What each system does
| System | Principle | Certification |
|---|---|---|
| Flexible barrier | Posts, support ropes, net and brake elements intercept the block in flight and stop it by controlled deformation | EAD 340059-00-0106 (formerly ETAG 027): MEL / SEL from full-scale impact tests |
| Drape mesh (free-hanging) | A mesh hung from a crest anchor line covers the face; loosened blocks stay under the mesh and slide or roll to the toe, where a ditch collects them | Mesh tensile strength and coating to EN 10223-3 or the manufacturer's ETA; no energy class |
| Anchored mesh (active) | Mesh pressed to the face by plates on soil nails or rock bolts; prevents detachment instead of guiding it | EAD 230025-00-0106 — see Anchored high-tensile mesh: how slope stabilization works (EAD 230025) |
Choose a barrier when
- The source zone is high above the road or structure and blocks bounce clear of the surface — measured bounce heights of several metres.
- Blocks are large: a drape mesh cannot hold the weight of big blocks accumulating behind it, a barrier is certified for the energy.
- The face is too high or too irregular to be covered economically, or the source zone cannot be reached.
- There is room at the toe or on a bench for the barrier line and its elongation.
Choose a drape mesh when
- Blocks loosen at the surface of a weathered or fractured face and roll or slide rather than fly — low bounce heights.
- The face is close to the road with no space for a barrier and its elongation.
- The block sizes are small to medium and a catch ditch or a low fence at the toe can take what the mesh delivers.
- The whole face is accessible from the crest for the anchor line, and rope-access crews can install and later clear the mesh.
Often both
On many Omani road cuttings the answer is a combination: a drape mesh on the weathered upper face and a low-energy barrier or catch fence at the toe, or a barrier below a source zone that cannot be draped. The combination is designed from the trajectory analysis, not chosen by habit. What decides is the measured bounce height, the block-size distribution and the position of the source zone — see How to choose the energy class of a rockfall barrier and Slope survey: drone photogrammetry and laser scanning.
Questions on this topic
Does a drape mesh have an energy class?
No. Drape mesh is not certified for impact energy; it is specified by mesh strength and coating. Only flexible barriers carry certified MEL and SEL values.
Can a drape mesh be used above a road with no ditch?
Only with a catch fence or barrier at the toe. The mesh guides blocks down; something must still collect them before the carriageway.
Sources
- EOTA, EAD 340059-00-0106; EOTA, EAD 230025-00-0106.
- EN 10223-3, steel wire products for fences and mesh.