Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION: METHOD, KIT AND SYSTEM FOR INJECTING GROUT
INTO A BOREHOLE, METHOD OF DEPLOYING A TUBE INTO A BOREHOLE FOR
GROUT INJECTION AND LEADER FOR USE IN A GROUT INJECTION SYSTEM
FIELD OF THE INVENTION
The present invention relates to the mining industry, and more particularly to
methods, kits and systems for injecting grout into a borehole for filling the
borehole.
BACKGROUND OF THE INVENTION
In the mining industry, boreholes may be drilled for exploration or definition
purposes. Exploration refers to the act of obtaining ground samples, usually
minerals, and evaluating
what elements constitute those samples and in what proportion. Definition
refers to the act of
obtaining ground samples wherein determined elements are known to exist and
evaluating in what
proportion these elements are present in the samples obtained.
Exploration and definition boreholes can be very long, sometimes up to 1000
meters
in length. Their diameter is usually relatively small, such as between 1 and 5
inches. They may be
drilled downwardly, such as from the ground level or from the floor of a mine
shaft; upwardly such
as from the ceiling of a mine shaft; or generally at any angle, such as
inclined upwardly or
downwardly.
Boreholes, when drilled, may cross water veins and as such may allow water to
flow
into the mineshaft in which they were drilled. If the water debit rate is
important, the borehole
should be plugged or filled.
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Boreholes may also compromise the structural integrity of the ground
surrounding
mine shafts, with undesirable consequences that may include cave-ins.
Finally, leaving boreholes unattended is also undesirable because of the use
of
explosives in the mineshafts. Indeed, the boreholes allow the blast to travel,
for example between
mineshafts that cross the boreholes.
Consequently, filling a borehole is usually desirable. This is accomplished
with grout,
which may be cement or the like suitable filling substance. The grout will be
poured into the
borehole and, when it sets, will consolidate the adjoining rock forming the
ground into a solid mass.
This both plugs the borehole and solidifies the ground around it.
1 0 If the borehole is very short, for example 15 meters or less, and
is downwardly
oriented, it is usually possible to simply pour grout into the borehole to
fill it. However, if the
borehole is long, for example 15 meters or more, the grout will not flow to
the bottom of the
borehole, usually stopping at about 15 meters, as a result of the grout
setting and/or the air pressure
in the borehole below the grout preventing the grout from flowing further into
the borehole. If the
borehole is upwardly oriented, pouring grout into the borehole through its
open end is simply not
possible without a pump, but otherwise the same problems as noted above exist.
Prior art systems for circumventing these problems include a rigid hollow
injection
tube that is inserted into the borehole. This injection tube comprises a
number of injection tube
sections that come in lengths of about three meters and can be threaded one at
the end of the other to
gradually form the injection tube into the borehole. An injection machine is
located outside the
borehole to help with this operation. Once the bottom of the borehole is
reached ¨ which can be
determined by counting the number of tubes inserted into the hole times their
length ¨ it is possible
to start grout injection. This is accomplished by pumping grout into the
hollow injection tube with
the injection machine. The borehole will thus be filled from its bottom
towards its open end. The air
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or water will be evacuated through the borehole open end, around the injection
tube, preventing
pressure buildup in the borehole.
Such a system indeed circumvents the problems mentioned above, however it
suffers
the important drawback of being very tedious to handle and very time-consuming
to install. It can
take up to a full day of work for two workmen to install all the tube sections
required to reach the
bottom of a 1000 meter borehole. Also, grout and other fluids present in the
borehole such as water
are still allowed to flow out through the borehole during the installation and
filling operations if the
borehole is an uphole or is upwardly inclined.
