The scope of work under this specification includes the supply, assembly, stone filling, and closing double twisted hexagonal woven wire mesh gabions. The gabions shall be placed on a prepared foundation surface, in accordance with the lines, grades, and dimensions shown and specified within the contract plan documents.
Product specification data must be submitted to project engineer or project owner for verification and approval prior to delivery of any material to the project site. All material used for construction for the gabion installation scope of work shall meet or exceed the gabion product specification requirements listed within this specification and shall be double twisted hexagonal woven wire mesh gabions conforming to ASTM A975-97 only. No Welded Wire Gabions will be accepted as an equal to the double twisted hexagonal woven wire mesh gabion product specified for this project.
American Society for Testing and Materials specification ASTM A975-97 (only) shall be used as a guideline for the following project specifications for constructing double twisted woven wire mesh gabions.
Gabions are double twisted hexagonal wire mesh box shaped baskets of various sizes and dimensions compartmented into internal cells. The gabion baskets are connected to adjoining gabion baskets and filled with hard durable stone to create flexible, permeable, durable monolithic structures. Gabions shall be manufactured with all components mechanically connected at the production facility.
Double twisted hexagonal mesh gabion baskets are available in three styles.
Style A:
Galvanized Gabions: double twisted hexagonal wire mesh made from steel wire which is galvanized zinc coated prior to being double twisted into mesh. The fasteners and lacing wire are made form the same zinc coated wire.
Style B:
PVC Coated Gabions: double twisted hexagonal wire mesh made from the same steel galvanized zinc coated wire as style A with an additional Poly Vinyl Coating (PVC) coating. The fasteners shall be stainless steel and the lacing wire shall be of the same PVC coating type as the mesh.
Style C:
Galfan Gabions: double twisted hexagonal wire mesh made from steel wire which is coated with a Zinc/Aluminum coating or Galfan coating.
| Test Description |
Galvanized/Galfan Gabions |
PVC Coated Gabions |
| Tensile strength of mesh parallel to wire twist: |
3500 lbs/ft |
2900 lbs/ft |
| Tensile strength of mesh perpendicular to wire twist: |
1800 lbs/ft |
1400 lbs/ft |
| Connection to selvedges: |
1400 lbs/ft |
1200 lbs/ft |
| Panel to panel: |
1400 lbs/ft |
1200 lbs/ft |
| Punch strength of mesh: |
6000 lbs/ft |
5300 lbs/ft |
Gabion Unit Size |
Capacity Cubic Yards |
No. Of Internal Cells |
6x3x3 |
2 |
2 |
9x3x3 |
3 |
3 |
12x3x3 |
4 |
4 |
6x3x1.5 |
1 |
2 |
9x3x1.5 |
1.5 |
3 |
12x3x1.5 |
2 |
4 |
6x3x1 |
.666 |
2 |
9x3x1 |
1 |
3 |
12x3x1 |
1.33 |
4 |
All gabion dimensions shall be within a tolerance limit of plus or minus 5% of the manufacturers stated dimensions.
Galvanized/Galfan Gabions |
4 inches - 8 inches |
PVC Coated Gabions |
4 inches - 8 inches |
The ranges of stone size listed above shall be equally graded and shall not be less than 4" in any given dimension and no larger than 8" in any given dimension.
The gabion basket shall be delivered to the job site folded flat and packed in bundles.
The gabion baskets shall be unfolded on a hard flat surface. The sides, ends, and internal diaphragms shall be folded upright into vertical position to form an open box shape. The back and the front panels of the gabion shall be connected to the end panels and center diaphragms. The top corner of the end panels and center diaphragms have a selvedge wire extending approximately 4 inches out from the corner edge. The end panels and the diaphragms shall be raised to a vertical position and the selvedge wire shall be wrapped around the edge wire of the top and back panels.
- Lacing wire: A piece of wire 1.5 times the length of the edge to be laced shall be cut off. If the edge of the basket is 3' long, no more than 4 to 5 feet of wire should be used at a time to lace edges. For vertical seams, starting at the bottom end of the panel, the lacing wire shall be twisted and wrapped two times around the bottom selvedge and double and single loops shall be alternated through at intervals not bigger than 4 to 6 inches. The operation shall be finished by looping around the top selvedge wire.
