SCAUT/Elkuch Group

Plug-in Crosscut Element – Installation in less than 90 Minutes

On 14 December 2017, the SCAUT consortium under the leadership of the Elkuch Group introduced the project “Crosscut Closure Module” to an expanded SCAUT audience in the Hagerbach Test Gallery (VSH). Michael Lierau, Elkuch managing director, gave a brief review of the development of the project and the collaboration with SCAUT. Afterwards, the placement of the closure module, the “Plug-in Crosscut Element (PCE)”, was demonstrated to the participants at a scale of 1:1.

The impulse for this innovation was given by the assembly situation in the Koralm Tunnel in Austria. The small diameter of the crosscut as well as the concrete buildings inside the cross connecting gallery prevent the installation of larger systems such as doors, fans, etc. to the inside of the crosscut wall. The idea of a prefabricated, fully equipped Plug-in Crosscut Element (PCE) was born in order to take account of the challenging installation environment. The idea had to be eventually abandoned for the Koralm Tunnel due to the progressed time plan. Nevertheless Elkuch further explored the idea together with industry partners, as the overwhelming feedback clearly indicated, that the highly BIM compatible concept was well received within the industry and had potential. Hence, since beginning of 2016, the consortium jointly developed a concept to the marketability stage.

Manufacturing and Installation of the PCE

The concrete element is manufactured in a workshop outside the tunnel, ensuring high process reliability and security. Outset for an accurate execution of the PCE is a 3D laser scan of the crosscut ends which set the basis for a CAD project. Available measurement technologies on the market are sufficient to provide the required accuracy. The adjustable mold is aligned with the crosscut’s geometry to reduce tolerances. After the armoring, all necessary interfaces (bolts, threaded sleeves, RFID tags etc. are precisely prepositioned. The mold is then filled with concrete to produce wall elements of a thickness between 25 and 30 cm.

Once cured, the pre-fabricated concrete wall element is set and mounted on jigs that provide fixation for the concrete element during the assembly, transport and installation.

Now, all additional sub-assemblies and systems such as fans or aeration tube interfaces, doors, control cabinets, etc. are mounted to the Plug-in Crosscut Element, until it is ready to be installed. Main objective of the project is, that a fully functional and verified system is entering the tunnel to minimize the installation time inside the tunnel.

When the tunnel is ready to receive the PCE’s, a rail car or a flatbed trailer loads the elements weighing 8 t apiece. In the case of a rail car, up to six PCEs for a workman shift (given 90 minutes installation time per PCE) are loaded. The PCEs are transported to their specific installation site. The rail car’s final position in front of the crosscut will be defined according to a laser based marking. The manipulator that moves the PCE into its final position in the crosscut can compensate a tolerance of +/-10 cm. Once the car is in position, guide rails, adapted to the respective tunnel geometry, are unfolded manually.

The manipulator can lift the PCE vertically, incline it and move it down. In order to avoid interference with the catenary wires, the PCEs has to be slightly tilted when moved into position in the crosscut.

The PCE is set into the block-out (with tolerance of 1–2 cm) of the crosscut. The manipulator’s adjustment capability allows for optimal placement. Once in place, the PCE is bolted to the crosscut and the manipulator is disconnected and pulled back on the rail car. In the next step, the block-out with the PCE is filled with a common grout for tunnel applications. The grout can cure (typically within 6 hours) without interfering with the following operations.

In order to seal the remaining opening around the PCE, a fire resistant filler is used. Products from various providers can be considered. Final step is plugging the PCE to the tunnel control and power system. This last operational step concludes a 90 minute installation procedure, and the team can move on to the next crosscut.

Cost and Time Advantages

Main cost driver of the PCE derive from the technical equipment mounted to the PCE. However, due to the concept of prefabrication, the PCE’s cost are reduced compared to the conventional method (up to 15 % less manufacturing cost). For example:

 Mounting racks for the door are avoided as they are simpler and integrated in the PCE.

 Installation cost is calculated on workshop level during the day and not at tunnel level. All works inside the tunnels are considered, e.g. drilling and sealing of the PCE is included in the cost calculation.

 Overall installation efficiency is higher as free access to all parts of the PCE is given at all time outside the tunnel.

 Concrete building costs are lower as finished concrete is used instead of site concrete.

The main advantages of the PCE system are the benefits from a much faster installation and commissioning time (up to 90% time saving). Currently, a well experienced installation team of three members need about three days for the installation and electrical connection of one cross connecting gallery door in the Loetschberg, Gotthard and Ceneri Base Tunnel. The PCE can be installed in less than 90 minutes.

Simplified logistics are another advantage, since only prefabricated elements have to be transported into the tunnel, instead of diverse construction materials. Waste materials and remainders do not have to be carted off, either. This leads to significant cost and time savings for the main contractor.

Presenting the Concept

Starting in February 2018, the PCE concept is presented by the SCAUT consortium to various interested clients and tunnel operators throughout Europe. This is slated to take place in the context of the “Crosscut of the Future” SCAUT project that is currently in development. Furthermore the demonstrations of the PCE assembly in the VSH are resumed, starting with February, 20. Interested parties can contact Christian Nutrice (" >) for more information and to schedule an appointment for a demonstration in the Hagerbach Test Gallery.

SCAUT is an industry initiative with the aim of developing and using underground urban space in a more focused way, guided by conceptual studies and technology projects.

Further information on the initiative’s concept and membership are available online on the SCAUT website (


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