Rock Africa - TECCO® & SPIDER® Slope Stabilisation Systems

TECCO stabilizes slopes susceptible to weathering, prevents breakouts and grows into one with nature.
TECCO slope stabilization system: the cost-effective alternative to supporting structures, shotcrete walls and conventional protection measures. Advantages of the system are:

• System components that are matched to each other act uniformly over the entire slope.
• Larger, arbitrary distances between nails is possible
• Prevents slipping via system pretensioning of 30 to 50 kN
• Laid in 30 X 3.5 m rolls, covering large surfaces.

A before and after TECCO mesh installation

Not all slope stabilizations keep their promises....

• Shotcrete covers: generally stand out as unaesthetic. Since the drainage systems are often insufficiently dimensioned or clogged at an early stage, there is a danger of uncontrollable water pressure build up and fine material washing out behind the shotcrete layer. The result is sudden failure of the protective structure with the possible collapse of the slope. Temporary shotcrete constructions, such as trenches, also hinder the groundwater circulation in the final state. They often require removal, entailing high costs.
  
• Supporting Structures: may necessitate extensive , cost-intensive excavation work and environmentally burdensome mass transport. The soil material is not incorporated directly into the bearing structure but rather replaced by a foreign body. The investment of time and efforts is typically very high for the construction measures. Moreover, the massive structures often disturb (or destroy) the natural scenery.
  
• Wire rope nets: were used in the past in combination with soil or rock nails as flexible slope stabilizations. The anchorage is inflexible and cost-intensive on account of the predetermined geometric form of the nets and the rigid, narrow anchor spacing. Connecting the relatively small net surfaces of the individual rope nets to one another also proves time consuming – and adaption to uneven grounds proves difficult. Moreover, the cross clamps are prone to corrosion.
  
• Hexagonal meshes: exhibit limited wire tensile strength and mesh load bearing capacity. Any rope reinforcements in the mesh cause a bearing behaviour that is non-uniform and difficult to control. The interfaces between panels form weak points. Undesirable bulges can occur since active pretensioning is practically impossible. These systems are under load only when the slope begins to fail. Breakouts are therefore only deterred on a limited basis. Insufficient protection and constant repair work are often the result. Also, the basis for dimensioning is lacking for adapting the stabilization measures to the existing static soil and rock requirements. All this can lead to liability problems.
  
• Geogrids mad of PET: are only suited to lighter tasks. Creep movements and breakouts in the slope soon lead to exceeding the load bearing capacity and to fracture. Sharp edges, as occur in the rock slopes, can easily cut through the grid, and the limited UV-resistance of the geogrid limits its lifespan.

The TECCO system is appropriate for stabilizing steep soil, sediment and rock slopes. The main reason being that after cleaning, levelling and profiling the surface, the TECCO steel wire mesh can be pretensioned on the slope at a defined force using soil or rock nails and spike plates. In short, the mesh adapts to the topography and so prevents not only slides and deformations, but also breakouts.

The TECCO steel wire mesh is anchored with soil or rock nails behind the sliding surface layer. Since the finely meshed panel – also adapts to the slope surface due to the pretensioning, it prevents earth masses and rock pieces from breaking out. In other words: Regularly emptying of pockets, as is usual with conventional wire nets, is a thing of the past.

The primary nails anchor the steel wire mesh. Additional short or driven nails are only necessary where the mesh must be pulled as tightly as possible over uneven surfaces or to close the boundaries. To satisfy special topographical or static conditions, optional boundary ropes can be built in that are fastened to lateral anchors and tensioned against them.

During the development of the TECCO slope stabilization system, a point was made of eliminating the disadvantages of other methods. The system consists of four main components that are carefully coordinated with each other:

1. TECCO steel wire mesh: TECCO mesh is made of high-tensile steel wire with a ultimate tensile strength of over 1770 N/mm2 and is manufactured on special machines that we developed ourselves. The wire is sufficiently tough, and does not behave in a brittle manner. It can be stretched over sharp rock edges without sustaining damage. The diamond shaped, three-dimensional mesh exhibits homogenous characteristics with a load bearing capacity of 150kN/m in the primary bearing direction (lengthwise). This makes it demonstrably several times superior to hexagonal meshes with or without longitudinal rope reinforcement. TECCO mesh is supplied in rolls measuring 30m X 3.5m.

   
   
   
   
   
2. Soil or rock nails: adapted to the local soil and rock static requirements, the TECCO mesh can be anchored in accordance with our dimensioning concept with commercial soil or rock nails. With the TECCO drilling device it is possible to drill directly through the mesh, even after installation.
   

   
   
   
   
3. TECCO system spike plates: In order to ensure optimal load transmission from soil or rock anchors to the TECCO mesh, Geobrugg has developed rigid spike plates that are reinforced with ribbing. They allow – via 16 mesh wires being acted upon – an active pretensioning of the system from 30 to 50 kN.

   
   
   
   
   
4. TECCO system compression claws: our compression claws permit mesh panels to be connected with a minimum overlapping of two meshes and still ensure one hundred percent force transfer. A homogenous, uniform membrane is formed. The compression claws are installed with the TECCO pressing tool.