SUMMARY OF THE INVENTION
The invention relates to a method of injecting grout into a borehole, said
borehole
comprising a peripheral wall, an open end allowing access from outside said
borehole into said
borehole and a bottom end opposite said open end, said method comprising:
= providing a leader comprising opposite fore and aft portions, a pressure-
bearing member between said fore and aft portions, and a leader passage
extending from a fore opening at the leader fore portion to an aft opening in
the leader aft portion;
= providing a tube attached to said leader and connected to said leader aft
opening;
= inserting said leader into said borehole with said fore portion first,
said
borehole defining an upstream portion located upstream of said pressure-
bearing member and a downstream portion located downstream of said
pressure-bearing member;
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= allowing said tube to extend outside of said borehole and to slide into
said
borehole as it is deployed therein;
= injecting an impelling fluid in said borehole downstream portion
exteriorly of
said tube resulting in pressure being applied on said pressure-bearing member
and said leader consequently advancing towards said borehole bottom end,
said leader carrying said tube with it to deploy said tube in said borehole;
while upstream fluid located in said borehole upstream portion is evacuated
out of said borehole through said leader passage and said tube;
= stopping the injection of said impelling fluid when said leader reaches a
leader
1 0 target position;
= injecting grout in said borehole downstream portion; and
= evacuating said impelling fluid from said borehole through said leader
passage and said tube while said grout is injected, including allowing said
impelling fluid to flow from said borehole downstream portion to said
borehole upstream portion.
In one embodiment, the method further comprises:
= sealing said borehole open end before injecting said impelling fluid in
said
borehole downstream portion; and
= providing a downstream fluid connection allowing access to said borehole
downstream portion exteriorly of said tube from outside said borehole, with
the step of injecting an impelling fluid in said borehole downstream portion
being accomplished through said downstream fluid connection and with the
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step of injecting grout into said borehole downstream portion being
accomplished through said downstream fluid connection.
In one embodiment, the step of allowing said grout to flow from said borehole
downstream portion to said borehole upstream portion comprises disabling said
pressure-bearing
5 member.
In one embodiment, said pressure-bearing member comprises a leader main body
and
a leader seal attached to and located outwardly of said main body, said
impelling fluid applying
pressure against said leader seal to force said leader towards said borehole
bottom end, said leader
seal substantially sealing an area between said leader main body and the
borehole peripheral wall,
the step of disabling said pressure-bearing member comprising said leader seal
rupturing when a
threshold pressure is achieved in said borehole downstream portion.
In one embodiment, said leader target position corresponds to said borehole
bottom
end and said threshold pressure will be achieved when said leader reaches said
borehole bottom end
and is prevented from further advance while impelling fluid continues to be
injected into said
borehole downstream portion.
In one embodiment, the step of sealing said borehole open end is accomplished
with a
borehole interface member inserted in said open end, said borehole interface
member comprising a
plug that seals said borehole open end, an inner channel extending through
said plug, and a tube seal
sized to receive said tube therethrough, said tube seal preventing fluid to
flow out of said borehole
through said inner channel but allowing said tube to slide into said borehole
through said tube seal
and said inner channel.
In one embodiment, said downstream fluid connection is provided on said
borehole
interface member such that access to said borehole downstream portion is
allowed through said
borehole interface member inner channel exteriorly of said tube.
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In one embodiment, stopping the injection of said impelling fluid when said
leader
reaches said leader target position is accomplished in either one of the
following cases:
= if there is a marked increase in impelling fluid flow out of said
borehole
through said tube; and
= if there is a marked increase of pressure in said borehole downstream
portion.
In one embodiment, the method further comprises the step of stopping the
injection of
said grout when grout overflows out of said borehole through said leader
passage and said tube.
In one embodiment, said impelling fluid comprises water.
The present invention also relates to a method of deploying a tube into a
borehole for
injecting grout, said borehole comprising an open end allowing access from
outside said borehole
into said borehole and a bottom end opposite said open end, said method
comprising:
= providing a leader comprising opposite fore and aft portions, a pressure-
bearing member between said fore and aft portions, and a leader passage
extending from a fore opening in said leader fore portion to an aft opening in
said leader aft portion;
= providing a tube attached to said leader and connected to said leader aft
opening;
= inserting said leader into said borehole with said fore portion first,
with said
borehole defining an upstream portion located upstream of said pressure-
bearing member and a downstream portion located downstream of said
pressure-bearing member;
= allowing said tube to extend outside of said borehole and to slide into
said
borehole as it is deployed therein;
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= injecting an impelling fluid in said borehole downstream portion
exteriorly of
said tube resulting in pressure being applied on said pressure-bearing member
and said leader consequently advancing towards said borehole bottom end,
said leader carrying said tube with it to deploy said tube in said borehole;
while upstream fluid located in said borehole upstream portion is ejected out
of said borehole at least partly through said leader passage and said tube;
and
= stopping the injection of said impelling fluid when said leader reaches a
leader
target position.
