Article 1 — Description
Furnish and install gabions and gabion mattresses .
Article 2 — Materials
This Item uses the following materials. Gabion. A wire fabric or mesh container, filled with stone, with a height of 1 ft. or greater. Gabion Mattress. A wire fabric or mesh container filled with stone and with a height of 6 in., 9 in., or 12 in. Referred to as “revet mattress” in accordance with ASTM A975. Furnish welded wire gabions and gabion mattresses in accordance w ith ASTM A974. Furnish Style 1 or Style 2 when galvanized wire coating is specified or Style 5 when PVC wire coating is specified. Furnish twisted wire gabions and gabion mattresses in accordance wit h ASTM A975. Furnish Style 1 when galvanized wire coating is specified or Style 3 when PVC wire coating is specified. Furnish producer or supplier certification that wire baskets, stiffeners, lacing wire, and spiral connectors conform to the applicable AST M specification. Furnish producer or supplier certification that any alternative wire fasteners that are proposed conform to the strength requirements shown in Table 1 when tested in conformance with the applicable ASTM specification. Submit certification for approval before beginning work. Table 1 Minimum Panel -to-Panel Connection Strength Application Strength (lb./ft.) Gabions, galvanized 1,400 Gabions, PVC -coated 1,200 Gabion mattress, galvanized and PVC -coated 700 Provide filler stone consisting of clean, hard, and durable stone that does not contain shale, caliche, or other soft particles. Stone appearing to contain such particles will be tested for soundness in accordance with Tex-411-A using magnesium sulfate. Stone with five- cycle magnesium sulfate soundness of more than 18% will be rejected. Use filler stones meeting the size requirements shown in Table 2. Prevent contamination when storing and handling stone. Use stone with a minimum bulk specific gravity of 2. 50 as determined in accordance with Tex-403-A . Table 2 Filler Stone Size Requirements Cage Height (in.) Allowable Filler Stone Dimensions Min (in.) Max (in.) Gabion mattress 6 3 5 9 3 5 12 4 8 Gabion 12 4 8 18 4 8 36 4 8 Provide Type 2 filter fabric when required in accordance with DMS -6200 , “Filter Fabric.” 708 Provide granular filter material when required consisting of hard, durable, and clean sand or gravel with a maximum particle size of 3/8 in.
Article 3 — Construction
The gabion or gabion mattress manufacturer must have a qualified representative who is available for consultation as needed from the beginning and throughout the duration of gabion or gabion mattress construction.
3.1 Foundation Preparation. Excavate the foundation to the extent shown on the plans or as directed. Remove
all loose or otherwise unsuitable materials. Carefully backfill all depressions to grade with suitable materials from adjacent required excavation or another approved source and compact the backfill to a density at least equal to the adjacent foundation. Remove any buried debris protruding from the foundation that will impede the proper installation and final appearance of the gabion or gabion mattress, and carefully backfill and compact voids as specified. T he Engineer will inspect the prepared foundation surface i mmediately befor e gabion placement.
3.2 Granular Filter Placement . Spread granular filter material, if required, uniformly on the prepared foundation
surface to the slopes, lines, and grades shown on the plans. Do not place filter material by methods that tend to segregate particle sizes. Repair all damage to the foundation surface that occurs during filter placement before proceeding with the work. Compaction of the filter material is not required but finish the material to present a reasonably even surface without mounds or windrows.
3.3 Filter Fabric Placement. Place filter fabric, if required, as shown on the plans. Place the filter fabric with its
long axis parallel to the centerline of the structure, highway, or dam. Overlap the uphill or upstream sheet over the downhill or downstream sheet. Ensure adjacent sheets of filter fabric have a minimum overlap of 2 ft. in each direction or, alternatively, provide a minimum overlap of 1 ft. and sew the adjacent sheets of filter fabric together. Lap the ends of rolls at joints by at least 2 ft. Secure filter fabric in place with nails or pins. Use 12- in. long, 3/16- in. diameter nails with 1.5- in. washers, or U -shaped steel pins with each leg at least 9 in. long. Space nails or pins at a maximum of 10 ft. in each direction and 5 ft. along the seams. Along the seams, place nails or pins through both strips of filter fabric at approximately the midpoint of the overlap. Place additional nails or pins as necessary to hold the filter fabric in position. Alternative anchorage and spacing may be used when approved. Keep the fabric material free of tension, stress, folds, wrinkles, or creases. Any defects, tears , holes, flaws, or damage to filter fabric may be cause for rejection. Repair torn or punctured filter fabric by placing a layer of filter fabric over the damaged area, ensuring a minimum overlap of 3 ft. beyond the damaged area in all directions, and securing the filter fabric in place with pins or nails . Store filter fabric out of direct sunlight and cover the filter fabric as soon as possible after placement, but within 3 days.
