Rockfa
Rockfall Protection
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.
Woven Nesh Rockfall Netting, Melbourne,Victoria
“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.
Steelgrid MO-Great Ocean Road, Victoria
- 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.
500KJ Flexible Rockfall Barrier -Perth,WA
- 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.
Reinforced Soil Rockfall Embankment, Italy
“Active” systems are those that act to prevent excessive movement of a rock detachment once it has occurred. Active systems include:
- Superficial reinforcing systems (Steelgrid BO and High Energy Absorption panels form an armoured mesh which is fixed to the rock slope through anchors)
A superficial reinforcing system is aimed
at the stabilization of the rock mass surface layer containing potentially
unstable rocks of a size typically 1-1.5m³. The complete system consisting of
anchors, steel cable panels, steel cables and mesh netting, is a basic “unit”
or cell enclosed between 4 anchor points.
To determine the most suitable system, the stiffness or rigidity of the facing and the forces transmitted to the anchors must be assessed. With these reinforcing systems, it is crucial that the facing provides a high resistance with minimal deflection in order to limit the displacement of the rock mass.
High Energy Absorption panels with a strength in excess of 200kN are available.
A superficial reinforcing system is particularly suited to areas where the accumulation of debris at the toe of a drapery system is not possible due to space constraints e.g. a road with a minimal shoulder width.
Design Suggestions
Geofabrics have a comprehensive rockfall protection product portfolio to ensure that our clients are offered the most appropriate and economical solution. Our design suggestions are carried out using the MACRO 1 and MACRO 2 software and typical anchorage, connection and product performance information can be provided if required.
Our long standing partnerships with leading Consulting Engineers and experienced installers in this highly specialised field, means that a “complete package” can be provided. Please contact us to discuss your specific project details.
