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<br />Design Guideline 3 <br /> <br />Wire Enclosed Riprap Mattress <br /> <br />Introduction <br /> <br />Wire enclosed riprap is commonly used in the state of New Mexico. The predecessor to this <br />erosion control technique is known as rail bank protection and has been used in Arizona, <br />Colorado and New Mexico since the 1970s. Wire enclosed riprap differs from gabions and <br />gab Ion (Reno) mattresses in that it is a continuous framework rather than individual <br />interconnected baskets. In addition, wire enclosed riprap is typically anchored to the <br />embankment with steel stakes which are driven through the mattress. Construction of wire <br />enclosed riprap is usually faster than gabions or gab ion mattresses, and it also requires less <br />wire mesh because internal junction panels are not used. Wire enclosed riprap is used <br />primarily for slope protection. It has been used for bank protection, guide bank slope <br />protection, and in conjunction with gabions placed at the toe of slope. <br /> <br />Design Guidelines <br /> <br />Guidelines for the dimensions, placement, anchoring, splicing, and quantity formulas are <br />shown on Figure 3.1. Design procedures for the selection of rock fill for wire enclosed <br />riprap can be found in Brown and Clyde (HEC-11) (1989), Simons et al. (1984) and Maynord <br />(1995). Guidelines on selection and design of filter material can be found in HEC-ll (1989) <br />and Holtz et al. (FHWA HI-95-Q38) (1995). The following guidelines and specifications <br />reflect construction procedures for wire enclosed riprap recommended by the New Mexico <br />State Highway and Transportation Department (NMSHTD). <br /> <br />1. Wire mesh fabric for riprap shall be hexagonal mesh or a .V" mesh meeting the <br />requirements listed in the specifications. <br /> <br />2. Steel stakes may be railroad rails, not less than 14.9 kglm (30 Ib per yard), 102 mm (4 <br />in.) 0.0. standard strength galvanized steel pipe, or 102 mm X 102 mm X 9.5 mm (4" X <br />4" X 3/8") steel angles. <br /> <br />3. If length of slope is 4.6 m (15 It) or less. only one row of steel stakes 610 mm (2 It) from <br />the top edge of the riprap will be required unless otherwise noted on the plans. <br /> <br />4. Dimensions of the thickness, top of slope and toe of slope extents, and total length of <br />protection shall be designated on the bridge or roadway plans. <br /> <br />5. The wire enclosed riprap thickness is usually 300 mm (12 in) unless otherwise shown on <br />the plans. Thickness is usually 460 mm (18 in) at bridges. <br /> <br />6. Longitudinal splices may be made with one lap of galvanized 9 gage tie wire, 9 gage hog <br />rings or 111/2 gage galvanized hard drawn interlocking wire clips. <br /> <br />3.3 <br />