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
Anisotropic Soil - A soil mass having different properties in different
directions at any given point referring primarily to stress-strain or
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.