Note: Descriptions are shown in the official language in which they were submitted.
~67~97
This invention relates to a method and means for
the lining of large diameter boreholes in the ground In -
particular, the invention relates to the cement grouting of
the walls of large diameter boreholes to prevent inward
crumbling and to provide a water barrier. `~
With the advent of improved borehole drilling
methods, it has now become common to provide cylindrical
boreholes in the ground which may be of a diameter of several
meters or more Such large diameter boreholes may comprise
mine shafts, mine ventillation ducts, conveyor ducts, below-
ground silos for storage of liquid, gas or wastes and the
like. Whether constructed by mechanical drilling or by
explosive shaft sinking methods, it is nearly always essen-
tial, unless the shaft is in strong, impervious rock, that
such large diameter boreholas be provided with a wall lining
to prevent the inward collapse or crimbling of the wall and/
or to pre~ent ingress of ground water In the past, such
borehole linings have generally been provided by the im~
planting of a steel tube shell within the borehole and then
filling any annular space between the shell and borehole wall
with grouting cement to give stability to the structure and
'~ ~ to anchor it in place, This method of lining is difficult and
costly to install. Large steel tube sections are heavy and
difficult to transport, especially to remote locations.
The tube sectionq must be connected together, usually by
welding in order to provide a continuous lining The
connected sections are difficult to position in the borehole
or shaft especially where the borehole is deep Such large
diameter boreholes may reach a depth of several hundred
meters or more,
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~67397
It has now been found that all of the afore-
mentioned difficulties and disadvantages can be overcome ~;
by employing a large diameter borehole lining a flexible
cylindrical tube of elastomeric material closed at the lower
end and having a diameter sufficiently less than the bore-
hole diameter to permit the placing of grout in the annular
space between the lining and the borehole wall, the said
lining preferably having on its outside, grout-facing sur-
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face, protuberances which become anchored in the grout so -
; 10 as to retain the lining in the borehole. ~-
The invention may be better understood by referring ~
to the appended drawing which shows a diagrammatic cut-away ~;
view of a large diameter borehole containing the flexible
lining of the invention.
With reference to the drawing, there is shown a
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,j large diameter borehole 1 of a diameter of, say 2 meters,
drilled or bored into earth or rock 2 BorehoLe 1 may
~ extend to a depth of a hundred or several hundred meters
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¦ depending on its intended use~ A flexible form tube or
lining 3 of elastomeric material is shown within and extending
nearly the full depth of borehole 1~ Lining 3 has a closed
in-the-hole end 4 which is just above the bottom of borehole
~ ~ 1. Small protuberances or prominences 5 are attached to and
'3, ~ are integral with the outside face of lining 3. Grouting
!! ~ material 6 such as portland cement, is shown filling part of
`5 ~ the void 7 between lining 3 and the borehole wall. A deli-
~1 very line 8 is provided to direct the grout into the void 7
s Within lining 3 is shown filling material 9 which may be,
for example, water, drilling mud or the like~ Material 9 is
1 30 adapted to retain the shape of lining 3 and prevent its
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67397
collapse while grout 6 is poured. Material 9 may be
delivered into lining 3 via delivery line 10. If desirable
air or other gas may be used to pressurize lining 3 which
air or gas is delivered through line 11. In such event the
out-of-hole end of lining 3 is shown closed about lines 10 !
and 11 for pressuriza~ion.
In use in the field, a lining 3 may be delivered
to the borehole site by truck or trailer as a-collapsed ~-
roll of elongated tubing. The lenyth of the lining from
its closed end 4 will be equal to the depth of borehole
and can be thus fabricated to size at the factory. Where
two or more sections require connecting together for very
deep boreholes, this can be done using conventional vul-
canizing or joining techniques for the type of elastomer
comprising the lining. Any slurried drilling mud is prefer-
ably removed from the borehole by pump and pipe (not shown
in the drawing). The presence of water can generally be
tolerated and need not be removed from the shaft. Using,
for example, a mechanlcal lowering device (not shown in the
drawings) the lining is lowered in its extended form, closed
end 4 first, into the borehole. To provide ballast or weight
to aid in lowering, a ~uantity of water or other dense liquid
can be pumped into lining 3 to collect at the lower end 4
When lowered end 4 of lining 3 contacts the bottom of bore-
hole 1, it can be raised slightly to provide a void between
end 4 and the borehole bottom. Integral pxotuberances 5
assist in centering lining 3 in the borehole and provide a
substantially equal void space 7 around lining 3. After
lining 3 has been extended to the full depth of the borehole,
the application of pressurized air through line 11 can be
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3 C1 673~37
used to inflate the lining and thus center it in the bore-
hole. After centering, a quantity of liquid filling ma-
terial such as water or dense drilling mud is pumped via
line 10 to fill a position, say several meters, of the lower end
of the lining. A pour of grouting material such as portland
cement mixture 6 is then pumped through line 8 to fill the
void area 7 adjacent up to the level of material 9. When
pour 6 has hardened or set, a further quantity of filling
' material 9 is pumped into lining 3 and a further pour of
grout 6 is emplaced. Successive pours are thus made until
the entire void area 7 throughout the borehole is occupied
with grout and the borehole is lined with cement. The
elastomeric lining, embedded in grout 6 by protuberances 5,
provided a further waterproof shell within the cement grout.
After completion of the grouting, liquid filling mate~ial 9
is pumped out of lining 3 leaving behind an elastomer-
covered grouted or cament linad borehole
The material of construction o lining 3 may be
any suitable elastomer which can be fabricated in the form
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;~ 20 of a large diameter tube, sealed at at least one end
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Examples of suitable matarials are "Hypalon", nylon, "Te~lon"*
or other rubber basea compounds. Generally, the lining will
have a wall thickness of rom about 1/8" to 1/2", depending
on the size of the borehole. Especially pre~erred materials
are elastomeric impregnated fabrics or wire mesh since these
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provide resistance against tears in the borehole and resist
, undue expansion under pressure External protuberances can
also more easily be integrally ormed or attached to such -
} a material
The invention as herein described provides substantial
advantages over the steel casing borehole lining method.
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*Regd~ Trade Mark - 4 - ;~
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~06~7397
Large economies can be realized through reduced weight :.
of the lining material. Handling and transportation costs .
are reduced as are labor costs in installing the lining
in the borehole, Furthermore, the nature of the lining
material provides improved resistance against chemical
corrosion, erosion and water ingress. The material cost
of an elastomeric lining are estimated to be less than one-
hali the cost oi equivalent steol linings.
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