The placement of tyres flat on the seabed is key to their ability to entrap sediment within their centres. The trapped sediment gives the mats a self-stabilising function and prevents the lowering of the seabed by scouring.
High energy flows transport sediment across scour prone sites. However, as they pass across the mat surface, these flows are disturbed and their speed reduces. As a result, sediment transport across the mats is disrupted and the sediment is instead entrapped within the mat’s void spaces, where it is retained due to the tyre’s shape. This process is illustrated in the diagrams to the right.
Ideal Density of Tyres
The density of tyres is perfectly suited to stabilise to the seabed and ensure scour is prevented. Being less dense than seabed sediment, tyres do not sink into the bed like denser materials such as rock and concrete. However, being denser than seawater, tyres remain in-situ where they are placed on the seabed.
Physical modelling has been undertaken by testing scaled models of the mats under a range of conditions in test tank facilities. This has given insight into mat performance and used to optimise and refine product design.