Double twisted hexagonal galvanized steel wire mesh baskets

Double twisted hexagonal galvanized steel wire mesh baskets

Gabions are metallic baskets made of double twisted metallic wire, with hexagonal meshes, manufactured according to the Directive 89/106/CEE, with Certificate of Factory Production Control. 

Gabions are filled with stones from the project site in order to produce flexible, permeable and monolithic structures, similar to the retaining walls and to serve as protection against erosion.

The dimensions of the galvanized gabions are presented in Table 1.

Specifications:

  • Tensile strength: the wire used to produce gabions has a tensile strength of 380-550 N/mm2, which exceeds the provisions of EN 10223-3, thus maximizing the strength of the end product. The dimensional tolerance is according to the EN 10218 (Class T1).
  • Elongation: shall not be smaller than 10%, according to EN 10223-3. The test shall be performed on a sample of minimum 25 cm length.  
  • Zinc coating: the minimum quantity of zinc is according to EN 10244-2.
  • Adhesion of zinc coating: the adhesion of the zinc coating to the wire shall be such that when the wire is wrapped six turns around a mandrel having four times the diameter of the wire, it does not flake or crack when rubbing it with the the bare fingers, in accordance with EN 10244.
  • The accelerated aging test of the exterior coating is performed in 28 cycles of condensation, in a wet SO2 environment according to EN ISO 6988.

The advantages of the double twisted gabions vs the classic ones:

Double twisted wire gabions

Classic gabions

The gabions made of double twisted wire with hexagonal mesh are in accordance with the European norms regarding the quality conditions necessary for the production and usage of gabions: EN 10223-3:2013 - Hexagonal steel wire mesh products and EN 10244:2009 - Non-ferrous metallic coatings on steel wire. The classical gabions, manufactured in site, are not in accordance with the European norms. 
The gabions made of double twisted wire are manufactured in accordance with the Directive 89/106/EEC, CPR – Construction Products 305/2011, EC certificate in accordance with ETA-09/0414 and have a Product Certificate.  
The gabions made of double twisted wire with hexagonal mesh prevent the meshes from unravelling, thus avoiding the deterioration of the gabions in case of an accidental cut during operation. The wire’s stretch resistance is of 380-550 N/mm2, and the mesh has a stretch resistance of minimum 50 kN/m, according to the requirements of norm EN 10223-3. The classical gabions, manufactured in site, are made of a simply twisted mesh, with high risk of mesh unravelling and gabion depletion. In this case, there are no specifications regarding the mechanical performances of the wire and the mesh.  
The structure of the gabions is reinforced due to the diaphragms internally positioned at a distance of maximum 1m, according to EN10223-3, thus creating confinement internal cells for the choke aggregates. All the panels of the gabions have frames which are reinforced with a wire of 3,4 mm diameter. The classical gabions do not have interior diaphragms and in case of an accidental cut the gabion can get entirely empty thus compromising the whole system.
All the components that form the double twisted wire gabions have a Class A anticorrosive treatment with Galfan (alloy 95%Zn+5%Al), minimum quantity of 245 gr/m² (for the wire with a 2,7 mm diameter), thus observing the requirements of the European norms EN 10223-3:2013 and EN 10244:2009.  The classical gabions have a PC steel frame which anticorrosive treatment cannot be tested according to the norms, and the mesh dost not have zinc coverage specifications, or a service time certified according to EN 10223-3. 
The frames of the double twisted wire gabions are made of 3.4 mm wire with anticorrosive protection class A (EN10223-3) with Galfan - 95%Zn+5% Al, minimum quantity of 265 gr/m². In this way the gabion has a resistant but also flexible structure, which allows the adaption to the morphology of the field in case of an excessive deformation of the support field. In the case of the classical gabions, manufactured in site, the exterior frame is made of welded PC bars which make the structure rigid. If the support field suffers deformations the stiffening elements have a tendency to break in the area of the welding points, which leads to excessive deformations of the gabion, thus the whole stability of the structure is lost.
The gabions with hexagonal mesh are tested according to the accelerated aging test, namely 28 cycles of discontinues exposures to Sulfur Dioxide (EN ISO 6988) and spraying with saline solution (EN ISO 9227) for 2.000 hours. In these conditions the products shall not present more than 5% rust (DBR - Dark Brown Rust). The classical gabions do not present this type of resistance and this leads to the impossibility of granting the safety in usage for the whole operation period of the structure.
The gabions are delivered preassembled and are ready for the immediate use. In this way the productivity is increased and the installation time is reduced.  The classical gabions need to be made in designated places in site and can only be transported in small quantities to the place where they need to be installed. 
The preassembled gabions made of double twisted wire with interior diaphragms can be shaped however needed according to the site necessities – observing the line of the tubular bridges, for the construction of convex or concave walls, for the introduction of guardrails / tubes in the interior of the structure of the gabion, etc. 

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