Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a cable bolt for stabilizing
a mine roof or walls. '!'"' '
When mining underground, the strata is usually of such ' ~-
a type that it is necessary to stabilize the roof and/or walls by ,
holding it in one mass, the conventional means for doing this
being the insertion of rock bolts approximately 6' long into the '
strata. When the strata is badly fractured beyond the limit that '-
a 6' rock bolt can reach, mines have resorted to cable bolting.
Cable bolting is currently being used in some mines with a limited
success. The method of utilizing cable bolting is to drill a hole
into the strata, insert a cable into the hole and pump in cement
grout between the cable and the hole. The grout however does not
adhere to the cable as well as to the hole and therefore, as an
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example, although a cable may have a rated tensile strength of 29 ,'
tons, it often cannot support a portion of roof weighin~ more than
17 tons as the roof and grout slip on the cable. '
In order to overcome this slipping between the cable
and the grout, the present invention was made in which outwardly 'A'~ '
extending protrusions are formed upon the cable so that the cable `
will not slip relative to the grout. These protrusions can be
of any suitable form but are preferably one of the ollowing or a ~
combination of the following: ,,~ , ,
1. steel ferrules pressed onto the cable at suitable
spacings;
2, small radius kinks formed in the cable;
3. strands of the cable are unwound for a short length
and opened to form a bulge on the cable and a void on the axial ~ ' '
centre line of the cable into which grout will enter.
For ease of use of the cable bolt, it is also prefer-
able to have a plurality of semi-flexible fingers at the top,end
of the cable which will effectively prevent the cable from falling
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out of the hole as it is being inserted. These fingers are there- ~ ~
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fore only of the required strength to hold the weight of the
cable before it is grouted in place.
The invention will now be descrihed with reference to ~`
the accompanying drawings listed below, in which preferred ~;
embodiments are detailed.
Figure 1 is a length of cable bolt having steel ferr~
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ules pressed onto the cable.
Figure 2 is an end elevational view of the cable bolt
of Figure 1 showing the disposition of the semi-flexible fingers
at the top of the bolt.
Figure 3 is a length of cable bolt showing a second
embodiment of the invention in which the cable strands are
unwound for a short length to form outwardly extending protrusi-
ons.
Figure 4 is a short length of cable bolt showing a `
third embodiment of this invention wherein short radius bends
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or kinks are forméd in the cablel and
Figure 5 is a view showing the cable bolt of Figure 1
20 in place in a mine roof. `
Referring to the drawings, the embodiment of Figure 1 ~
consists of a cable 1 upon which are placed steel ferrules 3 `
which are pressed onto the cable under an extremely large force
to solidly secure them to the cable. In practice, a force of
approximately 600 tons per square inch is utilized to insure '~
adequate securing of the ferrules upon the cable. If required,
other securing means such as welding could be used to secure
the ferrules to the cable although pressing of the ferrules onto
the cable is preferred. A ferrule S is also secured to the top
end of the cable and this ferrule is formed with a stud 7 at its
upper end through which are attached semi-flexible fingers 9 by
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means of a nut ll threaded onto the stud.
The embodiment of Figure 3 consists of a cable 13
having short sections 15 unwound such that the separate strands
17 extend in an arcuate manner outside the normal surface of the
cable to form protrusions, and also leave a vo:id along the axial
axis of the cable. -
The embodiment shown in Figure 4 consists of a cable
19 which is kinked as shown at 21 by the formation of small
radius bends 23 and a U-shaped bend 25. The kinks can be
arranged as shown in Figure 4, but will normally not be all
aligned in one plane but will be disposed radially around the
cable axis.
The method of using the cable bolt of this invention is
drilling a hole of a length of approximately 50' for accepting
the cable bolt, feeding the cable bolt upwardly into the hole,
the semi-flexible fingers holding the weight of the cable bolt
as it is being pushed into the hole, and putting a ~" diameter
plastic tube in the hole with the cable bolt so that one end of
the tube is drawn completely up to the blind end of the hole.
A ~" diameter plastic pipe is then inserted into the hole a
distance of approximately l' with a second ~" diameter plastic
plpe being inserted a distance of approximately 8' into the hole.
Cotton waste, or the like, is placed in the bottom of the hole
for sealing purposes and grout is pumped into the shorter ~"
diameter plastic pipe until it emerges from the longer ~" dia- -
meter plastic pipe. Grout pumping is then ceased, the grout
pump is disconnected and the shorter ~" diameter-plastic pipe
is kinked and tied so that the grout can then harden and serve
as a plug in the bottom of the hole. Approximately 24 hours
3~ later, the grout pump is re-attached to the 8' ~" diameter pipe
and pumping of the grout begins, the exposed end of the ~"
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diameter plastic tube being inserted into a pail of water so
that bubbles are expelled as the grout enters the hole. When
the bubbles stop emerging from the ~" diameter plastic tube, `
the hole will be full of grout and the grout pump can be removed. -
The cable bolt will then be able to accept tension loads after
the drying period of the grout has elapsed. Figure 5 shows the
cable bolt of Figure 1 in a bored hole 27, the ~" diameter `
breather tube 29, and for comparison purposes, two conventional ;
roof bolts 31 drawn to approximately the same scale.
It will therefore be appreciated that the cable bolt ~`~
as disclosed is capable of holding tension loads in strata up to
the breaking point of the cable as it is not possible for the ,
cable bolt to slip relative to the grout and the rock due to the `
protrusions spaced along the cable bolt,
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