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th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
velocity vectors on these cutting planes show dominant S-wave
motions (from right to left) in the central part of the specimen
while minor P-wave motions developed on the sides (with the
particle on the right moving downwards and the particle on the
left moving upwards). Though the P-waves travel faster, they
cause little interference at the central part of the specimen where
the receivers are located. At the time shown in Figure 7, the S-
wave front just passes cutting plane 1-1 but has not yet reached
cutting plane 2-2. A significant amount of additional particle
level information is available from DEM simulations, including
displacement vectors, contact forces, and contact slip. This
information is being analyzed as part of ongoing studies into the
fundamental nature of shear wave propagation in granular
assemblies.
7 REFERENCES
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Figure 7. Particle velocity vectors on different cutting planes of a DEM
specimen at a 10ms time point after excitation
6 CONCLUSION
This paper presents a DEM study of S-wave propagation in
random assemblies of spherical particles. DEM simulations
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respsone is free of factors such as cross-talk, systen delay, and
environmental noise. A multiple receiver setup allows for more
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Excitation frequency showed significant impact on the
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functioned as a low-pass filter when excited by a sine pulse with
different frequencies. Frequency components that were higher
than the resonant frequency were significanlly attenuated.
Dispersion was observed when the excitation frequencies were
low. The affect of excitation frequency on S-wave velocity
became less appreciable when the frequencies were higher than
the resonant frequency.
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The S-wave velocity increased with increasing effective
confining stress, and is describled by an emprical fomula
previously developed based on laboratory tests. The fitting
parameters obtained in this DEM simulation were similar to
those for sands and OC clays measured in the lab.
Zhao, X., and Evans, T. M. (2009). "Discrete simulations of laboratory
loading conditions." International Journal of Geomechanics, 9(4),
169-178.
Velocity vectors highlighted the complex motions of
individual particles during wave propagation. They showed
dominant S-wave motion along the central area of the specimen
along with minor P-wave motion on the sides.
