Accession Number:

ADA464041

Title:

The Effects of Microstructure on Shear Properties of Shallow Marine Sediments

Descriptive Note:

Journal article

Corporate Author:

NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE

Report Date:

2007-01-01

Pagination or Media Count:

14.0

Abstract:

This study was undertaken to investigate the implication of geoacoustic behaviors in the shallow marine sediments associated with the changes in geotechnical index properties. Two piston cores 270cm and 400cm in core length used in this study were recovered from stations 1 and 2, the western continental margin, the East Sea. Scanning electron microscopy SEM was employed to illustrate the effects of microstructure on shear properties. The direct SEM observation of sediment fabrics is inevitable to understand the correlation of the changes in geoacoustic properties to the sediment structure. The consolidation of sediments by overburden stress resulting in the clay fabric alteration appears to play an important role in changing shear properties. Water contents and porosity of sediments gradually decreases with increasing depth, whereas wet bulk density shows a reverse trend. It is interesting to note that shear wave velocities increase rapidly from 8 to 20 ms while compressional wave velocities significantly fluctuate, ranging from 1450 to 1550 ms with depth. The fabric changes in sediment with increasing depth for example, uniform grain size and well oriented clay fabrics may cause the shear strength increase from 1 to 12 kPa. Shear wave velocity is, therefore, shown to be very sensitive to the changes in undrained strength for unconsolidated marine sediments. This correlation allows an in-situ estimation of shear stress in the subsurface from shear wave velocity data.

Subject Categories:

  • Physical and Dynamic Oceanography
  • Properties of Metals and Alloys
  • Acoustics
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE