Successful tunnel project in Karlsruhe: coating and sealing systems from Sika

The new 1.6-kilometer-long car tunnel under Kriegsstrasse in Karlsruhe relieves the city center of through traffic. The tunnel walls in the north and south tubes were coated with products from Sika Deutschland GmbH. The high groundwater level also required highly efficient joint sealing of the structure. For this reason, the high-performance systems of the leading specialty chemicals company were also used here.

Combined solution disentangles individual traffic

In October 2022, the combined-solution-project was completed with the opening of the new car tunnel under Kriegsstrasse in Karlsruhe. The aim of the new infrastructure concept was to disentangle inner-city streetcar and individual traffic and thus make it safer and more attractive overall. The project also includes a new above-ground track in Kriegsstrasse above the car tunnel. With the Karoline-Luise Tunnel, Karlsruhe‘s main traffic axis on Kriegsstraße between the Ludwig-Erhard-Allee junction and the Karlstor gate will be moved underground. It was realized as a plastic fiber-reinforced reinforced concrete frame using the cut-and-cover method. The work was divided into ten individual construction sections with watertight excavation pits up to nine meters deep. These were given a concrete trough, which was later closed again with a cover.

Tunnel reliably sealed

Specific guidelines for the use of waterstops apply to tunnel structures. Road tunnels are subject to the ZTV-ING and the RIZ-ING guideline drawings. According to these, elastomer expansion waterstops to DIN 7865 must be used to seal the block joints. The waterstops are additionally fitted with injection hoses to ensure reliable grouting in the event of circumferential movement.

In the Karoline-Luise Tunnel in Karlsruhe, Sika Waterbar waterstops were used to seal the expansion and space joints. For the scheduled sealing of the construction joints, the multi-injectable injection hose SikaFuko VT-1 was used, for which a test report from MFPA Leipzig is available for an injectability of a 30-meter section. Normally, these hoses are designed for ten meters. During grouting, the neoprene strips are compressed and the injection material can escape along the entire length of the hose through eight longitudinal gaps. Repeated grouting can be performed by vacuuming as needed. The 3-component polyacrylate gel Sika Injection-311 served as the sealing material together with the dispersion component Sika Injection-315 PM. This acrylate material ensures multiple injections.

Deep hydrophobization for durable concrete protection

After the shell was completed, the interior work of the tunnel began. The coating work for both tubes was the responsibility of Heinrich Schmid GmbH & Co. KG was responsible. To protect the walls permanently against the penetration of chloride-containing water, the proven Sikagard-740 W deep hydrophobic coating was used. The solvent-free, 1-component hydrophobic impregnation based on silane is preferably used for vertical and horizontal components of traffic structures and facades and also increases the resistance of the concrete to frost and de-icing salt cycles.

Surface protection system OS 2 (B) System

The processing company then applied the surface protection system. Using two airless units on a trailer, the right and left tunnel walls were coated in parallel. Here, the 2-component colored epoxy resin dispersion Sikagard-340 WCT was used, which is especially suitable for the coating of tunnel structures and has a fire behavior classified in fire class B. It offers high carbonation protection and very good wet abrasion resistance. In addition, it has high stability on vertical surfaces. „With this new product, we were able to easily achieve the high gloss level required by ZTV-ING, Part 5 Section 4 for tunnel structures,“ explains Heinrich Schmid. „This was the first time we coated a surface of this size with Sikagard-340 WCT. The long pot life was an advantage with the two-coat airless application.“ The coating could be recoated after just three hours.

Tunnel coating with versatile properties

The high gloss level of Sikagard-340 WCT ensures higher luminous efficacy and thus enables energy-saving lighting. The star-listed tunnel coating is flame-retardant according to DIN EN 13501-1, and is extremely resistant to mechanical and chemical attack. Water is sufficient for cleaning; the addition of surfactants is not necessary.

Well-marked escape route system

The doors and tunnel blocks in the escape route system were coated with SikaCor EG-5 in the color green by the skilled workers of Heinrich Schmid GmbH. The 2-component, colored top coat based on acrylic polyurethane is mechanically resistant and can also be used as a marking paint. The application was carried out with a spraying system.

Quality control for fair-faced concrete

Gravel pockets and blowholes occurring in the exposed concrete were partially leveled with Sika Icoment-520 mortar. The 2-component fine filler for OS systems can be used in the thin-layer process to largely level out formwork distortions. It has a very good water retention capacity and the resulting shorter curing time.

Karlsruhe combined solution nearing completion

After the construction of the light rail tunnel under Kaiserstraße, the reconstruction of Kriegsstraße was the second sub-project of the Karlsruhe combined solution. The above-ground track increases the capacity of Karlsruhe‘s light rail network, while through traffic in the car tunnel makes rapid progress. Commissioning of the tunnel and thus completion of the conversion work was in October 2022.