U.S. patent application number 10/919271 was filed with the patent office on 2005-02-24 for drilling apparatus, method, and system.
Invention is credited to Brennan, Mike, Dolgin, Benjamin, Giraldo, Luis, Hill, John L. III, Koch, David, Lombardo, Mark, Shenhar, Joram.
Application Number | 20050039952 10/919271 |
Document ID | / |
Family ID | 34198134 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050039952 |
Kind Code |
A1 |
Hill, John L. III ; et
al. |
February 24, 2005 |
Drilling apparatus, method, and system
Abstract
A helical drag bit provided with spirally/helically positioned
cutting arms. The arms can create a spiral trench geometry in the
sidewall of a predrilled pilot hole. The cutting arms can terminate
in scoring cutting blades. The helical drag bit can be incorporated
into a system and method for measuring geo-tech characteristics.
The helical drag bit can be used in a system and method for
improving the holding capacity of rock bolts and similar devices
for use in the mining industry or in any circumstances where a
particulate substrate may benefit from support. Novel rock bolts
having new structures can be used with this improved hole geometry
or may form such improved hole geometry.
Inventors: |
Hill, John L. III;
(Woodbridge, VA) ; Brennan, Mike; (Bristow,
VA) ; Shenhar, Joram; (Fairfax, VA) ; Koch,
David; (Fredericksburg, VA) ; Lombardo, Mark;
(Arlington, VA) ; Dolgin, Benjamin; (Newington,
VA) ; Giraldo, Luis; (Fairfax, VA) |
Correspondence
Address: |
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
2101 L Street, NW
Washington
DC
20037
US
|
Family ID: |
34198134 |
Appl. No.: |
10/919271 |
Filed: |
August 17, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60496379 |
Aug 20, 2003 |
|
|
|
Current U.S.
Class: |
175/57 ; 175/388;
175/394 |
Current CPC
Class: |
E21D 21/0053 20160101;
E21B 10/44 20130101 |
Class at
Publication: |
175/057 ;
175/388; 175/394 |
International
Class: |
E21B 010/40; E21B
010/36 |
Claims
What is claimed as new and desired to be protected by Letters
Patent of the United States is:
1. A helical drag bit, comprising: a bit shaft having a tip-end;
and a plurality of cutting arms on said bit shaft, each of said
cutting arms having an axial length and being positioned around
said bit shaft with a consistently angled pitch; wherein said axial
length of each said cutting arm is greater relative to cutting arms
positioned closer to said tip-end of said bit shaft such that said
plurality of cutting arms are configured to cut a spiral groove
into an interior surface of a pilot hole.
2. The helical drag bit of claim 1, wherein said bit shaft is
segmented into stackable flights, each of said flights comprising
at least two said cutting arms.
3. The helical drag bit of claim 1, wherein each of said cutting
arms terminates in a scoring blade.
4. The helical drag bit of claim 3, wherein said scoring blades are
configured to cut a kerf in rock through which said helical drag
bit is drilling.
5. The helical drag bit of claim 1, wherein said helical drag bit
is part of a detached, self-driven, underground autonomous tethered
drill system.
6. The system of claim 5, further comprising a computer in
communication with said helical drag bit, wherein said system is
configured to measure geo-technical characteristics of a substrate
through which said helical drag bit is drilling.
7. The helical drag bit of claim 1, wherein said helical drag bit
is in communication with a computer and configured therewith to
measure geo-technical characteristics of a substrate through which
said helical drag bit is drilling.
8. A system for reinforcing a substrate, comprising: a helical drag
bit having a substantially cylindrical bit shaft and a plurality of
cutting arms on said bit shaft, each of said cutting arms having an
axial length and being positioned around said bit shaft with a
consistently angled pitch, wherein said axial length of each said
cutting arm is greater relative to cutting arms positioned closer
to a tip-end of said bit shaft such that said plurality of cutting
arms are configured to cut an optimal hole geometry into an
interior surface of a pilot hole; a reinforcing bolt structure
configured for insertion into said pilot hole; and an anchoring
means configured to hold said reinforcing bolt structure within
said pilot hole by interacting with said optimal hole geometry.
