CAN Geotechnical was enlisted to design and build a solution to stabilise a 30m length of failing retaining wall supporting a minor public highway adjacent to the garden of a private property.
3D monitoring of the wall had shown significant movement over time, with a large visible bulge forming. In keeping with the heritage nature of the surrounding area, the accepted solution involved tying back the wall with hollow bar self-drilling ties concealed within the fabric of the wall.
Undertaking probe drilling to better understand the rock profile beneath the site allowed CAN to produce a detailed design. This included a temporary works propping system to provide stability to the wall during the works. This anchoring system was designed by CAN, with the propping and scaffold access system being designed by TR Scaffolding. CAN installed anchors to tie down the props and ensure that the wall was made safe temporarily prior to the main anchoring works taking place.
Tie back anchors were then installed in a sequential manor, over reaching with an excavator drill carriage from the highway above. Tensioning and the reinstatement of the masonry was carried out at each tie location before progressing to the next to ensure the structure was not weakened.
During the course of the works, a separate failure of the upper wall happened above the initial works area along with a section of retaining wall further along from the worksite. CAN was able to undertake works to make safe, stabilise and reinstate these additional sections of the wall whilst on site. This included installation of micro piles to support a capping beam along the crest and dry sprayed concrete to temporarily make safe loose debris in the second failure area prior to stabilising with ties.
Following installation of the ties and reinstatement of masonry, the masonry was repointed in full to leave a visually improved finish to the safely stabilised wall.
Duration: 3 months
Client: South Gloucestershire Council
Location: Frenchay, Bristol