Abstract:Assuming that a stress wave in low strain tests spreads in semi-spherical mode,a method was established to calculate the disturbance of a tie beam in response to the frequency of the stress wave.This method is related to the geometry of the tie beam,bent cap,pier,and pile. Furthermore,a test method was designed to test the integrity of piles in a column-pile system,in which multi-channel equipment was required to record the behavior of the bent cap and pile. Tests were conducted to compare the integrity of the pile during the entire column-pile system procedure.The results showed that when pile top was free,the reflection signal could be detected after tie beam and pier were constructed.Sensors should be located vertically as a linear array that will facilitate the calculation of the stress velocity and allow the recording of the behavior of the reflection from the bent cap,pile toe,etc.In regard to abnormal signals,their peak time should be analyzed to determine their location according to the stress velocity of pier,tie beam,and bent cap.It is not recommended that the abnormal signals be analyzed using only the similar or opposite-phase method as has been the previous rule in pile integrity test when pile top was free.