a milestone in the european rail transport - world of …...brenner basis tunnel – a milestone in...

PORR ProjectsWorld of PORR 162/2013

Anton Ertl

IntroductionThe Brenner Basis Tunnel (BBT) forms the centrepiece of the2,200 km long Berlin−Palermo North-South-Corridor, alsoknown as the TEN-1-Axis. The European Union supports theexpansion of this cross-country railway section andcategorises it as preferential.

The Brenner Basis Tunnel is a level railway tunnelconnecting Austria and Italy. It runs from Innsbruck toFranzensfeste (55 km). Taking into account the alreadyexisting Innsbruck railway diversion, into which the BBTdebouches, the alpine breakthrough is 64 km long. Thismakes it the longest underground railway connection in theworld.

Major project: Brenner Basis TunnelImage: APA/BBT-SE

Schematic illustration, Brenner Basis TunnelImage: BBT-SE

Standard cross-section, Brenner Basis TunnelImage: BBT-SE

Brenner Basis Tunnel – A milestone in theEuropean rail transportConstruction sections Ahrental, Sillschlucht and Ampass


Layout drawing, exploration and access galleries Innsbruck AhrentalImage: BBT-SE

Ahrental access tunnel

Tunnelling 2,404 m

Cross-section 95 – 120 m²

Longitudinal gradient max. 11.6 %

Shotcrete 25,907 m³

Explosives 313,030 kg

Asphalt road surface 24,000 m²

The portal of the Ahrental access tunnel is located directlybelow the A13 Brenner motorway. The site installation area,representing part of the “Ahrental” infrastructure forconstruction logistics, is located in the immediate vicinity ofthe portal area. On account of the limited accessibility ofthese areas prior to construction measures, a new temporaryinterchange will be built, starting from the high quality publicroad network, to access the construction site area. Thisprovisional interchange is a non-public entrance and exit forthe site installation area as well as to the Ahrental portal andconsists of two ramps as well as a site road connecting thesetwo ramps with the site installation area. The construction ofthese access ramps was carried out in compliance with therequirement for uninhibited traffic on the A13.

The profile type of the Ahrental access tunnel is a two-lanetunnel with an excavation cross-section of up to 120 m². Thetunnelling began on 16 July 2010. The excavation wascarried out according to the principles of the New AustrianTunnelling Method and is divided into calotte, side wall andinvert broken out by blasting.

Because of the proximity of the Ahrental access tunnel to theWipptalstörung (Wipptal dislocation) the bedrock in this tunnelis thoroughly and clearly sectioned. The Wipptal dislocationseparates the rock of the Ötztaler und Stubaier Alps from thelarge quartz phyllite mass.

Accordingly, depending on the encountered rock type androck behaviour, either a deep invert arch or a flat invert wasinstalled.

Ice-age gravel deposits were found up to tunnel metre 30 inthe upper part of the tunnel cross-section. Both theoccurrence of this loose rock as well as the undercrossing ofthe A13 Brenner motorway under the specification of themotorway operator, ASFINAG, to keep the subsidence cavityon the carriageway low, required using several sections ofpipe-shielding to obtain a stiff and strong structure.

In particular, the extreme gradient of up to 11.6 % made thegreatest demands on personnel and equipment. To counterthe 200 m difference in elevation (20 bar water pressure),greatest attention had to be given to operating a redundantwater-retention system for the predicted volumes of water ofup to 30 l/sec. In addition, parallel to tunnelling work, theplaned backfill of the invert with drainage as well asbituminous carriageway was installed. The desired positiveeffect with respect to work efficiency and work safety tookhold.

The breakthrough to the Innsbruck-Ahrental exploratorygallery was on 11 October 2012.