In one embodiment, the method further comprises:
= sealing said borehole open end before injecting said impelling fluid in said
borehole downstream portion; and
= providing a downstream fluid connection allowing access to said borehole
downstream portion exteriorly of said tube from outside said borehole, with
the step of injecting an impelling fluid in said borehole downstream portion
being accomplished through said downstream fluid connection.
In one embodiment, said impelling fluid is one of grout and water.
The invention further relates to a grout injection kit for use in assembling a
grout
injection system for injecting grout into a borehole, comprising:
= a leader comprising opposite fore and aft portions, a pressure-bearing
member
between said fore and aft portions, and a leader passage extending from a fore
opening in said leader fore portion to an aft opening in said leader aft
portion;
= a tube attachable to said leader and connectable to said leader aft
opening;
= a borehole interface member comprising:
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= a plug;
= an inner channel extending through said plug and sized to allow said tube
to
loosely extend and slide therethrough ;
= a tube seal in said inner channel, sized to allow said tube to extend and
slide
therethrough while preventing fluid flow between said tube seal and said tube;
and
= a downstream fluid connection allowing fluid access into said inner
channel
exteriorly of said tube.
In one embodiment, the grout injection kit further comprises a fluid pump
connectable to said downstream fluid connection.
In one embodiment, the grout injection kit further comprises an additional
fluid pump
connectable to said tube.
In one embodiment, said pressure-bearing member comprises a leader seal
designed
to rupture at a determined pressure threshold.
1 5
The present invention also relates to a grout injection system for injecting
grout into a
borehole, comprising;
= a leader comprising opposite fore and aft portions, a pressure-bearing
member
between said fore and aft portions, and a leader passage extending from a fore
opening in said leader fore portion to an aft opening in said leader aft
portion,
said leader for insertion into said borehole with said fore portion first and
said
borehole thus defining an upstream portion located upstream of said pressure-
bearing member and a downstream portion located downstream of said
pressure-bearing member;
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= a tube attached to said leader and connected to said leader aft opening;
= a plug for sealing the borehole;
= a tube channel for allowing said tube to slidingly extend into said
borehole
from outside the borehole;
= a downstream fluid connection for allowing fluid access into said borehole
downstream portion exteriorly of said tube; and
= a fluid pump connectable to said downstream fluid connection.
In one embodiment, the grout injection system further comprises an additional
fluid
pump connectable to said tube.
1 0
In one embodiment, said leader comprises a main body and said pressure-
bearing
member comprises a leader seal attached to and located outwardly of said main
body, said leader
seal for substantially sealing an area between said leader main body and the
borehole peripheral
wall, said leader seal designed to rupture upon a threshold pressure being
applied thereagainst.
In one embodiment, the grout injection system further comprises a borehole
interface
member that carries said plug, said tube channel comprising an inner channel
extending through said
borehole interface member including through said plug, and said downstream
fluid connection
connects to said inner channel through said borehole interface member.
The present invention further relates to a leader for use in a grout injection
system,
said leader comprising opposite fore and aft portions, a pressure-bearing
member between said fore
and aft portions, and a leader passage extending from a fore opening in said
leader fore portion to an
aft opening in said leader aft portion.
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In one embodiment, the leader further comprises a main body, said pressure-
bearing
member comprising a leader seal attached to and located outwardly of said main
body, said leader
seal designed to rupture upon a threshold pressure being applied thereagainst.
DESCRIPTION OF THE DRAWINGS
5 In the annexed drawings:
Figure 1 is a schematic cross-sectional view of the grout injection system of
the
present invention, operatively installed about and within a borehole drilled
in the ground, during the
impelling fluid injection phase before the leader reaches the borehole bottom
end;
Figure 2 is an enlarged view of the area circumscribed by line II in figure 1;
10 Figure 3 is a an enlarged view of the area in figure 1 near the
borehole open end,
particularly showing the borehole interface member and the tube;
Figure 4 is similar to figure 1, but shows the leader having reached the
borehole
bottom end, the leader seal having ruptured and the impelling fluid flowing
from the borehole
downstream portion into the borehole upstream portion, the leader passage and
the tube;
Figure 5 is an enlarged view of the area circumscribed by line V of figure 4;
Figure 6 is similar to figure 1, but shows the grout injection system during
its grout
injection phase; and
Figure 7 is an enlarged view of the area circumscribed by line VII of figure
6.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Figures 1-7 show a grout injection system 20 for injecting grout into a
borehole 22.
