Multipoint Traveling Wave Decomposition Method and Its Application in Extended Pile Shaft Integrity Test

Abstract

Existing nondestructive pile integrity test (PIT) methods have certain limitations in the interpretation of test results for extended pile shafts supporting an existing structure. A novel multipoint traveling wave decomposition (MPTWD) method was developed in this study to address some of these limitations and predict the unknown length of an extended pile shaft with superstructure. The MPTWD method incorporates a test scheme that comprises multiple equally spaced sensors to separate the downward and upward waves and a corresponding data processing method. A pseudofrequency response (PFR) function was defined by dividing the measured upward wave by the downward wave in the frequency domain. Based on the PFR function, MPTWD results are obtained for a certain fictitious excitation. The unknown pile length can then be predicted by fitting the MPTWD results and the analytical solution to that of a laterally vibrating free-top pile. Because of their similar experimental layout, the MPTWD results are close to traditional PIT results and have fundamental advantages and disadvantages. The effects of technical test parameters on MPTWD results were investigated through a comprehensive parametric study. Then, the MPTWD method was applied in a field test, and the predicted pile length was found to be consistent with its actual precast length, verifying the feasibility and reliability of this novel method.