Idealized Sine Wave Approach to Determine Arrival Times of Shear Wave Signals Using Bender Elements

Qasim Khan, Sung-Woo Moon, Taeseo Ku

Research output: Contribution to journalArticle

Abstract

Determining small strain stiffness Gmax of soils in laboratory is generally achieved using bender elements. Shear wave propagation is affected by the soil medium and boundary conditions causing distortion in output signals, which introduces error in travel time estimates. This study proposes a novel technique for determining first arrival time in a systematic manner. Based on idealized sine waves, this technique modifies peak-to-peak results to find arrival times using the output frequency of received signal. By incorporating the initial half wavelength of received signals, five methods depending on the length of signal chosen for calculating the output frequency are proposed in this paper. The applicability of the proposed technique is evaluated based on signals reported in published literature and signals obtained for Singapore marine clay (uncemented and lightly cemented). For most soil types and testing conditions, it was demonstrated that the proposed technique produces close estimates with reported original arrival times. On the contrary, other techniques such as the peak-to-peak, cross-correlation, and cross spectrum often underestimated shear wave velocities when the output signals contains relatively low frequency contents. Consequently, the proposed technique significantly reduces subjectivity and produces improved reliability in estimating specific arrival times without the need of any frequency sweep. Moreover, by incorporating the quality and shape of signals into the analysis, better estimates of first arrival can be established especially for noisy signals or signals affected by near-field effects.
LanguageEnglish
JournalGeotechnical Testing Journal
DOIs
Publication statusAccepted/In press - 2019

Fingerprint

Shear waves
arrival time
S-wave
Soils
Travel time
Wave propagation
Clay
Stiffness
Boundary conditions
Wavelength
Testing
travel time
wave propagation
wave velocity
stiffness
soil type
boundary condition
soil
wavelength
clay

Keywords

  • Bender Elements
  • Shear Waves
  • First Arrival
  • Peak-to-Peak
  • Output Frequency

Cite this

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title = "Idealized Sine Wave Approach to Determine Arrival Times of Shear Wave Signals Using Bender Elements",
abstract = "Determining small strain stiffness Gmax of soils in laboratory is generally achieved using bender elements. Shear wave propagation is affected by the soil medium and boundary conditions causing distortion in output signals, which introduces error in travel time estimates. This study proposes a novel technique for determining first arrival time in a systematic manner. Based on idealized sine waves, this technique modifies peak-to-peak results to find arrival times using the output frequency of received signal. By incorporating the initial half wavelength of received signals, five methods depending on the length of signal chosen for calculating the output frequency are proposed in this paper. The applicability of the proposed technique is evaluated based on signals reported in published literature and signals obtained for Singapore marine clay (uncemented and lightly cemented). For most soil types and testing conditions, it was demonstrated that the proposed technique produces close estimates with reported original arrival times. On the contrary, other techniques such as the peak-to-peak, cross-correlation, and cross spectrum often underestimated shear wave velocities when the output signals contains relatively low frequency contents. Consequently, the proposed technique significantly reduces subjectivity and produces improved reliability in estimating specific arrival times without the need of any frequency sweep. Moreover, by incorporating the quality and shape of signals into the analysis, better estimates of first arrival can be established especially for noisy signals or signals affected by near-field effects.",
keywords = "Bender Elements, Shear Waves, First Arrival, Peak-to-Peak, Output Frequency",
author = "Qasim Khan and Sung-Woo Moon and Taeseo Ku",
year = "2019",
doi = "10.1520/GTJ20170121",
language = "English",
journal = "Geotechnical Testing Journal",
issn = "0149-6115",
publisher = "American Society for Testing and Materials",

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T1 - Idealized Sine Wave Approach to Determine Arrival Times of Shear Wave Signals Using Bender Elements

AU - Khan, Qasim

AU - Moon, Sung-Woo

AU - Ku, Taeseo

PY - 2019

Y1 - 2019

N2 - Determining small strain stiffness Gmax of soils in laboratory is generally achieved using bender elements. Shear wave propagation is affected by the soil medium and boundary conditions causing distortion in output signals, which introduces error in travel time estimates. This study proposes a novel technique for determining first arrival time in a systematic manner. Based on idealized sine waves, this technique modifies peak-to-peak results to find arrival times using the output frequency of received signal. By incorporating the initial half wavelength of received signals, five methods depending on the length of signal chosen for calculating the output frequency are proposed in this paper. The applicability of the proposed technique is evaluated based on signals reported in published literature and signals obtained for Singapore marine clay (uncemented and lightly cemented). For most soil types and testing conditions, it was demonstrated that the proposed technique produces close estimates with reported original arrival times. On the contrary, other techniques such as the peak-to-peak, cross-correlation, and cross spectrum often underestimated shear wave velocities when the output signals contains relatively low frequency contents. Consequently, the proposed technique significantly reduces subjectivity and produces improved reliability in estimating specific arrival times without the need of any frequency sweep. Moreover, by incorporating the quality and shape of signals into the analysis, better estimates of first arrival can be established especially for noisy signals or signals affected by near-field effects.

AB - Determining small strain stiffness Gmax of soils in laboratory is generally achieved using bender elements. Shear wave propagation is affected by the soil medium and boundary conditions causing distortion in output signals, which introduces error in travel time estimates. This study proposes a novel technique for determining first arrival time in a systematic manner. Based on idealized sine waves, this technique modifies peak-to-peak results to find arrival times using the output frequency of received signal. By incorporating the initial half wavelength of received signals, five methods depending on the length of signal chosen for calculating the output frequency are proposed in this paper. The applicability of the proposed technique is evaluated based on signals reported in published literature and signals obtained for Singapore marine clay (uncemented and lightly cemented). For most soil types and testing conditions, it was demonstrated that the proposed technique produces close estimates with reported original arrival times. On the contrary, other techniques such as the peak-to-peak, cross-correlation, and cross spectrum often underestimated shear wave velocities when the output signals contains relatively low frequency contents. Consequently, the proposed technique significantly reduces subjectivity and produces improved reliability in estimating specific arrival times without the need of any frequency sweep. Moreover, by incorporating the quality and shape of signals into the analysis, better estimates of first arrival can be established especially for noisy signals or signals affected by near-field effects.

KW - Bender Elements

KW - Shear Waves

KW - First Arrival

KW - Peak-to-Peak

KW - Output Frequency

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