Carousel of suitcases: CDM Smith surveys building ground for luggage tunnel at Frankfurt Airport

Fraport AG Frankfurt a. M., Germany
Fraport AGs goal is clearly stated: Digging a tunnel beneath the runways in soft soil, which subsides minimally or not at all, despite dynamic traffic loads, during flight operations. A demanding endeavor that can only succeed if the ground has been explored extensively. CDM Smith accepted this challenge.

Each year, more than 60 million passengers land or depart at Frankfurt Airport, which make it Germany's most important hub. At the same time, more than 27 million suitcases are handled each year - on peak days over 110,000 pieces a day.

To keep the waiting times short, with this high number of passengers and luggage, a clever conveyor system transports the luggage back and forth from, to and between the aircrafts. With the new Terminal 3, the baggage handling system must be expanded: By shield drive, a tunnel of 1.7 km will be driven under the existing runways, which will connect the existing terminals with the new terminal.

length of tunnel
tunnel diameter
allowed subsidence

To Fraport AG the smooth operation for all engineer work is of importance. Especially the runways must be able to be used without restriction during the construction phase and must not be subsided. Therefore, a maximum permissible subsidence of 10mm at ground surface must be observed. In addition, shutdowns of the tunnel boring machine must be avoided, due to high costs. Not an easy task, because the tunnel is built below groundwater level, in sands and gravel with scree.

A critical factor was the good cooperation between us as geotechnical and tunnel engineering consultants and the tunnel planners.
Dr.-Ing. Heiko Huber, Senior Project Ma­na­ger

Fraport AG commissioned CDM Smith to survey the subsoil and to estimate potential risks at building site - during operation and partly during the night. Adding to the difficult situation no exploratory drilling or surface extensions could be done beneath the runways. Nevertheless, to obtain a comprehensive picture of the subsoil, extensive field and laboratory tests were necessary.

We evaluated the soil for its abrasiveness, its potential for adhesion and the presence of scree. Together with the tunnel planners, we are now developing solutions for those route areas that harbor risks, and provide advice as geotechnical consultants.

The boundary conditions at Frankfurt Airport make this project particularly challenging, but also particularly exciting.
Project Details

Did you know?

Every hour, the baggage conveyor system at Frankfurt Airport transports over 20,000 suitcases back and forth between the airport buildings and aircraft. The conveyor belts have a total length of 81 km. To ensure that the luggage reaches its destination reliably, it lies individually in a coded plastic tub. At each turnout, a reader decides in which direction the baggage is forwarded - and extremely quickly: the cases travel up to 5 metres per second.

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