Rockfall Protection
Geotas and Rockfall Protection
Geotas, as the Tasmanian distributors of the Maccaferri range of Rockfall systems, have had plenty of experience across a range of sites, supplying the various products, and including installation of various systems This experience, combined with the knowledge base within Geofabrics Australasia, and the state-of-the-art Maccaferri design software, we know we can provide a solution.
Design Suggestions
To support design of rockfall protection we offer an advanced suite of software free to our clients. To assist engineers with the design process, the Geofabrics team of engineering specialists are available to give technical advice in the use of the software as well as provide training in-house or via seminars. Our team can also provide certified design if required.
Rockfall Embankments
Rockfall protection embankments are passive systems and an ideal solution when surface stabilisation systems cannot be installed (e.g. for very wide slopes) or where interception of falling rocks is not possible due to the whole slope being inaccessible.
The location (distance from the slope), the height and the size of the embankment is evaluated in relation to the slope morphology, the characteristics of the area and the kinetic energy of the falling rocks. The structure is assembled with units made of double twisted wire mesh, heavily galvanized with Galmac® (Zn – Al 5%), and polymer (self-extinguish PVC) coated steel wire adding excellent durability.
The embankments can be constructed from Maccaferri gabions, Terramesh, or the Terramesh Green system.
Advantages:
- Almost unlimited capacity >20,000kJ
- Withstand multiple impacts without repair
- Can contain vast quantities of debris
- Very low maintenance.
- Cost effective ($ per kJ) capacity.
Mesh Drapery Systems
Geofabrics range of Maccaferri rockfall drapery systems are designed to control rockfall movement by guiding falling debris to a collection point at the toe of the slope thus protecting structures from debris damage.
Protection of roads, buildings and other structures located directly at the toe of man-made cuttings or natural cliffs are a major challenge for engineers. Falling debris and rocks can be due to rock formation deterioration caused by plant action, thermal expansion, winds, cold and thaw, hydrostatic pressure and seismic action. Maccaferri double-twist wire mesh is the ideal product for use in rockfall drapery, due to its flexibility in all directions, and the fact that it will not unravel, even in the event of some wire breakage. It also does not inhibit the regeneration of vegetation, allowing the slope to return back to its natural state after repair.
Mesh Drapery Products
Maccaferri Rockfall Netting
Double Twist steel wire mesh is a highly efficient mesh combining ease and flexibility of use with unsurpassed cost-effectiveness. Used around the world for over 60 years, Maccaferri rockfall netting mesh is proven to offer robust, long lasting and cost-effective rockfall protection. On moderately steep slopes, or those where some vegetation may grow, the mesh should be kept as close to the slope as possible. On very steep and/or near vertical slopes, the net must be anchored at the top of the cliff, and left unanchored at the bottom, thereby allowing rocks and debris to fall into a collection ditch at the toe of the slope. A key factor is to have a safe and continuous anchorage at the top.
Roadside protection at Lachlan, and Esk Main Road
ADVANTAGES
- Does not unravel if wire breakage occurs making it cost effective with low maintenance requirements
- Flexible and versatile to match existing slope and rock profiles
- Different levels of coating protection for durability in a wide range of environments
- Does not inhibit regrowth of vegetation
Maccaferri Steelgrid
Maccaferri Steelgrid and Steelgrid HR is a high strength, high stiffness steel composite netting/drapery system combining the versatility and practical benefits of double twist mesh, with the excellent stiffness and mechanical durability of high tensile steel wire ropes.
The strain performance (stiffness) of the mesh is highly important in real world conditions as this determines the expected displacement of the mesh under load. A product with high tensile strength (some single twist meshes) is of limited use if it requires significant displacement in order to mobilise that resistance as this could cause serviceability failure.
The wires and ropes are coated with Zinc-Aluminium Galmac® galvanising to Class A level and can be additionally coated with a thermally bonded layer of PVC for maximum durability. Steelgrid HR has a range of system tensile strengths ranging from 50kN/m up to 180kNm. This allows projects to be both cost effective and a technically optimised solution for clients and designers alike.
ADVANTAGES
- Does not unravel if wire breakage occurs making it cost effective with low maintenance requirements
- Flexible and versatile to match existing slope and rock profiles
- Different levels of coating protection for durability in a wide range of environments
- Does not inhibit regrowth of vegetation
- Mesh is able to transmit loads directly to the top anchors and consequently reduce the stress on the mesh compared to other mesh types
- High strength at low strain and high punch resistance at low deformation (high stiffness).
Maccaferri HEA Panels
For applications where low deflection and high strength are required High Energy Absorption Panels offer containment of unstable rocks with minimal deformation.
The Maccaferri High Energy Absorption (HEA) panel is the stiffest product in the Mac.Ro systems range. Manufactured from a single continuous length of steel rope and joined at each crossing point with a high-resistance 3 mm wire double knot.
The patented ‘double knot’ exceeds the tear and pull apart resistance of traditional clips.
Due to the multi-axial performance of the HEA panel, loads are transferred effectively to the anchors on the rock slope face regardless of the anchor layout.
