d. Pneumatic Packer. The pneumatic packer shown in figure 20 has
proved suitable in soft and thin-bedded rocks where the drill holes are often
somewhat over size. In fact the EX (1-1/2-in.) size can be seated in a 4-in.
pipe when the proper rubber tubing is used and it is properly attached at the
e n d s . The length of rubber sleeve should not be less than 18 in. Under con-
ditions requiring large expansions and relatively high expanding pressure,
double -tapered collars at either end may be necessary to prevent rubber
b r e a k a g e . It is not suitable for high grout pressures, but it will withstand
100 psi under poor conditions and will hold up to 200 psi if the hole is not too
large or uneven. In weak sedimentary formations of alternating layers of
shale and sandstone or lime stone, this packer has proved invaluable. It is
now widely used where low pressures are dictated by foundation conditions.
A S P H A L T GROUTING EQUIPMENT. Commercial asphalt heaters sim-
19.
ilar to those used by roofing contractors have been found satisfactory for
heating asphalt for grouting. The heater should have a baffle near the outlet
to prevent lumps from entering the supply line. Gear pumps, reciprocating
pumps with ball valves, or 1-in. boiler-fed piston pumps have been used to
pump hot asphalt grout through 1-1/2 -in. black iron pipe. Mixers are not
needed for either hot asphalt or asphalt emulsions. A typical hot asphalt
grout plant is shown in figure 21. Cement grouting equipment can be used
for asphalt emulsions.
20.
C H E M I C A L GROUTING EQUIPMENT. The equipment required for
chemical grouting will vary depending on the chemicals being used. Basi-
tally this equipment consists of mixing tanks; variable speed, positive -
displacement-type pumps, control valves; and gages so that the proportion-
ing of chemicals can be closely controlled. Self-contained mobile units are
available that include all necessary components for the grout system. Gen-
erally, the se units have been developed by the grout manufacturer and are
designed for a specific chemical process. In any case, all grouting equip-
ment should be of a material that will not react with the chemicals being
used.
21.
a . Cement Grouting.
( 1 ) Plants. The grout plant should consist of a mixer, agitator. sump,
pump and necessary valves, gages, and lines to control the operation. Standby
equipment may be required depending on the nature of the job. Cement grout
plants vary in size from compact systems that may be truck-mounted to
large automated systems that require dismantling for moving. Figures 22
and 23 illustrate the two extremes. In figure 22 both the single and return
line pumping systems are shown with locations of valves and gages. The re-
turn line system is often preferred where grout take is small because of
(a) good pressure control with no waste, (b) reduction of grout-line clogging
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