DYNAMIC RESPONSE OF SAN FRANCISCO BAY MUD

Shear moduli and material damping of undisturbed samples of San Francisco Bay mud were investigated in the laboratory with the resonant column method. These properties were studied over a range in single-amplitude shearing strains from 0.0002 to 0.2 percent and over a range in confining pressures from 2.5 to 80 psi. Below a threshold shearing strain of about 0.001 percent, shear modulus and material damping of Bay mud were essentially independent of shearing strain amplitude. Above the threshold shearing strain, modulus decreased and damping increased as strain increased. Time of confinement was an important parameter in determination of the dynamic properties. Shear modulus continually incrased and material damping continually decreased with increasing time at a constant confining pressure at shearing strains below the threshold strain. An increase in shear modulus with time of constant confinement also occurred in Bay mud at shearing strains as high as 0.1 percent, and this increase was similar to that measured at low-amplitude strains. Cycling for 1000 cycles or less below a threshold degradation strain level of 0.01 percent had essentially no effect of the dynamic properties of Bay mud. However, cycling above this threshold degradation level caused a temporary decrease in modulus and increase in damping. The dynamic properties of the Bay mud rebounded with time after high-amplitude cycling to the original prperties as evaluated by the long-term time-effect. A close comparison between laboratory and published field shear wave velocities was found once the long-term time effect was taken into account. /Author/

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 940-959

Subject/Index Terms

Filing Info

  • Accession Number: 00179790
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 12 1978 12:00AM