Critical boulders or layers of stratified rock that cannot be cleared without posing a significant risk to people or infrastructure often have to be secured on excessively steep rock slopes. Ordinary cable nets have often been used for this task so far. The sides of the square or rectangular panels were typically 3 to 4 meters long. A fixed nail pattern was the result. Moreover, the resistance to local force transmission and to corrosion was limited. With the development of an innovative spiral rope net, combined with corresponding system spike plates, the transmission of force and the protection from corrosion have been significantly improved. It is also possible now to arrange the nails independently of the netting size, so that project-specific requirements can be perfectly met. The design of the innovative rock protection system is based on the results of field tests, model experiments, on standard tensile tests, and on tests to determine the local force transmission. The examples listed indicate the application areas for this new generation of flexible rock protection system.
The potential risk from rockfall and small-scale instabilities is increasing. One of the reasons is that environmental influences are becoming constantly more extreme. Another reason is probably also the fact that new infrastructure construction must be adapted to increasingly difficult geological formations or that existing construction has to be adjusted to the changing traffic situation or population development. In response to this, new methods, technologies and systems are being developed to offer economic solutions that are adapted to the situation. Critical blocks or rock masses must often be secured in overhanging rock faces, which it is not possible to clear without significant risk to people or infrastructure. Up to now, traditional wire rope nets made from stranded ropes have with a diameter of normally 8 – 10 mm, joined at the crossing points with cross clamps or wire coils been used for this purpose (see Figure 1). Sometimes a thicker rope running along the periphery is used to strengthen the boundary zone. A representative example of this system is the PENT FIX® system. When these are used as active protection, these square or rectangular panels require a fixed pattern for the securing points. In addition, their resistance to selective effects and their protection against corrosion is limited. This renders project specific adaptation and optimizing of the nailing difficult. Originally such systems were used for protecting creeping slopes. Deformation of the protection system was taken for granted. The development of a new kind of spiral rope net enables a significant improvement in load transmission, handling during installation and corrosion protection. There is therefore no longer any need for time-consuming stitching of the panels together. With this protection system, the nails can be arranged irrespective of the size of the net and thus adapted to the specific requirements of the project in an optimal way. The new spiral rope net is also ideally suited for drape systems for passive rock slope protection.
