An innovative slope stabilization

The Swiss Federal Institute of Technology Zurich, ETH Zürich for short, is building a new research and laboratory complex. The seven-floor building with around 21,000 m² of floor space is planned to be

The Swiss Federal Institute of Technology Zurich, ETH Zürich for short, is building a new research and laboratory complex.

The seven-floor building with around 21,000 m² of floor space is planned to be operational in three years. Aside from office workplaces and seminar rooms, it will also include laboratories and catering options. Construction began in 2015 and the foundation work, with which Bauer Spezialtiefbau Schweiz AG was commissioned, took place from December 2016 to March 2017. "A unique concept for stabilizing the 110-meter-long north-eastern slope had to be developed for this", reported Bauer project manager Niklas Haag.

First, Implenia constructed a back-anchored intermittent bored pile wall to secure the slope during the foundation work. Around 800 temporary anchors were placed. "However, to keep the slope-side terrain free of bulky and heavy stabilizing elements in the future, the extreme forces needed to be absorbed by an independent supporting structure", explained Niklas Haag. A solution was used that had previously never been achieved in those dimensions.

After excavating a 20-meter deep excavation pit, the cutting work for a total of 14 diaphragm wall segments began. Using a cutter unit on a Bauer MC 96 duty-cycle crane, the Bauer jobsite team then drilled trenches in the rock up to 26 meters deep. Then, giant reinforcement cages for each of the 1-meter wide and around 10-meter long segments were lifted using a crane – precise work in a tight space – after all, the excavation pit was right in the center of Zurich. A separate production platform was designed for the assembly of the 14 reinforcement cages – each weighing around 50 t. Each panel was then filled with around 270 m³ of concrete.

Bauer Spezialtiefbau Schweiz AG completed the diaphragm wall work at the end of March 2017. The 14 diaphragm walls are expected to be pre-stressed in spring 2018 and then the slope stabilization supporting structure will be built, piece by piece. The casing of the new GLC development and laboratory building will begin in parallel with this. The pre-stressed, diaphragm walls perpendicular to the slope will make up the lower part of the protection system, which will be complemented by a non-positively connected in-situ concrete vault.