Some observations on the performance of the signal matching technique in assessment of pile integrity

Hua You Chai, Chang Fu Wei, Kok Kwang Phoon, Yun Ming Yang

Research output: Journal PublicationArticlepeer-review

14 Citations (Scopus)

Abstract

The pulse-echo method is commonly used to assess pile integrity in a nondestructive way. One of the strategies for detecting relative variation in pile impedance is to analyze the wave reflections from the anomalies based on the 1-D stress wave theory. In current practice, however, several difficulties remain to be resolved in interpreting the wave patterns. Firstly, due to possible three-dimensional (3-D) behavior near the source and dispersion behavior far from the source, 1-D stress wave theory is not always applicable in analyzing the reflections from the anomalies. Secondly, reflections can be produced continuously along the shaft due to the pile-soil interaction, so that the reflection patterns are highly correlated to those from the pile body in complex layered soil profiles, and thus it is generally difficult to distinguish whether the reflections are produced by pile anomalies or by the changes in the soil profiles. In this paper, actual wave characteristics are analyzed based on numerical simulations and guided wave theory, the conditions for 1-D approximation are suggested, and the a method for uncoupling the soil resistance and the pile impedance effects is presented. The evaluation of pile integrity can be improved with help of the 1-D based signal matching technique. The technique is applied to experiments conducted on model piles, test piles for accreditation of pile inspectors, and routine in-situ piles. The results show that 1-D stress wave theory is approximately applicable in analyzing the reflections from deep anomalies under certain limited conditions, and the soil resistance and the pile impedance effects can be effectively uncoupled by relating the pile-soil interaction to the pile radius and the properties of the surrounding soils.

Original languageEnglish
Pages (from-to)246-258
Number of pages13
JournalJournal of Nondestructive Evaluation
Volume30
Issue number4
DOIs
Publication statusPublished - Dec 2011
Externally publishedYes

Keywords

  • Guided waves
  • Layered soils
  • Pile impedance
  • Pulse-echo
  • Signal matching

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering

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