Technical Manual: Conduits through Embankment Dams (FEMA 484)

Conduits through Embankment Dams• To eliminate or minimize the impacts of low density areas caused by difficultiesin compaction of the earthfill• To eliminate or minimize the potential for stress arching in the embankmentdam leading to low density zones and hydraulic fracture of the dam• To eliminate or minimize the potential for differential settlement leading to lowdensity zones and maintain a positive embankment pressure on the conduit• To allow access for periodic inspection by either man-entry or CCTV• To allow for future repairs, renovation, or changes in operating requirements• To allow for the most economical structural design while still addressing all ofthe items above considerationsDepending on the arrangement of the control features, type of conduit, purpose ofthe conduit, etc., specific shapes are used. Figures 46 through 50 show examples ofshapes typically used for single barrel reinforced cast-in-place concrete conduits.Figure 51 represents a shape commonly used with precast concrete conduits. A boxshape has been used in both reinforced cast-in-place and precast concreteapplications (Note: Most box shaped conduits have used vertical sidewalls.However, figure 52 shows a preferred shape with sloping sidewalls). A filter isFigure 46.—Conduitshape AFigure 47.—Conduitshape BFigure 48.—Conduitshape CFigure 49.—Conduitshape DFigure 50.—Conduitshape EFigure 51.—Conduitshape F76