Box Culvert Connection is a closed connection with a rectangular cross section. However, increasing the Corner Splay value from “0” (default) gives the Box Culvert an increasingly octagonal shape. A Corner Splay can be introduced for pipe strengthening purposes. The flow routing through a Box Culvert Connection is described in Analysis of Connections.
As illustrated in the image above, the addition of a Corner Splay reduces the Diameter / Base Width and Height of the connection to an extent, affecting its Capacity and Flow Velocity.
Parameters to specify:
Length, Slope, either Manning's n or Colebrook-White Roughness, Diameter/Base Width, Height, Corner Splay, see Connections Inputs.
Upstream (US) Cover Level, Upstream Invert Level, Downstream (DS) Cover Level and Downstream Invert Level.
Entering a value for Manning's n or Colebrook-White Roughness will clear the value of the other. Manning's n is used by default.
If the Slope or Downstream Invert Level are changed by the user, the other variable will be updated to match.
If the Height or Upstream Invert Level are changed by the user, the other variable will be updated to match.
Where possible connection levels are automatically set from Surface Data data, existing Stormwater Controls - SWC and existing Junctions. This is done following the rules below but can be overruled by the user. Where levels have been overruled by the user or by the Pipe Sizing procedure the values will be shown in red to indicate they are no longer following the rules below and will not be automatically updated.
US Cover Level
DS Cover Level