Geotextiles in Embankment Dams - Association of State Dam Safety ...

Glossarymg/m). The mass per unit area of a scrim is derived by multiplying the count by thelinear density in both directions and adding. (See Calendering.)Seam (ASTM D-4439, 2004): n – a permanent joining of two or more materials.Seam (ASTM D-4439, 2004): n – the connection of two or more pieces of materialby mechanical, chemical, or fusion methods to provide the integrity of a single pieceof the material.Seam allowance (ASTM D-4439, 2004): n – the width of fabric used in making aseam assembly, bounded by the edge of the fabric and the furthest stitch line.Seam assembly (ASTM D-4439, 2004): n – the unit obtained by joining fabricswith a seam, including details such as fabric direction(s), seam allowance, sewingtreads used, and number of stitches per unit length; and sometimes additional detailsof fabrication such as sewing-machine type and speed, needle type and size, etc.Seam design engineering (ASTM D-4439, 2004): n – the procedures used toselect a specific thread, a specific stitch type, and a specific seam type to achieve therequired seam strength.Seam efficiency, sewn (ASTM D-4439, 2004): n – in sewn fabrics, the ratioexpressed as a percentage of seam strength to fabric strength.Seaming Methods (Geotextile Seaming) (Frobel, 1987): The seaming ofgeotextiles has evolved from overlapping of fabric, seam joining with pins or staples,heat sealing or securing seams with adhesives, to the sewn seam. Often, the bestchoice is to specify the sewing of seam joints. By eliminating the wastefuloverlapping of fabric, sewn seams can offer a reduction in labor costs, quickercompletion of the installation phase, and superior results. Once a determination ismade to join seams by sewing, a decision must be made about seam and stitch type.There are three primary seam types that can be used for geotextile field sewing:“flat” seam, “J” seam, and “Butterfly” seam. There are only two stitch types that canbe effectively used in field sewing of geotextiles: the single-thread chainstitch (101)and the two-thread chainstitch (401). No “hard and fast” rule can be made abouthow far from the “turned” edge the stitching should be done. Typically, it is from 2-inch to 4-inch. The following are currently used geotextile seaming methods: (a) JSeam - Two parallel pieces of fabric are mated together, turned in the same directionand sewn with the required rows of stitches (Ssn-1; Ssn-2). (b) Flat Seam - Twoparallel pieces of fabric are mated and sewn together with either a single row ofstitched (designated Ssa-1) or possibly with two or more rows of stitches (Ssa-2, Ssa-3). This is also called a superimposed seam or prayer seam. (c) Butterfly Seam - Thisseam type should be considered when the fabric being used is loosely woven or has a175