GENERAL INFORMATION about the anchoring/attaching of netting.
The method for anchoring/attaching the rockfall protection netting should be determined on the basis of the on-site conditions, the rock quality and whether it should function purely as rockfall protection or if it should function as ice netting.
- Anchor bolts should be galvanized and powder-coated. M 16 or M 20
- For netting purely for rockfall protection in good rock, M 16 0.6 – 0.8 m long re-bar bolts anchored with polyester cartridges can be used.
- Where the netting is going to function as ice netting, M 20 0.8, 1.2 or 1.5 m bolts should be used. The bolts can be installed with polyester cartridges. In some cases it will be necessary to use longer bolts in order to be able to attach the net as vertically as possible.
- Fastening bolts with extra netting washers can be used as anchors where this is appropriate. The washers must then have a 20 or 25 mm hole to fit the M 20 M or 24 mm fastening bolt.
- Rockfall protection netting used as ice netting requires that the netting is attached 20-25 cm out from the rock face using 2 nuts and 2 washers. The netting must be attached as vertically as possible so that the water freezes and hangs in the netting.
- The bolt frequency should be around approx. 1 bolt per 4-6 m2 for rockfall protection netting in good rock and approx. 1 bolt per 4 m2 in poorer rock and where the netting is to function as ice netting. In some cases it will be necessary to supplement this with additional bolts. Normally bolt patterns are 2×2 or 3×3 and 1 in the middle. The latter provides automatic switching in the height of the bolts, which is preferable. Both patterns give approx. 1 bolt per 4 m2. which is a requirement from the Norwegian Public Roads Administration.
- The number of fixing bolts for the netting is then easy to find by taking the area of the netting and dividing it by 4, i.e 1,000 m2 of netting requires 250 fixing bolts.
Attaching at the top and bottom.
- Attachment at the top and bottom can be done either with top and bottom wire rope (10 mm) or with ties/rock ties. Mounted on M 20, 0.8, 1.2 or 1.5 m long fastening bolts with eye nuts or washers. The ties should be galvanized and powder-coated. Where desired, the top wire can be slightly raised so that that the netting captures stones etc. comings from above. Or it can be attached right down to the ground. This will be determined by the local conditions.
- The netting can also be attached only with washers at the bottom if desired. The distance between the bottom bolts that need to be set in a line should not exceed 1.5 meters.
Sewing/joining of netting at the seams
- The netting can be sewn with wire 2.2 / 3.2 mm galfan, galfan/PVC or black PA6 thread for PA6 netting.
- Or it can be joined with hog rings and a special pneumatic machine. This is currently the most common method.
- The data sheet shows the recommended distances for sewing wire and hog rings.
- The manufacturer’s recommendation is that when netting is sewn together side by side, the wire must be thicker than the wire of the netting itself See the data sheet.
What kind of netting should you use?
- For occupational safety and where the useful life of the net is not of the utmost importance, use galvanized mesh.
- In cases where useful life has greater importance, galmac (galfan) / PVC netting should be used.
- In cases where useful life is very important, such for road construction where a long-useful life is a requirement, Galmac (galfan) coated with black PA6 plastic should be used. This gives a useful life that meets what is expected by the Norwegian Public Roads Administration.
- Where the netting is intended to hold considerable weights of ice, the use of wire reinforced netting should be considered. Steelgrid has several versions, also with full PVC coating of the wires and ropes. Wire rope netting / HEA – Panels can also be used in combination with rockfall protection netting. If necessary, this netting is also available with full PVC coating when ordering larger quantities.