2546 Gabions and Mattresses

02 Nov.,2022

 

how to make gabion baskets

Section 2546. Gabions and Revet Mattresses.

2546.01 DESCRIPTION.
This work shall involve furnishing and placing compartmented, rectangular baskets made of woven wire, and filling the baskets with revetment stone. This specification covers materials and construction of baskets for Gabions and Revet Mattresses. The baskets shall be rectangular, variable in size, and manufactured either from:

a. Welded wire fabric meeting the requirements of ASTM a 974, Style 2, fabricated using uncoated steel wire conforming to ASTM A 853, with the fabric subsequently zinc coated by the hot dip process.

b. Double twisted hexagonal wire mesh meeting the requirements of ASTM A 975, Style 1 or Style 3, fabricated using soft temper galvanized steel wire, Class 3 coating, in accordance with ASTM A 641.

Gabions are intended for high strength installations in both horizontal and vertical structures. Revet Mattresses are intended for lower strength, horizontal or nearly horizontal structures. The work shall be done as shown in the contract documents and as specified herein. When specified, concrete grout shall be furnished, transported, and placed within the voids to the full width of the gabion basket without over consolidation.

2546.02 MATERIAL.
Materials used in construction of gabions and mattresses shall meet the following requirements. Baskets shall be fabricated as required for gabions, unless mattresses are specifically designated in the contract documents. At the Contractor's option, for lid fastening at edges and diaphragms, either the "Lacing Wire" or the " Steel Ring Fastener System" may be used.

A. Baskets.
Baskets shall be made of by twisting or welding a mesh from galvanized steel wire fabricated into hexagonal triple twist mesh units so bound as to prevent unraveling. For gabions, the mesh opening shall not exceed 4 1/2 inches (115 mm), and its area shall not exceed 8 10 square inches (5200 6450 mm2). For mattresses, the maximum linear dimension of mesh opening shall not exceed 3 1/4 inches (80 mm).

Twisted wire mesh for gabion baskets and revet mattresses shall be formed in a uniform hexagonal pattern with double twists so bound as to prevent unraveling. Welded wire mesh for gabion baskets shall have each connection welded to obtain a minimum average shear strength of 585 pounds (2600 N), with a minimum shear strength of 450 pounds (2000N). For revet mattresses, the minimum average shear strength of welded connections shall be 292 pounds (1300 N), with a minimum shear strength of 225 pounds (1000N).

1. Wire.
Wire shall be of the following minimum sizes:

  GABIONS MATTRESSES Mesh
Edges and selvage
Lacing and connecting 11 gauge (3.06 mm)
9 gauge (3.76 mm)
13 1/2 gauge (2.18 mm) 13 1/2 gauge (2.18 mm)
11 gauge (3.06 mm)
13 1/2 gauge (2.18 mm)

Wire for twisted wire mesh gabion baskets shall have a tensile strength of 60,000 psi to 875,000 psi (413.7 Mpa to 586517.1 MPa). Wire for twisted wire mesh revet mattresses shall have a tensile strength of 60,000 psi to 70,000 psi (413.7 MPa to 482.7 MPa). Wire for welded wire baskets and mattesses shall have a minimum tensile strength of 80,000 psi (550.0 MPa). Galvanizing shall be according to ASTM A 764 641, Class III 3, Type B Coating, except that all wire shall be coated with 0.80 ounce (244 g) of zinc per foot (square meter). Edge and selvage wire shall be made from the same material used for the wire mesh.

2. Steel Ring Fastener System.
The steel ring fasteners shall be made of either stainless steel or high tensile strength galvanized coated wire.

The galvanized 11 gauge (3.05 mm) wire shall have a tensile strength meeting the requirements of ASTM A 764, Class I Tensile, and Class III, Type B Coating and shall have a minimum of 0.80 ounce (244 g) of zinc per square foot (square meter).

The stainless steel 11 gauge (3.05 mm) wire shall be used only with PVC coated gabion baskets and mattresses, and shall have a tensile strength meeting the requirements of ASTM A 313, Type 302, Class I.

