Excavation of the exploratory tube with a 6.3m diameter SELI TBM for the Brenner Base Tunnel project below the Austro-Italian border is to be officially inaugurated at the end of this month.

The 20 month drive for the 10.5km long, first section of the exploratory tube that will eventually run the entire length of the 55km long main tunnels, is being undertaken by a joint venture contractor, ATB Consortium Tunnel Brenner.

The JV, which was awarded the e78.9M (US$124M), excl VAT, contract in the middle of last year, includes: Pizzarotti, Bilfinger Berger, Alpine Mayreder, Beton –und Monierbau, Jaeger, Seli, Collini Impresa Costruzioni, and Societa Italiana per Condotte d’Acqua.

Starting on the Italian side of the project, the works begin at Aicha where the double shield TBM will drive through Brixner granite with some faults and groundwater expected in defined areas. About half the drive is expected to be rock Class III, and 40% as Class II. Most of the first section of tunnel (9.5km) is to be lined with shotcrete and rock bolts, and the remainder will have segmental lining.

Other excavations for the section of tunnel include a 1.79km long adit, by drill and blast from Mauls. At the end of the adit there will be a 200m-300m long cavern opened up by NATM, and which will be used to receive and dismantle the TBM. Separately, a 400m long tunnel is to be excavated to remove spoil to the Riggertal deposit.

The contract, to be completed by 2010, is the first of four planned by the client, Brenner Basis Tunnel SE, to build the exploratory tunnel. The unified, single tube will later be used as the service tunnel between, and below, the main tunnels.

Tunnelling on the opposite, Austrian end, will start with a 5.6km long NATM excavation from Innsbruck to Ahrental, where a 2.4km long access tunnel will be built. The other section in Austria will see a 3.1km long adit at Wolf that then enables drives of 7.5km and 5.2km in opposite directions – the latter towards Italy. Coming towards it will be a 13.1km bore launched from a 3.9km long adit.

Overburden of up to 1,600m is anticipated for the stretches of tunnel works below the border, and an 8km long zone in the area is where the African and European tectonic plates meet to form the Alps. The main running tunnels to be bored through the area will have an excavated diameter of 9.6m.

Tunnel boring on the exploratory tunnel for Austro-Italian Brenner rail link started in April Tunnel boring – 1 Tunnel boring on the exploratory tunnel for Austro-Italian Brenner rail link started in April Tunnel boring – 2