Tests of pile integrity using the low stress method are tests of the quality of concrete piles in the ground. It is recommended to examine the integrity of piles on each foundation, especially if during the construction of piles there were doubts as to the integrity of concreting of the shaft of the piles or if there are specific ground conditions, e.g. a tense water table. The test consists in measuring the waveform, which is caused by a special hammer hitting the pile head. By measuring the delay time of the reflected signal and knowing the speed of the wave propagation you can determine the length of the pile. In the case of changes in the cross-section (narrowing or thickening), the wave is partially reflected earlier, which is reflected in the recorded parameters.
The undoubted advantages of the technology include the speed of testing, lack of additional constructions, ease of testing and its low price.