for Highway Construction Page 701 of 71 5 SECTION 715 – GABION AND REVET MATTRESS
715.01 Mesh .
Fabricate gabion panels for the base, ends, sides, diaphragms, and lids from welded or twisted wire mesh . Use only 1 type of wire mesh within a structure. Meet the requirements in Table 715.01- 1 below for individual wires of welded or twisted mesh: Table 715 .01-1 – Wire Criteria Characteristic Test Designation Requirements Minimum Tensile Strength ASTM A 370 60,000 psi Wire Size Wire Diameter Minimum Galvanizing US Steel Wire Gauge ASTM A 641 and ASTM A 90 11 0.120 in 0.116 in 0.80 oz/ft2 Wire Size Wire Diameter Minimum Galvanizing US Steel Wire Gauge ASTM A641 and ASTM A 90 9 0.148 in 0.144 in 0.90 oz/ft2 Provide welded wire mesh that meets ASTM A185, except 600 pounds force for 11 -gauge and 800 pounds force for 9- gauge wires on the weld shears. Wire gauges are United States Steel Wire Gauge (USSWG) after galvanizing. Manufacture gabion panels of the welded wire mesh from 11 -gauge or 9- gauge wire. Provide mesh to form a nominal 3 inch by 3 inch square grid pattern made by resistance welding in accordance with ASTM A185. Ensure the maximum diagonal dimension of a grid opening is 4.75 inches. Manufacture gabion panels of twisted wire mesh from 11 -gauge wire with 9 -gauge selvedge wires. Form a uniform hexagonal pattern and with a nonraveling twist. Do not exceed 4.75 inches on the major axis (maximum line dimension) of hexagonal openings.
715.02 Fabrication.
Fabricate gabions so the sides, ends, lids, and diaphragms can be assembled at the project site into a rectangular or square basket of required sizes. Construct gabions as a single unit. Weave the base, ends, and sides into a single unit or 1 edge of these members connected to the base section of the gabion so strength and flexibility at the point of connection is at least equal to that of the mesh . Where the length of the gabion exceeds its horizontal width, equally divide the gabion by diaphragms, of the same mesh and gauge as the body of the gabion, into cells whose length does not exceed the horizontal width. Provide the gabion with the necessary diaphragms secured in proper position on the base section so additional tying at this juncture will not be necessary. Securely selvedge or bound perimeter edges so the joints formed by tying the selvedges have the same strength as the body of the mesh. for Highway Construction Page 702 of 71 5 715.03 Packag ing and Marking. Ship gabions folded flat in bundles weighing less than 1,200 pounds. Ensure each bundle contains gabions of 1 size except odd numbers necessary to complete an order may be made into a bundle of less than the uniform number. Clearly mark this bundle to distinguish it from others. Clearly mark each gabion by color code or some other readily identifiable means to show size. Handle bundles without lifting the gabion mesh to avoid damage to wire or galvanizing. Provide copies of original wire tags that show size and heat number . The Engineer will reject delivered gabions that cannot be identified by heat number .
715.04 Dimensions.
Provide gabion meshes with the specified dimensions. The dimensions are subject to a tolerance limit of plus or minus 5 percent of manufacturer’s stated sizes.
715.05 Joints .
Provide wires used to form joints in accordance with ASTM A641 for zinc -coated (galvanized) carbon steel wire and that meet the requirements in Table 715.05- 2. Table 715.05 -2 – Wire Criteria Characteristic Test Designation Requirements Minimum Tensile Strength ASTM A370 60,000 psi Wire Size Wire Diameter Minimum Galvanizing US Steel Wire Gauge ASTM A641 and ASTM A 90 13.5 0.086 in 0.083 in 0.72 oz/ft2 Wire Size Wire Diameter Minimum Galvanizing US Steel Wire Gauge ASTM A 641 and ASTM A 90 9 0.148 in 0.144 in 0.90 oz/ft2 Ensure spiral binders have a 3 inch separation between continuous, successive loops. Provide internal connecting wires or preformed stiffeners with at least 13.5- gauge. Meet the minimum specification requirements with each wire. Alternate fasteners may be used if approved. Alternative fasteners must form a closed loop with an overlap of at least 1 inch when the ends are brought together and properly closed. Ensure the closed loop has an inside area that is large enough to enclose up to 4 selvedge wires. Provide fasteners that meet ASTM A764, with the same weight of coating in accordance with ASTM A641. Provide stainless steel that meets ASTM A313 for applications involving PVC -coated gabion baskets . Ensure the fastener resists a direct tension force across any axis of at least 600 pounds force while remaining closed. Submit random samples of fasteners for testing at least 10 business days before construction of gabions. Submit 12 formed and 12 unformed fasteners. Assemble the 12 formed fasteners at the project site and witnessed by the Engineer. Space fasteners at intervals of 4 to 6 inches with at least 1 fastener per gabion mesh opening. for Highway Construction Page 703 of 71 5 715.06 Gabion Fill Material . The fill material for the gabion baskets is rock ranging in size from at least 4 inches to a maximum of 8 inches, both measured in the greatest dimension. Provide rock that is sound, durable, well graded, and does not disintegrate on exposure to water or weathering during the life of the structure. Obtain rock for gabions from an approved source. Ensure the minimum unit weight of a rock -filled gabion is 110 pounds per cubic foot. Verify the gabion unit weight when directed.
715.07 Geotextile.
Meet the requirements of 718.06.
715.08 Testing.
When directed, test gabions that have not been previously tested and approved as follows:
1.Cubical -Celled Gabions. Test wire mesh of gabions with a 3 foot by 3 foot square cross -section for sufficient strength and flexibility when assembled and filled with rock as follows:
a.Loading and Configuration. Place an approximate 4,000 -pound line load over the center of a 12- foot long gabion (perpendicular to the long axis), that is unsupported under the middle 6 feet and anchored at each end. (A piece of concrete pipe 4-foot diameter or less with a weight about 4,000 pounds can be used to impose the required line load on the gabion).
b.Requirements: Deflection at the unsupported mid span of 0.50 foot or less. Visible reduction of wire size in a panel, loss of internal rock, and unraveling of twisted- mesh or weld breaks in welded- mesh is not allowed.
2.Mattress -Style Gabions. Test wire mesh of gabion mattresses, 1 foot or 1.5 foot high, for sufficient strength and flexibility when assembled and filled with rock as following:
a.Loading and Configuration. Initially support the base of a 3- foot wide by 12-foot long gabion 2.5 feet above the ground. A load will not be placed on the mattress. Remove about 3 feet of support from the end of the mattress.
b.Requirements. The cantilevered, unsupported end may sag and touch the ground. Visible reduction of the wire size in a panel, loss of internal rock, and unraveling of twisted- mesh or weld breaks in welded- mesh is not allowed. The Engineer may accept gabion systems that have been previously tested and approved. 716-717 for Highway Construction Page 704 of 715 SECTION 716-717 - RESERVED
Source: Idaho Standard Specifications for Highway Construction, 2023 Edition. Pages 737–739 of 768.