Note: Descriptions are shown in the official language in which they were submitted.
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A GROUT DELIVERY SYSTEM FOR A ROCK BOLT
BACKGROUND OF THE INVENTION
[0001] This invention relates, generally, to the delivery of grout to a rock
support
tendon and more particularly is concerned with a device to assist in
delivering grout
to a drill hole in which a rock support tendon is to be anchored.
[0002] As used herein "grout" includes a cementitious mixture and any other
settable mixture which can be employed to anchor a rock support tendon in
position,
and "rock support tendon" includes, without being limited, a rock bolt, a
cable anchor
and similar support devices.
[0003] The grouting of rock support tendons is a widespread practice. The
grout
protects the support tendons from any ground water which may be present and
which could cause the support tendons to corrode and, secondly, the support
performance of the support tendons is enhanced for the grouting increases the
capability of the support tendons to resist shear forces in the surrounding
rock.
[0004] When a rock support tendon is grouted in a drill hole, provision must
be
made for air which is trapped in the drill hole to escape to atmosphere. One
system
in use employs a first tube for delivering the grout to the drill hole and a
second tube
to allow air to escape from the drill hole. Ends of the tubes protrude into a
working
place at which the rock support tendon is installed and are subject to blast
damage -
a factor which can make grouting difficult or impossible.
[0005] In a second approach, of which the applicant is aware, use is made of a
hollow spherical device which is seated on an outer side of a bearing plate or
washer
which is engaged with a protruding end of the rock support tendon. Grout is
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delivered to the drill hole through the hollow interior of the device. The
spherical
device is however also exposed to the workplace and can therefore be damaged
by
blasting or by moving machinery.
[0006] An object of the present invention is to provide a device which
facilitates
delivery of a grout to a drill hole and which, to a substantial extent, is
protected
against damage of the aforementioned kind.
SUMMARY OF INVENTION
[0007] The invention provides a grout delivery device which includes a body
which
defines an internal volume, opposing first and second apertures in the body,
in
communication with the volume, through which a rock support tendon extends,
and a
grout formation on the body for connection to a grout source.
[0008] Preferably the body is at least partly flexible
[0009] The body may have a first body portion in which the first aperture is
located
and a second body portion in which the second aperture is located. The second
body portion may be movable relative to the first body portion at least to a
limited
extent.
[0010] The internal volume may be in the nature of a passage or chamber or a
similar space which is at least partly enclosed.
[0011] The flexibility of the body may be achieved in any appropriate way. For
example different portions of the body may be made from different materials.
Another possibility is for the body to be made with one or more lines of
weakness
which facilitate flexing of the body. A third possibility is for the body to
be formed
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with formations in the nature of a bellows or the like. These types of
construction are
exemplary only and are non-limiting.
[0012] The formation, for connection to the grout source, is preferably
located on
the first body portion.
[0013] The first body portion is preferably bulbous.
[0014] An outer surface of the first body portion, surrounding the first
aperture, is
preferably convex or semi-spherical, conical or the like. Thus a cross-
sectional
dimension of the first body portion measured between opposing points on the
outer
surface in a direction which is transverse to an axis of the first aperture,
may
increase in a direction away from a mouth of the first aperture.
[0015] The second body portion may be substantially tubular. A section of the
body
between the first body portion and the second body portion may be slightly
flared i.e.
of decreasing cross-section from the bulbous first body portion to the tubular
second
body portion.
[0016] The formation for connection to the grout source may be in the nature
of a
spigot and may include a formation which facilitates engagement of the spigot
with
an opening, in a member such as a bearing plate, through which the spigot is
passed.
[0017] The invention also extends to an assembly of a device of the
aforementioned
kind and a bearing plate which includes a central opening which is aligned
with the
first aperture of the device and a second opening through which the grout
formation
of the device passes and, preferably, with which the grout formation is
engaged.
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[0018] A rock support tendon may extend through the first and second apertures
and through the central opening of the bearing plate. A seal may be provided
at an
interface of the device and the rock support tendon in the region of the first
aperture.
