Okeechobee's Herbert Hoover Dam
One more tool for the underground construction man: STIFFNER comes as a polymer emulsion that is added to a body of liquefied
solids to transform it into a solid mass that can be handled with soil excavation tools, in a matter of a few minutes.
All possible applications have not been determined yet but two areas of construction where STIFFNER has been successful
are as follows:
ADSC World: drilled shaft dug under slurry through fine soils that tend to drop fines and form a
sludge accumulating over the settled sand. After this sludge has been disturbed during the process of removing the sand,
a cleaning bucket has difficulty in capturing this sludge as it agitates the bottom of the hole. That is when luck has it
that the bucket does not leak and is the same size as the hole. The solution to obtain a clean-hole-bottom is to drop a
'bomb'* of STIFFNER in the hole and to reintroduce the auger at the bottom and stir quickly for a minute. The drill
operator should feel some torque increase and weight on his flights. Coming out, the auger should be full.
Depending on the amount of solidified sludge more than one trip may be necessary. The ìbombî size will be determined
by the sludge columnís volume and the solids concentration to a second degree. The excavated product will be
undistinguishable from other excavated products removed by truck.
The same result can be duplicated on the surface, when disposal of accumulated sludge
in storage tanks is performed by vacuum trucks which is a very expensive convenience, especially when more water
has to be blasted in to loosen the sludge for it to be sucked. STIFFNER mixed in a sludge deposit with a backhoe
boom or similar can be clammed out or taken out with a skid steer bucket at a fraction of the cost.
Whenever the mud is too thick to be pumped, STIFFNER will turn it into a solid that you can shovel.
NATT World: in the USA, earth pressure balance (EPB) tunneling machines are generally preferred to
slurry shield machines where all the mining is conveyed in slurry form and separated on the surface. EPB work is simpler
and more conventional in its approach to conveying the muck to the surface. The typical means of extraction of soil out
of the EPB and onto a conveyor belt or muck car is via a continuous flight auger. When a soil condition presents itself
bringing water or liquefied soil through the auger, the only way to keep the pressure on the face if to lock up the gate
around the auger and in fact stop the mining. A quick method to go back in business is to inject through the shield a
certain quantity of STIFFNER while turning the cutting head. This will solidify the liquefied soils to a consistency
compatible with the controlled extraction process with the auger. In case of clean groundwater flowing through coarse
granular soils, fines must be introduced in the chamber before injecting STIFFNER. A thick bentonite slurry is the most
practical solution. With this proviso, STIFFNER will form the matrix within the gravel providing plasticity and
watertightness required for the auger to control the extraction process.
* In these times of terrorist threats, for those not used with this practice, we'd better explain:
a 'bomb' is a chemical additive contained in a ballasted plastic bag or fiber drum dropped at the bottom of a shaft
being drilled and experiencing a local difficulty such as a major slurry loss. The game plan is to provide a local
remedy without compromising the entire slurry column.
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