Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Conduits through Embankment DamsSlopingchimney filterConduitImpervious coreGranular drain (surrounded by filter sand)to convey seepage to downstream toe.The exit details are not shown.Homogenousembankment damVerticalchimney filterConduitGranular drain (surrounded by filter sand)to convey seepage to downstream toe.The exit details are not shown.Figure 88.—Typical configurations for chimney filters used in thedesign of embankments with conduit penetration. A chimney filtermay be constructed either on a slope (top) or with a verticalconfiguration (bottom) within the embankment dam.dams require the same configuration of foundation drainage features shown infigure 89, but the design shown is a typical one.Some low hazard embankment dams may not include a chimney filter for the entirelength of the dam, if the following factors are present:• The embankment dam is constructed of soil(s) with a good resistance to bothinternal erosion and backward erosion piping. Particularly important is thatdispersive clays are not used in the construction.136
Chapter 6—Filter ZonesFigure 89.—Typical design used for embankment dams with distinctlydifferent materials in the core zone and exterior shells of the dam.• Zones of widely varying grain size are not used adjacent to one another in thecross section. Examples include core zones of fine grained soil with exteriorzones of coarser gravel or rockfill.• Abrupt changes in the cross section transverse to the centerline are not present.Examples are bedrock ledges, closure sections, and excavated trenches.• Good oversight of construction is provided, including quality assurance andcontrol that are consistent and effective.• Special care is taken in following recommendations for compaction of fillsurrounding the conduit, as discussed in section 5.3.2.If a chimney drain is not included in the design of a low hazard embankment dam,the design measures for preventing internal erosion or backward erosion pipingalong the conduit may consist of three basic choices:1. A filter diaphragm is a valuable defensive design measure even for low hazardclassification embankment dams with favorable site conditions. The filterdiaphragm will intercept flow along discontinuities along the pipe or through137
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Technical Manual:Conduits throughEm
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PrefaceTens of thousands of conduit
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Prefacecondition. The hazard classi
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PrefaceLakeLine MagazineMaryland Da
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Conduits through Embankment Dams11.
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Contents23 Precast concrete pipe be
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Contents81 On first filling, a high
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Contents117 This conduit was severe
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Contents158 An example of a histori
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ContentsFigures in the AppendicesNo
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ContentsB-33 Aerial view of Como Da
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ContentsB-81 Cross section of Wiste
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ContentsMASW, multichannel analysis
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Symbolsc, cohesionE', modulus of so
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ContentsD 3350D 4221D 4253D 4254D 4
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IntroductionConduits convey water f
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IntroductionFigure 3.—A 15-inch d
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Introductionunstable. When seepage
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IntroductionAn embankment dam with
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A vortex may form at the location w
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IntroductionWater from the reservoi
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IntroductionFlowing water from the
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IntroductionThe process of dislodgi
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Introductionbe observable at the su
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IntroductionFigure 11.—Example of
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Introductionwhere conduits were ass
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Introduction• Conduits within lev
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IntroductionFigure 12.—An example
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Introductionmore recent practiced h
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IntroductionThe “best practices
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Chapter 1GeneralConduits have been
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Chapter 1—GeneralFigure 14.—Ant
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Chapter 1—GeneralFigure 17.—Fai
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Chapter 1—Generalmeans the condui
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Chapter 1—Generalfacilitate futur
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Chapter 2Conduit MaterialsVarious m
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Chapter 2—Conduit MaterialsFigure
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Chapter 2—Conduit Materials• Co
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Chapter 2—Conduit MaterialsSteel
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Chapter 2—Conduit Materials2.3.2
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Chapter 3Hydraulic Design of Condui
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Chapter 3—Hydraulic Design of Con
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Chapter 4Structural Design of Condu
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Chapter 4—Structural Design of Co
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Page 151 and 152: Chapter 5Foundation and Embankment
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Page 169 and 170: Chapter 6Filter ZonesZones of desig
Page 171 and 172: Chapter 6—Filter Zonesseepage or
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Page 181 and 182: Chapter 6—Filter Zonesbedrock sur
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Page 185 and 186: Chapter 6—Filter Zonesfiltering t
Page 187 and 188: Chapter 6—Filter Zonessoil. This
Page 189 and 190: Chapter 6—Filter Zones6.8 Specifi
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Page 193 and 194: Chapter 6—Filter Zones• For pre
Page 195 and 196: Chapter 7Potential Failure Modes As