ADVANTAGES
- Double knot connection for maximum strength transfer
- Multi-axial configuration for superior multi-directional strength performance
- High stiffness to limit rock detachment
- Heavily galvanised for durability
- Flexible for conforming to irregular rock shapes
Maccaferri Ring Nets
Maccaferri Ring Nets have the highest strength of any of any mesh in the range. Ring nets are ideal for situations where there is a combination of highly undulating slope face, large boulders and a high risk of dynamic impacts.
The nets are also used on rock slopes in simple drapery applications with large rock masses prone to failure where Ring Nets, with their high deformability characteristics, can absorb high impact loads. This high impact absorption characteristic is utilised in the rockfall catch fence application with a high energy level, typically >750 KJ. There are different ring nets available, depending on the required tensile strength, or absorption capacity.
ADVANTAGES
- Ring Nets allow high mechanical durability
- Multi-directional strength/strain performance
- Excellent dynamic impact resistance
- High durability and safety during maintenance operations
- Variety of coatings to balance commercial and performance requirements
- No overlapping mesh on lateral connections means fast installation and minimal waste
- Variety of lengths and widths available reducing installation time and waste
Debris Flow and Landslide Barriers
Debris flow fences act to catch landslide material to protect infrastructure below.
Debris flows and shallow landslides are highly mobile liquefied landslides containing a variety of material from fine particles to large boulders and tree branches. They are caused by excessive water on and within slopes, caused by rainfall, fire or similar. The likelihood of debris flows is increased when vegetation and other surface protection has been removed from vulnerable slopes, perhaps by wildfire or clearing. Debris flow fences act to catch this landslide material to protect infrastructure below.
FUNCTION
Our Debris Flow Fences are similar to our rockfall barriers (catch fences) but incorporate additional energy absorption elements and variable geometries. In addition, combinations of different diameter ring nets are often used as the containment mesh. Ring nets are ideal in these structures as they have inherent energy absorption capacity, before loads are transferred to the compression brakes. Larger diameter ring nets are placed along the bottom of the structure to enable water and small material flow to continue through the barrier. Our smaller diameter ring nets are used at the top of the debris flow structures.
Rockfall Catch Fence
When a drapery systems cannot be installed due to access, topographical or economic considerations Dynamic Rockfall Barriers/Catch Fences offer a rockfall protection solution for intercepting and stopping falling rocks and boulders.
FUNCTION
Geofabrics offers a range of Maccaferri rockfall barrier fence systems designed to intercept falling rocks which have detached from the rock face above which may cause damage to infrastructure below and in severe cases loss of life. Rockfall barrier fences of variable geometry are fabricated from a complex system of steel cables, connections of steel cables to structural elements, energy absorbing devices and anchorages, capable of high deformation capacities which are designed to be easily transported and assembled in extreme conditions.
The range of barriers for rockfall problems include debris flow barriers, dynamic rockfall barriers and hybrid and attenuation barriers. Geofabrics range of Maccaferri dynamic rockfall barriers are designed to deflect under load and absorb energy and are available with energy absorption capacity up to 8,500kJ.
Hybrid/Attenuator Fence
In situations where there is available “run-out” space beneath a rockfall barrier in which the rocks can ultimately stop or be collected harmlessly. Hybrid and Attenuator Systems combine the energy absorption capabilities of a dynamic rockfall barrier with the reduced maintenance advantages of drapery mesh on slopes.
The attenuator or hybrid fence is a system which combines high dynamic impacts when the rock hits the nets and guides the rock down to the end of the drape but does not stop them. Rotational energy of the rock is high in terms of total kinetic energy in this instance, unlike in the free falling situation. Thus, the governing criteria is therefore the resistance of the net at the time of impacts to minimise damage due to the slicing forces resulting from the rolling and bouncing effects of the rocks from up slope. Due to the difficulty in maintenance and hence high cost for these hybrid fences, the high resistance of the panel will be the most important consideration.
Advantages
- Less maintenance than standard catch fence, especially in difficult terrain
- An intermediate dissipating structure for very tall slopes with very frequent rockfall to reduce energy
- Lower foundation and anchor loadings
- Protect larger slope area compared to standard drapery mesh
- Can be installed at upper slope zone hence, intercept rocks at lower energy without increased maintenance
Flexible Structural facing for soil nailing
The objective of using Flexible Structural Facing is to provide stability to the face by supporting the soil in between the soil nail locations and transmitting the load from the soil to the nail heads via mesh membrane stiffness.
Flexible Structural Facing is an intermediate option between soft and hard facing for soil nail slopes. They are commonly used for cut slopes of moderate height with a slope angle between 33 and 60 degrees. The aim of having the flexible structural facing is to provide surface stability while vegetation is established.
The facing system can be rigid shotcrete, or a flexible structural environmentally friendly revegetating system such as MacMat R. Where high performance (greater mesh stiffness, steeper slopes or wider nail spacing) and revegetation are required, the innovative MacMat HS combines the reinforcing benefits of Steelgrid HR, and a 3-dimensional geomat in one product, meaning installation time is reduced and simplified.
Advantages
- Protects the exposed face from erosion
- Provides stability while vegetation establishes
- Cost effective option to hard facing
- Aesthetically pleasing with vegetation establishment