Improving the repeatability of bender element results by means of bender element configuration

1
Improving the repeatability of bender element
results by means of bender element configuration

• by
• C. R. I. Clayton, M. Theron and A.I. Best
• School of Civil Engineering and the Environment
• University of Southampton
• and
• Southampton Oceanography Centre

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Bender element configuration showing side-mounted
receivers with instrumentation
R3
R2
T1
Hewlett Packard 3582S Spectrum analyser
TTI TG1010 Function generator
LeCroy 9314 AM Quad 400MHz Digital oscilloscope
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Conventional time-of-flight transmitter to
receiver
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Co-planar side-mounted bender element
configuration
R2
R1
T2
Hewlett Packard 3582S Spectrum analyser
TTI TG1010 Function generator
LeCroy 9314 AM Quad 400MHz Digital oscilloscope
5
Hand picking traces of side-mounted receivers -
second peak
1st
2nd
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Group velocity, using side-mounted bender
receivers
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Results of different interpretation techniques
for group velocity
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Average and standard deviation
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Conclusions

• Side-mounted bender elements have the advantage
  that they can be relatively easily installed,
  without the need to modify triaxial platens.
• The use of two side-mounted receivers simplifies
  the handpicking of arrivals, and facilitates the
  use of cross correlation to determine group
  velocity.
• Group velocity measured between the two
  side-mounted bender receivers using cross
  correlation appears to be highly repeatable.
• Nonetheless, even for this Leighton Buzzard sand,
  and using high frequencies, there appear to be
  frequency effects.