Note: Descriptions are shown in the official language in which they were submitted.
33~)3~
This invention relates to a method of rock bolting where-
in a tube-formed bolt smaller than the hole is first inserted in-to
the Barlow and then expanded against the hole so that it becomes
anchored.
In a prior art method, a rock bolt is used that has a
short tube attached to its inner end, In the tube that has a
circular cross-section, a weak explosive is arranged to expand the
tube when detonating. Such bolts do not satisfactorily anchor in
all rocks and the method is not very simple and it causes safety
problems.
The invention provides a method of reinforcing rock
comprising:
providing a bolt that comprises an expansible elongated
tube which has a deep continuous longitudinal depression which
extends inwardly of the bolt toward the axis of the bolt and which
extends longitudinally of the tube over substantially the complete
length of the tube;
drilling a hole in the rock of a diameter large enough to
permit the unexpanded bolt to be freely inserted in the Barlow;
inserting the bolt in the Barlow; and
deforming said tube by bending by applying pressure to
the interior of said tube to expand said tube against the Barlow
over substantially the entire length of the bolt to expand said
depression outwardly substantially without stretching the material
of the tube so as to cause permanent gripping action of the tube
I
1 --
~33C~3~
-lo- 238~.5-2~D
against the inner surface of the Barlow, and thereafter relieving
said pressure.
The invention will further be described, by way of example
only, with reference to the accompanying drawings, wherein:
Figure 1 is a side view, partly in section of rock bolt accord-
in to the invention.
Figure 2 is an end view-seen as indicated by the arrows 2-2
in Figure 1.
Figure 3 is a cross section on a larger scale taken along line
10. 3-3 in Figure 1. It is also a cross-section taken along line 3-3
in Figure 6 and along line 3-3 in Figure 8.
Figure 4 is an end view as indicated by the arrows 4-4 in
Figure 1.
Figure 5 is a cross section corresponding to Figure 3 but
showing the rock bolt anchored ion a Barlow.
I
I.
~2~3303~
Fig. 6 is a side view, partly in section of the rock bolt shown in
Fig. 1, the ends of the rock bolt being modified.
Fig 7 is an end view seen as indicated by the arrows 7-7 in Fig. 6.
Figs 8 and 9 are side views of the outer end and bottom end respect
lively of another rock bolt according to the invention.
.
Fig. 10 is an end view seen as indicated by the arrows 10-10 in Fig. 9.
! 10
Figs 11-13 show the steps in sealing the bottom end shown in Fig. 9,
Fig. 13 being a view seen as indicated by arrows 13-13 in Fig. 12~
Figs 14, 15 and 16 are side views of the outer ends of other alterna-
live designs of rock bolts according to the invention.
Fig. 17 is a side view of the outer end of still another design.
jig. 18 is a side view corresponding to Fig. 17 but showing the rock-
bolt when it has been expanded.
Fig, 19 is a cross-section token along line 19-19 in Fig. 17.
Fig. 20 is a cross-section taken along line 20-20 in Fig. 18.
Figs 21 and 22 show two steps in joining two rock bolts in a Barlow.
The rock bolt shown in Fig. 1 comprises a tube 11 with a profile as
shown in Fig. 3. Between the points 13 and 14 in Fig. 3, the purify-
rye of the tube forms a circle arc 12 having a focus 15, a radius Rand a centre angle that exceeds 180 , actually the centre angle
exceeds also 270. The tube 11 has been drawn, rolled or folded to
have a deep depression that comprises two gently curved outer port
lions 16, 17 and a gently curved bottom portion 18. These three port
lions 16-18 can have the form of circle arcs as shown in Fig. 3. The
outer portions 16, 17 are bent more than 180 as shown in Fig. 3 and
the bottom portion 18 extends past the point lo and to or almost to
thy circular outer portion 12 of the tube. The two outer portion 16,
lZ~3303~
17 contact each other ore are at least adjacent each other. The die-
meter of the circle arc 12 is the largest gauge of the tube if.
Strengthening sleeves 19, 20 are disposed on both ends 21, 22 of thy
tube 11, and the bottom end 22 of the tube 11 is first punched and then
sealed by means of a weld 23. A tubular fitting 24 is inserted in the
outer end 21 of the tube before the end is punched and sealed by means
of a weld 25. In Figs 1 and 3, the bolt is shown before being used.
In Fig. 5, the bolt is shown anchored in a Barlow 26 by being ox
panted against the Barlow. Before being expanded, the bolt can be
freely inserted in the Barlow 26 since it is substantially thinner
than the Barlow. The tube 11 is expanded by being pressurized by
! a fluid for example water of a pressure ox for example 100-500 bar.
The water is supplied from an external source through the fitting 24.
The strengthening sleeves I 20 prevent the ends of the tube 11 prom
being expanded and the welds 23, 25 from brea~ing.If the tubes 11
are thin-walled and made of mild steel, a lower water pressure than
100 bar may be sufficient, but if the tubes 11 are thick-walled and
are made of harder steel, a higher pressure than 500 bar may be nieces-
Spry.
When the bolt is pressurized the outer circular portion 12 of the tube 11 will be bent into contact with the Barlow and the recession
16, 17, 18 will "roll" out in its outer portions 16, 17. The purify-
\ 25 fat length of the tube 11 is the same before and after the expansion
¦ which reduces the risk of cracking. Since the remaining recession 16-
18 is so large as shown in Fig. 5, it widens inwardly as shown or at
least it will have substantially parallel walls 27, 28. The pressure
will act on the walls 27, 28 in the direction of compressing the feces-
soon, and as a result, there is a force acting in the direction of widening the recession when the bolt is relieved of pressure, which
increases the frictional grip between the bolt and the Barlow.
