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
single packer test, the hole is drilled to the bottom of first test section and
the top of the test section is sealed off by a packer. Water is then delivered
to the test section and it is kept at constant pressure and the flow is
measured.
In highly fractured rock there is a high chance that water tends to leak
around the packer which gives inaccurate result. As such, multiple packers
are adopted instead in which three sections of the drillhole are sealed up
and water is pumped to them at equal pressure. This eliminates the
tendency for water to flow around the packers from the middle section.
Hence, a more accurate result could be obtained by measuring flow from
the middle section alone.
Fig. Illustration of multiple pack
7. What is the purpose of adding hydrogen peroxide in sedimentation
analysis? (SA1)
There are two major techniques of particle size distribution:
(i) Sieve analysis – for soil particles larger than 60μm they can be
separated by this method.
(ii) Sedimentation analysis – for soil particles smaller than 60μm, they
are too small to be sieved by sieve analysis. Instead, the particle
size distribution is worked out from the rate of settlement of soil
particles suspended in water by Stoke’s law.
In sedimentation analysis, the soil under testing is firstly boiled with little
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