The seal may be of any appropriate kind and, by way of example only, may be
constituted by a washer of a flexible material such as rubber which closely
surrounds
the rock support tendon and which engages with an annular gap between the
first
body portion and the tendon. Alternative the body can be formed with a small
collar,
which protrudes into the volume, and which closely surrounds an adjacent
surface of
the tendon.
[0019] The bearing plate could have any suitable shape and, for example, is
domed
or flat or semi-conical,
[0020] The device may be used in different ways. In one form of the invention
an
elongate tube is engaged with the body in direct communication with the second
aperture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention is further described by way of examples with reference to
the
accompanying drawings in which:
Figure 1 is a side view of a device according to the invention;
Figure 2 shows the device in perspective;
Figure 3 is a cross-sectional view, from one side, of the device shown in
Figure 1;
Figure 4 shows, in cross-section, the device engaged with a rock support
tendon, in
one mode of use;
Figure 5 shows the device used with a rock support tendon in a different mode
of
use,
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Figure 6 shows the device when used with a cable anchor; and
Figures 7 and 8 are perspective and cross-sectional views respectively of a
device
according to a different form of the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
[0022] Figures '1, 2 and 3 of the accompanying drawings are side, perspective
and
cross-sectional views respectively of a device 10 used for delivering grout to
a rock
support tendon, according to the invention.
[0023] The device includes a body 12 formed by a first body portion 14 and a
second body portion 16.
[0024] The body encloses an internal volume 18, in the nature of a chamber.
[0025] The first body portion 14 is bulbous and has a convex or semi-spherical
outer surface 20. A first aperture 22 is centrally positioned in the convex
surface.
[0026] The second body portion 16 is formed by a short tube 24 which
terminates in
a second aperture 26 which directly opposes the first aperture. An
intermediate
section 28 between the body portions is flared and reduces in cross-section
from the
bulbous first body portion to the tubular second body portion.
[0027] As is evident particularly from Figure 3 the first body portion 14 has
a region
30 which is formed with ribs which impart to the region a bellows-type
appearance.
As a consequence the region 30 is flexible, at least to a limited extent, and
the first
body portion can thus be moved relative to the second body portion to some
extent.
[0028] It is desirable for the body to be flexible, at least to a limited
extent, for
reasons which are described hereinafter. This flexibility can be achieved
using any
suitable technique and the scope of the invention is not limited to the use of
the
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bellows-like strucutre. For example the body could be made from one or more
parts
and the region 30 or the flared section 28 could be made from a softer and
more
flexible material than remaining portions of the body. Other approaches to
achieve
this desired property of flexibility are of course possible e.g. by forming
appropriate
sections of the body with lines of weakness which promote bending or flexing
of the
body,
[0029] In this example of the invention (refer to Figure 3) an inwardly
extending
collar 34 is positioned at a rim of the first aperture and extends into the
volume 18.
[0030] A small spigot 38 is positioned on the outer surface 20. The spigot is
to one
side of the first aperture and has a frusto-conical leading end 40 followed by
a small
shoulder 42. A passage 44 extends through the spigot.
[0031] Figure 4 illustrates, in cross-section and from one side, one way of
using the
device 10. A rock support tendon 46 has an elongate rigid shank 50 which
extends
through the opposing first and second apertures 22 and 26. A bearing plate 52
is
passed onto the shank over the convex outer surface 20 of the bulbous first
portion.
The bearing plate has a domed central area 54 which is sized to fit closely
over the
convex surface 20. The shank extends through a centrally positioned opening 56
in
the bearing plate. A shaped washer 58, as is known in the art, is placed over
the
shank and this is followed by a nut 60 which is threadedly engaged with a
protruding
end 62 of the shank.
[0032] The bearing plate is formed with a small opening 64 and the spigot 38
of the
device is passed through this opening. The shoulder 42 abuts and engages with
a
portion of the outer surface of the bearing plate which surrounds the opening.
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[0033] The shank extends through the tubular second portion 24 into a drill
hole 70
formed in a body of rock 74. An outer edge 76 of the bearing plate abuts a
surface
of a rock face 78 surrounding the drill hole 70.
