Pipeline anchoring

REQUIREMENT

To prevent any movement or uplift, a 300m long 900mm diameter outfall pipeline was secured to the seabed in Harwich harbour using mechanical ground anchors stainless steel ground anchors with 16mm grip bars.

SOLUTION

Operating from a barge, Keliston Engineering assembled the pipe which was floated out into the harbour and sunk with concrete collars to the seabed 8-10m below, where it was secured with 36 pairs of mechanical ground anchors.

Using a purpose built rig mounted onto a vibrating hammer, each anchor was driven through 6m of silt and a further 5m of dense gravels before being tensioned to a working load of 90kN.

Polypropylene straps were secured across the pipeline between each pair of anchors by means of webbing cleats to restrain the pipe and prevent it floating off the seabed should it ever become empty. Even under extreme sea water conditions mechanical ground anchors proved to be an extremely efficient and cost-effective means of securing the outfall pipeline.