FEDRO N1 UPlaNS St Gallen East - West, reinforcement of retaining walls, bridge foundations and galleries in a landslide slope

The A1 motorway is being globally rehabilitated in the region of the city of St Gallen. An approx. 2 km long section runs through a creep slope (creep rates of approx. 4 mm/year) with a gradient of approx. 20°. The route runs almost continuously in galleries, on bridges or in cuttings or fills, which requires various retaining walls.

Within the framework of the UPlaNS St Gallen West – St Gallen East, and due to the persistent creep deformations and the deficits of the installed anchor systems (lack of corrosion protection, poor steel quality and therefore end of service life) measures were developed to maintain the safety of the anchored supporting structures (bridge foundations, retaining walls and galleries).

Based on a detailed geological investigation with boreholes of up to 80 m depth as well as extensive long-term monitoring (inclinometers, anchor load cells, pore water pressure sensors, geodetic measuring points, ...), the causes of creep and the hydrogeological conditions could be investigated and necessary measures planned and implemented. Based on back-calculations, risk analyses and residual use considerations, the measures could be optimized and installed on only a few of the 27 structures investigated. These were mostly anchor reinforcements with the associated wall and longarine constructions.

3 double bridges, 2 galleries, 18 retaining walls

Construction costs: CHF 435 million / 14 million (total costs / costs of geotechnical works)

Phases 31-53

In addition to geotechnical engineering and foundation, Gruner also provided services in the following areas:

  • Environment
  • Engineering Structures
  • Route

Bundesamt für Strassen (ASTRA) / Office fédéral des routes (OFROU) / Swiss Federal Roads Office (FEDRO)

Geotechnical engineering and foundation,


Your contact person

Laurent Pitteloud
Head of Geotechnical Engineering
+41 61 317 63 76 | bGF1cmVudC5waXR0ZWxvdWRAZ3J1bmVyLmNo

Gruner AG
St. Jakobs-Strasse 199
CH-4020 Basel

References on the subject

Actelion office and laboratory building
SBB Zurich Stadelhofen - Influence of tunnel construction on existing structures with finite element models
Court Expertise, Inspection Mandate, Second Opinion
Double-track expansion Goldach-Rorschach City
Roche building 2, Basel