Anchor worksImage: PORR


Intersection area Ahrental access tunnel and exploratory galleryImage: PORR

Blasting a heading faceImage: PORR

Innsbruck−Ahrental exploratory gallery

Tunnelling 5,469 m

Cross-section 25 – 75 m²

Longitudinal gradient 0.4 – 0.6 %



Flowing concrete 10,500 m³

The construction-logistical infrastructure is located on thegrounds of the Sillschlucht site installation along with thecontainer units for the client's representatives, local buildingsupervision, construction and control surveying, geologists,geotechnical engineers as well as the project and sitemanagement. In addition to access bridges built in preliminarylots, various slope and rock consolidation work wasnecessary, as well as the laying of an asphalt-pavedconstruction road, before tunnelling work began.

Tunnelling work in the Sillschlucht of the Innsbruck–Ahrentalexploratory gallery began following the ground breakingceremony in December 2009.

The tunnel will be built by blasting, again according to theprinciples of the New Austrian Tunnelling Method, but, due tothe tight cross-section conditions, divided only into calotteand invert. A median drive performance of approx. 6.5 m perworking day was achievable with the four to six blastingsdaily. The very tight space conditions of this single-lane

exploratory gallery, in particular, made it necessary toconstruct double-lane 20 m long lay-bys regularly at adistance of 250 m.

Especially the supply of the drive with lining material andconcrete, bringing out the rubble, fresh-air supply and allother logistical details of a line construction site, make thisdrive special.

The tunnelling work for the Innsbruck exploratory gallery inthe direction of Brenner was ended once the junction wasreached with the Ahrental access tunnel after 3,658 m.

In the context of this construction contract, the clientadditionally ordered the production of a 657 m long “Northdrive”, which will in the future discharge the mountain waterdirectly into the adjoining Sill River. In the course of thissection of the tunnel, an existing scour sluice gallery (distance20 m) as well as an access tunnel (distance 1 m) of anadjacent power plant had to be passed under. The thresholdvalues determined by expertise report by the power plantoperator were 5 mm/sec and, by changing the useddetonation system (dual-shock detonator), this value wasadhered to for each detonation.

About 30 m in front of the planned breakthrough point, themining method drive was stopped. The breakthrough wascarried out by large-hole boring with a diameter of 800 mm.This work was completed at the end of 2012.

The production of the 3,660 m long dewatering channel with aflowing-concrete mixer over the entire drive-length wascarried out directly upon ending the drive works in thissection. In advance the invert profile was milled to its targetlevel using a mining milling machine. Following that work, theconcrete invert channel was produced in a total of fiveconcreting steps. Daily performance rate of up to 200 linearmetres of flowing concrete were achieved. The alternativeinvert channel production worked out by means of valueengineering was convincing on account of the outstandingquality of the finished product.

Work began on the 1,150 m extension of the exploratorygallery in the southern direction with the breakthrough of theAhrental entrance gallery to the Innsbruck-Ahrentalexploratory gallery in October 2012.

At the end of this drive, from tunnel metre 4,750, a 50 metre-long cavern with an excavated cross-section of 240 m² will bebuilt. This will be needed as an assembly hall for tunnelboring machines for future construction lots of the BrennerBasis Tunnel.


Sillschlucht site installation areaImage: PORR

Intersection area, Innsbruck-Ahrental exploratory gallery with the northernextensionImage: PORR

Invert gutter production after four of five working stepsImage: PORR

Cutter head of the 800 mm large-hole drillingImage: PORR

Ahrental South storage siteAll of the excavated material from the drives described beforeis stored on a permanent basis at the Ahrental South earthexcavation storage area in accord with the 2008 WasteDisposal Ordinance. To keep the area not covered withhumus and not planted as small as possible during theoperational phase, the packing of the stored material wascarried out in four steps.

The material is deposited in layers of 60 cm maximum incompacted condition. The testing of the compaction isperformed with surface-covering dynamic compaction control(FDVK). In addition, to verify proper compaction, the Proctordensity was measured and several seepage tests and largeshear tests were carried out.

