ABSTRACT

Offshore pipelines are commonly buried around 1.5 metres below the sea bed surface. Burial is used as a means of protection from fishing activities and hydrodynamic loading and if backfilled can prevent movements due to thermal expansion on commissioning of the pipeline. A pipeline plough, towed along the sea bed by a support vessel is one of the most common means by which pipelines are buried. Ploughs use a large share (see Fig. 1) to ‘cut’ a trench and often the pipeline runs through the plough and is laid directly into the trench as it is formed. It is important that a minimum cover to the pipeline is maintained, along with a relatively constant trench profile to maintain support, which can be particularly tricky when ploughing through geohazards such as sandwaves, (see Bransby et al. 2010a, b). For commercial reasons all these aims need to be achieved in the shortest possible time period.