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
straight pipes are derived from their corresponding maintenance methods.
15. What is the difference between road gullies and catchpits?
Both road gullies and catchpits are the two basic types of drainage inlets of
drainage system. Though they are designed to catch stormwater, road
gullies and catchpits are intended to catch stormwater at different locations.
Catchpits are designed to receive stormwater from slopes and stream
courses. There is no standard design of catchpits and they can take
different forms and shapes like inclusion of sand trap to improve the quality
of collected stormwater and to prevent the blockage of drains. On the other
hand, road gullies are intended to receive stormwater from roads only.
16. Is reinforcement needed in precast concrete manhole units? (M1)
Precast concrete manholes are normally constructed by placing the bases
of manholes firstly. The walls of precast manholes are formed by placing
the precast concrete rings one on top of the other up to the required height.
Someone may notice that reinforcement used for resisting the lateral earth
pressure and surface loads are not considered in some design. It is
discussed in Concrete Pipe Association of Great Britain that analysis of soil
pressures shows that standard unreinforced precast units are capable of
resisting uniformly distributed pressures (e.g. loading condition in a
manhole) down to a depth of 150m. If very severe road traffic and side
loads are encountered, an additional concrete surround of about 150mm
may be provided.
Fig. Precast concrete manhole
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