9. The system of claim 8, wherein said optimal hole geometry
comprises a spiral groove in the interior surface of said pilot
hole.
10. The system of claim 8, wherein said anchoring means is
grout.
11. The system of claim 8, wherein said anchoring means is a
mechanical anchor comprising axially extending regions
corresponding to said optimal hole geometry.
12. The system of claim 8, wherein said reinforcing bolt structure
comprises axially extending regions corresponding to said optimal
hole geometry.
13. The system of claim 8, wherein said helical drag bit and said
reinforcing bolt structure are part of the same structure.
14. A method of cutting a spiral groove into the interior surface
of a pilot hole, comprising: inserting a helical drag bit into a
pilot hole, said helical drag bit having a substantially
cylindrical bit shaft corresponding in size to said pilot hole and
a plurality of cutting arms on said bit shaft, each of said cutting
arms having an axial length and being positioned around said bit
shaft with a consistently angled pitch, wherein said axial length
of each said cutting arm is greater relative to cutting arms
positioned closer to a tip-end of said bit shaft; and rotating said
helical drag bit in a direction corresponding to said consistently
angled pitch.
15. The method of claim 14, wherein said bit shaft is segmented
into stackable flights, each of said flights comprising at least
two said cutting arms.
16. The method of claim 15, wherein only one flight of said helical
drag bit is advanced into said pilot hole at a time.
17. A method of enlarging a pilot hole, comprising: inserting a
helical drag bit into said pilot hole, said helical drag bit having
a substantially cylindrical bit shaft corresponding in size to said
pilot hole and a plurality of cutting arms on said bit shaft, each
of said cutting arms having an axial length and being positioned
around said bit shaft with a consistently angled pitch, wherein
said axial length of each said cutting arm is greater relative to
cutting arms positioned closer to a tip-end of said bit shaft and
each said cutting arm terminates in a scoring blade; and rotating
said helical drag bit in a direction corresponding to said
consistently angled pitch.
18. The method of claim 17, wherein said wherein said bit shaft is
segmented into stackable flights, each of said flights comprising
at least two said cutting arms.
19. The method of claim 18, wherein only one flight of said helical
drag bit is advanced into said pilot hole at a time.
20. The method of claim 17, wherein said scoring blades of said
cutting arms cut a kerf into a substrate through which said helical
drag bit is rotating.
21. A system for supporting a substrate with a rock bolt,
comprising: a rock bolt, said rock bolt being configured for
insertion into a rock bolt hole; and at least one protuberance on
said rock bolt, said at least one protuberance being configured
such that it will form a groove in a wall of said rock bolt hole
when said rock bolt is inserted into said rock bolt hole, wherein
said rock bolt is thereby supported in said rock bolt hole at least
in part by said at least one protuberance and said groove.
22. The system of claim 21, wherein said groove is at least
partially formed by a rotation of said rock bolt.
23. The system of claim 21, wherein at least a portion of said
groove is semi-annularly shaped.
24. The system of claim 21, wherein at least a portion of said
groove is spirally shaped.
25. The system of claim 21, wherein a plurality of said
protuberances are provided on said rock bolt.
26. The system of claim 25, wherein said plurality of protuberances
are all the same size.
27. The system of claim 25, wherein each protuberance of said
plurality of protuberances has an increased radial length relative
to any protuberance closer to a tip end of said rock bolt.
28. The system of claim 21, wherein said at least one protuberance
is rounded.
29. The system of claim 21, wherein said at least one protuberance
is angular.
30. The system of claim 21, further comprising an adhesive.
31. The system of claim 30, wherein said adhesive is grout.
Description
[0001] This application claims the benefit of U.S. provisional
patent application No. 60/496,379, filed Aug. 20, 2003, the
entirety of which is hereby incorporated by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The invention relates to helical drag bits and rock bolt
systems, which can be used for geotech, mining, and excavation
purposes. The invention also relates to methods of using such
helical drag bits, and systems incorporating such helical drag bits
and rock bolts.
[0004] 2. Related Art
[0005] Known drilling systems may employ roller cone bits, which
operate by successively crushing rock at the base of a bore. Roller
cone bits are disadvantageous because rock is typically resistant
to crushing. Other known rock drilling systems employ drag bits.