In the current phase of construction the storage site holds adumping volume of nearly 450,000 m³.

Excavated earth storage at Ahrental South in April 2012Image: PORR

Ampass entrance gallery

Tunnelling 1,370 m

Cross-section approx. 35 m²

Gradient 1.3 %



The portal of the Ampass entrance gallery is located at theeastern outskirts of Innsbruck. The start of construction inSeptember 2011 was simultaneously the first mainconstruction measure of the Brenner Basis Tunnel and thus amilestone for the realization of this European railway project.

In the course of this construction measure, two temporaryjunctions were built at the A12 Inntal motorway in Ampass andTulfes for construction-logistical supply of the Ampassentrance gallery as well as for future BBT construction lots.

The material excavated from the entrance gallery is depositedon a permanent basis at the site at Ampass. The successiveelevation of the terrain of the storage area in the course of itsproduction meant that the existing natural gas high-pressure


line DN400 PN70 had to be rerouted over a length of 625 min running gas-supply operation outside the heat periods(May to October) in two steps of tapping and plugging.

The portal of the Ampass entrance gallery lies immediately inthe area of the L283 state road, which means that the roadhad to be diverted to a previously constructed 13.5 m long cutand cover tunnel. It was therefore necessary in advance tobore and concrete two separated bore pile rows with 18 borepiles each and a length of 8 metres as the later left and righttunnel walls. A tunnel arch was concreted onto these borepiles and on this the new state road was built. Once the trafficflow had been rerouted, the production and stabilisation of theportal front area as well as excavation work beneath the roofcould begin.

Upon completion of the site installation area, the tunnellingwork began at the Ampass entrance gallery in May 2012.

On account of the single-lane drivable cross-section in theAmpass tunnel, two lay-bys and a turning bay are planned at330 m distance from each other. The rescue gallery will bebuilt in the direction of Tulfes and Bergisel at the end of theaccess tunnel parallel to the existing Innsbruck railwaydiversion.

Over the first 300 m the Ampass entrance gallery crossesprimarily glacial deposits, mostly built up of morainesediments. In this section of the tunnel the loosening methodwas to use an excavator with the aid of a partial cuttingmachine for a non-aggressive removal of the rock. Thecutting area was stabilised by the regular use of horizontalspits.

After that, from a depth of about 300 m, stone from theInnsbruck quartz phyllite zone was excavated. These manifestan intensive cleavage with flat to medium-steep incidentangles. Locally there are tectonically delimited incursions oflime and dolomite marble as well as metamorphic greenstone. These types of rock can only be loosened by blasting.

A 550 m long conveyor is used to transport the excavatedmaterial along the northern side of the state road L283 fromthe portal to the storage area at Ampass South. Projectedtransport performance is 100 t per hour. The extremely tightcurve radii of only 180 m for the conveyor posed a majorchallenge to the systems engineering. With a number ofindividual and detailed solutions, the operation represents acritical situation, but it functions to everyone's satisfaction.

Ampass portal with rerouted state road and workshop buildingImage: PORR

Cut-and-cover method and bore piles at the Ampass portalImage: PORR

TBM ITC 312 in operationImage: PORR


Tunnel drive workImage: PORR

Conveyor constructionImage: PORR

Project data

Client Brenner Basistunnel BBT SE

Type andScope ofContract

Tunnel structure and carriagewayconstruction; construction of infrastructurefor construction logistics

Location ofthe project

Innsbruck / Tyrol

Project inconsortium

Strabag – PORR (commercial leadmanagement)

Date ofcontractaward

Innsbruck-Ahrental exploratory section: Nov.2009Ampass entrance gallery: Aug. 2011

Constructiontime

Innsbruck-Ahrental exploratory section: 50monthsAmpass entrance gallery: approx. 25 months

Projectcompletion

End 2013

a milestone in the european rail transport - world of …...brenner basis tunnel – a milestone in...

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