Rock Africa - Applications

Civil Engineering Applications

Road and Infrastructure Protection
A case in point was the flagship Chapman's Peak Drive upgrade where the tourist route between Hout Bay and Noordhoek was upgraded and safety improved by the judicious use of Geobrugg RXI barriers. For less onerous conditions and lower energies other barriers are available, however all of which have the common theme of protecting property and lives. For more information please email us for a brochure, or click here, or visit the Geobrugg website here.

RXI Barrier, Chapman's Peak Drive

Mesh and spiral rope nets for unstable rock slopes
TECCO® mesh is manufactured from a 3mm high-tensile steel wire with a tensile strength of 1,770N/mm². Together with a pattern of bolting or anchoring, it stabilises steep, unconsolidated rock and rock slopes.

The robust SPIDER® spiral rope net of high-tensile 4mm steel wire, prevents block breakouts from rock slopes and secures loose rocks, rock spurs and overhangs, also unstable rock formations with a very irregular surface structure and coarse block weathering.

The TECCO and SPIDER rockfall drapes protect rock slopes up to 100m high, where the rockfall capture space is small or the kinetic energy is too high for barriers. The rockfall drape is fastened to a support rope at the top and hung over the rockslope. Rockfall events therefore take place in a controlled manner between the mesh and the rock face and are directed into the catchment zone at the toe of the slope. For more information please email us for a brochure, or click here, or visit the Geobrugg website here.

Mining Applications
Rock Barriers
Steeper pit walls may result in better access to ore pockets and less removal of non-ore waste rock. However, the danger of rockfall, breakouts or partial failure of pit walls often prevents such plans as traditional protection measures with steel beams, wire ropes and meshes often will not give sufficient protection.

In open-pit mines flexible rockfall barriers — crash-tested to extreme impact energies — are increasingly installed to allow for steeper pit walls while at the same time providing effective protection for workers, equipment, access roads, tunnel portals and buildings. Reduced mining costs and the value of additional ore considerably exceed the installation cost of flexible barriers.

In line with the hazard potential — determined from the pit profile, falling height and anticipated rock mass — we supply you with flexible barriers for retention capacities of 100kJ, 250kJ, 500kJ, 1,000kJ, 1,500kJ, 2,000kJ, 3,000kJ and 5,000kJ. Barrier heights between 2m and 9m are possible.

Mesh and spiral rope nets for unstable rock slopes
Mesh and spiral rope applications are identical to the civil engineering applications described above.


TECCO high-tensile chain link mesh for Underground Mining and Tunnelling Ground Support

1. TECCO for surface support of tunnels
   The TECCO chain-link mesh is made of high-tensile steel wire with a tensile strength of 1’770N/mm2. The wire is sufficiently though, and does not behave in a brittle manner. It can be stretched over sharp rock edges without sustaining damage. The mesh is diamond shaped and along the edges, the wires are bent over and double twisted in such a way that this connection is as strong as the mesh itself. TECCO mesh is produced in rolls and can be manufactured in widths up to 3.5m and in tailor-made lengths corresponding to the tunnel surface. Due to the use of high-tensile wire, the mesh is very light in relation with its strength (G80/4 2.6 kg/m2). For corrosion protection the wires are coated with a special aluminium- zinc coating (GEOBRUGG SUPERCOATING) which has a higher corrosion resistance than standard galvanising. Comparison tests with conventional galvanised wires yield at least a three or four times longer lifespan.
   
   Field of Applications:
   General surface support in tunnels ( mesh only or mesh in shotcrete)
   - Failures in high stressed ground conditions (rock burst)
   - Squeezing ground
   - Subsequent reinforcement of shotcrete solutions
   - Tunnel reconstruction

2. Testing of the high-tensile chain-link mesh TECCO
   In order to determine the mechanical properties of the TECCO mesh, it was tested extensively for static and dynamic loading at the Western Australian School of Mines (WASM).
   
   2.1) Static Testing
   The static response of high-tensile chain-link mesh was determined by test work
   in the WASM laboratories in Kalgoorlie. The figure opposite shows the response
   of three samples of the high-tensile mesh TECCO G80/4 where a 1.3 X 1.3 m panel was loaded with a 300 X 300mm steel plate. The high-tensile mesh was able to bear a load of up to 100 – 110 kN before it failed at the edge of the loading plate. Weld mesh in comparison failed with approximately 40 kN, and mild steel chain-link failed with less than 20 kN using the same test setup. All mesh types require some displacement at the beginning to be activated and loaded.
   
   It was also found that the high-tensile chain-link mesh can sustain an increase in load even after a wire has failed. It also does not unravel once a wire has failed. In earlier tests, the high-tensile mesh was tested in a way quite similar to an application in tunnelling (with four bolts and plates). It was established on that occasion that the rupture is generally starting at the crossing points but is not sheared over the edge of the plates due to the higher steel quality of the mesh compared to the mild steel plates.

   2.2.) Dynamic Testing
   By using the momentum transfer method the TECCO mesh was tested at the dynamic testing facility of WASM. The mesh panel is installed in a loading frame in which a steel weight can be dropped onto the mesh from different heights. The rebound of the loading frame is stopped by buffers while the loading mass impacts the mesh sample without being separated. This test arrangement simulates the situation with installed mesh tunnels. The whole dynamic tests are instrumented with high-speed video cameras, load cells and accelerometers.
   
   It was established that the high-tensile chain-link mesh is able to absorb energies or up to 10-12 kJ in such a configuration. This is equal to stopping a rock burst mass of 100kg which was previously accelerated to 4.5-5 m/s. This value represents the value of the energy absorption of the mesh only and does not include any absorption by the rock mass itself or the yielding bolts. Welded wire mesh (wire diameter 5.6mm and 100mm wire spacing) showed energy absorption capacities in the area of 1-2 kJ in the same test setup.

2.3.) Numerical Model
Using the calibrated finite element program it is possible to simulate and vary the dynamic response of any project boundary condition for setup and loading.

3.) Installation of TECCO Mesh in Tunnels

The difference between the installation of welded wire mesh and the installation of TECCO mesh is the stiffness of the products. The welded wire mesh is relatively stiff and delivered and applied in sheets. The TECCO mesh is only stiff i one direction but rollable in the other. Therefore it is delivered in rolls and will be installed in a different way to the wire mesh.

3.1.) Advantages of the TECCO mesh in Underground Mining and Tunnelling

• Simple and fast mechanised installation (faster than welding wire mesh).
• higher energy absorption than conventional welded wire mesh.
• Rolls of mesh are picked up with the TECCO handler, minimising manual handling.
• Depending on ground conditions it is eventually possible to use less anchors through the higher load capacity of the TECCO mesh.
• Different width mesh with 2mm-4mm wire thickness available.
• Less over-lapping of mesh in tunnels and drives compared to welded wire mesh.
• Greater corrosion properties than welded wire mesh.
• Easy transport and storage of TECCO mesh.

It is the task of our engineers and partners to analyze the problem together with you in detail and then, together with local consultants, to present solutions. Painstaking planning is not the only thing you can expect from us, however; since we have our own production plants on three continents, we can offer not only short delivery paths and times, but also optimal local customer services. With a view towards a trouble free execution, we deliver preassembled and clearly identified system components right to the construction site. There we provide support, if desired, including technical support – from installation right on up until acceptance of the structure.

Rock Africa - Applications