Pile
TECHNICAL
Integrity
Testing
Applications and limitations
By Drs. Hamed Layssi and Farid Moradi
A solid, stable and safe foundation is a must have in
the development of every major infrastructure to
ensure their efficient, reliable and safe operation for
the many years to come. Geotechnical site investi-gation
is used as the first step to identify the properties of
soil layers.
Piles and deep foundations are commonly used when the
soil condition is poor. This is especially true for construction
of infrastructure in coastal areas, northern permafrost and
in-land deserts. Piles are used to transfer the load of heavy
superstructure to the substrate. Other solutions normally
involve improving and stabilizing the mechanical properties
of weak soils using chemical and mechanical methods.
In order for piles to properly transfer superstructure load
to the bedrock, they should be free of defects in materials
and workmanship. However, construction and installation
of these elements, whether they are cast-in-place piles, or
driven piles, might affect the integrity of pile elements. Such
defects can be related to the consistency of pile materials
(honeycombed area, segregated concrete or concrete with
voids) or related to construction practice (i.e. soil inclusion,
bulging, necking). Such deficiencies can directly impact load-bearing
capacity of piles and contribute to partial settlement
of the superstructure.
In most cases, the pile head is the only accessible area.
Engineers rely on non-destructive testing (NDT) methods
to evaluate the quality and integrity of piles (Rausche et al
1992). These testing techniques are used in different stages of
a pile lifecycle, including:
• Quality control after construction or driving
• Routine inspection over life cycle
• Damage inspection because of major environment load-ing
(e.g. earthquake)
• Condition assessment for seismic and structural upgrade,
re-using piles in new construction, etc.
Several NDT methods have been developed to study and
analyze the integrity and quality of piles. Most of these meth-ods
use ultrasonic waves to study the pile elements. Low
strain impact integrity testing is a common tool for assessing
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