Covanburn Projects
The 60 Steps Retaining Wall
Client
Glasgow City Council
Value
£200,000
Location
Glasgow
The 60 Steps are a much-loved feature of Glasgow’s West End. Dating back to the 1870s, the steps connect Kelvinside Terrace with Queen Margaret Road.
The Category B listed 60 Steps retaining wall had a severe bulge at the base. The Council commissioned an investigation that revealed voids in the wall construction and poor road drainage contributing to material loss. A temporary prop had been installed, and stonework stitched with Cintec anchors in 2012.
A key aspect of the brief was to ensure that there was no further damage to the wall or to surrounding properties whilst the works were carried out.
In order to complete the stabilization works, the backfill to the wall was removed before strengthening works were carried out, and then backfill was then reinstated. This had to be completed without disturbing the front face or causing damage to adjacent services or tenement buildings.
The key actions carried out by Covanburn were:
To ensure that there was no further damage to the wall or to surrounding properties whilst the works were going on, vibration monitoring was installed on the wall itself and close to the adjoining tenement flats. This was reviewed daily as the piling was taking place.
In addition, a grid of approximately 60no survey points was established on the wall. This was surveyed regularly throughout the whole contract to check there were no excessive movements in the wall whilst the work was going on.
Due to the narrow streets and the large height difference between the upper and lower parts of the retaining wall, the site was very restricted, so a working platform was constructed on Kelvinside Terrace South to provide a level surface for the plant and also to protect the carriageway beneath.
On completion of the piling, the ground between the piles and the retaining wall was fully excavated out down to the pavement level of the lower carriageway. Temporary works were designed and installed for the deep excavation. Fume extraction and gas monitoring were installed to ensure the safety of the workforce.
Once the ground behind the wall was fully removed, the foundation of the wall was underpinned in sections using concrete to ensure no further settlement or movement.
Then lightweight granular fill was carefully placed and compacted behind the wall. As the fill came up, additional steel ties were attached from the retaining wall to the new piles, anchoring the face.
After the repair to the rear of the wall was complete, the temporary timber and concrete propping was removed from the pavement on Queen Margaret Road. Masonry repairs were carried out to remove the weakened and bulging section of the wall and new drainage was installed in the carriageway to prevent the flooding which had been exacerbating the poor condition of the stonework.
Finally, landscaping works were carried out to the area at the top of the retaining wall, and a new fence put in to replace the existing one.
As well as working to guarantee stabilization and strengthening of the wall, we also installed new drainage in the carriageway to make sure that flooding wouldn’t cause similar damage as it had done in the past.
Whilst working on the 60 Steps project, we were keen to ensure good relations were maintained with the residents throughout the works, which we did by monitoring and reviewing the project on a daily basis.
