in the so-called "Padastertal" valley.