GEWI^® Plus Soil Nails Secure Bypass around the Spa Town Ax les Thermes in the French Pyrenees

Ax les Thermes is located in the south-east of France, near Andorra and very close to Spain. The town is situated at an elevation of 720m and is not only popular with skiers, but has been known for its eighty thermal springs for over 2,000 years.

Federal Road No. N20, which runs directly through Ax les Thermes, was at one time the most important connection with Andorra. In order to allow for increasing traffic volume, construction began on a new 5.5km long bypass. The new roadway runs around the upper part of Ax les Thermes.

After forest clearance, work began on the roadway itself. Geological conditions were characterized by fine-grained gneiss granite and granite gneiss. These rock layers called for systematic blasting and an ex-post stabilization of the steep rock face.

Initially, vertical holes were drilled in order to place explosives in the rocky crests. A total of 450,000 m³ of rock were fitted with explosives. The methods used had to be adapted to the construction site’s complicated geometry with its steep gradients. Specialized foundation contractors SEMEN TP and STIPS (ALPHAROC) used a hydraulic excavator named “stork” because of its long arm. The arm is fitted with a drill that makes it possible to function in this difficult terrain. An attached compressor assures the drilling equipment’s independence. For additional safety, pits were excavated at the rock face to accommodate spoil and to protect residential buildings below from falling debris.

Once the excavation work, which was carried out by the ROGER MARTIN Company in several steps, was completed, the steep rock faces were stabilized using soil nails. DSI France supplied a total of 51,000m of GEWI^® Plus Soil Nails including accessories such as nuts, anchor plates and spacers. In addition, DSI’s French partner SAGGAM supplied more than 8,000m² of mesh for this project.

Due to the fact that the area was difficult to access, a solution had to be found for transporting the pumping supplies and equipment needed for grouting the DYWIDAG Soil Nails that had an average length of 10m. The contractor suggested building a mobile pumping station. A skip was converted into a mobile pumping unit especially for this purpose. Thanks to the conversion of the skip into a mobile grouting machine, all of the installation locations of the soil nails could be reached. The highest soil nail rock wall was 56m tall.

During the two-year construction period, the quick response time of the DSI teams was one of the decisive factors for the rapid construction progress. DSI France is proud to have contributed to the successful completion of this unusual construction project with the flexibility and the technical know-how of its employees.