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

Geotextiles in Embankment DamsGrain-Size Analysis (Mechanical Analysis) (Frobel, 1987): The process ofdetermining gradation or grain-size distribution.Gradient ratio (ASTM D-4439, 2004): n – in geotextiles, the ratio of the hydraulicgradient through a soil-geotextile system to the hydraulic gradient through the soilalone.Gravel (ASTM D 653, 2002): Rounded or semi-rounded particles of rock that willpass a 3-inch (76.2-mm) and be retained on a No. 4 (4.75-μm) U. S. standard sieve.Grids (Frobel, 1987): A geosynthetic made by drawing, in one or two perpendiculardirections, a perforated plate made of a polymer such a polyethylene orpolypropylene. In the process, the small perforations become large rectangularopenings, usually one to 10 centimeters (0.5 inch to 4 inches). The strands have alarge degree of molecular orientation as a result of the draw. Grids are typically usedfor soil reinforcement.Hazard (FEMA, 2004): A situation that creates the potential for adverseconsequences, such as loss of life, or property damage.Hazard potential classification: A system that categorizes embankment damsaccording to the degree of adverse incremental consequences of a failure ormisoperation of a dam. The hazard potential classification does not reflect in anyway on the current condition of the embankment dam (i.e., safety, structuralintegrity, flood routing capacity).Heat Bonded (Frobel, 1987): A process by which fabric filaments are weldedtogether at their contact points by subjection to a relatively high temperature.High-Density Polyethylene (HDPE) (Frobel, 1987): A polymer prepared by lowpressurepolymerization of ethylene as the principal monomer. (See Polymer.)Homogeneous:Constructed of only one type of material.Hydraulic conductivity (ASTM D-4439, 2004): (k), n – the rate of discharge ofwater under laminar flow conditions through a unit cross-sectional area of a porousmedium under a unit hydraulic gradient and standard temperature conditions (20°C).Hydraulic fracture: A separation in a soil or rock mass that occurs if the appliedwater pressure exceeds the lateral effective stress on the soil element. Hydraulicfracture may occur if differential foundation movement is allowed. Soils compacteddry of optimum water content are more susceptible to hydraulic fracture.Hydraulic Gradient (ASTM D 653, 2005): The change in total hydraulic head perunit distance of flow.166