E10160-200722
FOP
Page 17
Tamping of compressed bentonite is not required. Prior to setting the sand in place, lower
a cylindrical weight down the borehole to ensure that it is clear from any obstructions and,
if necessary, rinse the borehole until clear water emerges.
Note: It is also possible to place the piezometer into a sand filled canvas bag. The bag
then acts as a sand filled intake zone.
Typical installation of piezometers in a borehole
Note that an alternate way to install piezometers in boreholes is to fill the entire borehole
with grout after having lowered the instruments. This method, known as the Fully Grouted
Borehole Installation, is peculiar in that:
Piezometers are installed with filter end upward.
Proper care must be taken for preparing a grout mix that will mimic as well as
possible the stiffness and permeability of the surrounding ground. This is achieved
by selecting the proper water-cement ratio. Mixtures shown in the table below can
be used as a starting point. The cement and water are mixed first. When proper
ratio is reached, bentonite powder is slowly added until as heavy as feasible to
pump.