Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Conduits through Embankment Dams• Other joints.—Some HDPE pipe products have integral threads or snap jointsthat allow sections to be easily joined without special equipment. However,these should only be used for nonpressurized applications in low hazardembankment dams due to the potential for pullout. Some types of plastic pipeuse gasketed or glued bell and spigot joints. HDPE pipe cannot be joined bythreading or solvent bonding.Flotation.—When grouting an HDPE slipliner within an existing conduit, it is likelythat the slipliner will “float” or be displaced upward by the fluid pressure of thegrout in the annulus between the existing conduit and slipliner. Due to the relativelylight weight of HDPE pipe, floatation can be more pronounced with this material.Floating of the slipliner may not allow for grout to completely encase the HDPEpipe and therefore reduce the overall strength of the structure. Floatation can alsoresult in vertical misalignments, which may alter the hydraulics of a conduit,especially one that would flow under open channel conditions.Steps should be taken to address this floating potential, such as using spacers orblocking between the existing conduit and the slipliner. Figure 169 shows anexample of spacers being attached to the HDPE slipliner by extrusion welding.Some manufacturers have recommended that the HDPE pipe be filled with water toreduce flotation of the pipe during grouting. However, this does not always preventflotation, because water is not as dense as the surrounding grout, and blocking is stillnecessary. Other manufacturers strongly advise against filling the HDPE pipe withwater and instead recommend properly installed blocking and staged grouting.HDPE pipe is flexible and can conform to alignment changes; therefore, a largerHDPE section is more applicable than a rigid slipliner section, such as steel. Thistends to greatly minimize the potential distance an HDPE slipliner can float (i.e., byreducing the size of the annulus) and reduces the potential adverse effects of anydisplacement. One caution is that since the HDPE slipliner is more flexible, it mayrequire more spacers than a rigid liner for the same span lengths, to controlfloatation, and provide sufficient room to fully encase the liner. However, if thealignment in the existing conduit varies, then the flexible liner will adapt more easilyto the alignment, but will still require sufficient spacers to ensure adequateencasement. Spacers extending the full length of the HDPE slipliner are notrecommended. Spacers should be designed to allow grout to fill the annulusbetween the existing conduit and the HDPE slipliner. The type and spacing ofspacers will vary depending on the standard dimension ratio (SDR) of the HDPEslipliner and should be based on the recommendations of the HDPE pipemanufacturer.Entrance and terminal structures.—The sliplining of an existing conduit mayrequire partial or full removal and replacement of certain structures to improverelease capabilities or to facilitate construction. Figure 170 shows an intake structure302
Chapter 12—Renovation of ConduitsFigure 169.—Spacers being attached to an HDPE slipliner using anextrusion gun.Figure 170.—The intake structure has been removed as part of a conduitrenovation.303
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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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Chapter 5Foundation and Embankment
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Chapter 5—Foundation and Embankme
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Chapter 6Filter ZonesZones of desig
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Chapter 6—Filter Zonesseepage or
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Chapter 6—Filter ZonesFigure 87.
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Chapter 6—Filter Zones3. Upstream
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Chapter 6—Filter Zonesbedrock sur
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Chapter 6—Filter Zoneszones, and
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Chapter 6—Filter Zonesfiltering t
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Chapter 6—Filter Zonessoil. This
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Chapter 6—Filter Zones6.8 Specifi
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Chapter 6—Filter ZonesVarious deg
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Chapter 6—Filter Zones• For pre
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Chapter 7Potential Failure Modes As
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Chapter 7—Potential Failure Modes
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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 10—Evaluation by Geophysi
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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 Historiesdownstre
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Appendix B—Case HistoriesThe caus
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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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