- Ring wire fasteners: The rings shall be installed at the top and bottom connections of the end and center diaphragms. The ring spacing intervals shall be based on the minimum pull apart strength as listed above. The minimum spacing intervals of the ring fasteners shall be no less than 3 fasteners per 1' of seam. The use of a mechanical tool is required for hog ring fastening operations. The use of a manual tool shall be acceptable with a Tiger Tite wire fastener. The ring wire fasteners shall be made from the same wire as the gabion basket except for PVC coated gabions which shall use stainless steel wire fasteners.
Empty gabion baskets shall be assembled individually and placed on the approved surface to the lines and grades as shown or as directed, with the position of all creases and that the tops of all sides are level. All gabion baskets shall be properly staggered horizontally and vertically as shown in the construction drawings. Finished gabion structures shall have no gaps along the perimeter of the contact surfaces between adjoining units. All adjoining empty gabion units shall be connected along the perimeter of their contact surfaces in order to obtain a monolithic structure. All lacing wire terminals shall be securely fastened. All joining shall be made through selvedge-selvedge or selvedge-edge wire connection; mesh-mesh wire connection is prohibited except in the case where baskets are offset or stacked and selvedge-mesh or mesh-mesh wire connection would be necessary. As a minimum, a fastener shall be installed at each mesh opening at the location where mesh wire meets selvedge or edge wire.
- The initial line of gabion basket units shall be placed on the prepared filter layer surface and adjoining empty baskets set to line and grade, and common sides with adjacent units thoroughly laced or fastened. They shall be placed in a manner to remove any kinks or bends in the mesh and to uniform alignment. The basket units then shall be partially filled to provide anchorage against deformation and displacement during the filling operation. The stone shall be placed in the units as specified or directed by the manufacturer.
- Deformation and bulging of the gabion units, especially on the wall face, shall be corrected prior to additional stone filling. Care shall be taken, when placing the stone by hand or machine, to assure that the PVC coating on the gabions will not be damaged if PVC is utilized. All stone on the exposed face shall be hand placed to ensure a neat compact appearance.
- Gabions shall be uniformly overfilled by about 1-3 inches to account for future structural settlements and for additional layers. Gabions can be filled by any kind of earth filling equipment. The maximum height from which the stones may be dropped into the baskets shall be 3'.
Gabion stone placement,
When excavation and foundation preparation are completed, the pre-assembled gabions shall be placed in their proper location according to the plans provided. Gabions shall then be connected together and aligned prior to filling with stone. The stone fill shall have a gradation as listed or specified within the contract specifications or as listed within this specification. The stone fill shall be placed into the gabion units in 1' lifts. Cells shall be filled to a depth not exceeding 1' at a time. The fill layer should never be more than 1' higher then any adjoining cell. Connecting wires shall be installed from the front to back and side to side of the individual cells at each 1' vertical interval for gabions with a depth of 3'. The voids shall be minimized by using well graded stone fill and by hand placement of the facing in order to achieve a dense, compact stone fill. All corners shall be securely connected to the adjoining basket of the same layer before filing the units. When more than one layer of gabions is required, in order for the individual units to become incorporated into one continuous structure, the next layer of gabions shall be connected to the layer underneath after this layer has been securely closed. Gabions shall be uniformly overfilled by about 1-2 inches to account for structural settlement.
The lids of the gabion units shall be tightly secured along all edges, ends and diaphragms in the same manner as described for assembling. Adjacent lids may be securely attached at the same time. The panel edges shall be pulled to be connected using the appropriate closing tools where necessary. Single point leverage tools, such as crowbars will not be acceptable. All end wire shall then be turned in.
Gabions shall be double twisted hexagonal woven wire mesh gabions only conforming to ASTM A975-97 specifications as manufactured by Terra Aqua Gabions, Inc., (800)-736-9089 or approved equal.
|