[0034] The device 10 can be used in two ways, at least, depending on the
nature of
the rock support tendon with which the device is engaged. In one mode of use a
tube 80 is engaged with a leading end of the tubular second portion so that
the
second aperture 26 is in direct communication with an interior of the tube.
The tube
can be clamped or otherwise fixed to the tubular second portion. The tube
extends
into the hole 70 to a required extent. Grout from a grout delivery system, not
shown,
can then be injected into the passage 44 in the interior of the spigot. The
grout flows
into the volume 18 and then passes into an elongate annular volume 82 which
surrounds the shank and which is bounded by the inner surface of the tube. As
the
grout advances air is expelled from the drill hole, travelling on an outer
side of the
tube. The air eventually reaches atmosphere through paths which are formed on
an
outer side of the device 10.
[0035] In a second mode of use, illustrated in Figure 5, the shank, designated
50A,
is formed with an elongate, axially extending, air passage 84. In this mode of
use
the tube 80 is not used. When grout is injected into the volume 18 it emerges
from
the second aperture 26 and fills an annular gap 86 between an outer surface of
the
shank 50A and an opposing inner surface of the drill hole. Air trapped inside
the drill
hole can escape, as the grout advances, by entering a mouth of the passage 84
which is located at a far end of the shank. When grout starts leaving the
passage 84
it is evident to an operator that the drill hole has been completely grouted.
[0036] In Figures 4 and 5 the rock face 78 is generally perpendicular to the
longitudinal direction of the drill hole. This is not necessarily the case. In
many
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applications, particularly in arduous underground conditions, the rock face is
inclined
to the axial direction of the hole. Clearly, the orientation of the rock
support tendon is
determined by the hole direction. Similarly, the orientation of the bearing
plate is
determined by the orientation of the rock face surrounding the mouth of the
drill hole.
It is for this reason that a degree of flexibility of the body of the device
is required.
The tubular second portion is inserted into the drill hole and is therefore
not able to
be moved to any meaningful extent. The bulbous first portion which is captured
by
the domed bearing plate must be movable, together with the bearing plate,
relatively
to the rock support tendon. The bellows-like region 30 allows this movement to
take
place.
[0037] Figure 6 shows the use of the device with a tendon 46A which includes
an
elongate, slightly flexible, cable 50B, and not a rigid shank.
[0038] An end 90 of the cable projects from a mouth of a drill hole 70 formed
in a
rock body 74, and passes through a volume 18 inside a device 1 OA which is
similar
to the device 10, but which includes an additional tubular spigot 98. Other
parts of
the device I OA, which are the same as parts of the device 10, bear similar
reference
numbers. The device 10A is located inside a bearing plate 52 in that it has an
opening 100 through which the spigot 98 extends.
[0039] A breather tube 102 extends through the spigot 98, and the volume 18,
into
the drill hole 70 and, alongside the cable 50B, to an inner end of the drill
hole.
[0040] A barrel 106 is passed onto the end 90 and a wedge 108 is engaged with
the
end 90 and the barrel, which bears against an outer face of the bearing plate
52.
These components are used to tension the cable, as is known in the art. Grout
is
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injected into the drill hole through the spigot 44 and fills the annular space
between
the cable and a wall of the drill hole. Air is expelled through the breather
tube 102.
[0041] Figures 7 and 8 show another device 10B according to the invention in
perspective and in cross-section respectively. The device has a body 12B with
a
first, frusto-conical, portion 14B and a second, tubular, portion 16B. The
portion 14B
has a plurality of apertures 112, and two formations 98B and 44B which
correspond
to, and which perform the same functions as, the spigots 98 and 44
respectively.
The apertures 112 weaken the body and allow for a degree of relative movement
between the body portions 14B and 16B. A passage 18B, through the body 12B,
acts in the same way as the volume 18.
[0042] The device 10B is used in the same wary as the device 10A, but
preferably
with a bearing plate of a corresponding shape i.e. not as domed as the bearing
plate
52.