Borehole 22 may be, for example, an exploration or definition borehole for
mining purposes that has
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been made in ground G with any suitable drilling equipment. The grout to be
injected in borehole 22
probably has the purpose of filling borehole 22, although how much grout is
injected is up to the
system operator. The term "grout" used herein refers to any suitable filling
material for filling
borehole 22, such as cement for example.
Figures 1-3 show that borehole 22 comprises a peripheral wall 24 of generally
cylindrical shape. Borehole 22 has an open end 26 allowing access from outside
borehole 22 into
borehole 22 and a bottom end 28 opposite open end 26. Borehole 22 may be an
uphole as suggested
in the drawings, or it could alternately be a downhole, or inclined at any
angle upwardly or
downwardly.
Grout injection system 20 comprises a leader 30 (figures 1 and 2) comprising
an
elongated, generally cylindrical main body 32 about which a pressure-bearing
member in the form
of an annular leader seal 34 is installed. Leader 30 defines opposite fore and
aft portions 30a, 30b on
either side of leader seal 34.
A leader passage 36 extends within leader main body 32. Passage 36 includes a
number of fore openings 38 in leader fore portion 30a, an aft opening 40
located at leader aft portion
30b and a central orifice 39 between fore and aft openings 38, 40.
Grout injection system also comprises a flexible tube 42 that can be made, for
example, of plastic material. Although tube 42 could theoretically be rigid,
for example by providing
threadable tube sections, this is seen as unpractical and providing a flexible
tube is much more
advantageous. Tube 42 comprises opposite first and second ends 42a, 42b and is
attached to leader
at the tube first extremity 42a. More particularly, first extremity 42a is
connected to a coupling
43 provided at leader aft opening 40 about aft opening 40.
Grout injection system 20 further comprises a borehole interface member 44
(figures
1 and 3) for insertion into the open end 26 of borehole 22. Borehole interface
member 44 comprises
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a main body 45 that carries an annular plug 46 made of a suitably fluid-tight
material, such as rubber
or the like, that seals the borehole open end 26 in fluid-tight fashion. An
inner channel 48 extends
through main body 45. As detailed hereinafter, tube 42 loosely extends through
inner channel 48.
Borehole interface member 44 also comprises a tube seal 50 provided at an
extremity of main body
45 opposite plug 46. Tube seal 50 restricts inner channel 48 and is sized to
snugly receive tube 42
therein for preventing fluid to flow out of borehole 22 around tube 42 while
allowing tube 42 to
slide into borehole 22 through tube seal 50. A downstream fluid connection in
the form of a
downstream fluid conduit 52 extends transversely away from main body 45.
Downstream fluid
conduit 52 is in fluid connection with inner channel 48 for allowing fluid
access into borehole 22
through inner channel 48 exteriorly of tube 42.
The main body 45 of borehole interface member 44 may comprise several body
portions that are screwed to each other to facilitate installation and
maintenance. For simplicity,
main body 45 has been shown schematically in the figures as a unitary element,
but it is understood
that its construction could be fragmented or otherwise customized as will be
obvious for someone
skilled in the art.
Although the friction-fit of plug 46 in borehole 22 contributes to retain
borehole
interface member 44 in borehole open end 26, a retaining plate 54 is used to
hold main body 45 in
place, with retaining plate 54 being bolted to the ground with rock bolts 56.
Retaining plate 54 has
an aperture 58 through which main body 45 extends and main body 45 is fixedly
attached to
retaining plate 54, for example with two body portions of main body 45 being
screwed to each other
on either side of aperture 58 to sandwich retaining plate 54.
Main body 45 comprises a valve 60 controlled by an activation handle 62
allowing
inner channel 48 to be selectively closed. Valve 60 allows closure of inner
channel 48 even if tube
42 extends therethrough, the tube 42 then being compressed and closed by valve
60. Valve 60
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remains opened until the filling of borehole 22 with grout is completed, as
detailed hereinafter.
