Abstract: Previous researches on the limitations of low strain integrity testing with wave reflection method were focused on the size effect of stress wave propagation. The limitations of integrity testing for hand-dug pile in consideration of the pile-forming process and the pile’s surrounding strata were rarely researched. With the construction site of a powerplant in Hunan province as an example, we carried out a large number of field low-strain tests on hand-dug piles, and analyzed the collected time-history curves. Through core-drilling method, we checked the foundation piles with abnormal time-history curves, and estimated their integrity. We conclude that the pile tip reflection is affected by surrounding strata, properties of the bearing layer of pile tip, and pile length. The low strain testing with wave reflection method is interfered by hole-protection wall, variation of pile surrounding strata, and secondary reflection at the interface with different impedances. It will probably fail to detect under the influence of interaction between pile and soil.

Key words: low-strain integrity testing with wave reflection method, hand-dug pile, core-drilling method, limitation