There are some problems such as plane-section assumption and three dimensional effects in dynamic testing on cast-in-situ concrete thin-wall pipe pile with large diameter. The plane-section assumption is not always satisfied in low strain dynamic testing of pipe pile without cap

because the nonaxisymmetric bending mode is excitated. The measuring point on top of pile at angle of ninety degree will suffer less high-frequency interference. So

the reflected wave signal is distinct and clear at this point. Both analytical and numerical results indicate that the reflection peak from pile bottom and defect is obvious at the top of pile with cap. The high-frequency interference at different points with different distance from the center of cap pile has the same frequency but different velocity amplitude. The point with distance 0.5k from the center of cap pile surfers minimum interference.