Rockfall protection systems are a key element in the design and maintenance of road and railway infrastructure networks and have a direct impact on safety. For this important reason, a new approach that encompasses the overall analysis of the rockfall structural system, and not just the individual components, is necessary.
A key distinction must be made between active and passive protection systems so that the most suited type of protection is selected.
“Passive” systems are those which do not affect the process of the rock detachment, but rather focus on containing and intercepting falling and sliding debris, thereby averting danger to infrastructure and its users. Passive systems include:
- Simple drapery systems (Woven mesh rockfall netting, Steelgrid MO and Macmat R)
Simple mesh draperies are usually installed along rock slopes whose surface can break down into fragments not smaller than the opening of the double twisted mesh (60mm to 80mm) and generally not larger than 0.5m in diameter. On moderately steep slopes, or slopes where some vegetation may grow, the mesh should be kept as close as possible to the
slope.
On very steep or nearly vertical slopes, the mesh should be anchored at the top and bottom of the cliff and left unanchored down the slope. However, to limit the containment area between the mesh and rock face some nailing or pegging of the mesh down the slope between the top and bottom anchorages may be necessary.
The drapery type selected is based on the expected accumulation of debris at the toe. The volume of the debris “pocket” will have a direct influence on the forces experienced in the netting and so a protection with the relevant strength parameters should be selected.
Galmac (95% Zinc 5% Aluminium Mischmetal Alloy) or Galmac + PVC coated materials are available depending on the “working design life” as per the Durability and Construction Products Directive 89/106/EEC Guideline.
- Rockfall protection barriers (Flexible catch fences from 500KJ to 5000KJ)
Rockfall barriers (catch fences) of variable geometry are made of a complex system of steel cable panels or ring net panels, steel cables connected to structural elements, posts, energy dissipater devices and anchors.
Flexible rockfall barriers dissipate energy with system deformation, thus enabling the system to withstand energies typically in the range of 500KJ to 5000KJ.
The rockfall barriers (catch fences) supplied by Geofabrics are complete kits i.e. they include all parts required for a standard installation as mentioned previously.
- Rockfall protection reinforced soil embankments (Double sided Green Terramesh or Gabion facing)
These systems are ideal when superficial reinforcing systems cannot be installed (e.g. for very wide slopes) or interception of falling rocks using drapery systems is not possible due to the entire slope being inaccessible.
Reinforced soil embankments enable contractors to use locally available material from site for the backfill thereby creating a vegetated embankment facing (Green Terramesh) which reduces the environmental impact of the system
