InfraStructures - Octobre 2006 - On a Crawler Track in the Emergency Gallery

On a Crawler Track in the Emergency Gallery

Jürgen Kronenberg, Putzmeister AG
Special Collaboration

To improve safety in the 2,3 km long Heslacher Tunnel in Stuttgart, Germany, a pedestrian escape gallery parallel to the two-track tunnel has been under construction since January 2005. Due to the small cross section, an unconventional solution is required for concreting work.

Within the formwork, the emergency gallery has a cross-section of only 10 m2. For the operating construction company, Baresel GmbH, only compact and relatively narrow machines are considered for the concreting work. A Putzmeister BSA 1005-D GRF concrete pump, set up on a crawler track only approximately 1,7 m wide, fulfilled these requirements at a height of less than 2,4 m. Thanks to the crawler chassis, the machine is self-driving and can adapt its position as construction work progresses at any time.

The concrete is transported from outside the escape gallery to the BSA concrete pump using a 2,5 m3 grabbing dumper, which delivers the material directly in front of the crawler track-BSA onto a 6 m long conveyor belt. This belt transports the concrete over the last few metres and delivers it into the pump hoppers.

Block lengths of 8 meters
During construction of the bottom plate, two 18 m3 bottom plate blocks are concreted each day, with arched concreting one block (approximately 30 m3 is finished a day. The block length is about 8 m. Concrete delivery to the placement site is then via a pipeline approximately 6 m long, which runs underneath the concrete pump and above the crawler track and which has been extended with a 3 m pipe segment. The Baresel employees have connected a 6 m hose to it, which forks into two lines in the shape of a Y. The two lines run to formwork supports and are fed alternately with concrete. A guillotine cuts off the supply of concrete into the supply line which is not currently required. For cleaning, the crawler track-BSA moves at about walking pace on its own chassis in front of the tunnel portal.

The Heslach Tunnel, as the continuation B14 main road, connects Stuttgart center with the A8 motorway in the southwest of the city. With approximately 48 000 vehicles passing through it each day, this underground feeder is an extraordinarily heavily used stretch of tunnel. To offer vehicle passengers a possibility to escape in the event of an accident, retrofitting the gallery had become necessary.

It consists of the 415 m long escape gallery I west constructed in the Heslach Tunnel years ago and the new 410 m long escape gallery I east. Both sections are connected by several crossways with the main tunnel.