In Fig. 6 a bolt is shown that differs from the ode shown in Fig. 1
by its ends. Two end plates, 31, 32 have been friction welded to the
tube 11 and the fitting 24 has been friction welded to the outer
plate 31. The fitting 24 can of course instead be affixed to the end
plate 31 by means of threads. It is an advantage that a threaded
~;~33~13~
fitting tube can be removed and replaced by a hook or another means
in which for example conduits can be mounted when the bolt has been
anchored.
In Fig. 8, the outer part ova bolt is shown that comprises a tube 11
which in contrast to the bolt shown in Fig. 1 has not the recession
16-18 along its entire length but which has a circular outer end 34
that is too wide to be inserted into the Barlow. An end plate 35
with a threaded hole 36 for 2 fitting tube has been friction welded
to the outer end of the tube 11. In Fig. 9 there is shown the bottom
end of the bolt shown in Fig. 8. In Figs 11-13, the steps of making
the end are shown. The end of the tube 11 is flattened as shown in
Fig. 11 and bent as shown in Figs 12 and 13 before the longitudinal
recession 16-18 shown in Fig. 3 is made so that the bottom end of the
bolt will be as shown in Fig. 9. Thus, a tube with a circular cross-
section is used for making the bolt according to Figs 8 and 9 and the
tube is given the profile shown in Fig. 3 as the lose step, whereas
a tube having the profile shown in Fig. 3 is used for making the bolts
shown in Figs 1 and 6.
In Fig. 14, the outer end of a rock bolt is shown which is modified
from the rock bolt shown in Fig. 6 in that the outer strengthening
sleeve 19 is threaded along its entire length so that a plate 41 can
be clamped against the rock by means of a nut 42. The sleeve 19 can
be secured to the tube for example by being welded to the tube 11 or
to the end plate 31 of the tube.
In Fig. lo, the outer end of a bolt is shown on which a plate 43 is
welded to the end of the tube 11. sigh pressure water can be supplied
to the tube through a hole 44 in the plate 43.
In Fig. 16 which also shows the outer end of a bolt, there is a hole
45 in the sleeve 19 through which water can be supplied to expand the
bolt. A rock engaging plate 46 has been loosely put onto the tube 11
before the sleeve 19 is mounted on the tube and fixed thereto. The
plate 46 will take support on the sleeve 19 when the bolt is inserted
in a Barlow and the plate 46 contacts the rock.
1~3303~7
on contrast to the design of Fig. lo the plates 43 and 46 shun in
Figs 15 and 16 cannot be tightened after the bolts have been anchored.
Such tightening after the anchoring is, however, not necessary since,
when the bolt is being expanded, it starts to expand at its axial mid
portion and gets stuck there and as the expansion proceeds, the length
of the bolt will decrease a few millimeters. This reduction of the
length of the bolt will cause the plate to be forced against the rock
provided that the plate is in contact with the rock before the expand
soon starts.
In Fig. 17, the outer end of a rock bolt similar to the one in Fig. 16
is shown. A threaded bolt 47 is inserted in the outer end as shown
and it is held in position while the bolt is being expanded. The-bolt
will be clamped and affixed because of the expansion of the tube if as
can be seen in Figs 18 and 20. The bolt 47 can be used as a support
in which for example conduits can be suspended in a tunnel
A bolt according to the invention, for example the bolt shown in Fig. 1
I can be provided with a cutting edge at the front end so that it can be
20 fused to drill its own hole. Flushing fluid can during the drilling be
supplied through the depression 18 shown in Fig. 3.
In Figfi 21 and Thor is illustrated a way of joining short rock bolts
to form a long rock bolt. At first, a bolt 38 according to Fig. 1 or
Z5 Fig. 6 is inserted in the Barlow. It has a joining sleeve 39 attached
to its outer end. Then when the bolt 38 is expanded the sleeve 39 be-
comes Secured to the bolt by friction. Now, when this bolt 38 is an-
cored in the Barlow, another bolt 40 is inserted in the Barlow to
extend into the sleeve 39. When this bolt is expanded, it will be so-
cured to the sleeve 39 by friction. Thus, the two bolts 3B, 40 and the joining sleeve 39 form a long rock bolt together.
The illustrated rock bolts are anchored by a friction grip along sub-
staunchly their entire length. The bolts are preferably made of mild
steel so what they will adapt to the irregularities of the Barlow,
for example to the helical form of the Barlow. Most Berlioz are
somewhat helical and also when they are so little helical that the he-
local form is not easily noticed, the helical form improves the anchor-
30~
coring.
The expansion as deacrîbed above is carried out by means of pressure fluid from a external source. Alternatively, it can be carried out
in other wave, for example by means of an explosive in the bolt. The
bolt can also be an open tube that has one or more longitudinal depress
sons and the expansion can be carried out mechanically by means of a
mandrel that is forced into the tube.
Although expansion rock bolts with a prime object of supporting the
strata have b Den described above, expansion bolts according to the in-
mention can by used for other purposes, for example when the prime
object is to anchor a comparatively short bolt so that it can carry
an external load of any kind.
