The Challenge

The retaining wall is positioned at the back of a 4 storey property with a drop down to the rear garden of the property in front. The wall has moved and started to bulge and movement is clear to see. The supporting concrete walls on either side of the garden on top of the retaining wall have cracked wide open in 2 places and the entire wall is need of reinforcement as without this it will collapse with possible catastrophic repercussions due to its loacation so close the another property and the 4 storey building that is placed above it.

The Solution

There are two elements to the reinforcing. Firstly the rear wall can be reinforced horizontally from the rear elevation to offer resistance to the out of plane loads from the retained soil. This will also stitch across the vertical crack visible from the rear of the wall. The reinforcing across the wall would then be extended into the party walls on either side. Installation is achieved by cutting horizontal slots across the wall to a depth of around 40mm, injecting Bond Flex grout and installing the Bar Flex stainless steel reinforcing. The top of the wall is reinforced vertically with Cem Flex ties which are installed into a 16mm diameter drilled hole around 1.4m deep, injected with Bond Flex grout and then the Cem Flex tie is inserted.

The main restraint to the retaining wall is offered by the installation of 60mm diameter Heli Piles installed through 67mm cored holes at an angle of 30° down from horizontal to a depth of up to 5m. Each installation would be proof tested in tension to a load of 40kN. The connection with the wall is made by filling the cored hole, around the Heli Pile, with Bond Flex grout and then screwing a stainless steel M12 stud into the end of the Heli Pile which will extend through a stainless steel pattress plate on the surface of the wall with a stainless steel angled washer with a stainless steel dome nut to cap it off.

Installation

Due to a poor access the compressor was placed on the street in front of the property and the line to the Rhino air compressed pile driver was run through the property to the gardens. This would be totally impossible with any other product. The installatiion of Bar Flex would take place while the Heli Piles are installed until refusal. The timing data of installation is transmitted back to head office and after 10 days work the wall is fully reinforced and completely safe.