(1) Casing. A casing may be driven,
jetted, or pushed to the
full depth
is pumped into the soil.
to be treated and then withdrawn as grout
T h e es-
cape of grout up the contact surface of the
casing and the soil may
be a
p r o b l e m . This method is used extensively
in chemical grouting at
shallow
depths.
(2) Grout sheath. In this method a flush-joint grout pipe is grouted in,
using a special brittle grout that prevents leakage up the outside of the pipe.
The grout pipe is then withdrawn a short distance, leaving a brittle grout
sleeve below the pipe. Grout is then pumped into the soil through cracks
produced by the pressure of the grout in the brittle grout sleeve below the
end of the grout pipe.
( 3 ) Pierced casing. A patented method has been developed for soil
grouting in which the casing is grouted in using a special grout. The casing
is then pierced at any selected point using a powder-impelled projectile fired
from a device lowered into the casing.
(4) Tubes a manchette. In this patented method a perforated pipe is
grouted into the hole with a special sleeve grout. The perforations are cov-
ered with short sections of a rubber sleeve (manchettes) on the outside of
the pipe that act as one-way valves. A double packer is used to control the
treatment location. The pressure on the grout pumped into the hole between
the confining packers causes it to push past the small rubber sleeves cover-
ing the perforations, rupture the sleeve grout, and enter the soil. This de-
vice is suitable for injecting cement, clay, or chemical grout. In some in-
stances the same holes and the same rubber-sleeved vents have been used
for the injection of each of these grouts separately and in rotation into a soil.
This permits economical impermeabilization of soil containing large voids
with an expensive chemical grout by first filling the large voids with less
costly clay and cement grout.
12.
CRITIQUE.
--.
a
Stage
Grouting.
( 1 ) Advantages. All grouting, regardless of depth of zone, is done from
the top of rock, usually through a short pipe set in the top of the hole. This
eliminates the need for packer assemblies required for stop grouting. A
smaller hole can be used for stage grouting than for stop grouting since no
packer is involved. Stage grouting has a flexibility that permits special at-
tention to be given to almost any local condition encountered, provided the
specifications are written to permit payment for the contractor's efforts.
Drill cuttings from lower zones cannot clog groutable openings in higher
z o n e s . The grouting of all zones is done through a single hole, making drill-
ing costs much less than for series grouting, which requires a new hole for
each cycle of drilling and grouting.
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