“We were commissioned to build a retaining berlinese-type wall for the vertical excavation that will be carried out in cluster D of the testing facilities hosted in building 2173, also known as SM 18,” explains Marco Framarin, project manager at Terracon.
The work was carried out entirely inside the building and involved the execution of micropiles of different diameters:
• 220mm-diameter piles, 6m and 11.5m long, reinforced with steel pipes with 139.7mm diameter
• 150mm-diameter piles, 11.5m long, reinforced with steel pipes with 101.6mm diameter
The geotechnical information provided showed an upper layer comprised of backfill material with gravel, pebbles and limestone blocks up to 2m depth, followed by an underlying unit comprised of clay with very hard boulders up to approximately 9.5m and molasse-type sedimentary rocks up to 11.5m depth.
As a result of the combination of drilling methods, a peak production of 69m was achieved in a shift with the MC 8 D. In total, 1,272m were drilled between end of March and end of April, including 598m with 150mm diameter and 674m with 220mm diameter (144m of which were in extremely low overhead conditions).