A rockfall barrier — also called a rockfall fence, catch fence or flexible rockfall barrier — stops a falling block with a net, ropes and braking elements that deform. Its class is certified by a 1:1 impact test under ETAG 027 / EAD 340059, from 100 kJ to above 4,500 kJ; the choice follows the measured energy, the bounce height and the space available.
- 100 – > 4,500 kJ
- Energy classes 0–8 (MEL)
- EAD 340059
- 1:1 vertical drop test, continues ETAG 027
- MEL ≥ 3 × SEL
- SEL: two impacts, no repair between
- A ≥ 50 %
- Residual height after the MEL test, category A
What it does
A flexible rockfall barrier stops a block that has broken off a slope on a catch line. The energy is absorbed by the deformation of the net and the support ropes and by the controlled elongation of the braking elements; the posts carry the net and the forces go into the ground through the anchors. Compared with rigid structures such as a concrete gallery or an embankment, it takes the same energy with far less mass and in a narrower space.
A barrier is defined by two numbers: the energy it can stop (kJ) and the height at which the net keeps holding the block after an impact. Both are established by testing, not by a catalogue sentence.
Classes: MEL and SEL
ETAG 027 (continued as EAD 340059-00-0106) classifies a barrier by a 1:1 vertical drop test. MEL (maximum energy level) is the energy stopped in a single impact; SEL (service energy level) is the energy stopped in two consecutive impacts with no repair in between. The manufacturer sets MEL at no less than three times SEL.
| Class | SEL (kJ) | MEL (kJ) |
|---|---|---|
| 0 | no test required | 100 |
| 1 | 85 | 250 |
| 2 | 170 | 500 |
| 3 | 330 | 1,000 |
| 4 | 500 | 1,500 |
| 5 | 660 | 2,000 |
| 6 | 1,000 | 3,000 |
| 7 | 1,500 | 4,500 |
| 8 | > 1,500 | > 4,500 (open-ended; the actual value is in the ETA) |
After the MEL test the residual height is declared in three categories of the nominal height: A ≥ 50 %, B 30–50 %, C ≤ 30 %. In the SEL test, after the first impact and with the block still in the net, the residual height must be at least 70 % of the nominal height. These figures are written in the system's European Technical Assessment (ETA) and declaration of performance (DoP); a quotation refers to the same documents.
For scale: 500 kJ is the kinetic energy of a 2.7 t block, about 1 m³ of rock, travelling at 69 km/h (E = ½·m·v²).
Barrier families
| Family | Energy range | Where | Page |
|---|---|---|---|
| GBE | Certified types from 100 to 5,000 kJ (GBE-100A-R … GBE-5000A V2); with and without retaining ropes | Road cuts, slopes above settlements; lines with room for elongation | GBE barriers |
| RXE | 500 – 8,000 kJ (manufacturer's brochure, 2017) | High energy, tight space, lines close to infrastructure | RXE barriers |
Both families are Geobrugg AG products; Artusa has been Geobrugg AG's representative in Türkiye since 2009. The net panel is either a ring net (ROCCO) or a high-tensile woven mesh (TECCO); which one comes with the system is stated in its documents.
Barrier, drape mesh, gallery or ditch?
- Barrier or drape mesh. If the block breaks away and bounces down the slope, an energy-absorbing flexible barrier; if it detaches from the surface and rolls, a drape mesh that covers the surface. The bounce height and the position of the source zone decide it, not the budget. Full answer
- Barrier or concrete gallery. A flexible barrier is the lighter, faster-built answer for single impacts below the certified energy limit. When the block mass or the fall height goes beyond the certified classes, or events are very frequent, a concrete gallery or an embankment is discussed. Full answer
- Barrier or catch ditch. With enough width and depth a ditch is the easiest solution to maintain; it has no certified energy class, and its performance is defined by width, depth and floor slope. Where the road platform is narrow or the land cannot be acquired, a barrier takes its place.
Selection: four inputs
| Input | Where it comes from | What it decides |
|---|---|---|
| Design energy | Block mass × impact velocity, trajectory analysis, safety factor (ONR 24810: 1.00 / 1.05 / 1.15) | Class (MEL ≥ design energy; on sections with frequent events SEL is checked as well) |
| Bounce height | 95 % fractile of the trajectory analysis, terrain roughness | Nominal barrier height |
| Space | Distance between the line and the protected structure | Maximum allowed elongation; whether a low-elongation type such as RXE is needed |
| Ground | Anchor ground, rock quality | Anchor type and length; pull-out test programme |
These inputs are measured on site. The energy class estimate gives the first order of magnitude; the final class comes from the trajectory analysis. The clauses for a tender specification are ready on our barrier specification page (Turkish).
Installation, step by step
- Setting out. The line axis, post and anchor positions are marked from the design.
- Anchors and base plates. Drilled and grouted to the ground; pull-out tests follow the programme.
- Posts. Erected on the base plates.
- Support ropes and braking elements. Installed to the manufacturer's installation manual.
- Net panels. Hung and connected; the number and torque of the rope clips are checked item by item at acceptance.
- ID tag. Every installed line gets a barrier tag: system type, class, installation date and the next inspection in one place.
What to do after an impact and how often to inspect is in inspection and maintenance.
Sources: ETAG 027 (EOTA, April 2013) Table 2; EAD 340059-00-0106; Geobrugg AG RXE brochure EN.170808; ONR 24810.
Frequently asked
How is the energy class of a rockfall barrier determined?
The kinetic energy is found from the mass and impact velocity of the design block, multiplied by the safety factor, and the smallest certified MEL level above that value is chosen. The velocity comes from a trajectory analysis or the energy-line approach, not from a catalogue. Full answer
How is the barrier height chosen?
For the bounce height expected at the barrier axis; it does not follow from the energy calculation. The bounce height comes from the trajectory analysis and is checked against impact marks on site.
Where on the slope is a rockfall barrier installed?
Not next to the structure to be protected, but where the energy of the block drops and the ground can hold anchors. Moving the line upslope lowers the energy but makes access harder and raises the cost.
What is done after a rock hits the barrier?
First the line is made safe and the event is recorded; then the block is emptied from the net, the brakes, ropes and anchors are checked and damaged parts are replaced with identical ones. The system is re-tensioned in the order the manufacturer defines. Full answer
What decides the cost of a rockfall barrier?
Seven things: energy class (kJ), barrier height, line length, access to the slope (road, rope access or helicopter), anchor length and drilling metres for the ground type, scaling along the route, and transport. One class up, the same line grows in posts and anchors as well; that is why the class is set by measurement, not by estimate. Full answer
What do you need from us for a quotation?
The site coordinates, slope height and angle, the asset to be protected, the observed block size and, if available, photographs and records of earlier events. These give an order of magnitude; the firm quotation follows the site survey. Full answer
Tools for this solution (Turkish)
Energy class estimateTrajectory pre-analysisResidual height checkSpecification completer