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Section 11

Completion of Tunnel Shell

Installation of mass concrete including the tunnel drainage shafts (71,000 m³) | construction of side walk-ways, incl. cable troughs, cable chambers, cable protection ducts (69 km) | underground cables and cable channels in the main tunnels, the rescue shafts, rescue tunnels and crossways| road surfacing in the rescue tunnels

ARGE ALPTRANSIT BRENNER provides the following items in Section 11 Completion of Tunnel Shell:

  • Seals – 51,000 m
  • Mass concrete – 71,000 m³
  • Side walkways, including cable channels – 69,000 m
  • Cable trenches and cable routes in the main tunnels, rescue shafts, rescue tunnels and crossways
  • Running surfaces in the rescue tunnels
  • Other reinforced concrete works

Placing of mass concrete 

The 71,000 m³ mass concrete is placed in two stages.

Stage 1 - red: Concrete placed up to the top edge of the emergency drainage channel; delivered by mobile mixers or concrete pump and compacted by poker vibrators.

Stage 2 - green: Completion of remaining concreting up to finished level. Delivered by mobile mixers or concrete pump, compacted by vibrating screed.
The regulating concrete layer is placed in a separate operation over the mass concrete.
The point to note here is the low thickness of the layer compacted by vibration.
The concrete is compacted by a vibrating screed, using the same principle as a concrete extrusion machine
.

Placing of mass concrete

Placing of mass concrete<br />

Installation of side walkways

Two forming techniques were used for the installation of the 69,000 m of side walkways.
The side walkway in the area of the slab track, about 41,000 m of the total, were laid with a slipform paver. The side walkway in the area of the mass-spring systems, about 28.000 m of the total, is installed using con-ventional formwork (propped single-sided formwork).

Formwork concept

Formwork concept<br />

Slipforming:

A special formwork system, which is attached to a caterpillar tracked vehicle, is continuously fed with concre-te from a mobile mixer along a conveyor belt.

The stiff consistency of the concrete and the slow forward speed of the vehicle, which is directly related to the cross-sectional area of the concrete being laid, means that the extruded concrete retains its shape. The whole cross section of the concrete is compacted to the correct profile by hydraulic poker vibrators.

The clear width of the tunnel cross section allows the side walkways to be laid by machine without complete-ly stopping or at least without significant interference with transport movements along the tunnel.

Conventional formwork:

A conventional formwork method must be used in the area of the mass-spring-systems.
Formwork and concreting is done in 2 stages here.

In stage 1 the various cable protection ducts and reinforced hoses are placed first. Then the formwork is erected and the concrete placed and compacted up to the underside of the cable trough.

In stage 2, after the concrete up to the underside of the cable trough has set, the cable trough formwork is erected, bolted down and the side walkway completed in a further concreting operation.

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