Assessment of pile integrity by low-strain stress wave method

This paper discusses the application and limitations of the stress wave method for the assessment of pile Integrity. Equations for the calculation of wave reflection and transmission are derived as related to the interpretation of test results. An idealized pile with a necking linkend section is analyzed using the theoretical equations to show typical wave reflections from the necking section and from the pile toe. The instrument used for pile integrity testing is briefly described. Original data from a field verification exercise of pile integrity testing in Beijing, China are presented and interpreted. Original data from a test performed on a precast prestressed concrete pile connected in four segments in Hang Kong are also presented and interpreted. The data measured from the field show that the measured velocity wave is, in general, more complicated than that described by the idealized stress wave equation. Factors affecting test results and limitations of the testing method are discussed and summarized in this paper.