Culvert Drainage Question
You are required to designa culvert for a proposed road crossing across a concrete lined stormwater
The stormwater drain has a uniform grade of 0.0012 m/m and is approximately trapezoidal in
section with a bed width of 8m and side slopes of 1V:1H. The normal depth in the floodway at the
design discharge is 0.85 m. Calculate the design discharge in the floodway. You may assume the flow
Pipe culverts, 10 metres long are to be incorporated in the proposed roadway. The culverts will be
laid at the same grade as the base of the stormwater drain. The inlet has a precast concrete
headwall with square-cut barrels.
The culvert needs to be designed such that no excavation of the base or sides of the stormwater
drain is required. One (1) metre of the channel base width should be allocated to the headwall and
infill required between the multiple culvert barrels, reducing the maximum total width available for
the culverts to 7 metres.
If the road pavement is to be 1.9 m above the floodway base at the culvert inlet, design a suitable
set of pipe culverts to achieve at least 200 mm of freeboard to the pavement level.
Standard pipe culvert sizes to be used as per the table on the following page.
Your design needs to meet the required freeboard, however your design does not need to be
optimised and you may present any culvert design that meets these criteria. Full working should be
provided to support your final design.
If a number of culvert configurations were trialled before achieving a satisfactory design, provide a
brief summary of what designs were trialled before achieving a final design.
As part of your assignment submission, include a paragraph reflecting on the adequacy of your
design. In particular, your discussion should address:
Your rationale for selecting your culvert configuration for testing,
The degree to which the freeboard requirement is met, and
The afflux above the normal depth that results from the culvert.
The design workings and final design should include;
Use of any relevant tools and guidelines including identified reference and key information
Use of consistent bas units in all working and answers
Use of appropriate diagrams to explain workings/design
Rigorous investigation undertaken
Use key values to make decisions and final recommendation
Nominal dimensions of concrete pipe and box culverts
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