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
Level One (Core FAQs)
Part I: Site Investigation
1. What is the difference between Dynamic Probing and Standard
Penetration test? (SI1)
Standard Penetration Test (SPT) is an in-situ dynamic penetration test to
provide information on the properties of soil. It may also collect a disturbed
soil sample for grain-size analysis and soil classification. SPT involves the
driving of a standard sampler through a distance of 450mm into the bottom
of a borehole using the standard weight of 63.5kg falling through 760mm.
Dynamic Probing Test as per BS1377: Part 9: 1990 involves the driving of
a metal cone into the ground through a series of 1-metre length steel rods.
These rods are driven from the surface by the hammer system on the rig
which drops 63.5 kg weight onto the rods through a fall of 760mm. The
number of blows that is required to drive the cone down each 100mm
increment is then recorded until a required depth is reached or a refusal is
achieved. Dynamic Probing has many applications. For instance, it may be
used to estimate the depths of at the interface between hard and soft strata
and to trace the outline of objects buried underground.
SPT test is used to provide valuable information on soil properties.
However, the main use of dynamic probing is to interpolate information
between boreholes/trial pits swiftly and to supplement information found
from boreholes and trial pits at a low cost. For instance, dynamic probing is
carried out close to a borehole where the underground conditions are
identified. As such, by using the dynamic probing, the result of borehole
can be extended to other areas in between two boreholes.
2. When would engineers use Cone Penetration Testing instead of
Standard Penetration Test? (SI2)
(I) Standard Penetration Test is carried out in boreholes at 1.5-2m intervals.
However, Cone Penetration Testing allows a continuous record of
ground resistance profile.
(II) Disturbance to ground is less by Cone Penetration Testing when
compared with Standard Penetration Test.
(III) The use of Cone Penetration Testing is faster and cheaper when
compared with the combination of boring, sampling and Standard
Penetration Test.
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