Q

Can the results of PIT tests be confirmed by comparing them with the piling records?

A

Certainly comparing the PIT results with installation records is always advised. This is particularly true for augered cast-in-place or continuous flight auger (CFA) piles with installation records obtained with a magnetic flow-meter and with depth increments of 600 mm (2 ft) or less (such as Pile Dynamics’ Pile Installation Recorder would produce). In addition, one should always compare results of PIT with the soil profile. There may be systematic changes in the PIT records that correspond to soil layers. For example, if a loose sand overlays a stiff clay, the pile may have a bulge in the sand and then return to nominal dimension at the clay layer. In this case the relative reduction should not be interpreted as a defect since the nominal diameter is maintained. It is also good to compare the PIT records with each other, to try to establish the normal result and then to determine those that substantially deviate, particularly if a reflection indicating a defect is observed (i.e. large reflection with the same sign as the input pulse). In summary, all information available should be considered when determining final acceptance of foundations using the PIT method.