Conventional drag bits operate by shearing rock off at the base of
the bore. Drag bits can be more efficient than roller cone bits
because rock is typically less resistant to shearing than to
crushing.
[0006] Most state of the art rock cutting processes are
accomplished by the shearing action or grinding motion of some
cutting tool. These cutting actions result in a noisy work
environment coupled with the undesirable excitation vibrations that
are transmitted to the drill unit home structure. A parameter of
paramount importance in any drilling process is the "weight-on-bit"
which is the axial force acting on the bit during the cutting
process. Normally this force is relatively large and may be
generated via proper anchoring of the drill machine to the drilled
surface or as an alternative, weight-on-bit may be provided by the
self-weight of the drill unit structure.
[0007] U.S. Pat. No. 5,641,027 to Foster ("the '027 patent";
assigned to UTD Incorporated) discloses a drilling system
incorporating a bit with thread cutting members arranged in a
helical pattern. Each subsequent cutting member is wedge shaped
such that the threads cut by the bit are fragmented, i.e., snapped
off. The bit disclosed by the '027 patent is suitable for enlarging
a bore formed by a pilot drill bit. The entirety of the '027 patent
is hereby incorporated by reference herein.
[0008] A Low Reaction Force Drill (LRFD), such as that disclosed in
the '027 patent, is a low-energy, low mass, self-advancing drilling
system. Energy expenditures have been demonstrated by studies to be
at least five times less than other prior art systems suitable for
similar drilling purposes. The distinct advantages of the LRFD are
its low energy drilling capability as a function of its unique rock
cutting mechanism, its essentially unlimited depth capability due
to its tethered downhole motor and bailing bucket configuration,
its self-advancing capability by self-contained torque and
weight-on-bit by counteracting multiple concentric rock cutters and
bracing against rock or regolith. Additional LRFD advantages may be
found in its large non-thermally degraded intact sample production
(>1 cm.sup.3) with position known to within 15 mm, and finally,
the large diameter hole it produces that allows for down hole
instrumentation during and post drilling. The system has
application for shallow drilling (1 to 200 meters) through
kilometer class drilling in a broad range of materials. It would be
advantageous to utilize the advantages of this system in a new drag
bit geometry, while also mitigating disadvantageous characteristics
of this system with a new bit.
[0009] It would be advantageous to have a helical drag bit that
utilizes fewer power resources and that can operate with or without
fluid lubrication. It would also be advantageous if such a drag bit
could operate under extreme cold and near vacuum conditions, such
as those found at extra-terrestrial sites.
[0010] A problem encountered by geologists or other rock mechanics
investigators is the difficulty of obtaining accurate compressive
strength measurements of rock in the field, particularly in situ
during drilling. In conventional drilling, several drilling
variables must be simultaneously monitored in order to interpret
lithologic changes, including thrust, rotational velocity, torque,
and penetration rate. This is true because with each conventional
bit rotation the amount of material removed is a function of all of
those variables. It would be advantageous for a geo-technical
system to enable geologists and others to obtain accurate substrate
characteristic measurements in situ.
[0011] In the mining industry, roof falls in coal mines continue to
be the greatest safety hazard faced by underground coal mine
personnel. The primary support technique used to stabilize rock
against such events in coal and hard rock mines are rock bolts or
cable bolts. Both of these primary support techniques involve
drilling holes in rock and establishing anchoring in those holes.
Current fatality and injury records underscore the need to improve
these operations.
[0012] As the primary means of rock reinforcement against roof
collapse, rock bolts play an important role. As collected from rock
bolt manufacturers by NIOSH, approximately 100 million rock bolts
were used in the U.S. mining industry in 1999 and of those,
approximately 80% used grout as a means of anchoring the bolt to
the rock (up from approximately 48% in 1991) with the vast majority
of the remaining percentage of rock bolts using mechanical anchors.
Cuts through mountainous terrains by highways and railways also
extensively use rock bolts or cable bolts for rock mass
stabilization.
