The small-strain shear modulus depends on stress in uncemented soils. In effect, the shear-wave velocity, which is often used to calculate shear stiffness, follows a power equation with the mean effective stress in the polarization plane Vs=α(σ'm/1 kPa)β, where the α factor is the velocity at 1 kPa, and the β exponent captures the velocity sensitivity to the state of stress. The small-strain shear stiffness, or velocity, is a constant-fabric measurement at a given state of stress. However, parameters α and β are determined by fitting the power equation to velocity measurements conducted at different effective stress levels, so changes in both contact stiffness and soil fabric are inherently involved. Therefore, the α and β parameters should be linked to soil compressibility CC. Compiled experimental results show that the a factor decreases and the b exponent increases as soil compressibility CC increases, and there is a robust inverse relationship between α and β for all sediments: β≈0.73-0.27 log[α/(m/s)]. Velocity data for a jointed rock mass show similar trends, including a power-type stress-dependent velocity and inverse correlation between α and β however, the α-β trend for jointed rocks plots above the trend for soils.
|Original language||English (US)|
|Journal||Journal of Geotechnical and Geoenvironmental Engineering|
|State||Published - Oct 1 2014|
Bibliographical notePublisher Copyright:
© 2014 American Society of Civil Engineers.
- Compression index
- Contact effects
- Coordination number
- Granular fabric
- Shear-wave velocity
- Velocity-stress power relations
ASJC Scopus subject areas
- Environmental Science(all)
- Geotechnical Engineering and Engineering Geology