Bramham Wall Stabilisation Controlled Demolition – Soil Nailing/Anchoring – Meshing
Condor was tasked with the stabilisation of a stone wall in Bramham. The wall supported an important road in the village as well as forming the back of resident’s gardens. The wall through a build up of water had a collapse leaving blocks of sandstone in gardens and the road unusable.
Hinko Construction, who we have collaborated with on projects before, contacted Condor when it was clear the wall needed anchoring. Access to the wall was another contributing factor to Condor securing the works. The soil nailing could only be completed from the gardens, however the space was very limited thus excavators could not be used.
The Husqvarna DXR 310 proved to be the solution as it could be tracked through the narrow access and still provide the power to install the anchors.
The works consisted of three phases:
• Firstly, the wall had to be shaped and carved to give a smoother flat face. This had to be done because the collapse was not even leaving boulders over hanging and fractured. The wall face had to be smoother to allow the mesh to sit right after anchoring.
• Secondly, the wall had to be anchored using our Husqvarna with rotary percussion Marini drill and the pumping of grout into the wall.
• Thirdly, the wall had to be meshed to provide not only stability but also a bedding for a layer of shotcrete to be sprayed followed by a more aesthetic finish of sandstone brickwork.
Phase One – Controlled Demolition
As stated above the wall needed shaping before the anchors could be installed. The face was shaped using our Husqvarna equipped with a hydraulic pecker. The Husqvarna is lightweight at well under two tonnes therefore after consultation with the geo-technical engineer it was determined that the slope could be shaped from the crest as well as the toe of the wall.
The wall was slowly moulded to the shape desired ensuring a steady controlled demolition making sure that only the required material was removed to allow the installation of anchors.
Phase Two – Soil Nailing/Anchoring
Once the wall had been prepped and all loose rocks cleared away the soil nailing could begin. A geotechnical design was proposed for the location of the anchors, the Husqvarna was manoeuvred carefully through the gardens taking care of any obstacles. The methodology was to install anchors starting at the crest of the wall working our way down to the toe.
This was to be achieved by erecting a scaffold in two lifts firstly to install the top two rows, then the middle two rows and finally the bottom two rows from the ground. The anchors were to be drilled using air flush to reach the depth required and then to be grouted, this reduces massively the amount of spilled grout in the gardens.
The grout used not only bonded the anchor to the rock inside the wall but also filled the voids under the road, giving a much stronger stability.
After installation and grouting of all anchors had been completed the Husqvarna was removed from site.
Phase Three – Meshing
The final phase was to affix a rigid checkerboard style steel mesh over the anchors and fix it in place using plates and nuts, the mesh was laid with an appropriate overlap to form an inter-connected lattice.
Each anchor had its own plate and nut fixed onto it essentially pulling the mesh tight with the wall, this was accomplished using a air powered nut tightener. Once all nuts had been tightened the excess bar on each anchor was cut flush.
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