Optional Components:

• Boundary ropes: depending on the situation, the stabilization can be optimized with boundary ropes – primarily in uneven terrain or where conditions can be unstable on the upper slope.
• TECMAT erosion control matting: we offer khaki gray TECMAT erosion control matting for revegetation with hydro or dry seeding. It is laid in rolls of 25 X 2m underneath the diamond shaped TECCO mesh structure, to help promote and ensure the establishment of vegetation.
  
  The TECMAT erosion control mat with irregular loop structure is designed for application with the TECCO slope stabilization system. The flexible, three-dimensional erosion control mat made of environmentally-friendly polypropylene in laid beneath the TECCO mesh as an underlay. It is pressed against the slope profile by the TECCO mesh. The open three-dimensional loop structure is very adaptable and therefore hugs the slope. Either wet or dry seeding material can easily be sprayed through –also in smaller local cavities between the erosion control matting and the subsoil. The TECMAT mat absorbs the impact energy of raindrops on one hand and thereby diminishes washing out by rainfall. On the other hand, it improves adhesion for quick and sure root establishment and so favors successful revegetation of the slope – even in extreme locations.
  

TECCO System Testing
Targeted material testing provides a solid basis for the design of the system. The Bavaria Regional Trade Institute LGA (Landesgewerbeanstalt in Germany) and other independent testing institutes have validated the load-bearing performance of the TECCO system in numerous laboratory tests ( longitudinal and transverse pulling direction, compression claws, perforation with/without soil and shearing). In particular the interactions of the system elements mesh/spike plate/anchorage were also tested and the ultimate tensile strength and bearing resistance determined. Test of the mesh connecting elements moreover verified that the load-bearing capacity of the system demonstrably achieves 100% - thanks to the TECCO compression claws – also on the interfaces.

Dimensioning and Optimizing: the RUVOLUM Dimensioning Model
Input parameters for the dimensioning of TECCO slope stabilizations, are among others, the measured data that have been obtained from experiments and tests. The RUVOLUM model allows for the determination of the maximal effective forces on the fastening points (nails) as a function of slope gradient, soil or rock condition, critical layer thickness and nail spacing. At the same time, the dimensioning model considers earthquake-induced slope instabilities and slope-parallel water-streaming pressures.

Based on the calculations, the TECCO system allows optimal adaption to the soil and rock static requirements and allows for the most appropriate nail configuration in accordance with local conditions. This increases the appropriate bearing resistance of the slope.

Corrosion Protection
Another key factor which makes the TECCO system very economical is the corrosion protection concept.
Basically all of the steel components (spike plates and compression claws) are hot-dip galvanised and TECCO mesh is coated with the zinc/aluminium GEOBRUGG SUPERCOATING. This considerably improves the corrosion resistance of the wires in the TECCO mesh: Comparison tests with conventional galvanised wires show that TECCO has at least a three or four times longer lifespan.

For the super coating, the wires first run through a zinc bath and afterwards a zinc/aluminium bath. The result is an eutectic alloy with 5% aluminium and 95% zinc. Thanks to this smooth surface remains after being attacked by corrosion, since the corrosion leads to a reduction of the zinc layer and to formation of an aluminium oxide layer. This latter guarantees the protected object an economical lifespan even in corrosive environments ( roads, railways, industry, coastal and volcanic regions).

Installation is exceptionally easy and with better safety aspects compared with other systems
In contrast to other stabilization measures such as supporting structures, for example, costly excavation work is omitted: The slope is only cleared of vegetation, shrubs are cut back, and the slope is levelled. Thanks to the flexibility of TECCO mesh, site-specific, natural slope forms can be preserved without problems. Depending on the project requirements, measures against erosion and for drainage need to be implemented, but only when appropriate.

The high-tensile strength of the steel wire mesh, in comparison to conventional meshes, permits significantly larger nails spacing, which combined with the installation-friendly connecting elements, considerably simplifies installation. Since the mesh can be laid out before nailing, it already affords a baseline protection during the installation work. This is made possible by the development of the TECCO drilling aid which allows drilling through the laid-out mesh panel, without damaging the corrosion protection. In addition, easily understood instructions simplify the installation.

In general, no maintenance is required provided that the slope stabilization system is correctly installed, fastened and pretensioned, and has not been damaged through external influences. The main reasons for this are:

• The active pretensioning reduces bulges and prevents breakouts
• The TECCO steel wire mesh can be pretensioned against the subsoil via nailing and spike plates, a pretensioning force of 30 to 50 kN is applied to the mesh. The resulting compressive forces act on the slope’s surface to prevent bulges and outbreaks – thereby making related maintenance work unnecessary.
• The targeted application of reinforcing elements (eg. special anchor plates or wire ropes) permits massive increases in the safety factor of the stabilization measures on a project specific basis.