3. Basket Fabrication.
Baskets shall be fabricated as shown in the contract documents. Standard sizes are as follows:

GABIONS

Dimensions, ft. (m)* Number of Cells
or Compartments
Capacity
yd3 (m3)
Length Width Height 4.5 (1.4)
6 (1.8)
9 (2.7)
12 (3.6)
6 (1.8)
9 (2.7)
12 (3.6)
6 (1.8)
9 (2.7)
12 (3.6) 3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9) 3 (0.9)
3 (0.9)
3 (0.9)
3 (0.9)
1.5 (0.5)
1.5 (0.5)
1.5 (0.5)
1 (0.3)
1 (0.3)
1 (0.3) 1
2
3
4
2
3
4
2
3
4 1.5 (1.1)
2.0 (1.5)
3.0 (2.3)
4.0 (3.1)
1.0 (0.8)
1.5 (1.1)
2.0 (1.5)
0.66 (0.5)
1.0 (0.8)
1.33 (1.0) REVET MATTRESSES Dimensions, ft. (m)* Number of Cells
or Compartments
Capacity
yd3 (m3)
Length Width Height 9 (2.7)
12 (3.6)
9 (2.7)
12 (3.6)
9 (2.7)
12 (3.6) 6 (1.8)
6 (1.8)
6 (1.8)
6 (1.8)
6 (1.8)
6 (1.8) 0.50 (0.157)
0.50 (0.157)
0.75 (0.23)
0.75 (0.23)
1.0 (0.3)
1.0 (0.3) 3
4
3
4
3
4 1.00 (0.73) 6 (5.2)
1.33 (0.97) 8 (6.69)
6 (5.2)
8 (6.69)
6 (5.2)
8 (6.69) *Dimensions are subject to a tolerance of ±5%.

Baskets shall be fabricated into panels in such a manner that the base, sides, and ends can be assembled into a single, rectangular unit of the specified size. All perimeter edges of the baskets shall be selvaged with the specified wire so that the selvaged connections have the same strengths as the body of the mesh.

Baskets will normally be furnished in bundles of flat panels of appropriate sizes. On site assembly is intended.

The gabion units shall be furnished with the necessary diaphragms secured in proper position on the base, in a manner so that no additional tying at this juncture will be necessary.

The mattress units shall be subdivided into compartments 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 a manner that no additional tying at this junction will be necessary.

4. Elongation.
The wire mesh shall permit elongation equivalent to a minimum of 10% of the length of the section under test without reducing the gauge or tensile strength of the individual wire.

5. Elasticity.
A section of the mesh 6 feet (1.8 m) long and not less than 3 feet (0.9 m) wide, after first being subjected to the elongation test described above, shall withstand a load test of 6,000 pounds (26.7 kN) for gabions and 4,000 pounds (17.8 kN) for mattresses, applied to an area of 1 square foot (0.1 m2), approximately in the center of the section under test. The details of this test are as follows: An uncut section of mesh 6 feet (1.8 m) long, not less than 3 feet (1 m) wide, and including all selvage binding, shall have the ends securely clamped for 3 feet (1 m) along the width of the sample. When the width of the sample under test exceeds 3 feet (1 m), the clamps will be placed in the middle portion of the width, and the excess width will be allowed to fall free on each side of the clamped section. The sample shall then be subjected to sufficient tension to cause 10% elongation of the sample section between the clamps. After elongation and while clamped as described above (and otherwise unsupported), the section shall be subjected to a load applied to an area of 1 square foot (0.1 m2), located approximately in the center of the sample section between the clamps, and in a direction perpendicular to the direction of the tension force. The sample shall withstand, without rupture of any wire or opening of any mesh fastening, an actual load, so applied, equaling or exceeding 6,000 pounds (26.7 kN) for gabions and 4,000 pounds (17.8 kN) for mattresses. The ram head used in the test shall be circular with its edges beveled or rounded to prevent cutting of the wires.

6. Certification.
The manufacturer may be required to furnish test results, which show compliance with elongation and elasticity requirements, as a condition of source approval.

Each shipment of wire structures to a job site shall be accompanied by a certification which states that the material meets the requirements of this specification. A shipment shall consist of all materials arriving at the job site at substantially the same time.

All certifications shall be signed by an authorized representative of the company.

B. Anchor Stakes.
Anchor stakes shall be 2 inch (50 mm), nominal diameter, galvanized, standard weight pipe meeting requirements of ASTM A 53. The length will be shown in the contract documents.

C. Engineering Fabric.
Engineering fabric shall meet requirements of Article 4196.01, C.

D. Revetment Stone.
Revetment stone for filling baskets shall be broken stone or gravel boulders meeting the following requirements. All stone and boulders for the project shall be from one source or from sources similar in geological origin.

1. Durability.
Unless otherwise specified, the stone shall be taken from a source which does not exceed 10%, when subjected to the freezing and thawing test, Laboratory Test Method 211, Method A.

2. Abrasion.
The stone shall be taken from a source which does not exceed 45%, when tested in accord with AASHTO T 96, Grading A or B.

3. Size.
Unless otherwise specified, the stone or boulders for gabions and mattresses shall be processed so that the sizes range from 4 inches to 8 inches (100 mm to 200 mm) in nominal dimensions, and 3 inches to 5 inches (76.0 mm to 127 mm) is recommended for mattresses.

Stone sizes shall be inspected visually by a certified aggregate technician.

