STRESS CONDITION EFFECTS ON DYNAMIC PROPERTIES OF SOIL

Laboratory tests, using resonant column method, have been conducted to evaluate the shear modulus and the damping characteristics in dry and saturated specimens of variable soils. The hollow cylindrical samples tested are 25 cm in height, 10 cm in outside diameter and 6 cm in inside diameter. The specimens are fixed at the bottom and the oscillators are fastened to the rigid mass on the top of the specimen. The confining pressure is supplied by air pressure and the axial load is applied independently of the confining pressure to produce the anisotropic stress conditions. The frequency of the torsional excitation was varied until the oscillator specimen system resonated in testing. The strain amplitude varied from 0.000005 to 0.0005 in these tests. The shear moduli were calculated from the resonant frequencies and other parameters as above. The damping characteristics were obtained by the amplitude-time decays in the free vibrations. Test results obtained showed such dynamic properties of soils as follows: (1) Under constant values of other parameters, shear moduli vary with 1/2 power of the mean principal stress (p) and decrease with increase of void ratios and shearing strain amplitudes. Furthermore, damping capacities decrease with increase of p and increase with increase of strain amplitude. However, damping capacities take constant values irrespective of change of void ratios under constant values of other parameters. (2) While the value of p is kept constant, the shear modulus is nearly constant irrespective of the value of the deviator stress (q) until the stress ratio, q/p, reaches some value, say 1.0. However, beyond this value of q/p, shear moduli begin to decrease with increase of q/p. This phenomenon would be due to the anisotropic stress condition and the corresponding anisotropy in the inner structure of specimens. /Author/

Media Info

  • Features: Figures; References;
  • Pagination: p. 311-327

Subject/Index Terms

Filing Info

  • Accession Number: 00128530
  • Record Type: Publication
  • Report/Paper Numbers: Tech Memo #1023 Pt II
  • Files: TRIS
  • Created Date: May 14 1976 12:00AM