What is a Pile Integrity Test?
​A pile integrity test is the procedure for determining the integrity of individual vertical or inclined piles by measuring and analyzing the velocity and force response of the pile induced by an impact device - usually applied axially and perpendicularly to the pile head surface. A pile integrity test (PIT), is also known as "low strain impact integrity testing of a deep foundation" and is a widely used non-destructive test method for the evaluation of pile quality, integrity and to help estimate the unknown length of existing piles and foundations. The PIT method works best for column type foundations, such as piles and drilled shafts. The method provides a rapid and simple tool for evaluation of a number of piles in a single working day.
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PROCEDURE:
Initially all types of contamination should be removed to reach a solid and sound concrete surface. The pile head surface should be accessible, above water, and clean of loose concrete, soil or other foreign materials resulting from construction. This step is very important because the connection between the sensor and concrete should be solid. The acceleration sensor should be placed on concrete firmly. To do so, a couplant material should be used to attach the acceleration sensor the pile head.  An impactor (usually a hand-held hammer) is used for impacting pile head; the impact should be applied axially with the pile. Motion transducers should be capable of detecting and recording the reflected echoes over the pile top. Acceleration, velocity, or displacement transducers can be used for this purpose. At the minimum, an acceleration transducer should have an Analog to Digital Converter with 12-bit resolution; and a Sample Frequency of at least 25 KHz. The location of the sensor should be selected away from the edges of the pile. The integrity testing should be performed no sooner than 7 days after casting or after concrete strength achieves at least 3/4 of its design strength, whichever occurs earlier.
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The distance between the impact location and the sensor should be no larger than 300 mm. Several impacts are applied to the top of the pile. The reflected echoes are then recorded for each individual impact. As an alternative, the average can be determined and used. As mentioned earlier, an acceleration transducer can be used for the purpose of this test. In this case, the apparatus shall provide signal conditioning and integrate acceleration to obtain velocity. The apparatus shall balance the velocity signal to zero between impact events.