LARGE AMPLITUDE VIBRATION EFFECTS ON THE SHEAR MODULUS OF SAND.
MICHIGAN UNIV ANN ARBOR
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The report is concerned with the effect of large amplitude steady- state vibrations on the shear modulus of sands. The torsional resonant column method was employed for this research using two specially constructed devices. One device torsionally oscillates a 4 cm diameter, 27 cm long solid cylindrical specimen while the second device tests a hollow cylinder of sand having a 4 cm inside diameter, a 6 cm outside diameter, and a 30 cm length. The purpose of the hollow cylinder was to obtain a more uniform shear strain throughout the sample. The aim of the two testing programs was to determine the shear modulus of C-190 Ottawa sand as a function of void ratio and confining pressure before and after large amplitude torsional vibration had been applied. The effect of large amplitude vibration was to increase the low amplitude shear modulus by as much as 100 percent. The increase could not be accounted for on the basis of void ratio change. Vibration amplitude shear strain amplitude in the hollow specimen and cycles of torsional vibration are considered in presenting the data. The increase in low amplitude shear modulus was accompanied by an increase in damping indicating a change in the mechanical characteristics of the sample caused by the different patterns of vibration history. Author
- Soil Mechanics