The three dimensional effect in low strain integrity testing of cast-in-place large-diameter pipe pile(PCC pile) is mainly presented by the difference of velocity responses at the points with different radius angles between exciting and receiving points. Based on the analytical formula founded by the authors

the dynamic response characteristics of every vibration modes are studied. The variations of total velocity responses on pile top along circumferential and radial directions are analyzed. The research indicates that: the total velocity response at 90º point mainly derives from the axisymmetric mode. The reflected wave crests at 45º

135º and 180º point are close to the axisymmetric mode; but the incident wave crests have a greater difference. The total responses on pile top mainly derive from the first order vibration mode along radial direction

while the other modes along radial direction have little contribution. The velocity responses are the superposition of low order modes; but the circumferential modes higher than tenth order have little contribution. The incident wave crests derive from many modes

while the reflected wave crests mainly derive from the axisymmetric mode. The high-frequency interference waves mainly derive from the first order non-axisymmetric mode

the peak value and phase of which are different from various points. The high-frequency interference at 90º point is the least; and the phase from 0º to 90º point is contrary to that from 90º to 180º point. The velocity responses have little difference among different points along radial direction but have great difference along circumferential direction.