A measure of the change in strength of clays upon disturbance: For ordinary clays St = 1 to 4, sensitive clays 4 to 8, ‘quick’ clays 16 - 100.
The flow of water through soil.
The force transmitted to a body of soil due to the seepage of groundwater.
J = i gw V
The seepage force per unit volume.
j = i gw
The average velocity at which groundwater flows through the pores; the ratio of the volume flow rate to the average area of voids in a cross-section.
vs = q / Av
(See also flow velocity)
A measure of the change in strength of clays upon disturbance: For ordinary clays St = 1 to 4, sensitive clays 4 to 8, ‘quick’ clays 16 - 100.
The downward movement of ground or ground surface; the downward movement of a foundation.
Factors used in a general equation giving ultimate bearing capacity which provide adjustment relating to the shape (e.g. strip, square, circle)
The ratio of the change in shear stress
to the resulting change in shear strain.
The angular distortion or change in
shape of a body of material.
The maximum shear stress which a material can sustain under a given set of conditions. In soil mechanics it is necessary to refer shear strength to the strain at which the strength is measured.
critical shear strength
tc = c'c + s' tanf'c
peak shear strength
tp = c'p + s' tanf'p
undrained shear strength
tc = su
residual shear strength
tr = c'r + s' tanf'r
The force per unit area acting tangentially to a given plane or surface. Units: kPa.
Conditions in the ground when it is undrained; loading or unloading will cause changes in pore pressures, but not immediately in volume; these excess pore pressures dissipate with time due to consolidation.
(Also SL) The water content below which further reduction in water content causes no further reduction in volume.
The shear stress on the shaft of a pile of a pile or caisson or cone penetrometer.
Note: Although known as ‘skin friction’, the shear stress may not vary with normal stress.
Negative pore pressure created by capillary attraction in fine soils and in unsaturated soils.
The ratio of the mass of a body or a substance to the mass of an equal volume of water; the ratio of the density of a body or a substance to that of water.
The total surface area of all particles in a unit mass of soil. Units: m˛/g.
The total volume of a quantity of soil
containing a unit volume of soil grains.
v = 1 + e
The state boundary surface (SBS) is the boundary (usually in q’:p’:v space) to all possible stress-volume states of a soil. If a soil with a state on the state boundary surface is unloaded, the subsequent state will be inside the SBS, upon re-loading the subsequent state will move back onto (but not beyond) the SBS. In other words, stable states cannot exist outside the SBS.
A measure of the distance between
the current state (A) and the critical state; expressed as a ratio of stresses
or as a difference of specific volumes
Ss = p´A / p´c
Sv = vA - vc
steady state pore pressure (uo)
The pore pressure at equilibrium when all excess pore pressures have fully dissipated.
Susceptibility to distortion or volume change under load.
A measure of the change in size or shape of a body, relative to its original size or shape. (Direct strain is the ratio of change in length to original length; shear strain is the angle of distortion; volumetric strain is the ratio of change in volume to original volume.)
A function introduced in the solution of the Laplace equations defining two-dimensional seepage flow; the flow-quantity interval (Dq) between stream lines (flow lines) can be stated as DY = Dq.
See also potential function.
The intensity of force per unit area; normal stress is applied perpendicularly to a surface or plane, shear stress is applied tangentially to a surface or plane.
The past history of loading and unloading associated with a soil.
The symbol S when placed in front of a quantity indicates that the quantity is a sum or total.
swelling / recompression index (Cs, k)
The slope of the swelling (unloading) and recompression (reloading) line.
Cs = 2.303 k
where k = slope of v:ln s´ swelling/recompression line.