Valve 60 can be of any known type, for example a ball valve.
As shown in figure 1, while the first extremity 42a of tube 42 extends into
borehole
22, its second extremity 42b extends outside of borehole 22. The portion of
tube 42 located outside
Grout injection system 20 further comprises an impelling fluid reservoir 66
containing impelling fluid. Downstream fluid conduit 52 links impelling fluid
reservoir 66 to main
A manometer 70 is provided on downstream fluid conduit 52 to measure the
impelling fluid pressure at that position. Since downstream fluid conduit 52
is in substantially
In use, it is possible to inject grout with grout injection system 20 into
borehole 22, to
partly or completely fill borehole 22. Since the purpose of injecting grout
into a borehole is usually
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to fill it entirely, the following description will refer specifically to such
an operation of completely
filling borehole 22. However, it is understood that the system operator may
decide to inject any
desired quantity of grout into borehole 22.
To accomplish the grout injection, parts of a grout injection kit according to
the
present invention will be assembled. The grout injection kit comprises at
least leader 30, tube 42 and
borehole interface member 44 and fluid pump 68. It is noted that the grout
injection kit could be sold
separately from fluid pump 68 whereby purchasers could provide the pump
themselves, or the grout
injection kit could be sold including fluid pump 68. It is assumed that the
purchasers of the grout
injection kit would use their own reservoirs 66, 74, 75.
To operatively install the grout injection system 20 from the grout injection
kit, and
as shown in figures 1-3, the tube first end 42a is first inserted through the
inner channel 48 of
borehole interface member 44 until tube 42 extends entirely through borehole
interface member 44.
Tube 42 notably extends through tube seal 50 so as to be slidable therein
without however allowing
fluid flow between tube seal 50 and tube 42. The tube first end 42a is
securely attached to aft
1 5
coupling 43 of leader 30 so that tube 42 is in fact connected to the leader
passage 36 through leader
aft opening 40.
Leader 30 is then inserted into borehole 22 with its fore portion 30a first
and with the
tube 42 extending outside of borehole 22 such that its second end 42b will be
situated exteriorly of
borehole 22. Once leader 30 is located inside borehole 22, leader seal 34
substantially seals an
annular area between leader main body 32 and borehole peripheral wall 24.
Borehole 22 thus defines
an upstream portion located upstream of leader seal 34 and a downstream
portion located
downstream of leader seal 34, with these upstream and downstream portions
being of variable
dimensions as leader 30 travels in borehole 22, as detailed hereinafter. It is
noted that it is likely that
borehole 22 will have a somewhat irregular peripheral wall 24 as a consequence
of the drilling
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operation, and the seal between leader seal 34 and the borehole peripheral
wall 24 may be imperfect
in practice resulting in some fluid being allowed to flow between the borehole
upstream and
downstream portions, albeit in limited fashion. This is why the present
specification refers to leader
seal 34 "substantially" sealing the area between leader main body 32 and
borehole peripheral wall
5 24, in that the seal may not be perfect.
Borehole open end 26 is then sealed by inserting borehole interface member 44,
and
more particularly plug 46, into bore hole 22 at open end 26. This includes the
installation of
retaining plate 54 that is sandwiched within main body 45 of borehole
interface member 44;
retaining plate 54 is bolted to the ground with rock bolts 56. Borehole
interface member 44 is
10 consequently securely installed at and within borehole open end 26.
In the embodiment shown in the drawings, the portion of main body 45 opposite
seal
46 extends exteriorly of borehole 22, allowing easy access to downstream fluid
conduit 52.
Downstream fluid conduit 52 is connected to fluid pump 68 that is in turn
connected to impelling
fluid reservoir 66 to ultimately link reservoir 66 to inner channel 48 of
borehole interface member
15 44.
Fluid pump 68 is actuated to inject impelling fluid from reservoir 66 through
conduit
52 and the inner channel 48 of borehole interface member 44 exteriorly of tube
42 and into the
downstream portion of borehole 22. Impelling fluid will notably fill the area
between leader seal 34
and tube seal 50 at which point the pressure in this section will increase
until the force exerted on
leader seal 34 becomes sufficient to force leader 30 to advance into borehole
22. Continued injection
of impelling fluid in the borehole downstream portion will force leader 30 to
advance gradually
towards borehole bottom end 28.