[0013] While a broad range of anchoring techniques have been
developed, grouting and mechanical expansion anchor bolts are the
more common, together comprising over 99% of rock bolts used in
coal mines in the U.S. The decline in the use of mechanical bolts
is attributed to the fact that grouted rock bolts distribute their
anchoring load on the rock over a greater area and generally
produce better holding characteristics.
[0014] As a major contributor to a roof control plan, rock bolts
have been studied to determine optimum installation spacing,
length, and matching of anchoring with geologic conditions. The
main ways rock bolts support mine roofs are typically described as
follows: beam building (the tying together of multiple rock beams
so they perform as a larger single beam), suspension of weak
fractured ground to more competent layers, pressure arch, and
support of discrete blocks. Cable bolting (where cables are used in
place of steel rods as bolts) performs similar functions. While
rock bolts play a critical role in mitigating rock mass failure,
many other mine design factors come into play to create a stable
mine environment including (but not limited to) opening dimensions,
sequence of excavation, matching of bolt anchor and length with
opening and geologic conditions, and installation timing.
Notwithstanding the importance of these other factors, if the rock
bolts used in rock stabilization do not perform well, miners are at
risk.
[0015] Bolt installation characteristics near roof falls have been
identified as contributing to failure. One documented and regularly
occurring rock bolt failure mechanism is loss of grout shear bond
to the rock wall of the bolt hole. Key contributors to the
integrity of the grout interlocking with the rock mass are the
diameter of the hole relative to the diameter of the bolt, resin
vs. cement type grouts, rock type and condition of the hole.
[0016] Smooth bolt holes consistently produce a reduction in rock
bolt load bearing capacity over rough walled holes. To address
this, bolt hole bit manufacturers intentionally use reduced
tolerances in their manufacturing on the center of bit peaks, and
setting of bit cutter inserts in such a way as to induce a wobble
during drilling, as well as loose bit mounting to drill rod, with
the ultimate result of ridges being left on hole walls. The
approach generally produces increased anchoring capacity. However,
even with these variations in bolt hole smoothness, anchorage
capacity increases, but failure of the rock-grout interface is
still common.
[0017] While considerable research into rock bolting has been
conducted to date, gaps still exist in areas that could lead to
vast improvements in rock bolt performance. For example,
significant pull-test studies have been performed and optimal hole
diameter to bolt diameter ratios have been identified for maximum
anchorage capacity, and hole condition has been identified as an
important contributor to ultimate holding capacity. A relatively
unexplored feature in rock bolt holding capacity is hole geometry.
It would be advantageous to optimize bolt hole geometry for
improved holding capacity.
[0018] Other problems are also encountered in the field of rock
bolt hole drilling: dust and noise. During most rock bolt drilling
operations, the operator stands directly at the controls, a couple
of feet away from the machinery and the actual drilling process.
Research by NIOSH has identified potential for high silica dust
levels around roof bolters in coal mines and attributes much of the
cause to the vacuum collection and filtering of air used in the
drilling process. While significant research into dust hazards and
health effects has been conducted by NIOSH (and previously by the
U.S. Department of Interior, Bureau of Mines), the measures to
improve the environment for rock bolt drillers has been limited
almost entirely to worker protection actions.
[0019] Noise near mining machinery has also been studied.
Engineering solutions to the mitigation of high noise levels are
always preferred over administrative solutions or personal
protective equipment. The key is to make those engineering
solutions cost-effective.
[0020] Similarly, dust protective equipment is useful, but
low-dust-by-design solutions offer greater opportunity for seamless
incorporation and effectiveness in improving the safety and health
environment for miners.
SUMMARY
[0021] The invention relates to novel helical drag bits as well as
to systems incorporating such helical drag bits and to methods of
using them. The invention overcomes to a substantial extent the
disadvantages of the prior art. Thus, according to one aspect of
the invention, the helical drag bits incorporate one or more
spirally/helically positioned cutting arms of increasing radial
length as they are positioned in a direction moving away from the
tip-end of the drag bit. The cutting arms can create a spiral
trench geometry in the sidewall of a predrilled pilot hole.
[0022] In an alternative embodiment, the cutting arms terminate in
scoring cutting blades. These blades serve to cut a relatively
smooth pilot hole bore extension into the sidewalls of the hole,
thereby enlarging the hole diameter. The cutting arms of this
embodiment can be used with those of the previous embodiment
without the scoring blades or may be used by themselves.
