Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Conduits through Embankment DamsFigure 110.—CMP corrosion within anoutlet works conduit.Figure 111.—CMP corrosion on the invert of an outletworks conduit.Figure 112.—CMP corrosion withinan outlet works conduit caused bya leaking pipe joint.Figure 113.—An outlet works conduit that hasexperienced corrosion and failure.186Figure 114.—Spalled concrete andexposed reinforcement in an outletworks conduit.
Chapter 8—Potential Defects Associated with Conduitsand have differing products of corrosion. Soil-related bacterial corrosion producesoxidation scale, which is active in organic, poorly drained soils of nearly neutral pH.This scale is usually black, but upon being exposed to aerated conditions in conduits,becomes rust colored. Water-related bacterial corrosion produces nodular oxidation,which exists on pipe surfaces associated with a water source of nutrients. Localperforations on the pipe invert characterize nodular oxidation. Nodular oxidationresults from sulfate-reducing bacteria activity.Polyethlene plastic pipe is not subject to galvanic action and will not corrode.Naturally occurring water and soil conditions will not affect the pipe.8.2 Poor design and constructionGood design and construction practice can extend the service life of a conduit.However, poor design and construction practice can greatly shorten it. Much of thefollowing discussion was adapted from USACE’s Evaluation and Repair of ConcreteStructures (1995b, pp. 3-1 to 3-14) for reinforced cast-in-place concrete. Some of themost common areas where poor design and construction practice can affect conduitsare:• Poor design practice.—Design errors may be divided into two general types: thoseresulting from inadequate structural design and those resulting from lack ofattention to relatively minor design details. Common design errors include:1. Inadequate structural design.—Inadequate structural design exposes theconcrete to greater stress than it is capable of carrying, or greater strainthan its strain capacity. This may result in excessively high compressivestresses and appear as spalling. Similarly, high torsion or shear stressesmay also result in spalling or cracking. Also, high tensile stresses will resultin cracking. To prevent this from occurring, the designer must complete athorough and careful review of all design calculations. Any renovationthat makes use of existing conduit must be carefully reviewed.2. Poor design details.—While a conduit may be adequately designed to meetloadings and other overall requirements, poor detailing may result inlocalized concentrations of high stresses in otherwise satisfactory concrete.These high stresses may result in cracking that allows water to access theinterior of the concrete. In general, poor detailing does not lead directlyto concrete failure; rather, it contributes to the action of one of the othercauses of concrete deterioration described in this chapter. A frequentcause of cracking in conduits is improperly spaced joints. Thermalcracking can also result in conduits where joint spacings are too long orare not provided in the conduit to accommodate for changes of length. Ingeneral, all of these problems can be prevented by a thorough and careful187
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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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Page 195 and 196: Chapter 7Potential Failure Modes As
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Page 215 and 216: Chapter 8Potential Defects Associat
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Page 231 and 232: 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 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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