A substantial soil nailed slope was required by the University of Exeter to enable construction of new accommodation blocks for 1200 students.

Project details

The site topography meant that the slope to the rear need to be excavated into to accommodate some of the building's footprint. As the overall cut slope was to be over 7.0m high and excavation had to be kept to a minimum, it was decided that soil nailing was the preferred option. Phi Group worked closely with their colleagues at Keller to provide a complete solution for Vinci, with Keller installing the soil nails and Phi Group installing the facing systems.

The challenge

The timing was a key issue on this project, so Keller mobilised multiple rigs to reduce the soil nailing time. There was careful collaboration required as the facing system requires a structural back mesh to be installed as the soil nailing is carried out. There is therefore a signifficant benefit where just one company carries out the complete package.

The solution

The excavation was completed in sections, with the soil nailing operation being undertaken in a top down method. This minimises temporary earthworks issues as the slope is excavated as it is stabilised with the soil nails. The facing is then installed from the bottom up, and filled with a clean stone. The slope angle was 70 degrees for the lower 5.0m, with space available for the top 2.0m to be excavated at a shallower angle and faced with a geoweb system.
In all nearly 2,000m2 of facing was installed.