Environmental Engineering Reference
In-Depth Information
Figure 20.11.
Survey point in soils susceptible to shrink and swell.
Figure 20.12.
An example of embankment dam piezometric conditions.
vertical permeability (k
h
/k
v
) of the earthfill is 15:1. Pore pressures in the embankment and
foundations are important from slope stability considerations, and for the potential for a
'blowout' or 'heave' condition to form at the toe of the embankment. Piezometers may be
installed to check and monitor design assumptions.
The following points should be noted:
- An observation well, installed at A, with a sand surround and/or slots for its full length,
will reach equilibrium at the phreatic surface at D;
-The pore pressure at A, i.e. the pressure that would be measured by a piezometer tip set
at point A, is equal to the difference in elevation of A and the point where the equipo-
tential through A meets the phreatic surface at C. Note that this may be much less than
the difference in elevation from A to D, due to head losses in seepage flow through the
earthfill;
