Note: Descriptions are shown in the official language in which they were submitted.
2Q1~1262
Docket No. 0529-IR-RD
ROCK DRILLING METHOD AND APPARATUS
BACKGROUND OF THE lNv~ lON
During construction it i8 often de~irable to
drill horizontal holes in rock under roadways and
building foundations without disturbing those
structures. Such horizontal holes may be used for
05 utility services, or drainage, or the like, and for
this purpose it is desirable to have a straight
hole economically drilled with a minimum of ground
disturbance.
To accomplish such holes it is common to dig
a shaft on either side of the structure and by
means of auger in soft ground, or a rock drill in
harder ground, drive the hole from shaft to shaft.
This is accomplished by utilizing conventional
drilling techniques which push the auger or rock
drill utilizing a rotary drill string. The auger
or drill and trailing drill string is inserted in
sections and driven from one of the shafts to the
other.
Core drills have been developed for small
diameter holes which are relatively effective in
drilling accurate straight holes between two
locations. However, effective core drilling is
limited to holes of about 4 to 8 inches or smaller
because the cores must be drilled in segments,
2S usually a maximum of twenty (20) ft. and removed.
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Docket No. 0529-IR-RD
In larger size holes the process would be slow
and the cores become increasingly difficult to
remove, particularly in hard rock. As a result, a
common practice has developed in boring larger
05 diameter holes to first bore a cored hole and
therea~ter force a series of rotary ring reamers
through ths hole to increase the hole size to the
diameter deslred.
Reaming is also time-consuming and in general
produces a hole which i~ rough and/or cork screwed
and as the size increase~ it becomes more difficult
to maintain the progress without buckling the drill
string creating the rotary drive and force on the
ring cutters. An improvement to thls method
lS involves the pulling of the ring cutters back
through the hole but since this is a progressive
stepwise operation the difficulty of the reamer
walking about the hole diameter, although improved,
still continues.
SUMMARY OF THE I~v~NllON
In the present invention a horizontal hole is
accomplished by first sinking a shaft on either side
of the hole to permit access. Next, a small
diameter hole between the shafts of approximately 4"
is bored by core drilling. A drill string is next
inserted in the hole. A modified clustered drill,
generally of the type shown and described in U.S.
Patent No. 4,729,439, entitled "Gang Drill
Construction" and assigned to Ingersoll-Rand
Company, the assignee of the present invention, is
~o attached to the drill string. For purposes of this
:
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Docket No. 0529-IR-RD
invention the center drill is removed and replaced
by a section of drill rod or center feed rod which
supplies the gang drill with pressure fluid from
its opposite end, that is the end that normally
05 contains th~ rock cutting bits. This permits the
cluster drill to b~ rQversQ mounted to th~ drill
string insertQd in th~ cored drill hole. The gang
drill i8 then suppliQd with pres~urQ ~luid to
operate the circumferentially mounted impact rock
drills. The drill string is then rotated and
withdrawn through the hole tailing and rotating the
cluster drill. Pressure fluid and rock drill
cuttings exit the large diameter hole in the
conventional manner. As an added feature, sections
of auger may be attached to the back of the gang
drill to effect additional cleaning of the
horizontal hole as the gang drill is drawn through
the hole and rotated. This will reduce the overall
air requirements necessary for cleaning the hole.
It is therefore an object of the present
invention to provide a method and apparatus for the
drilling of accurate large diameter horizontal
holes in hard rock. It is an ob;ect of the
invention to drill such holes in hard rock at high
speed with efficiency and minimum air consumption.
It is yet a further object to accomplish the
drilling of large diameter horizontal holes in hard
rock by utilizing easily modified and available
cluster drills, and simple rugged and reliable
boring equipment of a small size compared to
similar methods for similar size holes in hard
rock.
- 200126Z
These and other objects are obtained in an
apparatus for drilling larger diameter holes in hard rock
comprising: a cluster drill adapted for receiving pressure
fluid and rotation from a drill string at its rock
- 5 impacting end, the adaptation further comprising a means
for receiving pressure fluid and connecting the cluster
drill to a drill string provided at the impact end of said
cluster drill on its centerline, a drill string connected
to the means for connecting the drill string, the drill
string further rotating and drawing the cluster drill into
a drilled hole containing the drill string and enlarging
the hole as it progresses.
It is a further object of the present invention to
include auger means attached at the back end of the cluster
drill for assisting in the removal of rock particles as the
cluster drill progresses through the hole. The removal
being accomplished by a combination of the auger trailing
and rotating with the drill and exhaust pressure fluid
- 20 thereby minimizing pressure fluid consumption in the
removal of rock drill particles.
According to a still further broad aspect of the
present invention, there is provided a gang drill for
increasing the diameter of bored holes in hard rock. The
drill comprises a plurality of individual percussion
producing rock drills in a cylindrical drill body. The
body has a rearward end and a forward end. The forward end
has bit ends of the drills exposed for rock cutting
arranged peripherally around the body. A drill string is
connected at the centerline of the drills to the body at
its forward end and at the centerline of the drills, for
rotating and drawing the drills through a previously
drilled bore hole to enlarge the previously drilled hole.
- 35 The body totally encloses the drills. The body is further
provided with alignment means, securing means, and means
~a~
~- 2001262
for supplying pressure fluid for each of the drills. The
pressure fluid enters the drills internally of the body and
exits the drills externally to the body at its forward end,
whereby the body forms a peripheral passage for exiting of
S the rock cuttings and provides protection for individual
drills. The means for supplying pressure fluid from the
forward end of the body comprises a center core rod of
approximately the same dimensions as an individual
percussive drill allowing substitution for same and thereby
provides for reversal of the direction of drilling of the
gang drill.
