Rev. 9-1-95
GABION REVET MATTRESS
616-R-102
DESCRIPTION. This work shall consist
of open mesh wire mattresses assembled, tied, and filled with
approved aggregates, and constructed in accordance with these
specifications and placed in conformance with the lines, grades,
and dimensions shown on the plans or as otherwise directed.
MATERIALS. The revet mattress shall
be made of hexagonal triple twist mesh with heavily galvanized
steel wire.
(a) DIMENSIONS. Wire mattress unites
shall be supplied as shown on the plans. All mattress units
furnished by the manufacturer shall be of uniform width and
subject to a tolerance of " 3 percent.
(b) FABRICATION. Wire mattress units
shall be fabricated in such a manner that the base, sides, and
ends can be assembled at the construction site into a rectangular
unit of the specified size. The body of the mattress units shall
be of single unit construction. The base ends and sides shall be
formed of a single woven mesh unit. The top shall be a separate
woven unit of the same mesh and wire specification as the body.
The mattress units shall be
subdivided into compartments, 610 mm (2 ft) long, extending over
their full width by the insertion of diaphragms made of the same
mesh as the rest of the mattress. The diaphragms shall be factory
secured in proper position at the base with a continuous spiral
wire, in such manner that additional typing at this junction is
not necessary.
All perimeter edges of the mesh
forming the mattress unit shall be securely selvedged so that the
joints formed by typing the selvedges have a least the same
strength as the body of the mesh.
Lacing wire shall be supplied in
sufficient quantity such that all sides, ends, and diaphragms of
the body. The lacing wire shall be in accordance with the same
specifications as the wire specified for the mesh.
The wire incorporated into the mesh
constituting the body of the mattress and the lacing wire shall
be made of galvanized steel wire having a nominal diameter of 22
mm (0.0866 in.). The nominal diameter of the mesh wire shall be
22 mm (0.0866 in.). The nominal diameter of the selvedge wire
shall be 27 mm (0.1063 in.). A separate unit shall be fabricated
for the top which shall be of the same wire quality and diameter
as the body for its corresponding constituent parts.
The tensile strength of the wire
shall be in the range of 414 to 552 MPa (60,000 to 80,000 psi).
The minimum zinc coating of the wire shall be 20 g/m5 (0.70 oz/
sft.) of uncoated wire surface as determined by tests conducted
in accordance with Federal Specifications QQ-W-461H, Class 3. The
maximum linear dimension of the mesh opening shall not exceed 86
mm (3 1/4 in.) and the area of the mesh opening shall not exceed
3870 mm5 (6 in.5).
c) ELONGATION. The wire mesh shall
permit elongation equivalent to a minimum of 10 percent of the
length of the section under test without reducing the gauge or
tensile strength of individual wire.
(d) LOAD TEST. An uncut section of
the mesh of not less than 1830 mm (6 ft) long and not less than
920 mm (3 ft) wide, after first being subjected to the elongation
test described above, shall withstand a load test of 200 kN/m5
(4,000 lbs/sft) applied to an area located approximately in the
center of the section under test. The details of the test are as
follows.
An uncut section of mesh 1830 mm (6
ft) long, not less than 920 mm (3 ft) wide and including all
selvedge bindings shall have the ends securely clamped for 920 mm
(3 ft) along the width of the sample. When the width of the
section under test exceeds 920 mm (3 ft), the clamps shall be
placed in the middle portion of the width and the excess width
shall be allowed to fall free on each side of the clamped
section. The sample shall then be subjected to sufficient tension
to cause 10 percent elongation of the sample section between the
clamps as described above. The unsupported section shall be
subjected to a load applied to an area of 0.09m5 (1 sq ft)
located in the approximate center of the section between the
clamps and in such a direction perpendicular to the direction of
the tensile force. The sample shall withstand, without rupture of
the wire or opening of mesh fastening, an actual load so applied
equaling or exceeding 18kN (4,000 lbs). The ram head used in the
test shall be circular with its edges beveled or rounded to
prevent cutting of the wires.
(e) SINGLE WIRE CUT. The wire mesh
shall be fabricated in such manner as to be non-ravelling. This
is defined as the ability of the mesh to resist pulling apart at
the twists or connections forming the mesh when a single wire in
a section of mesh is cut and the section of mesh then subjected
to the load test described above.
(f) ZINC COATING AND TENSILE
STRENGTH. The tests shall be conducted in accordance with Federal
Specifications QQ-W461H, Class 3.
(g) CERTIFICATION. A type C
certification in accordance with 915 will be required for the
revet mattress.
(h) AGGREGATE. The wire mesh mattress
shall be filled with clean, hard, riprap type stone of minimum
size of 80 mm (3 in.) and maximum size of 150 mm (6 in.). Both
stone measurements shall be made in the greatest dimension.
CONSTRUCTION REQUIREMENTS. The revet
mattress bases shall be supplied folded flat, placed in bundles.
Lids shall be delivered in separate bundles. Single mattress
bases shall be removed from the bundle, unfolded flat on the
ground, and all kinks and bends flattened.
The mattress shall then be assembled
individually, by erecting the sides, ends, and diaphragms,
ensuring that all creases are in the correct position and the
tops of all sides level, all in accordance with the
manufacturer's recommendations.
The four corners of the mattress
shall be laced first, after overlapping the mesh, followed by
lacing the edges of the internal diaphragms to the sides.
The lacing procedure shall consist of
cutting a length of lacing wire of approximately 1 1/2 times the
distance to be laced. This distance shall not exceed 1525 mm (5
ft). The wire terminal shall be secured at the corner by looping
and twisting, then laced with alternating single and double loops
at approximately 100 to 130 mm (4 to 5 in.) intervals.
The assembled mattresses shall be
carried to the project site and placed in their proper location.
For structural integrity, all adjoining empty mattresses shall be
laced along the perimeter of their contact surfaces in order to
obtain a monolithic structure.
The mattress units shall be filled
with stone to assure good alignment and to avoid bulging of the
mesh with a minimum of voids between stones. After the units have
been filled, the lids shall be placed so that they meet the sides
and end of the mattresses. The lids shall then be secured to the
sides and ends with lacing wire in the manner described above for
assembling.
When a complete mattress unit cannot
be installed because of space limitation, the unit shall be cut
to fit in the manner shown on the plans.
METHOD OF MEASUREMENT. Riprap quality
stone required to fill the wire mesh cages that form the gabion
revet mattress will be measured by the cubic meter (cubic yard)
in accordance with the dimensions shown on the plans or as
directed, complete in place and accepted.
BASIS OF PAYMENT. The accepted
quantities of riprap quality stone, measured as set out above,
will be paid for at the contract unit price per cubic meter
(cubic yard) for gabions. The costs of all materials, labor, and
equipment necessary to complete the work including the wire mesh
cages and installation hardware for gabion revet mattresses shall
be included in the cost of this work.