[0023] The embodiments of the helical drag bit can be incorporated
into a system and method for measuring geo-tech characteristics of
drilled substrates. The measurements can be made in situ during
drilling.
[0024] The helical drag bit can be used in a system and method for
improving the holding capacity of rock bolts and similar devices
for use in the mining industry or in any circumstances where a
particulate substrate may benefit from support. The helical drag
bit can produce an improved rock bolt hole geometry, which can
interact with mechanical or chemical holding means to improve
pull-out capacity in the support structure. Conventional as well as
novel rock bolts (having new structures) can be used with this
improved hole geometry. Such novel rock bolts can incorporate the
helical drag bit design or can excavate a rock bolt hole in a
similar way.
[0025] The above-discussed as well as other advantages can be
better understood from the detailed discussion below in view of the
accompanying figures referred to therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIGS. 1a and 1b are views of a helical drag bit flight
portion in accordance with an embodiment of the invention;
[0027] FIGS. 2a and 2b are views of a helical drag bit flight
portion in accordance with an embodiment of the invention;
[0028] FIGS. 3a and 3b are views of a helical drag bit flight
portions during fabrication in accordance with an embodiment of the
invention;
[0029] FIGS. 4a and 4b are views of cutting arm inserts in
accordance with an embodiment of the invention;
[0030] FIGS. 5a and 5b are views of a helical drag bit flight
portion in accordance with an embodiment of the invention, with
FIG. 5b being a detail of a portion of the view shown in FIG.
5a;
[0031] FIG. 6 is a perspective view of a helical drag bit flight
portion in accordance with an embodiment of the invention;
[0032] FIG. 7 is a view of two helical drag bit flight portions in
accordance with an embodiment of the invention;
[0033] FIG. 8 is a view of a stack of helical drag bit flight
portions in accordance with an embodiment of the invention;
[0034] FIG. 9 is a view of a drilling system incorporating a
helical drag bit in accordance with an embodiment of the
invention;
[0035] FIG. 10 is a view of the drilling system of FIG. 9, shown in
sequential drilling steps 0-4 in accordance with an embodiment of
the invention;
[0036] FIG. 11 shows a detailed view of a hole of formed by a
device in accordance with an embodiment of the invention;
[0037] FIG. 12 is a view of two helical drag bit flight portions
having scoring cutting arms in accordance with an embodiment of the
invention;
[0038] FIG. 13 is a view of helical drag bit flight portions having
scoring cutting arms in accordance with an embodiment of the
invention;
[0039] FIGS. 14-16 are cross-section views of a substrate and a
rock bolt in accordance with exemplary embodiments of the
invention;
[0040] FIG. 17 is a graph comparing the pullout strength of a
conventional rock bolt used in a prior art rock bolt hole with that
of a conventional rock bolt used in combination with a rock bolt
hole formed in accordance with an embodiment of the invention;
[0041] FIG. 18 shows a cross-section view of a substrate and a rock
bolt in accordance with an exemplary embodiment of the
invention;
[0042] FIGS. 19a-19d show a cross-section view of a substrate and a
rock bolt in accordance with an exemplary embodiment of the
invention;
[0043] FIGS. 19e and 19f show a cross-section view of a substrate
and a rock bolt in accordance with an exemplary embodiment of the
invention; and
[0044] FIGS. 20a-20c show exemplary embodiments of rock bolts in
accordance with the invention.
DETAILED DESCRIPTION
[0045] The invention relates to helical drag bits, systems
incorporating the bits, and to methods of using the bits and
systems. Throughout this detailed description, the terms "helical
drag bit" and "helicutter" are used interchangeably. The term
"flight" indicates a portion of a segmented bit shaft, which
comprises cutting arms. The term "cutting arm" is interchangeable
with "cutter." The terms "resin" and "grout" are also used
interchangeably.
[0046] The helical drag bits of the invention provide an
advancement mechanism that move cutters along the circumference of
a pilot hole, such as a pilot rock bolt hole. Simultaneously, the
bit advances the cutter along the length of the pilot hole, thereby
introducing machined grooves into the walls of the pilot hole. The
rates of cutter movement along the circumference and length of the
pilot hole may be varied independently to produce a variety of
geometries, including evenly and unevenly spaced grooves.
