Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 4—Structural Design of ConduitsMastic in jointCement-mortar coatingPrestress wireSteel cylinderConcrete coreSteel spigot ringRubber gasketSteel bell ringMastic in jointFigure 68.—Prestressed concrete cylinder pipe (PCCP)details (lined cylinder).Cement-mortar coatingWelded wire meshMastic in jointSteel cylinderPrestress wireConcrete coreSteel spigot ringRubber gasketSteel bell ringMastic in jointFigure 69.—Prestressed concrete cylinder pipe (PCCP) details(embedded cylinder).For guidance on design and construction parameters pertaining to:• Thermoplastic.—See section 12.1.1.• Thermoset plastic.—See section 12.2.Plastic pipe used within low hazard embankment dams is often not encased inreinforced cast-in-place concrete. Use of plastic pipe in new, low hazardembankment dams is generally limited to small diameters (less than 12 inches).However, use of a filter diaphragm or collar is a valuable defensive design measure,even for low hazard classification embankment dams with favorable site conditions.Some designs may not employ a filter diaphragm around the conduit, but eliminatingthis valuable and relatively inexpensive feature should be carefully considered and97