6-1 Chapter 6 DIVISION 600 - MISCELLANEOUS CONSTRUCTION SECTION 601 - GABIONS AND MATTRESSES
601.01 Description This work shall consist of furnishing, ass embling, filling with
stones and lacing wire mesh baskets, hereafter called gabions o r mattresses, constructed in accordance with these specifications and placed in conformity w ith the lines, grades and dimensions shown on the plans or established.
601.02 Materials Materials shall conform to the requirements specified in the
following Sections of Division 700 - Materials. G a b i o n 711.02 S t o n e s f o r G a b i o n s 711.03 M a t t r e s s e s 711.07 S t o n e s f o r M a t t r e s s e s 711.08
601.03 Fabrication Gabions and mattresses shall be manufactur ed so that their sides,
ends, lid, and diaphragm(s) can be assembled to form rectangula r units of the specified dimensions. Gabions shall be of a single unit construction. The front, ba se, back and lid shall be woven into a single unit. The ends and diaphragm(s) shall be f actory connected to the base. The base, sides, and two ends of mattresses shall be of a sing le unit construction woven into a single unit. Diaphr agm(s) shall be factory connec ted to the base. The lid may be a separate unit. Perimeter edges of the mesh forming the gabion or mattress sha ll be securely fastened so that joints have at least the same strength as the wire mesh itself. The wire mesh shall be fabricated to be non-raveling. Non-rav eling is defined as the ability to resist pulling apart at any of the twists or connect ions forming the mesh when a single wire in a section of mesh is cut and the section of mesh then subjected to the load test described in the materials specification. The gabion length shall be 1½, 2, 3, or 4 times its horizontal width. The horizontal width shall not be less than 36 i n. However, all gabions furni shed by the manufacturer shall be of uniform width. Where the gabion length exceeds 1½ times its horizontal width, the gabion shall be equally divided into cells by diaphragm(s) of t he same mesh and gauge as the gabion body. Mattresses shall be at least 6 ft by 6 ft and equally divided by transverse diaphragms. 6-2
601.04 Assembling Gabions and mattresses shall be supplied fo lded flat, tied in
pairs and packed in bundles. Single units shall be removed fro m the bundle; unfolded flat on the ground and all kinks and bends flattened. The units shall be assembled individually by erecting the fron t side, back side, ends, and diaphragm(s), assuring that all creases are in the correct position and the tops of all sides level. The four corners of each unit shall be laced first, followed b y the edges of internal diaphragm(s) to the sides. The lacing procedures for lacing corners and units together sh all consist of cutting a length of lacing wire approximately 1½ times the distance to be laced, not to exceed 5 ft, securing the wire terminal at the corner by looping and twistin g, then proceeding to lace with alternating single and double loops at approximately 5 in intervals and securely fasten the other wire terminal. The mattresses shall not be assembled in their final location, except as required for lacing adjacent units together. This is to maintain a uniform bedding surface for installation as described in Section 601.051. At the option of the Contractor , approved locking wire fastene rs may be used in lieu of lacing wire provided they are used in every mesh opening alo ng the joint, each ring is formed such that the ends interlock and the fasteners be of sta inless steel construction with a minimum thickness of 0.125 in, meeting the requirements of ASTM A213, Type 302.
601.05 Installation of Gabions The assembled gabion units sha ll be placed in the
proper location. All adjoining empty gabions shall be placed a long the perimeter of the gabion contact surfaces to obtain a monolithic structure. Once the gabion units are laced together, they shall be stretc hed to effective alignment. This operation shall be carried out after several e mpty gabion units have been positioned. The first gabion in the line shall be partially fi lled to provide the necessary anchorage prior to stretching. Stretching shall be carried out using a means of stretching of at least 1 ton capacity. While under tension, the gabion shall be carefully controlled against any possible unraveling. Whenever gabion structures require more than one tier, the upp er empty gabion tier, while under tension, shall be laced to the top of the lower one . 601.051 Installation of Mattresses If the mattress is to be p laced in the dry, the assembled unit shall be placed in the proper location after it is assembled as described in Section 601.04. Several empty units shall be laced together al ong the contact surfaces to 6-3 obtain a monolithic structure. Care shall be taken to maintain a uniform surface on the bedding material. If the mattresses are to be placed underwater, they may be lac ed together, filled in the dry, and then placed in final position. If the mattresses are polyvinyl chloride coated, they shall no t be dragged, but shall be placed in a manner so as not to damage the coating. 601.052 Filter Fabric A filter fabric in accordance with Secti on 722.02 - Drainage Geotextile, shall be placed on the subgrade, backslope, and sid es of the excavation. If earthfill is to be placed over the gabions, filter fabric shall be placed top of the gabions before earthfill placement.
601.06 Filling Gabions and mattresses shall be filled in stri ct accordance with the
manufacturer’s recommendations, one copy of these recommendatio ns will be supplied to the Resident. Care shall be taken when placing stones inside gabions and mattresses in an effort to prevent distortion and ensure proper alignment. Care shall be taken when placing fill material to assure that the sheathing on coated units will not be broken or damaged. Gabions shall be filled in layers, 1 ft at a time. Two connec ting wires shall be placed between each layer in all cells along all exposed faces of the gabion structure. All connecting wires shall be looped around two mesh openings and t he wire terminals shall be securely twisted to prevent their loosening. The cells in any row shall be filled in stages so that local d eformation will be avoided. At no time shall any cell be filled to a depth exceed ing 1 ft more than the adjoining cell. Along all exposed gabion faces, the outer layer of stone shall be carefully placed and packed by hand to ensure proper alignment and a neat, compact, square appearance. No sharp edges of stone shall prot rude through the wire mesh. The last layer of stone shall be leveled with the top of the gabion or mattress to allow proper closing of the lid and provide an even surface for the next course. Gabions and mattresses shall be well packed and full without e xcessive bulging. 601.061 Filling of Hand Filled Gabions The assembled gabion u nits shall be placed in the proper location. A form shall then be placed along the front face and any side face not adjacent to an already placed gabion, and anchored to formwork on the back face to provide a rigid frame rectangle before filling with stone. The forms shall be sufficiently braced and tied to prevent dis tortion while the stones are being placed.