Tunnels become more environmentally friendly

New technology protects the climate and nature

Tunneling DBU
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The construction of tunnels and road or railway tracks is complicated: Hundreds of cubic meters of earth must be moved, the groundwater level lowered, the excavation with concrete and retaining walls to be secured. With the help of the German Environmental Foundation (DBU), the civil engineering and construction equipment company Wallenhorst (Lower Saxony) now wants to develop a construction method that does without these superfluous auxiliary structures and protects the environment.

"If developed successfully, the disposal and transport of excavated soil as well as the demand for concrete could be reduced by almost half, " said DBU General Secretary Fritz Brickwedde at the official project start on 25 June 2004. If the new procedure succeeds, it will make a significant contribution to the natural, Climate, noise and flood protection.

Without massive retaining walls no tunnel

Tunnels that are being built open to date must be protected by massive retaining walls that extend up to 20 meters into the depths. The groundwater is lowered in the excavation pit, the soil is excavated and a meter-thick bottom made of underwater concrete is pulled in. The actual tunnel is then built into this type of shell. However, once the work is done, the retaining walls and the underwater concrete must remain in the ground, although they have no function for the tunnel. With consequences for nature and flood protection, because such buildings have a massive impact on groundwater flows.

The aim of the Wallenhorst company is to set up a mobile wall without special groundwater drainage, which can be relocated depending on the construction progress and makes groundwater lowering and the use of underwater concrete superfluous. A special machine produces the respective blocks of the structure in segments, lowers them to the required depth in the excavation and fixes them with liquid concrete, which presses them under the tunnel segments.

Brickwedde: "With the new method, a clear tunnel opening of eleven meters per meter of tunnel length can save 90 cubic meters of concrete and 22.5 tonnes of carbon dioxide. With regard to the greenhouse gas, which contributes to global warming, that is more than two-thirds of the amount that an average three-person household in Germany causes per year. "When constructing a street trough and a trough structure on a railway line, the new method should be Proven practicality. display

Less pollution

The technology opens up considerable possibilities for reducing the environmental impact compared to conventional construction methods. It is a precautionary approach that integrates environmental protection and a reduced impact on nature into the new construction method. Brickwedde: "Trough structures in themselves are important elements of ecologically compatible traffic design. Since they are often built in a sensitive environment, both the groundwater issues and the halving of the structural founding and transport services have a significant ecological importance. "

The DBU supports the project with 205, 000 euros.

More about tunneling.

(German Federal Environmental Foundation (DBU), 28.06.2004 - DLO)