Juste. Intelligent. Sûr.

Division IU Tunnelling, Ed. Züblin AG

Les deux nouvelles galeries de secours de l’un des plus vieux tunnels routiers d’Allemagne ont été réalisées avec une solution ingénieuse.

The goal

Improving safety
This project was to adapt the tunnel’s escape galleries to current safety standards.

The project

Summary :
The new escape galleries are to shorten the length of the escape routes of the 622 m long Lämmerbuckel tunnel.

Challenge :
Planning and design were of particular importance for this site, as safety was at the heart of the project. MEVA was commissioned to design a tailor-made solution, a formwork that should allow minimal intervention on the existing tunnel.

Solution

Joint planning
For this small, but difficult construction project, MEVA supported the construction company Ed. Züblin AG by providing detailed formwork plans, special formwork and creative solutions made from standard panels.
Innovative 3D study for a tailor-made solution
The two emergency galleries are almost similar in terms of construction and differ mainly in their length. The formwork could therefore be implemented in the two galleries.

Work began with the construction of the tunnel head, to connect the emergency galleries to the existing road tunnel. The upper part of this connection was partly made with special formwork to match the shape of the vault of the dug tunnel.

The one-sided formwork, consisting of custom-made elements and panels from Mammut 350 wall formwork, was supported with the STB 300 bracing truss , which can be used for pouring heights of up to 3.30 m . In addition, the layout of the special formwork was carried out indicating the installation of the joint cover strip.
A half-moon hanger
The first block of the emergency gallery, located directly against the head of the tunnel, has a niche for the power supply. It is because of this that the section of the tunnel widens at this point. To reproduce the dimensions accurately, the work had to be carried out using a half-moon hanger. This formwork was designed down to the millimeter by MEVA engineers.

To position this special formwork in the form of a half-moon correctly on the formwork carriage and succeed in placing it in the niche of the tunnel, the half-moon hanger was first placed in the frame. The formwork carriage was then placed under the hanger and then adjusted to the nearest millimeter.

Les pièces de raccordement, installées en amont pour solidariser le coffrage spécial au chariot, ont ensuite été resserrées. L’étanchéité entre le cintre demi-lune et le chariot du coffrage a été assurée par la mise en place de profils en caoutchouc.
Smooth transition
The part excavated with the tunnel boring machine is followed by an open section at the level of each emergency gallery. To achieve the transition between the two differently shaped sections, MEVA engineers used special wooden pieces. These pieces were first used as fixing for the seals of the transition block, then as formwork to pass from a circular section to a polygonal section.

This special wooden formwork was then placed on the Mammut 350 wall formwork and could then be reused on the construction site as a wall stop, in particular during the construction of the open section of the tunnel. Mammut 350 formworkwas also implemented on all the other sections of the site, because with a resistance of 100 kN/m² to the pressure of fresh concrete, this formwork is ideal for civil engineering works. It is also available in a wide selection of sizes, with panels from 125 x 25 cm to 350 x 250 cm.
Checking the plumb to carry out the project
After having made the footing with wall formwork in the lying position, it was necessary to erect walls 3 m high. Thanks to the large panels of the Mammut 350 formwork , the walls could be cast without an extension, which facilitated the progress of the work.

For the alignment of the formwork, EuMax site props were implemented diagonally at the level of the slope of the excavation. Thanks to the adjustable extension length and the spindle that allows precise adjustment, adjusting the props was quick and easy.

The wall formwork at the end of the gallery was thus able to be produced in three or even four rotations. MEP mobile formwork tableswere implemented with MevaFlex formwork to form the slab. The two relief galleries terminate in wing walls and a canopy. The diagonal walls are primarily intended to retain the ground and return to the same level at the entrance to the galleries.

The result

Site manager Alfred Elst was very satisfied with the work done and particularly praised the quality and practicality of the formwork plans:

Au vu de l’importance du trafic sur l’axe est-ouest de l’autoroute A8, la sécurité du tunnel est un critère décisif qui, en cas d’urgence, peut sauver des vies.

Wolfgang Reimer, le président de la région de Stuttgart

Le cintre demi-lune conçu par MEVA était parfaitement adapté aux dimensions de l’ouvrage et les plans 3D ont été d’une grande aide. Les détails, qui étaient ainsi bien visibles, ont facilité la mise en place du coffrage.

Alfred Elst, chef de chantier, division IU Tunnelling, Ed. Züblin AG

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