3.4 Assembly and Installation . Place PVC -coated materials , if wire coating is specified, when the ambient
temperature and the temperature of the coated wire are more than 15°F above the brittleness temperature of the P VC. Assemble empty gabion or gabion mattress units individually and place them on the approved surface to the lines and grades shown on the plans with the sides, ends, and diaphragms erected to ensure all creases are in the correct position, the tops of all sides are level, and all sides that are to remain exposed are straight and plumb. Fill the basket units after transporting them to their final position in the work. Place the front row of gabion or gabion mattress units first and successively construct units toward the top of the slope or the back of the structure. Place the initial line of basket units on the prepared surface, and partially fill them to provide anchorage against deformation and displacement during subsequent filling operations. Stretch and hold empty basket units as necessary to remove kinks and provide a uniform alignment. Connect all adjoining empty gabion or gabion mattress units with lacing, wire spiral binders, or approved fasteners along the perimeter of their contact surface to obtain a monolithic structure before filling. 709 Provide continuous stitching with alternating single and double loops at intervals of no more than 5 in. if lacing wire is used. Securely fasten all lacing wire terminals. Provide connections meeting the joint strength requirements in accordance with Article 459.2., “Materials.” These requirements apply to all connections , including attachment of end panels, diaphragms, and lids. Join twisted wire baskets through selvage- to-selvage or selvage- to-edge wire connection; do not use mesh- to-mesh or selvage- to-mesh wire connection except where baskets are offset or stacked, in which case join each mesh opening where mesh wire meets selvage or edge wire. Carefully fill the basket units with stone, using hand placement to avoid damaging wire coating, to ensure as few voids as possible between the stones , and to maintain alignment. Machine placement of stone will be allowed if approved. Correct excessive deformation and bulging of the mesh before further filling. F ill the basket units in a row in stages consisting of maximum 12-in. courses to avoid localized deformation. Do not at any time fill a cell to a depth exceeding 1 ft. more than its adjoining cell. Do not drop stones into the basket units from a height greater than 36 in. Place two uniformly spaced internal connecting wires between each stone layer in all front and side gabion units, connecting the back and the front faces of the compartments for gabion units more than 2 ft. high. Loop connecting wires or preformed stiffeners around two twisted wire -mesh openings or a welded wire joint at each basket face, and securely twist the wire terminals to prevent loosening. Place the outer layer of stone carefully along all exposed faces and arrange it by hand to ensure a neat and compact appearance. Overfill the last layer of stone uniformly by 1–2 in. for gabions and 1 in. for gabion mattresses to compensate for future settlement in rock while still allowing for the proper closing of the lid and providing an even surface with a uniform appearance. Make final adjustments for compaction and surface tolerance by hand. Stretch lids tight over the stone fill, using an approved lid- closing tool, until the lid meets the perimeter edges of the front and end panels. Do not use crowbars or other single- point leverage bars for lid closing. Close the lid tightly along all edges, ends, and internal cell diaphragms with spiral binders or lacing wire or with other wire fasteners if approved. Ensure all projections or wire ends are turned into the baskets. C ut, fold, and wire the basket unit together to suit site conditions where a complete gabion or gabion mattress unit cannot be installed due to space limitations , as shown on the plans, or as directed. Fold the mesh back and neatly wire it to an adjacent basket face. Complete the assembling, installation, filling, lid closing, and lacing of the reshaped gabion or gabion mattress units in accordance with this Section.
Article 4 — Measurement
Gabions will be measured in place by the cubic yard of stone-filled gabions. Gabion mattresses will be measured in place by the square yard of surface area or by the cubic yard.
Article 5 — Payment
The work performed and materials furnished in accordance with this Item and measured as provided under “Measurement” will be paid for at the unit price bid for “Gabions” of the basket wire coating specified, and per square yard of “Gabion Mattresses” of the thickness and basket wire coating specified or per cubic yard of “Gabion Mattresses” of the basket wire coating specified. The unit price bid is full compensation for wire baskets, stone fill, lacing and fasteners, filter fabric, granular filter material, excavation, grading and backfill, materials, tools, equipment, labor, and incidentals. Filter fabric and granular filter material, if used, will not be paid for directly , but will be subsidiary to this Item .