Drag embedment anchor penetration in layered sands and through cable and pipeline trenches

Cable Burial Risk assessment (CBRA) is undertaken to identify risks to offshore renewable energy cable infrastructure. CBRA assumes uniform soil conditions and does not recognise the effect of the cable installation methods. Centrifuge model testing was undertaken to explore the performance of a shipping anchor (AC-14) when encountering layered sand soil profiles. In addition, anchor interaction with both cable plough trenches and backfilled V-shaped pipeline plough trench routes were investigated. For a specific anchor, in loose over dense sand layers, penetration is stopped with minimal penetration into the underlying dense layer irrespective of the thickness of the loose layer for the anchor size investigated. Testing a recent layered soil CBRA approach indicated that it performed well when inputs were based upon well-characterised model anchor performance. Anchor interaction with vertical cable plough trenches showed limited modification of anchor behaviour. Similar observations were made for the V-shaped backfilled trenches where the anchor approached at 90 or 45° to the trench. When the anchor followed the route of the trench it dived through the trench and backfilled material and into the underlying dense soil. For CBRA methods to improve there is a need for high-quality characterisation of different anchor types in a wider range of soil conditions where realistic installation practices are considered.