In the long run, the TECCO slope stabilization system has proven to be as effective a measure as it is economical. The summary below outlines the most important reasons why:

Dimensionability, documentation and ecology

• The TECCO slope stabilization system consists of system components that are design-engineered conceived as a whole and functionally coordinated with one another.
• The load-bearing performance of the TECCO system, load transmission of the anchorage via the spike plate to the mesh, the ultimate tensile strength and the bearing resistance have been tested and validated by the LGA (Landesgewerbeanstalt) in Nürberg and other independent testing institutes in numerous laboratory experiments. We are happy to give you access to the relevant documents.
• With the RUVOLUM dimensioning concept, the measure is optimally dimensioned for the soil and rock static requirements. In order to simplify the dimensioning, we have developed our own software.
• The active pretensioning of the high-tensile TECCO mesh prevents later breakouts and visible deformations. The liability risk is thus reduced to a minimum.
• Thanks to its matt-finish aluminium galvanization, TECCO mesh blends unobtrusively into the landscape.
• From the viewpoint of landscape protection, less foreign matter needs to built into the slope, since a lighter mesh can be constructed with the high-tensile steel wire, meaning that fewer anchor points are required. At the end of its lifespan, the TECCO mesh can simply be removed and recycled.
• After a natural or directed revegetation, the TECCO stabilization is hardly visible, and very often not at all.
  Assured quality, no maintenance, long lifespan
• Geobrugg manufacturers TECCO for the particular geographic region at four locations on three continents with identical, self-developed machines.
• When properly constructed, the TECCO slope stabilization fundamentally remains maintenance free.
• In contrast to shotcrete, TECCO mesh prevents a dangerous and uncontrolled water pressure build-up.
• The TECCO system holds back later slope failures or breakouts.
• Laboratory tests and long term experiments under the most varied environmental conditions document that a very long lifespan is achieved, even in corrosive environments (coastal or volcanic regions) and in areas with intensive winter service (salt).
• Wilful destruction of the mesh is only possible with special tools because of the high-tensile wire quality.
  

The TECCO slope stabilization system is ideally combinable with reinforcements in road zones. Where an existing road requires widening on the valley-side or where deformations have occurred in the shoulder zone, the placing of concrete beams is frequently the most economical solution. At the same time the concrete rails can also carry forces from slope movements and direct them into the stable subsoil – via vertical micropiles arranged in pairs, combine with nails driven in with an upslope incline. To secure the slope below the road the upper boundary rope of the TECCO mesh is simply fixed to the concrete beam by eyebolts.

Competent, Project-specific Advice and Planning

• As our client you can make use of Geobrugg's know-how gained from numerous projects that we have carried out on all continents and with the most varied geologies.
• Our engineers will support you and your local planners with the dimensioning of the protective measure.
• We work with RUVOLUM, the TECCO specific dimensioning model that meanwhile has stood the test of hundreds of cases, in order to plan solutions that satisfy the existing risk situation and the topographical conditions.

Factors that convince the building contractor....
Thanks to well thought-out overall construction with light-weight components and just a few installation-friendly component parts, TECCO slope stabilizations can be installed with minimal effort and cost. The following points are decisive:

Higher contractor efficiency and optimized drilling works

• The slope must only be cleared of vegetation and levelled. No additional excavation work is necessary.
• Since the number of soil rocks or nails – in comparison to conventional meshes and rope nets – is optimized and the distances between them are correspondingly greater, the outlay for drilling work is directly.
• With the TECCO drilling aid you can drill directly through the TECCO mesh that has already been laid out. On one hand this affords a certain stabilization of the subsoil even before nailing (occupational protection for the installers). On the other hand this procedure also allows additional nails to be set later, as necessary.
  Simplest installation in shortest time
• With the well-illustrated installation instructions in the product manual, your construction unit will complete the installation with the few and simple components quickly and flawlessly.
• Each TECCO roll (30m X 3.5m) will cover a slope surface of 105m2 in one work step. Compared with conventional meshes this means significantly fewer seems of interfaces (reduced installation effort) and only the smallest overlapping area (minimal mesh loss).
• The mesh panels can be connected quickly and securely with the TECCO pressing tool and the TECCO compression claws.
• It’s no problem to shorten the TECCO rolls to the required measure or to sew them together, and the cuts can be reused, so that there is no waste material.
  

About “product liability”
Rockfall, slides, mudflows and avalanches are natural events and therefore cannot be calculated. This is why it is impossible to determine or guarantee absolute safety for persons and property with scientific methods. This means that to provide the protection we strive for, it is imperative to maintain and service protective systems regularly and appropriately. Moreover, the degree of protection can be diminished by events that exceed the absorption capacity of the system as calculated to good engineering practice, failure to use original parts or corrosion (i.e. from environmental pollution or other outside influences).

We develop and manufacture technologically mature protective systems from steel wire nets. These are now in use around the world. Our dynamic and static (barrier) systems provide tested protection against:

• Rockfall
• Avalanches
• Mudflows
• Slope instabilities
• They help to protect people and infrastructure from the forces of nature.

Rock Africa - TECCO® & SPIDER® Slope Stabilisation Systems