Trenching and Burial

The vulnerability of pipelines, umblicals and cables at, or below seabed are well known. In the offshore renewable sector, in excess of 80% of insurance claims are related to cable damage but most of this damage occurs during installation.

Selecting and optimising the best burial tool for the product and the required burial depth results in efficient offshore operations, reduced numbers of trenching passes and reduced opportunity for damage to the product. As technology agnostic consultants who are specialists in this field, Cathie are well placed to advise contractors, developers and operators in the correct approach for their project.

Resulting from our breadth of work in this discipline, Cathie hold in-house trenching asset performance models for the majority of jetting, plough, mechanical and hybrid burial assets on the market. These models, in conjunction with our detailed understanding of the seabed environment, enables our teams to produce accurate performance predictions for burial assets, focussed on trenching speed and the number of required passes to reach the desired burial depth. Our specialist engineers are available on location during the project to monitor performance of the asset and to validate the performance models, prior to gathering data for back analysis and continual refinement of our models. Our capabilities extend to assessing configuration and performance of burial assets in backfill mode, or the potential to achieve burial through natural backfilling.

Cathie are commonly engaged in the primary design of new burial tools or the substantial modification of existing trenching assets. We are able to utilise conventional, or large deformation FE and FD techniques such as ALE adaptive meshing or Coupled-Eulerian-Lagrangian methods, in conjunction with the operation of scale models to demonstrate and optimise burial tool performance prior to fabrication. In this area, we have been engaged with the University of Durham on a EPSRC Supergen project to develop new, large deformation modelling methods.

Trenching and seabed burial services include:

Trenching equipment suitability assessment

Trencher performance prediction

Trencher design and optimisation

Supervision of onshore & offshore trenching operations

Performance assessment and forensic studies

We assess complex scenarios such as trencher performance utilising methods including:

  • 2D and 3D finite element analysis (Abaqus, Plaxis)
  • Finite difference modelling
  • Bespoke in-house software
  • Scale trencher trials

We also carry out back analysis of trencher data after installation to refine trencher prediction models:

  • Charting
  • Data Management
  • Post lay burial risk assessment to establish adequate burial depths and target additional projection

At Cathie, we consider practical approaches for all manner of installation issues from pile tip buckling to suction caisson critical under pressure, and everything in between, including jack-up analysis, trenching and burial assessment. Pile driving monitoring is also delivered by our specialist team in G-Octopus. Because design is only part of the story.