Flexible rope nets have been used in alpine regions for some decades for protecting rock slopes against unstable boulders or critical rock masses. The configuration of the protection measure was often based on the years' of experience of individual specialists. There was a lack of adequate dimensioning concepts or extremely simplified models were used. To better understand the supporting behavior of flexible rope nets and their interaction with nails or extruded piles, to thoroughly analyze the force distribution and investigate the influence of dynamic influences, comprehensive large scale field tests were carried out in Felsberg near Chur, Switzerland. This paper summarizes the information gained and conclusions drawn for the practical application of flexible rope nets anchored by nails or rock anchors.
Flexible rope net systems frequently open up interesting and cost effective application possibilities. Often used in the past or still in use are square or rectangular nets of stranded ropes with a diameter of normally 8–10 mm, joined at the crossing points with cross clamps or wire coils. Sometimes a thicker rope running along the periphery is used to strengthen the boundary zone. A representative example of this system is the PENTIFIX® system. The nail pattern is determined by the size and geometry of the panels. This renders project specific adaptation and optimizing of the nailing difficult. Moreover the manufacturing process was optimized to the degree that nets can now be produced on machines in rolls. This has decisively influenced the application: Previously the panels were separately installed and fixed to nails distributed in the corner zone of the net. Now 3.5m wide nets can be placed rationally and flatly in rolls up to a length of 20 m. These are force-locked together at the sides by shackles, with minimum slip.