A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
flowing full or even under submerged condition. As such, the headwater
level is increased in order to flow through the culvert and this in turn
increases the flooding risk associated with high headwater level.
Fig. Tailwater level in culvert.
13. What is the significance of critical slope in hydraulic design of
box culvert? (BC1)
Critical slope is the minimum slope in which maximum discharge shall
occur without requiring the box culvert to flow full. For box culverts with
slope less than critical slope, at low headwater it tends to flow full and
eventually requires a higher headwater depth to convey the same amount
of water required for culverts with slopes greater than critical slope.
14. What is the difference between on-line storage and off-line
storage in the design of storage pond? (HD9)
The design of storage pond is commonly divided into on-line storage and
off-line storage. The on-line storage concept involves the inclusion of
storage facilities in series with the pipelines so that overflow at the storage
facilities is allowed. One simple application of on-line storage is to enhance
a large size of drainage pipes. However, for heavy rainfall situation, the
spare capacity of drainage pipes will be rapidly exhausted. On the other
hand, off-line storage (e.g. underground storage tank) refers to storage
facilities in parallel with the pipeline and the return flow to the main pipeline
is only allowed when the outflow pipelines are not surcharged.
15. What are the effects of hydraulic jump? (HD6)
The use of hydraulic jump in hydraulic engineering is not uncommon and
the creation of such jumps has several purposes [58]:
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