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Modular Gabions Specification

Gabions shall be made of welded steel wire mesh of a nominal size of 75 mm x 75 mm. Note: other sizes can be specified.

Dimensions: Gabions shall be supplied in various lengths and heights. The length shall be in multiples of the width. The width shall not be less than 0.915 m. Dimensions for heights, widths and lengths are subject to a tolerance of +/- 5% of manufacturer’s stated sizes.

Modular Mattress Specification

Mattresses shall be made of welded steel wire mesh of a nominal size of 38 mm x 75 mm.

Dimensions: Mattress shall be supplied in various lengths. The thickness shall be 150 mm or 230 mm. The horizontal width shall be 1.83 m. Dimensions for heights, widths and lengths are subject to a tolerance of +/- 5% of manufacturer’s stated sizes.

Installation

Foundation Preparation: The foundation on which the gabions are to be placed shall be cut or filled and graded to the lines and grades shown on the drawings. Surface irregularities, loose material, vegetation, and all foreign matter shall be removed from foundation surface area. When fill is required, it shall consist of materials conforming to the specified requirements. Gabions and bedding or specified geotextiles shall not be placed until the foundation preparation is completed, and the subgrade surfaces have been inspected and approved by the engineer or the engineer’s representative. Compaction of bedding or filter material will be required per plans and specifications. The surface of the finished material shall be to grade and free of mounds, dips or windrows. Extra care should be taken with foundation preparations in order to ensure a level and smooth surface. Geotextile shall be installed in accordance with the requirements of the plans and specifications.

Assembly and Placement

The assembly and placement of gabions shall be in accordance with the following procedures:

Assembly. Rotate the gabion panels into position and join the vertical edges with fasteners for gabion assembly. Where lacing wire is used, wrap the wire with alternating single and double half hitches at intervals between 100 mm to 130 mm. Where spiral fasteners are used, crimp the ends to secure the spirals in place. Where ring type alternate fasteners are used for basket assembly, install the fasteners at a maximum spacing of 150 mm. Use the same fastening procedures to install interior diaphragms where they are required. Interior diaphragms will be required where any inside dimension exceeds 91 cm for gabion baskets thicker than 300 mm. Diaphragms will be installed to assure that no open intervals are present that exceeds 91 cm. For baskets 300 mm or less rectangular cells are allowed with dimensions 91 cm in one direction and not to exceed 183 cm in the perpendicular direction.

Placement. Place the empty gabions on the foundation and interconnect the adjacent gabions along the top, bottom, and vertical edges using lacing wire or spirals. Wrap the wire with alternating single and double half hitches at intervals between 100 mm to 150 mms. Spiral fasteners are commonly used for the assembly and interconnection of welded mesh gabions. Spirals are screwed down at the connecting edges then each end of the spiral is crimped to secure it in place. Lacing may be used as needed to supplement the interconnection of welded mesh gabions, and the closing of lids. Interconnect each layer of gabions to the underlying layer of gabions along the front, back, and sides. Stagger the vertical joints between the gabions of adjacent rows and layers by at least one-half of a cell length.

Filling Operation: After adjacent empty wire gabion units are set to line and grade and common sides properly connected, they shall be placed in straight-line tension to gain a uniform alignment. Staking of the gabions may be done to maintain the established proper alignment prior to the placement of rock. No temporary stakes shall be placed through geotextile material. Connecting lacing wire and other fasteners (as allowed) shall be attached during the filling operation to preserve the strength and shape of the structure. Internal connecting cross-tile wires shall be placed in each unrestrained gabion cell greater than 450 mm in height, including gabion cells left temporarily unrestrained. Two internal connecting wires shall be placed concurrently with rock placement, at each 300 mm interval of depth. In welded mesh gabions these crossties or stiffeners will be placed across the corners of the gabions (at 300 mm from the corners) providing diagonal bracing. Lacing wire or preformed wire stiffeners may be used. The gabions shall be carefully filled with rock, either by machine or hand methods, ensuring alignment, avoiding bulges, and providing a compact mass that minimizes voids. At no point in the filling process may rock be mechanically placed from a height of over 900 mm from machine to fill area. Machine placement will require supplementing with handwork to ensure the desired results. The cells in any row shall be filled in stages so that the depth of rock placed in any one cell does not exceed the depth of rock in any adjoining cell by more than 300 mm. Along the exposed faces, the outer layer of stone shall be carefully placed and arranged by hand to ensure a neat, compact placement with a uniform appearance.

The last layer of rock shall be uniformly leveled to the top edges of the gabions. Lids shall be placed over the rock filling using only approved lid closing tools as necessary. The use of crowbars or other single point leverage bars for lid closing is prohibited due to the potential for damage to the baskets. The gabion lid shall then be secured to the sides, ends, and diaphragms with spiral binders, approved alternate fasteners, or lacing wire wrapped with alternating single and double half hitches in the mesh openings. Any damage to the wire or coatings during assembly, placement and filling shall be repaired promptly in accordance with the manufacturer’s recommendations or replaced with undamaged gabion baskets.

Resistance of the Coating

The protective coating must be resistant to the destructive effects of immersion in acidic, salt, or polluted water; exposure to ultra violet light; and abrasion; and shall retain these characteristics after a period of not less than 3,000 hours under tests in accordance with ASTM G-23.

Stone Diameters: 100 mm - 200 mm

Notes:

  1. A nonwoven geotextile such as Syntex polypropylene may be used behind the wire to prevent migration of fines.
  2. When abrasion is prevalent, Galfan coated alloy gabions may be used.

The data in all tables is intended as guides only and is not intended as a warranty or guarantee. Permathene Ltd. reserves the right to change the specification contained herein without notice.