Offshore structures sit on seabeds that move. Currents and waves scour sand from around foundations, expose cables where they enter a structure, and undermine pipelines at free spans and crossings.
Rock bags are placed from a vessel crane, one at a time, to exact positions. That makes them a precise alternative to large volumes of dumped rock where only local protection is needed, or where a repair has to be made quickly.
Uses offshore
- Scour protection around monopiles, jackets and other foundations
- Cable protection where array or export cables leave the seabed to enter a J-tube or foundation
- Cable and pipeline crossings, as a cover or separation layer
- Pipeline stabilization and free-span support
- Remedial work where existing protection has been lost
Why placement precision matters
Dumped rock from a fall-pipe vessel is efficient for long runs, but it is a large mobilization for a few local locations. Rock bags are placed by the ring from a crane, with ROV or survey checking position, so a small number of bags can protect a specific point without a dedicated rock-dumping vessel.
Because the net holds the rock together, the bags drape over cables and pipelines and into scour holes without point loads from individual large stones.
Technical documents
We publish a document on windfarms and rock bags, plus technical specifications and a Service Life & Durability Summary. Request them through the form on the rock bags page.
Offshore loading includes waves and combined wave and current action. The ratings in our size table are for currents only; send metocean conditions and we will advise on size and layout.
Questions
- Can rock bags be installed from a standard vessel crane?
- Yes. Each bag has a single lifting ring, so it can be lowered by crane and released at the seabed. Positioning is usually checked by ROV.
- Do rock bags damage cables they are placed on?
- The rock is held in a flexible net, so the bag drapes over the cable rather than dropping individual stones onto it. Confirm the approach with the cable owner's requirements.
- Is there a document on rock bags for wind farms?
- Yes, 'Windfarms and rock bags'. Request it through the documents form on the rock bags page.
Published by EVOSNT Trading FZCO, manufacturer of EVO Rock Bags. Product figures are from our technical specifications. General guidance only; the project engineer is responsible for the final design.
