GLOSSARY
Activity of Clay - The ratio of plasticity index to percent by weight of the
total sample that is smallar than 0.002 mm in grain size. This property is
correlated with the type of clay material.
Anisotropic Soil - A soil mass having different properties in different
directions at any given point referring primarily to stress-strain or
permeability characteristics.
Capillary Stresses - Pore water pressures less than atmospheric values
produced by surface tension of pore water acting on the meniscus formed in
void spaces between soil particles.
Clay Size Fraction - That portion of the soil which is finer than 0.002 mm,
not a positive measure of the plasticity of the material or its
characteristics as a clay.
Desiccation - The process of shrinkage or consolidation of the fine-grained
soil produced by increase of effective stresses in the grain skeleton
accompanying the development of capillary stresses in the pore water.
Effective Stress - The net stress across points of contact of soil
particles, generally considered as equivalent to the total stress minus the
pore water pressure.
Equivalent Fluid Pressure - Horizontal pressures of soil, or soil and water,
in combination, which increase linearly with depth and are equivalent to
those that would be produced by a heavy fluid of a selected unit weight.
Excess Pore Pressures - That increment of pore water pressures greater than
hydro-static values, produced by consolidation stresses in compressible
materials or by shear strain.
Exit Gradient - The hydraulic gradient (difference in piezometric levels at
two points divided by the distance between them) near to an exposed surface
through which seepage is moving.
Flow Slide - Shear failure in which a soil mass moves over a relatively long
distance in a fluidlike manner, occurring rapidly on flat slopes in loose,
saturated, uniform sands, or in highly sensitive clays.
Hydrostatic Pore Pressures - Pore water pressures or groundwater pressures
exerted under conditions of no flow where the magnitude of pore pressures
increase linearly with depth below the ground surface.
Isotropic Soil - A soil mass having essentially the same properties in all
directions at any given point, referring directions at any given point,
referring primarily to stress-strain or permeability characteristics.
7.1-G-1
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