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As leader 30 advances in borehole 22, it carries tube 42 with it to deploy
tube 42 in
borehole 22. Tube 42 is allowed to slide into borehole 22 from outside
borehole 22 through tube seal
50.
As suggested in figures 1-3, as leader 30 advances in borehole 22, upstream
fluid is
evacuated from the borehole upstream portion to prevent an augmentation of the
pressure in the
borehole upstream portion. This upstream fluid comprises any fluid naturally
present in borehole 22,
such as air, and is likely to also comprise some limited quantities of
impelling fluid that may seep
between leader seal 34 and borehole peripheral wall 24 from the borehole
downstream portion into
the borehole upstream portion. The evacuation of this upstream fluid will be
accomplished through
the leader inner passage 36 and then through tube 42 to be exhausted out
through tube second end
42b. More particularly, the upstream fluid will flow from the borehole
upstream portion, through
leader fore openings 38, leader central orifice 39 and leader aft opening 40
into tube 42. A receiving
reservoir (not shown) could optionally be provided if the upstream fluid is
required to be
recuperated, for example if substantial quantities of impelling fluid are
evacuated at this stage.
1 5
The injection of impelling fluid will be stopped by stopping the operation
of pump 68
when leader 30 reaches a leader target position. The leader target position of
leader 30 may
correspond to the position of leader 30 when it reaches the borehole bottom
end 28 as suggested in
figure 4, or at any other desired intermediate injection position along
borehole 22 as determined by
the system operator. An intermediate injection position could be reached if
for example a
determined length of tube 42 has been deployed in borehole 22. In any event,
when pump 68 is
stopped, the advance of leader 30 will be interrupted at the leader target
position if leader 30 is not
otherwise prevented from further advancing into borehole 22 such as by leader
30 hitting the
borehole bottom end 28 or by tube 42 having reached a maximum deployment
length and its feeding
into borehole 22 being consequently stopped by the system operator, e.g. by
blocking spool 64.
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As suggested in figures 4 and 5, leader seal 34 is disabled when leader 30
reaches its
leader target position. Although this could be commanded remotely from outside
borehole 22 and
accomplished with a mechanical, electromechanical or other suitable disabling
devices (not shown),
according to the present invention leader seal 34 is disabled by rupturing
under increased pressure
by the impelling fluid. This increased pressure occurs when leader 30 is
prevented from further
advance, such as when leader 30 will reach the borehole bottom end 28, and
before fluid pump 68 is
stopped. That is to say, fluid pump 68 will continue to feed impelling fluid
into the borehole
downstream portion once leader 30 reaches its leader target position,
increasing the pressure in the
borehole downstream portion until leader seal 34 ruptures. Leader seal 34 is
consequently designed
to rupture when a given pressure threshold is reached, and operation of the
grout injection system 20
assumes that this pressure threshold will be calibrated according to expected
operating pressures
within a given borehole.
If the operator of grout injection system 20 wishes to confirm whether leader
30 has
reached its leader target position over and beyond leader 30 being blocked in
its advance, he can
have tube 42 be marked for length so as to be able to measure the length of
tube 42 that has been
inserted into borehole 22 at all times. If leader 30 blocks at an undesirable
intermediate position
along borehole 22 and the operator realizes that this undesirable intermediate
position does not
correspond to the desired leader target position per the length of tube that
has been deployed into
borehole 22, the operator may stop the injection of impelling fluid and
retrieve tube 42 and leader 30
from borehole 22, optionally evacuating the impelling fluid from borehole 22,
to then use a drilling
device to ensure that the borehole 22 is properly cleared and its peripheral
wall 24, properly smooth.
The entire grout injection system installation can then be restarted as
detailed above, including
insertion of leader 30 into borehole 22 up to the point where it was before,
and beyond.
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When leader 30 reaches the borehole bottom end 28 and the leader seal 34
ruptures,
impelling fluid will be allowed to flow from the borehole downstream position
to the borehole
upstream position, then through leader passage 36 into tube 42, this resulting
in a marked increase in
impelling fluid flow out of borehole 22 through the tube second end 42b as
shown in figure 4.
