Outlet Coefficients

For the dimensioning of manholes according to circular nº 5 "Bureau of Public Roads", when considering exit control, the dam calculation requires the Ke coefficient:

• Concrete Pipe

  Design Entrance	Ke
  Projecting from fill, Socket end of pipe (groove-end)	0.2
  Projecting from fill, Square cut end	0.5
  Headwall or headwall and wingwalls, Socket end of pipe (groove-end)	0.2
  Headwall or headwall and wingwalls, Square-edge	0.5
  Rounded (R = 1/2 D)	0.2
  Mitered to conform to fill slope	0.7
  End-Section conforming to fill slope	0.5
  Beveled edges, 33.7º or 45º bevels	0.2
  Side- or slope-tapered inlet	0.2

• Pipe. or Pipe-Arch. Corrugated Metal

  Design Entrance	Ke
  Projecting from fill (no headwall)	0.9
  Headwall or headwall and wingwalls square-edge	0.5
  Mitered to conform to fill slope, paved or unpaved slope	0.7
  End-Section conforming to fill slope	0.5
  Beveled edges, 33.7º or 45º bevels	0.2
  Side- or slope-tapered inlet	0.2

• Box, Reinforced Concrete

  Design Entrance	Ke
  Headwall parallel to embankment (no wingwalls), Square-edged on 3 edges	0.5
  Headwall parallel to embankment (no wingwalls), Rounded on 3 edges to radius of D/12 or B/12 or beveled edges on 3 sides	0.2
  Wingwalls at 30º to 75º to barrel, Square-edged at crown	0.4
  Wingwalls at 30º to 75º to barrel, Crown edge rounded to radius of D/12 or beveled top edge	0.2
  Wingwalls at 10º to 25º to barrel, Square-edged at crown	0.5
  Wingwalls parallel (extension of sides), Square-edged at crown	0.7
  Wingwalls parallel (extension of sides), Side- or slope-tapered inlet	0.4