Top12 is a stainless reinforcing steel developed by Steeltec in Switzerland that has been reliably used in over 1,500 applications for more than 20 years. The high-alloy material, grade 1.4003 (EN 10088), contains at least 12 percent chromium by mass and is therefore significantly more corrosion-resistant than conventional reinforcing steels. Top12 helps reduce the life-cycle costs of infrastructure projects. Top12 can be processed using conventional methods and requires only a thin concrete cover.
The geotechnical variant is characterized by increased strength, which directly leads to material savings. As a result, geosynthetic anchor systems can be designed to be more compact and lighter, offering advantages in transport, handling, and installation – particularly in difficult terrain. At the same time, the otherwise mandatory inspection for defects in the casing pipes after installation is no longer required.
Thus, the special steel Top12 is the ideal solution for many engineering and geotechnical applications, particularly when it comes to anchoring foundations, walls, and retaining walls in the construction of viaducts, tunnels, and roads. Rock faces are also secured against landslides using Top12 anchors. The ribbed special steel is manufactured by Steeltec at its Emmenbrücke facility.
Nestled between the mountain and the lake
The renovated section of the K2b cantonal highway lies between Bürgeln and the Lucerne/Schwyz cantonal border and runs directly along the mountainside above Lake Lucerne. On one side, a steep rock face rises high into the sky; on the other, the terrain drops down to the lake. The roadway was widened to seven meters, and the sidewalk was expanded to a width of 2.6 meters. A cantilevered structure on the lake side – similar to balconies on houses – with retaining walls at both ends supports the entire 350-meter-long structure and is firmly anchored to the rock with prestressed Top12 anchors. The mountainside is also stabilized with Top12 anchors, thereby protecting the road landslides and rockfalls. Additional temporary anchors were set into the rock for the platforms on which materials and machinery were stored during the construction phase, as there was no other space available for them in the rugged terrain. The construction work spanned a period of two years and was completed in early 2026. Permanent anchoring was achieved using Stahlton AG’s “Spanntop” Protection Level 2b anchoring system with Top12 as the stainless steel tension member. To ensure the structure blends in better with the landscape, the concrete for the beams and walls was colored.
Safety for Exposed Structures
Top12 anchors from the Swiss Steel Group secure numerous Swiss infrastructure structures in exposed locations. Examples include the Viamala Pass Road in Graubünden, which winds through the gorge of the same name, and the Müllitobel protective gallery near Vals, which was also constructed in extremely rugged terrain. In the canton of Bern, the ski ramp attached to the Schilthorn mountain station and the lift tower (Canton of Bern) were permanently anchored into rock and permafrost using 18-meter-long Top12 anchors. Top12 anchors were also used not far from the Emmenbrücke site, at the 340-meter-long and up to 23-meter-high Reussthal retaining wall at the foot of a forested steep slope.
Wherever this corrosion-resistant special steel is used, the durability of structures and their service life can be significantly increased – even in exposed, challenging terrain – for up to 100 years.
In brief:
Cantonal Road K2b (section between Bürgeln and the Lucerne/Schwyz cantonal border)
Top12 Application: Permanent prestressed anchors with a diameter of 36 mm, protection class 2b in accordance with Swiss Standard SIA 267:2013
Client: Canton of Lucerne, Transportation and Infrastructure (vif)
Construction period: September 2023 – December 2025