Leader 30 not advancing anymore in borehole 22 while impelling fluid continues
to be pumped into
borehole 22 will also result in a marked increase in first fluid pressure as
measured at manometer
70, especially before the rupturing of leader seal 34. Either one or both of
these situations will cue
the operator to stop the operation of pump 68 and consequently the injection
of impelling fluid and
suggest that leader 30 has reached the bottom end 28 of borehole 22, i.e. its
leader target position.
When seal 34 ruptures, it may help stabilize the position of leader 30 in
borehole 22
in its leader target position to avoid subsequent accidental movement of
leader 30. Indeed, upon
rupturing, seal 34 will form flanges that will interact in a wedging
relationship with the borehole
peripheral wall 24.
As suggested in figure 6, once the injection of impelling fluid has been
stopped, the
emptied impelling fluid reservoir 66 is replaced by a grout reservoir 74.
Grout reservoir 74 is
operatively connected to fluid pump 68 and to downstream fluid conduit 52. An
evacuation reservoir
75 is optionally connected to the tube second end 42b. To facilitate this last
operation, tube 42 could
be cut at a desired length outside of borehole 22 and its newly cut second end
42b inserted into
evacuation reservoir 75, with spool 64 and any useless excess length of tube
42 being removed.
Optionally, a distinct additional pump (not shown) could be installed for
pumping
grout, instead of using fluid pump 68 that may be specific to a certain type
of impelling fluid.
As suggested in figures 6 and 7, fluid pump 68 is actuated to inject grout in
borehole
22. More particularly, grout will be pumped from grout reservoir 74 in
downstream fluid conduit 52,
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borehole interface member inner channel 48 exteriorly of tube 42 and into the
borehole downstream
portion
While grout fills borehole 22 from its open end 26 towards its bottom end 28,
the
impelling fluid is gradually evacuated from borehole 22. With leader seal 34
having been previously
disabled, impelling fluid located in borehole 22 will flow from the borehole
downstream portion to
the borehole upstream portion, then through leader passage 36, tube 42 and
into evacuation reservoir
75.. The grout itself, through the action of fluid pump 68, will push on the
impelling fluid to achieve
this result. Of course, suitable relative liquid/gaseous states and relative
densities of the grout and
impelling fluid should be considered for this result to be achieved.
Injection of grout will be stopped by the operator by cutting off fluid pump
68. This
can be done for example when grout overflows out of borehole 22 through tube
42 into evacuation
reservoir 75, cueing the operator that borehole 22 is filled with grout.
Alternately, the volume of
injected grout could be measured by the operator and the grout injection could
be stopped at a
determined target volume.
When grout injection is completed, the grout will gradually set, effectively
at least
plugging borehole 22 and possibly filling it entirely, to help prevent fluid
flow through borehole 22
and structural failure about borehole 22.
Valve 60 can optionally be closed with handle 62 to prevent accidental fluid
outflow
from borehole 22 while the grout sets. All tubing, pumps and reservoirs
located outside of borehole
22 can be removed. The borehole interface member 44 is intended to remain at
borehole open end
26 with its plug 46 maintaining an airtight seal at the borehole open end 26.
According to the present invention, the impelling fluid can comprise water or
any
other suitable fluid including liquid or gas such as air.
CA 02806070 2013-02-14
According to the present invention, it can consequently be seen that the grout
injection is possible in boreholes having any orientation, including upholes
or downholes. With a
flexible tube 42, even curved holes can be filled. The advance of leader 30
and the injection of the
impelling fluid and the grout are indeed all independent of the gravity in
their operability. Borehole
5 interface member 44, with its plug 46, prevents water or grout to spill
out of the borehole as it is
being filled even if it is upwardly inclined.
According to the present invention, borehole 22 can be filled with grout from
its open
end 26 towards it bottom end 28 without pressure buildup, since the leader 30
is first moved to the
borehole bottom end 28, carrying tube 42 with it, before grout injection
begins. Fluid located in
10 borehole 22 may be evacuated through leader passage 30 and tube 42
during both the impelling fluid
injection and the grout injection.
