Coda wave analysis to monitor processes in soils

Sheng Dai*, Frank Wuttke, Juan Carlos Santamarina

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Small-strain elastic wave propagation is a constant-fabric phenomenon ideally suited to monitor processes in soils. However, the determination of very small changes in travel time limits our ability to resolve changes in soil stiffness caused by internal processes or changes in boundary conditions. The first-arrival reflects the fastest path between the source and receiver of the propagating wave field; later arrivals in the coda correspond to longer paths after multiple boundary reflections and internal scattering. Therefore, time shifts between the codas of two consecutive signals are longer and easier to detect than between the signals' first arrivals. Slight changes in coda waves can be determined by cross-correlating time windows, time-stretched signals, or frequency-stretched spectra. Basic coda analysis assumes a homogeneous velocity change throughout the medium, propagation modes (P, S) that are equally affected by the process and the preservation of VP=VS ratio during the process. The resolving power of coda wave interferometry is explored in an experimental study conducted with quartzitic sand subjected to loading, creep, and unloading stages. The results reveal that coda wave analysis can be used to detect changes in wave velocity on the order of δV/V <0:1%(this corresponds to a stress change smaller than δσ/σ≈1% in uncemented soils). Such a high velocity resolution permits the study of creep, aging, and diagenetic processes even in relatively short duration tests.

Original languageEnglish (US)
Pages (from-to)1504-1511
Number of pages8
JournalJournal of Geotechnical and Geoenvironmental Engineering
Volume139
Issue number9
DOIs
StatePublished - Sep 9 2013

Keywords

  • Aging
  • Coda wave interferometry
  • Creep
  • Cross correlation
  • Ottawa sand
  • Stiffness-stress response

ASJC Scopus subject areas

  • Environmental Science(all)
  • Geotechnical Engineering and Engineering Geology

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