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Gabion Mattresses for Flood Protection Embankment

Triple Twisted Hexagonal Mesh Gabion Mattresses are mostly used in projects of Flood Embankment and intake works. Gabions types are boxes and mattresses. Aerct supplies quality gabions system for flood protection, with detailed requirements for the gabion wire, mesh fabric, filter fabric, stones and construction of gabions work as following.

Joining of Gabions by Tie Wire
The correct joining of separate gabion mattresses with triple twist every two meshes

Mesh Materials Forming Gabions
Hexagonal Triple Twisted Wire Mesh Details

Gabion Mattresses for Stones Filling
Gabion Mattresses to be filled with stones of 75 to 200mm

Technical Requirements of Gabion Mattresses:

1. Wire Fabric for Gabions

All wire used in the fabrication of gabions (including selvage wire and lacing wire) and in the wiring operating during construction (including tie wire) shall be annealed mild steel wire, having an average strength of 38-50 kg/mm2. Wire thicknesses are as given below.

Gabion type Wire Size
(mm)
Mesh Size
(mm)
Box gabions 2.7 80*100
Mattresses 2.2 60*80
Lacing Wire 2.2 150
Selvedge wire(boxes) 3.4  
Selvedge wire(mattress) 2.7 200

All wire shall be galvanized meeting international standard of "Galvanized Coatings on Wire".
The minimum weight of the zinc coating shall be according to the figures shown in the table below:

Nominal Diameter of wire
(mm)
Minimum weight of
coating
(gr/mm2)
2.2 240
2.7 260
3.4 275

The adhesion of the zinc coating to the wire should be such that, when the wire is wrapped
six turns round a mandrel of 4 times the diameter of the wire, it does not flake or crack to
such an extent that any flakes of zinc can be removed by rubbing with the bare fingers.

Wire mesh fabric shall be hexagonal triple twist mesh. The tightness of the twisted joints shall
be such that a force of not less than 1.7kN is required to pull on one wire to separate it
from the other wire provided that each wire is prevented from turning and the whole
process is done in one plane. Ultimate failure load in the direction of the weave will be
about 43 kN/metre length. Longitudinal elongation of mesh will not exceed 10%.

Joining of Gabion Boxes and Mattresses and edge treatment:
The mesh cages shall be subdivided into cells by wire-mesh diaphragms with a maximum
dimension of 1.0 m for boxes, and 2 x 0.6 m for mattresses.

All edges of gabions, diaphragms and end panels shall be selvedged in such a way as to
prevent raveling of the mesh and to develop the full strength of the mesh. The amount of

lacing wire should be approximately 5% of the gabion weight.

The gabion mesh shall be cut, folded and wired together to form joints, angles, curves or slopes which are not possible to obtain in the structures with the standard rectangular gabions, the mesh must be cleanly cut, and the surplus mesh cut completely out, or folded back or on to, and neatly wired to an adjacent gabion face. The cut edges of the mesh shall be securely laced together with binding wire.

2. Filter Fabric for Gabion Mattresses Embankment Works

Gabions and mattresses should be laid on a filter fabric.
The filter fabric shall be of a non-woven melted fabric consisting of a mixture of
polypropylene and polythene or other similar materials. The fabric shall be resistant to ultra
violet rays and sunlight.
Where overlapping of fabric is required, the overlap shall not be less than 500 mm and
shall be sewn with a lock type stitch in such a manner that it produce a joint as durable as
the fabric.
The grade of fabric shall weigh not less than 350 gr/m2 and have a thickness of 0.5 mm.
Tensile strength shall be not less than 2kN/m. Permeability (ViH50) shall be not less than
60l/s*m2.
Storage and handling of the fabric in no case shall be the geotextile be exposed to direct
sunlight, ultra violet rays, temperature greater than 60o C, mud, dirt, dust and debris, to
the extent that its strength, toughness or permeability characteristics are diminished.
In some cases it will be necessary to cut back the fine sand layer in the bank to a depth of

20 cm and replace with as-dug river gravel.

3. Stones for Gabions

Stone used for gabions and gabion mattresses shall be clean, natural, hard and durable
with a minimum density of 2,650 kg/m3. Stone shall be well graded within the following
limits, but at least 85% by weight of the rock fragments shall have a size equal to or larger than 100 mm. No rock shall be capable of passing through the mesh.

Gabion type Minimum
dimension
(mm)
Maximum
dimension
(mm)
Box gabions 100 250
170 mm mattress 75 120
230 mm mattress 75 150
300 mm mattress 75 200
500 mm mattress 75 200

Stone shall preferably be rounded rather than angular.

4. Method of Construction

a. Gabions and gabion mattresses shall have internal diaphragms of the same mesh as
the enclosing fabric.

b. Gabion shall be installed in a workmanlike manner, the gabion shall be placed on smooth surface, final line and grade shall be approved by engineer.

c. Rock pieces shall be generally uniformly graded from 75mm to 200mm for mattresses, 100mm to 200mm for gabion box.