Generally inexpensive and often underrated, the Pile Integrity Test (PIT) if accurately conducted provides ample information that can save a building sitting on piles from collapse ab initio. The question is how much information engineers try to deduce from this ‘simple’ test and how seriously people take results from the test. The PIT primarily serves to check the uniformity of the pile shaft as well as its depth, but most people are only concerned about depth or better still, only accustomed to determining the depth and not necessarily the other parameters that can be deduced from the test. As much as it is quite easy to conduct the test, correctly analyzing and interpreting the data obtained from the test is not for everyone. There are a couple of defects that could be read from this test that can help engineers make informed decisions about the subject piles e.g., the presence or absence of necking, bulges, soil inclusion, cracks, voids, inconsistencies in the concrete mix, etc. But if you can’t read the wave signals (reflectograph) properly, you won’t be able to get the best out of the test.
When a pile doesn’t extend to the required termination depth, there is the likelihood that it is not founded in the suitable bearing stratum; this may cause it to underperform in its key function of bearing and transmitting the load of the building/structure on it properly unto the underlying earth. Likewise, if your piles happen to extend up to the depth required but have defects within their shaft, they may become ‘surplus to requirement’.
Necking in piles for instance is particularly dangerous because it can create a huge loss of strength within the piles. Bulges although originally recognized as defects because they largely alter the uniformity of the pile shaft, they are seen as positive defects in that they eventually contribute or add to the mass and invariably, the strength of the pile.
Soil inclusion doesn’t help for uniformity in the strength characteristics of the pile and can be particularly harmful where the volume of inclusion is significant, particularly with respect to the position along the shaft where the inclusion occurs. For instance, for end-bearing piles, the entire load is transmitted to the end portion of the pile unto the ground so if there is massive soil inclusion there, it might cause the pile to fail. The same applies to cracks and voids. Voids and cracks or even excessive honeycomb within piles can create avenues for water and other undesirable earth materials to constantly infiltrate the pile and cause damage over time, including eventual failure of the pile.
Although the general unspoken rule is to conduct PIT on at least two-thirds of the total number of piles installed on a site especially for upward of 50 numbers, I would normally advise that all piles undergo PIT because each is somewhat unique to the rest and one bad pile poses a risk to the others and subsequently the entire structure. In Nigeria, the test would cost an average of $10 per pile and results can be obtained directly on the field.
Test Engineers at Bobpenoz observe that the PIT test provides a lot of latent information that constructors might have been ignoring because most people conducting these tests do not have sufficient expertise to properly analyze the data obtained, and project owners and handlers do not know where to find the right experts. The information from PITs helps engineers working on the foundation to know if they can rework affected piles, discard them outrightly, and subsequently replace them before even proceeding with the rest of the foundation. A stitch in time saves nine, therefore an accurate PIT can save you from incredible losses and ‘from the pit’.
