Earls Mill Road Retaining Wall Ground Anchors and Strengthening

Following the appearance of several large cracks to the corner and face of the retaining wall, and the evident sinking of the steps inside the wall leading to the houses behind, Amey, working with Plymouth City Council commissioned a full geotechnical investigation. The investigation works were carried out by The John Grimes Partnership a firm of Civil, Structural and Geotechnical Consulting Engineers.

The John Grimes Partnership Investigation included coring ten 127 mm diameter holes through the wall with some extending to the bedrock. Core samples were examined to assess the backfill material composition and condition. The report concluded that the wall movement causing the cracking and sinking of the steps were caused by pressure from the saturated and settlement of the backfill materials behind the wall. They proposed using Rock anchors drilled through the backfill material and into the rock behind the wall and strengthening of the existing wall to prevent any further movement.

As experienced and respected drilling specialists, Saxton Drilling were selected for this element of the works. This first stage entailed core drilling through the existing wall and backfill material to reach the bedrock behind. The anchors were then fitted and grouted in position. After testing each anchor, cast self aligning plates bolted securely in position. Works were carried out using a drill rig mounted in a custom built basket fitted to a telehandler.

The next step was to demolish the feature masonry wall on the corner and base of the wall. Excavation of the footing of the wall followed and the protection of the 11KV cable running along the base of the wall.

Holes were drilled into the original foundation and steel starter bars fitted and resin anchored in position. New steel reinforcement was then fitted into position and secured in place New concrete foundations were laid and new wall position marked out.