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
(ii) It aids in the cutting of paving blocks near edge courses because
paving blocks could lie over edge courses and the positions of
cutting could be marked accurately without any difficulty. However, if
a wall instead of edge courses is located adjacent to the pavement,
it is practically difficult to position the paving block over the gap
because of the physical hindrance of the wall.
(iii) It could be designed as surface drainage channel to convey
stormwater to a discharge point.
(iv) It acts as a frame which defines the shape of pavement.
8. For compaction of paving blocks, should the jointing sand be
applied before or after the compaction process? (S4)
The common practice is to apply jointing sand at the first place followed by
subsequent compaction. However, there are several potential problems
associated with this method. Firstly, the presence of sand provides support
to paving blocks leading to inadequate compaction. Secondly, the excess
jointing sand may be crushed during compaction and leaves stains on the
surface of paving blocks. Thirdly, damaged paving blocks appear to be
difficult for removal owing to frictional grip by jointing sand.
The alternative method is to carry out compaction firstly and then followed
by application of joint sand and then re-compaction is carried out again.
This method eliminates all the shortcomings of the first method described
above. However, it suffers from the demerit of two passes of compaction
instead of a single stage of compaction is required. Moreover, the
compaction operation tends to be noisier because of the absence of the
infilling sand which helps to reduce noise level. The direct contact between
individual paving blocks is more vulnerable to spalling during compaction.
9. Can all utility detectors detect the depth of utilities?
In Hong Kong, underground utility detectors are normally divided into two
types: electromagnetic detector and ground penetrating radar (GPR).
For electromagnetic detector, it can detect the signals emitted by metallic
utilities themselves by passive mode. While in active mode, the detector
has to pick up the signals through a transmitter and sonda connected
directly to the non-metallic utility. Both the alignment and depth can be
found in active mode while only alignment can be found in passive mode.
The electromagnetic detector available in market can detect utilities up to
depth of 3m.
267