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We measure shear response in packings of glass beads by pulling a thin, rough, metal plate vertically through a bed of volume fraction ϕ, which is set, before the plate is pulled, in the range from 0.575 to 0.628. The yield stress is velocity independent over 4 decades and increases exponentially with ϕ, with a transition at ϕ≈0.595. An analysis of the measured force fluctuations indicates that the shear modulus is significantly smaller than the bulk modulus.
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Métayer et al. (2011) studied this question.
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