Page 197 and 198: Chapter 7—Potential Failure Modes
Page 215 and 216: Chapter 8Potential Defects Associat
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Chapter 8—Potential Defects Assoc
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Chapter 9Inspection and Assessment
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Chapter 9—Inspection and Assessme
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Chapter 10Evaluation by Geophysical
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Chapter 10—Evaluation by Geophysi
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Chapter 11Appropriate Emergency Act
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Chapter 11—Appropriate Emergency
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Table 11.2.—Potential problems an
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Chapter 12Renovation of ConduitsThe
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Chapter 12—Renovation of Conduits
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Chapter 13Replacement of ConduitsGe
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Chapter 13—Replacement of Conduit
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Chapter 14Repair and Abandonment of
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Chapter 14—Repair and Abandonment
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ReferencesThe following references
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ReferencesBureau of Reclamation, De
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ReferencesCooper, Chuck, E. Wesley
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ReferencesJacobsen, S., “Buckling
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ReferencesNatural Resources Conserv
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ReferencesU.S. Army Corps of Engine
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ReferencesWooten, R. Lee, Peter S.
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Additional ReadingThe following ref
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Additional ReadingCarter, Brent H.,
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Additional ReadingJohnson, Brian, J
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Additional ReadingNatural Resources
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Additional ReadingU.S. Army Corps o
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Additional ReadingVan Aller, Hal, R
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GlossaryThe terms defined in this g
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Glossary• Backward erosion piping
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GlossaryCathodic protection system
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GlossaryConsequences (FEMA, 2004):
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Glossarymalfunction or abnormality
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GlossaryDrawdown (FEMA, 2004): The
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GlossaryFailure mode (FEMA, 2004):
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GlossaryGate chamber: An outlet wor
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GlossaryImpervious: Not permeable;
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GlossaryLeakage (FEMA, 2004): Uncon
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GlossaryOpen cut: An excavation thr
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GlossaryPolyvinyl chloride (PVC): A
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GlossaryResistivity: A measure of t
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GlossarySettlement (FEMA, 2004): Th
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GlossaryStandard Proctor compaction
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GlossaryThermoset (ASTM F 412, 2001
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GlossaryReferencesAmerican Concrete
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IndexAAbandonment of conduits, 225,
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IndexCompaction of backfill, 6, 10,
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IndexDDamembankment, 113-130, 333-3
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IndexExisting conduit, 23, 31, 45-5
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IndexHydraulic fracture, 4-11, 17,
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IndexMechanical caliper, 246Metal c
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IndexPressure flow, see Conduit, pr
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IndexSliplining, 39, 45-47, 51, 164
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IndexUUltrasonic pulse-echo, 245, 2
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Appendix AHistory of Antiseep Colla
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Appendix A—History of Antiseep Co
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Appendix BCase HistoriesIndexDam Lo
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Appendix B—Case HistoriesDam Loca
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Appendix B—Case HistoriesProject
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Appendix B—Case HistoriesFigure B
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Appendix B—Case Historiesproject,
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Appendix B—Case Historieswatersto
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Appendix B—Case HistoriesLessons
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Appendix B—Case HistoriesThe cond
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Appendix B—Case Historiesroadway.
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Appendix B—Case Historiesentire c
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Appendix B—Case Historieshauled i
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Appendix B—Case Historiescoal tar
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Appendix B—Case Historieshistory
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Appendix B—Case Historiesarea, a
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Appendix B—Case Historiespipe. Du
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Appendix B—Case Historiesinvert o
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Appendix B—Case Historiesof sever
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Appendix B—Case HistoriesThe down
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Appendix B—Case Historieshose and
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Appendix B—Case HistoriesADownstr
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Technical Manual: Conduits through Embankment Dams (FEMA 484)

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