E. Grout.
Article 2507.02, B, shall apply.

2546.03 CONSTRUCTION.
The area shall be excavated and/or smoothed, as necessary for proper placement of the gabions or mattresses, as shown in the contract documents. The contract documents may also require compaction of the prepared surface, or placement of selected or special backfill material in preparing the surface.

When designated in the contract documents, engineering fabric shall be placed under and behind the baskets. The fabric shall be placed in vertical strips, or transverse to the flow line, lapped at least 3 inches (75 mm) with the downstream strip to the outside of the structure.

The baskets shall be assembled at the construction site into rectangular baskets of the specified sizes. They shall be of single unit construction; the base, lid, and sides shall be woven into a single unit, and the ends shall be connected to the base section, in a manner so that strength and flexibility at the point of connection is at least equal to that of the mesh.

The baskets shall be carefully placed into their proper positions, for slope and alignment as shown in the contract documents. When the slope is not shown, the faces of gabions shall be sloped 1 (horizontal) to 6 (vertical).

When designated for mattresses, anchor stakes shall be driven into position, as shown in the contract documents. The top of the anchor stake should be at the elevation of the tops of adjacent baskets. The anchor stakes shall be securely tied to adjacent baskets at the top and the base of the baskets.

Adjacent baskets shall be connected in a manner so that the connection is strong enough that a failure will occur in the mesh, rather than the lacing. Adjoining gabions and mattresses are to be connected at vertical corner edges and diaphragms. Stacked gabions are to be also connected at the horizontal edges, front and back. All connections shall be laced with loops at approximate 4 inch (100 mm) intervals, and as recommended by the manufacturer. Gabions 3 feet (0.9 m) high placed in a line shall be tensioned with a come-along or other means during filling to achieve proper alignment.

Each basket shall be carefully filled with the revetment stone specified. Machine placement will be permitted. However, considerable handwork is necessary and will be required to assure orientation for maximum density without bulges, a compact and dense exposed face, and maximum aggregate contact with the lid and other baskets placed or to be placed in the structure.

Gabions 3 feet (0.9 m) high shall be filled in three lifts, 1 foot (300 mm) at a time, orienting the stones with each lift as necessary.

When a 3 foot (0.9 m) high cell is to be exposed in the finished structure, two connecting wires shall be securely installed between each lift, connecting each cell face to be exposed with the opposite face or diaphragm. The wires shall be located with equal horizontal spacing. The wires shall be installed by looping each end around two mesh openings, then wrapping the wire tightly around itself with at least four full wraps. The end of the wire shall be locked in place by lacing it under the previous lap. (For each 3 foot (0.9 m) high cell with one face to be exposed, four connecting wires are required. For the same cell as an end unit, there are two exposed faces and eight connecting wires are required.)

Connecting wires are not required for mattresses.

The lids shall be fastened in place at edges and diaphragms as specified above.

If steel ring fasteners are used, spacing shall not exceed nominal 5 inches (±1.0 inch) (125 mm (± 25 mm)).

Special features or details may also be required. These shall be constructed as shown in the contract documents.

When specified, grout shall not be placed until the gabion has been inspected and approved by the Engineer. Sufficient jarring of rocks may be done to aid penetration of the grout so that all voids shall be filled and the grout fully penetrates the basket. Placement of grout shall meet the requirements of Article 2507.03, G.

When the structure is completed, the earthwork shall be finished as shown in the contract documents.

2546.04 METHOD OF MEASUREMENT.

A. Gabions or Mattresses.
The Engineer will calculate the volume of gabions or mattresses, satisfactorily placed. When placement is according to the contract documents, plan quantities shall be used.

When anchor stakes are required for mattresses, the Engineer will count the anchor stakes placed.

Associated earthwork will be measured according to Article 2402.12 or Article 2102.13.

B. Concrete Grout for Gabions.
Article 2507.04 shall apply.

2546.05 BASIS OF PAYMENT.

A. Gabions or Mattresses.
For the number of cubic yards (cubic meters) of gabions or mattresses placed, the Contractor will be paid the contract price per cubic yard (cubic meter). This payment shall be full compensation for furnishing and placing engineering fabric as shown in the contract documents, for furnishing, assembling, and placing the baskets, and for furnishing and placing the revetment stone in the baskets.

For the number of anchor stakes placed, the Contractor will be paid the contract price for each.

Special features or details will be paid for as shown in the contract documents; they may be made incidental, with no separate payment.

B. Concrete Grout for Gabions.
Article 2507.05 shall apply.

The Contractor will be paid for associated earthwork in accordance with Article 2402.13 or Article 2102.14. For small quantities, the contract documents may designate this work as incidental; and will not be paid for separately.

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