Technical Manual: Conduits through Embankment Dams (FEMA 484)

GlossaryStandard Proctor compaction test: A standard laboratory or field test procedureperformed on soil to measure the maximum dry density and optimum water contentof the soil. The test uses standard energy and methods specified in ASTM StandardTest Method D 698.Standardized dimension ratio (SDR): Ratio of the average specified outsidediameter to the minimum specified wall thickness for outside diameter controlledplastic pipe.Standards (ASCE, 2000): Commonly used and accepted as an authority.Steel pipe: See Pipe, steel.Stoping: The sequence of soil removal at the bottom of hole followed by roofcollapse. This bottom-up erosion process forms a cavern in the embankmentmaterial, typically with steep sides.Stoplogs (FEMA, 2004): Large logs, timbers, or steel beams placed on top of eachother with their ends held in guides on each side of a channel or conduit so as toprovide a cheaper or more easily handled means of temporary closure than abulkhead gate.Storage (FEMA, 2004): The retention of water or delay of runoff either by plannedoperation, as in a reservoir, or by temporary filling of overflow areas, as in theprogression of a flood wave through a natural stream channel.Strain gauge (ASCE, 2000): A device that measures the change in distancebetween closely spaced points.Strength design method (ACI, 2000): A design method that requires service loadsto be increased by specified load factors and computed theoretical strengths to bereduced by the specified phi factors. Also, known as ultimate strength designmethod.Subsidence: A depression, indicating subsurface settlement or particle movement,typically not having clearly defined boundaries.Suffosion: Seepage flow through a material that causes part of the finer grainedportions of the soil matrix to be carried through the coarser grained portion of thematrix. This type of internal erosion is specifically relegated only to gap graded soils(internally unstable soils) or to soils with an overall smooth gradation curve, but withan overabundance of the finer portions of the curve represented by a “flat tail” tothe gradation curve. While a crack is not needed to initiate this type of internalerosion, a concentration of flow in a portion of the soil is needed.417