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WONDER MUD®, PUSHLUBE:
Trenchless Technology has seen a tremendous progress over the last 20years, not only in this country but
in many much less developed countries were urbanization is more acute that in our spacious land. This is
a multi-disciplinary industry and we have followed certain sectors with more interest than others. A main
area of interest is the various forms of pipe jacking: auger boring, microtunneling with non-man-entry
machines, mini-tunneling with slurry shield or Earth Pressure Balance (EPB) shield. Aside from boring
a clean hole on target without undermining the ground, the second concern is controlling the friction
forces along the jacked pipe not to run short of jacking capacity before the end of the drive. Our
experience with mineral muds and polymer slurries has helped many contractors staying out of trouble or
getting out of trouble. We formulate lubricating slurries on a case by case basis, generally combining a
clay with a polymer and chemical additives according to soil, ground water and type of pipe used.
WONDER MUD® and bentonite is the basic formulation for granular soils. The primary criterion is as low a
filtrate loss possible to confine the slurry within the annulus. In swelling shale, a concentrated
polymer cream like PUSHLUBE will prevent the shale from absorbing water, hence from swelling. The same
PUSHLUBE has been used successfully in relining work of old gas lines with swaged HDPE pipe.
When the ground is very coarse and loose gravels may bridge and bind and eventually damage the pipes at
a joint, especially clay or mortar resin types, a more pasty lubricant is recommended and GEOGREASE
formulations may be used. Depending on the drive lengths, larger diameter lubrication plumbing may be
in order to limit internal pumping pressures.
When engineers contemplate shallow drives and consider the potential for secondary settlements as a
result of the delayed decompression of the annulus, they specify a post drive grouting phase which is
typically ineffective and expensive. As a compromise, we have developed a low filtrate loss
lubricating slurry that is a highly retarded self-hardening slurry that fills the annulus and
ultimately sets into a solid of sufficient strength to match the surrounding ground. SLOWGROUT®
has been accepted by Owners as an enhanced quality assurance benefit.
In many instances, the jacked pipe is only a protective casing for the product pipe or duct bank.
The space between the two must be filled with a volumetrically stable, low-hydration-heat grout.
Cellular concrete or more specifically foam grout is an option but with some
limitations regarding placement length, diameter limitation and cost. A successful solution for
self-performing contractors is to flood the annular space with our IMPERMIX® self-hardening slurry
through bulkheads at each end of the drive with risers to the surface. The mixer on the surface is the
only equipment required, the mixer centrifugal pump dispensing the backfill slurry in the line, from the
lower end. Typically, a 2,000 LF drive is not a length limitation, this covers almost all jacked pipe
drives. Given IMPERMIX's long setting time, the work can be carried out over a number of days, without
or with interruptions. The cost per CY in place is a fraction of any other method. The end product is a
durable firm non-shrink, chemically stable, homogenous lightweight grout encasement.
In the electric power transmission business, the amount of power that can be transmitted through an
underground cable varies with the ability of the heat generated according to Joule's law to dissipate
into the ground. A factor called thermal resistivity defines the characteristics of a
solid to transfer radiant heat energy. The higher the material's density, the lower the thermal
resistivity coefficient. Formulating a highly sanded grout capable of being placed perfectly in a
fairly small annular space over a very long distance without detrimental hydration heat susceptible of
damaging the plastic ducts was the challenge. Eventually, we formulated a 130 pcf grout (16% moisture)
showing a thermal resistivity of 53 C-cm/watt fully saturated and 92 C-cm/sec in near dry conditions,
which are exceptionally good numbers while the placement is rendered easy by very long setting times,
good plasticity and no measurable heat of hydration. Although the project for which this in house
research was cancelled, a new product with a good value is now available to the power-transmission
Industry. Welcome to THERMGROUT. A similar application for THERMGROUT is the backfilling of loops in
geothermal wells, a most energy efficient way of heating and cooling homes and small
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