The general rule for the minimum number of impacts for low strain integrity testing is: The more, the better (assuming that each signal is collected properly). Increasing the number of impacts, and using the average signal will reduce the effect of background noise, and helps enhance repeatable parts of the signal, which will improve data visualization and makes interpretation much easier.
For circular (Diameter less than 500 mm) and rectangular cross sections, place the sensor near the center of the pile and strike several times around the pile head (i.e. 10 impacts).
For piles with larger diameter (i.e. Diameter > 500 mm) additional locations should be considered to obtain useful integrity information about the pile. Choose a minimum of 3 different locations. Collect adequate number of impacts for each location.
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