According to a still further broad aspect, the core
rod is provided with a thread at its forward end for
attachment to the drill string and is connected to the
rearward end of the body by attachment means. The core rod
is provided with a central passage formed therein for
receiving pressure fluid from the forward end of the body.
According to a still further broad aspect, the gang
drill has attached at its rearward end an auger means for
assisting in the clearing of drilled debris with the auger
means being rotated with the drill body.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l shows a cross section view of a clustér
drill modified according to the present invention for
forward pressure fluid supply and rotation.
Fig. 2 is an end view of the cluster drill.
Fig. 3 shows a pictoral representation of the
horizontal reverse drilling system according to the present
invention.
~t-~ 2001262
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Fig. 1 a cross section of the
modified cluster drill is shown and generally designated by
Reference Numeral 1. The drill is comprised of a
- cylindrical body barrel 2 having an end plug 3 at its
forward or work producing end and a back head 4 at its
rearward end. A plurality of downhole drills 5 are mounted
in the barrel body 2 in a manner previously disclosed in
U.S. Patent No. 4,729,439 which issued on March 8, 1988 and
entitled Gang Drill Construction.
In general, each of the individual drills 5 are
mounted in a bore 6 in the plug 3 and a tapered bore 7 in
the back head 4. The tapered bore 7 cooperates with a
taper 8 on each of the individual downhole drills 5. Each
of the downhole drills 5 are retained in their respective
tapered bores 7 by means of a cap nut 8. Pressure fluid is
distributed to each of the circumferentially mounted
downhole drills 5 by means of radial distribution bores 9.
In the prior art, cluster drill, the drill string
is attached to the back head and supplies pressure fluid to
the radial distribution bores. In the present invention
the center drill is removed and replaced with a core rod
10. The core rod 10
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Docket No. 0529-IR-RD
is provided with a central bore 11 which now supplies
pressure fluid to the back head. The core rod 10 i~
provided with a thread 12 at its forward end 13 and
is connected to the back head by a thread 14 or or
05 other convenient mQans.
Attached also to the back head i8 a socket
flange 15 which permits attachment of an auger to the
back heAd end o~ the drill. Mounted to each of the
downhole drills 5, is a rock drill bit 16 (~hown in
~O phantom) whlch is impacted upon by the downhole drill
and thereby fragment and remove rock p~rticles. Fig.
2 showc the orientation of the downhole drills 5
about the central axis provided by the core rod 10.
It should be appreciated by one skilled in the art
that pressure fluid (commonly compressed air) may be
supplied via the core rod 10 through the radial
distribution bores 9 in the back head 4 to each of
the individual downhole drills 5. The pressure fluid
creates a hammering action which is transmitted to
the drill bits 16.
As shown in Fig. 3 the reverse cluster drill 1
is attached to a drill string 20 which is inserted in
a previously bored core drill hole 21 of
approximately the same diameter as the drill string.
The drill string 20 is in turn attached to a boring
machine 26 of the type shown, for example, the boring
machine supplied by NLC Company, Ltd. of Tokyo, Japan
and distributed under the trade name Longyear Boring
Machines. The boring machine 26 provides both
rotation and tractive force to the drill string in
operation to produce a bored hole 24.
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Docket No. 0529-IR-RD
To produce a horizontal bore hole, shafts 25
and 25a are dug at either end of the intended bore
hole. A boring ma~h~P 26 is next deployed in one
of the shafts (for example 25) and mountQd on a
05 foundation 27. The boring machin~ i8 utilized to
produce a drilled hole generally by a core drill in
the 4 to 6 in. r~nge bQtween sha~ts 2S and 25A in a
conventional manner utilizing drill string segments
to advance the core drill.
On completion o~ the cored hole thQ core
drill is removed and replaced with the cluster
drill according to the present invention. The
drill string is then withdrawn and rotated carrying
with it the cluster drill 1 and an attached auger
30 which would be inserted in sections 30
following the cluster drill by means of a service
crane 32 or the like.
Pressure fluid is supplied to the cluster
drill 1 by an air compressor 31 (for example)
through the boring machine and drill string to
produce rock cutting impact action on the rock
drill bits 16. As the drill is drawn through the
hole it enlarges it to the desired diameter, D2.
The drill string in the smaller diameter Dl acts to
centralize and stabilize the core drill as it is
drawn into the larger diameter hole which it is
producing. The drill string being in tension and
acting as a centralizing stabilizer creates a
straight true hole with the cluster drill.
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Docket No. 0529-IR-RD
PressurQ fluid exiting the cluster drill 1
and the action of the rotating auger 30 trailing
the cluster drill and attached thereto by the
threads of socket flange 15, cleans thQ debris
05 produced out of the large diameter hole and
deposits it into shaft 25A where it may be
removed. once the cluster drill reaches the shaft
25 it is removed and the segments of the auger are
likewise removed completing the ~ob. Use of the
auger greatly reduces the amount of air required
for hole cleaning. However, air alone may be
utilized to clean the hole.
The drilling system according to the present
method has been utilized in boring holes o~ 500 to
800 millimeters (20 to 32 inches in diameter) in
hard rock with hole lengths of 78 meters (230 ft.)
with boring speeds substantially in excess of
existing drilling methods. Longer and larger holes
are well within the capability of this drilling
system.
Having described my invention in terms of a
preferred embodiment, I do not wish to be limited
in the scope of my invention except as claimed.
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