Highway 1 – protective netting
Slope Protection with Rockfall and Energy Absorber Netting
Highway 1 in the Shoresh-Hemed Section
Pamco Engineering, Ltd. executed slope protection works and installed energy absorber netting as part of the widening works performed along Highway 1 in the section between the Shoresh Interchange and the Hemed Interchange constructed by the main contractor Gili & Yoel Azaria Ltd.
The road widening works are characterized by the presence of two types of slopes that require the application of various protection solutions.
Protection for cut slopes was applied from top to bottom in which galvanized rockfall netting was installed that was anchored with bolts and cables.
Slopes north and south of Highway 1 are characterized by unique natural vegetation and springs. Cutting works, including the removal of loose rocks, were prohibited in order to preserve these natural assets. The concern for rockfall from these slopes that may impact traffic on the highway mandated the application of a protection solution at the bottom of the slope without impacting or anchoring to the slope itself. The method chosen was with the use of a rock fall barrier manufactured by Trumer Schutzbauten GmbH and Rud Barriertech GmbH.
Description of the protective measures
Rockfall barrier with double twisted wire mesh:
Use was made of a rockfall protective mesh manufactured by the
French company Avaroc. This mesh is comprised of double twisted
steel wires coated with Galfan zinc and aluminum anti-corrosion
coating. The mesh was tested in accordance with the requirements of
the European NF EN 10223 standard. Mesh opening size is 80 x 100
mm with 3 mm thick wire. A technical product sheet is attached.
Basic construction details are also attached.
Rock fall barrier energy absorber netting:
TSC-100-oA model netting that absorbs energy at a rate of up to 100
kJ and TS-300-oA model netting that absorbs energy at a rate of up to
300 kJ, both which are manufactured by Trumer Schutzbauten GmbH.
These meshes comply with the most stringent European standards:
ONR 24810 – Austrian standard for Technical protection
ETAG 27 – European Technical Approval Guideline of Falling
Rock Protection Kits).
Netting was installed at heights of 2 m, 3 m and 4 m as planned. The
system installed is a flexible system that does not need anchoring
of any type to the slope. The system consists of Omega type netting
with the ability to elongate to as much as 4 m when deployed between
cantilevered poles anchored into concrete bases. Moments and lateral
forces are absorbed with drilled and grouted GEWI bolts. Each
netting segment has an energy absorber element in the form of a
massive metal spring that enters into action after the absorption
capability of the netting itself is fully exhausted. A basic cross–
section is attached.
Rockfall protective netting with double twisted wire mesh The design is based on a specification issued by the soils consultant Eng. Ilan Birnbaum. The design is based on limiting the height of berms to 9 m, top anchoring with the use of GEWI bolts every 4 m, bottom anchoring and a system of crossing cables. The netting was installed as the rock cutting advanced from above to below. A site inspection was held with the participation of Geologist Moshe Yarkoni upon completion the of each cut berm. In critical locations where local faults or particularly jointed rock was identified, additional anchoring bolts were drilled to a depth of as much as 5 m and the netting was installed more densely.
Rock fall barrier energy absorber netting
Geometric constraints were encountered stemming from the
A site inspection was held with the participation of Geologist
Rock parameters were obtained from the foundations
Hazardous cross-sections were identified based on these
Simulations were run for various slope cross-sections with the roadway cross-section, which mandated siting of the fence relatively close to the toe of the slope while leaving a safety margin between the slope and the metal railing that enabled extension of the netting. Moshe Yarkoni and a geologist representing the netting manufacturer in order to determine the size of the boulders that might dislodge from the slope and fall onto Highway 1. Characterization of rock size constituted the most important parameter when running simulations of dislodgment of the rocks and their falling toward the netting. consultant Eng. Ilan Birnbaum. simulations. The various cross-sections were obtained as a built-in product of a laser survey of the slopes performed by the Mabat 3D company.
use of GeoRock2D software developed by GeoStru for purpose of running simulations using the Colorado Rockfall Simulation Program (CRSP) model. The simulations included the study of extreme conditions of dislodgment of an isolated 0.75 m³ block or 3 blocks each having dimensions of 0.45 x 0.45 x 0.45 m. The two simulations made it possible to examine differing kinetic energy conditions as well as variations in monitoring height that dictated the height of the netting. A netting simulation at Cross-section 518+1.46 is attached.
Stages of installation:
Marking of the fence alignment by a surveyor and marking of the centers of the bases.
Drilling of anchoring bolts with the use of a drilling template that minimizes deviations to the greatest possible extent. Three
anchoring bolts are drilled in each base to depths of as much as 5 m. Due to their tight spacing, all of the foundations bolts cannot be drilled at the same time. Two opposing bolts are drilled and grouted and the third bolt is completed thereafter.
Grouting is then performed from the bottom of the borehole upward. In order to maintain the location of the bars, a special grouting template has been prepared that holds the bolts in place during grouting.
Supplementary drilling and grouting of the third bolt is then performed in each base.
Excavations are then performed for purposes of constructing a concrete base.
The concrete base is then cast.
Bolts are then drilled diagonally for purposes of stabilizing the netting sections and connecting with the energy absorber components.
The netting poles are then assembled on the bases and the base plate is locked with nuts.
The netting is then assembled, and the upper and lower cables and the intermediary cables in the high netting are tensioned. The cables are tensioned using Tirfor manual hoists to connect the energy absorber components.
Supplementing rockfall netting is then added that covers the system at the sides of the slope to prevent the passage of small stone blocks.