Civil Engineering Reference
In-Depth Information
Table 8.1
Summary of methods of carrying out integrity tests on piles
General method
Type
Relative cost
Advantages
Disadvantages
Acoustic
(section 8.2.1)
Single hole
ultrasonic logging
High cost if
inspection
hole has to
be drilled
The system scans the pile concrete radially
for a distance of approximately 100mm
around the drilled hole or installed tube.
The method is relatively rapid, some tens
of tests being possible daily
Pre-selection is generally required as it
is usual to install purpose made tubes
in the pile for the equipment. It is
necessary to employ plastic tubes for
this purpose, with the attendant risk
of collapse, steel tubes being
unsuitable for
single
hole logging. The
installation of the tube adds to the
reinforcement steel in restricting free
concrete flow and may in itself lead
to defects. Poor bonding of the tube
to the concrete may yield an
anomalous response. Unless a hole is
drilled, it is not possible to inspect
right to the base of a pile by this
method. Specialist interpretation is
generally necessary
Twin tube
ultrasonic logging
Medium cost,
depending on
expense of
casting-in
inspection
tubes
By using a suitable number of inspection
holes, the major portion of a pile core
may be inspected. The inspection may be
carried out to the base of the pile. Speed
of testing similar to single-tube method
(per traverse) at about 500 to
1000m/day
As for single-tube method except that
inspection to the base of the pile is
routine. The number of inspection
tubes required increases with pile
diameter, and multiple tubes are
usually necessary for large-diameter
bored piles
Radiometric
(section 8.2.2)
Single-tube
radiometric
logging;
backscatter
technique
Medium to high
cost if hole
requires to
be formed
The system may be used on freshly cast
piles and is fairly sensitive to voids or
inclusions. Almost the full depth of the
pile may be inspected. A zone
approximately 100 mm radially from the
inspection hole is examined (not
It is usual to use cast-in tubes with the
disadvantage of pre-selection and
added congestion in the pile in the
pile shaft. The number of inspection
holes required increases with pile