One advantage of the present invention is that deploying tube 42 to the bottom
end 28
of borehole 22 is simple: even for very long holes, such as those that measure
about 1000 meters, it
can take only about an hour or two to deploy the tube therein, and a single
operator is sufficient to
15 accomplish this task. This is a very significant time saving compared to
the manual section-by-
section installation of prior art rigid hollow injection tubes that took two
workmen up to a full
workday to accomplish.
The present invention also generally relates to a method of deploying tube 42
into
borehole 22 for grout injection, whereby tube 42 may be used to evacuate air
for the injection of an
20 impelling fluid that may, in fact, be the grout itself. Indeed, by
injecting grout directly in the
borehole downstream portion, the advance of leader 30 will still be enabled by
the grout applying
pressure on leader seal 34. Also, the upstream fluid is still evacuated
through the leader passage 36
and tube 42, preventing pressure buildup upstream of leader 30 and the
injected grout. However, this
method of injecting grout into the borehole 22 without first deploying tube 42
in borehole 22 is more
CA 02806070 2013-02-14
,
21
risky: it would be very difficult to correct any problem occurring during the
advance of leader 30
since the borehole 22 would be partly filled with grout already, making it
very difficult if not
impossible to retrieve the leader 30 and start over if a problem occurs such
as if leader 30 becomes
stuck in borehole 22 during its advance before it reaches the borehole bottom
end 28.
According to the present invention, grout injection system 20 generally
comprises a
tube channel for allowing tube 42 to slidingly yet sealingly extend into
borehole 22 from outside
borehole 22. In the embodiment shown in the drawings, the tube channel is
formed by the borehole
interface member inner channel 48; however in an alternate embodiment (not
shown) the tube
channel could be distinct from the borehole interface member, for example
being provided as a
conduit, or even simply a hole, that extends through ground G exteriorly of
the borehole interface
member 44 and through which tube 42 extends. Similarly, the downstream fluid
connection, in the
embodiment shown in the drawings, is shown as the downstream fluid conduit 52
that connects to
the borehole interface member inner channel 48, but it could be entirely
distinct from the borehole
interface member 44 and be embodied by an alternate downstream fluid conduit
or access (not
shown) that extends exteriorly of the borehole interface member 44 and allows
access to the
borehole downstream portion.
In one alternate embodiment (not shown), if the borehole is a downhole or is
downwardly inclined, it could be envisioned to inject impelling fluid to push
the leader into the
borehole without however sealing the borehole open end. Of course, this would
not be as efficient
and is not a preferred way to carry out the invention, since applying pressure
on the leader's pressure
bearing member would be more difficult. In this alternate embodiment, no
borehole interface
member is used and the borehole downstream portion is readily accessible
through the borehole's
open end through which the tube may loosely slide.
CA 02806070 2013-02-14
. ,
22
Leader seal 34 could be made of any material capable of allowing leader to be
pushed
along borehole 22 while rupturing when submitted to a pressure equal to or
greater than the
threshold pressure value. Semi-rigid Rubber is envisioned as one acceptable
material that could
further allow leader seal 34 to slightly resiliently deform against the
borehole peripheral wall 24
when leader 30 is inserted into borehole 22 to obtain the above-mentioned
substantial seal between
leader seal 34 and borehole peripheral wall 24. More generally, it should be
noted that the pressure
bearing member, shown as leader seal 34 in the drawings, could alternately be
formed differently
than an annular seal 34. The general purpose of the pressure bearing member is
to allow pressure by
the impelling fluid to bear thereon for forcing the leader towards the
borehole bottom end. The
pressure bearing member can be formed integrally with the leader's main body,
or be a distinct part
attached thereto.
In an alternate embodiment (now shown), grout could be injected through the
tube
once leader 30 has reached the borehole bottom end 28, instead of being
injected through the
downstream fluid conduit 52. The pump 68 (or the above-mentioned additional
pump) would then
be connected to the tube second end 42b. The impelling fluid would be
evacuated through the
borehole interface member inner channel 48 and downstream fluid conduit 52. A
problem with this
embodiment, however, is the risk that the leader will be carried towards the
borehole open end 26
with the injected grout and that the leader and tube jam somewhere along the
borehole 22.
