E

earth pressure coefficients
earth pressure coefficients for undrained conditions
effective stress (s')
effective stress ratio (h)
efficiency of a pile in a group (x)
elastic deformation
elevation head (h_z)
equipotential
excess pore pressure (ü)

The ratio of the horizontal effective stress acting on a supporting structure and the vertical effective stress in the soil at that point:

K_o = coefficient of earth pressure at-rest(when e_h = 0)
K_a = coefficient of active earth pressure (as the structure moves away from the soil)
K_p = coefficient of passive earth pressure (as the structure moves toward the soil)

For a smooth wall:
K_a = tan²(45° - ½f´)
K_p = tan²(45° + ½f´)
See also earth pressure coefficients in undrained conditions

These are defined in terms of total stresses as follows:
s_h = s_v - K_au s_u
(as the structure moves away from the soil)
s_h = s_v + K_pu s_u
(as the structure moves toward the soil)
For a smooth wall, K_au = K_pu = 2

The stress in a soil mass that is effective in causing volume changes and in mobilising the shear strength arising from friction; the principle of effective stress states that "all changes in a soil’s volume, shape or shearing resistance are due exclusively to changes in effective stress".

effective stress = total stress - pore pressure

s' = s - u

The ratio of deviator stress to mean effective normal stress
h = q´ / p´
(similarly, tan f´_mob = t´ / s´)

For a given pile in a group, the ratio of the average ultimate load in the group to the individual ultimate load on that pile; piles on the outside of a group are generally more heavily loaded than those near the centre. For driven piles in sands x may be greater than 1; for bored piles x may be as low as 0.6.

Deformation caused by a change in loading that is recovered completely when the load is removed.

In seepage problems, the height of a point above a given datum.

In a flow net, lines connecting points of equal total head; usually drawn so that the interval, or equipotential drop, is constant. Equipotentials intersect flow lines and impermeable boundaries at right angles.
N_d = number of equipotential drops in a flow net between the inflow and outflow boundaries.

The amount of pore pressure greater or smaller than the long-term steady-state pore pressure (u_o); excess pore pressure is dissipated during consolidation.