EVO Rock Bags come in three sizes: 2 ton, 4 ton and 8 ton, rated for currents up to 3.2, 3.6 and 4.0 m/s placed singly and 4.7, 5.3 and 5.9 m/s placed as a group.
The deciding figure for most jobs is the design current velocity at the bed, at the place the bags will sit. Enter it below to see which sizes meet it.
Rock bag size selector
Enter the design current velocity at the bed, with your safety margin already applied.
Results appear here.
Ratings are for currents only and are a starting point. Wave loading, slopes and the final design are for the project engineer to confirm.
Ratings and dimensions
Single and grouped ratings are the flow velocities at which the bags show no movement, placed on their own and placed together. Imperial figures are on the rock bags page.
| Size | Mesh | Rock size (mm) | Height (m) | Diameter (m) | Volume (m³) | Empty weight (kg) | Single (m/s) | Grouped (m/s) |
|---|---|---|---|---|---|---|---|---|
| 2 ton | 25 mm | 50 – 200 | 0.4 | 1.9 | 1.13 | 6.0 | 3.2 | 4.7 |
| 4 ton | 25 mm | 50 – 200 | 0.6 | 2.4 | 2.71 | 12.5 | 3.6 | 5.3 |
| 8 ton | 50 mm | 75 – 200 | 0.85 | 3.0 | 6.00 | 39.0 | 4.0 | 5.9 |
Four steps to a size
- Find the design velocity at the bed where the bags will sit, from the hydraulic study, the propeller wash calculation or the site's design flood. Apply your project's safety margin.
- Decide on single or grouped placement. Grouped bags touch and interlock, and resist higher currents. Most aprons and revetments are grouped.
- Pick the smallest size whose rating is above your design velocity. A bigger bag also covers more area per lift, which can reduce the number of placements.
- Check other loads: wave action, slope angle, ice and debris. Our published ratings cover currents only.
Beyond 5.9 m/s, or with waves
If the design velocity is above 5.9 m/s, or waves govern, contact us with the site conditions. As the manufacturer, we can advise on layout, multiple layers or a combined system.
Questions
- What does 'grouped' mean in the ratings?
- Bags placed touching each other in a continuous layer. They interlock and resist higher velocities than a bag on its own.
- What rock goes into each size?
- 50 to 200 mm rock for the 2 and 4 ton bags (25 mm mesh), and 75 to 200 mm for the 8 ton bag (50 mm mesh). Crushed concrete can also be used.
- Do the ratings include waves?
- No. They are current ratings. Send wave conditions and we will advise.
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.
