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Effect of frequency and vertical stress on cyclic degradation and pore water pressure in clay in the NGI simple shear device

  • Author(s): Mortezaie, AR
  • Vucetic, M
  • et al.
Abstract

The effects of the frequency of cyclic shearing and vertical consolidation stress on the cyclic degradation and cyclic pore water pressure in normally-consolidated kaolinite clay having PI 5 28 were investigated with the help of the cyclic strain-controlled Norwegian Geotechnical Institute (NGI) simple shear test. The testing program encompassed three cyclic shear strain amplitudes, γc50:1, 0.25, and 0.5%, two vertical effective consolidation stresses, σvc=5220 and 680 kPa, and three frequencies, f 50:001, 0.01, and 0.1 Hz. The results reveal that the cyclic degradation parameter, t, which measures the rate of cyclic degradation with the number of cycles, increases substantially with f and decreases with σvc. If f is increased 10 times, t may increase by 20-50%. If s9vc is increased from 220 to 680 kPa, the t parameter may decrease by 20-38%. The cyclic pore water pressure normalized by σvcdecreases with f and σvc. © 2013 American Society of Civil Engineers.

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