What should be done when reinforcement extending above the pile top generates spurious vibrations which interfere with the PIT data?
Heavy reinforcement (e.g., more than 1% steel relative to concrete area) extending above the pile top more than 1 m (3 feet) often causes vibrations which interfere with the signal from impedance changes below the pile top. The best remedy is experimenting with different hammer sizes and softness/hardness of the hammer tips, which may produce signals with frequencies which cause less interference (note that while Pile Dynamics supplies hammers with only one type of tips, hammers with soft tips may be purchased in the marketplace). Applying very light impacts (while compensating with a higher acceleration gain), may also yield record improvements. Bending the reinforcement away may be helpful, but that is often neither possible nor desirable. Dampening these vibrations by clamping heavy materials between the rods may be helpful, however, that is very time consuming and not necessarily successful. Unfortunately, this is a problem that oftentimes cannot be satisfactorily solved.