[0047] Two exemplary embodiments of helical drag bits in accordance
with the invention have spirally/helically positioned cutting arms
10 that are spaced apart over the outer surface of a bit shaft 12,
as shown in FIGS. 1a, 1b, 2a, and 2b. FIG. 1b shows the bit flight
20 of FIG. 1a from a top view and FIG. 2b shows the bit flight 20
of FIG. 2a from a top view. These figures show bit flights 20
having cutting arms 10 that extend away from the bit shaft 12 with
a radial length 14 (measured from the center of rotation) for each
arm 10. The radial length 14 generally corresponds to the cutting
depth of the individual arms 10. The radial length 14 of the arms
10 can increase, as shown in FIG. 2b (and FIG. 8), with each
individual arm 10 from a bottom arm 10a to a top arm 10b so that
each successive arm 10 has a deeper cutting depth in a direction
moving away from the tip-end 16 of the bit shaft 12 (see FIG.
8).
[0048] As shown in FIGS. 3a and 3b, which depict top and side views
of an exemplary bit flight 20 during fabrication of the cutting
arms 10, the arms 10 are designed to track in a spiral manner,
having a uniform axial pitch 18 following a consistent spiral
track, similar to a self-starting thread tap. Bit flights 20 are
fabricated with a hub 38, which is used during operation of the bit
system to stack bit flights 20 and turn the stacked flights 20. The
hub 38 may be any suitable shape, but is preferably round with
hexagonally formed borehole. Bit flights 20 may initially be
fabricated with a continuous spiraling thread 10a, which is later
machined to shape individual cutting arms 10 of a selected radial
length 14 and geometry. Various cutting arm 10 geometries are
within the scope of the invention, as shown in FIGS. 1a-2b and 6-8.
As shown in FIG. 8, the basic flight members 20 of the bit can be
stacked with additional flights 20 also having cutting arms 10 of
an ever-increasing radial length 14 in a direction away from the
tip-end 16. In this way, a maximum desired cutting depth can be
achieved in a low energy bit.
[0049] FIGS. 4a and 4b show edge inserts 11, which can be part of
the cutting arms 10 in embodiments of the invention (see FIG. 9).
Such edge inserts 11 are typically attached to the arms 10 by
brazing. These inserts 11 can provide a superior cutting material
than that of unadorned arms 10. The inserts 11 can be, for
instance, polycrystalline diamond or carbide. On smaller cutting
arms 10, as shown in FIGS. 5a and 5b, pockets 13 are provided in
the bit shaft 12 for brazing the inserts 11 onto the arms 10. In an
alternative embodiment, the cutting edge of the cutting arms 10 can
be incorporated into the cutting arm 10 without need for an insert.
Such is the case when the cutting arms 10 are made of a
heat-treated alloy or when they are made for a one-time use, as in
the case of self-drilling bolts, for example.
[0050] The helical drag bit is used to further cut the sidewalls of
a pilot hole to achieve a modified sidewall geometry. The bit
excavates the sidewalls of the pilot bore, leaving a relatively
well-defined spiral or interlocking cut along the depth of the
bored hole. The ultimate depth of the cut into the sidewalls
depends on maximum axial cutting arm length 14. During cutting,
debris can be removed from the cutting area and "swept" towards the
center of the hole by the shape of the arms 10. Cuttings can then
be removed from the bore hole in a hydraulic, pneumatic, or
hollow-stem auger process. Other embodiments, methods, and systems
using the bit are envisioned.
[0051] FIG. 6 shows a bit flight 20 to be used in latter stages of
a bit stack. As shown, the cutting arms 10 of the flight 20 are
considerably longer than those shown in FIGS. 1a and 2a, for
example. Also, FIG. 6 shows an embodiment where a distinct cutting
arm 10 geometry is used. The cutting arms 10 shown in FIG. 6 also
terminate in edge inserts 11, which provide increased cutting
capability. FIG. 7 shows a pair of bit flights 20a and 20b and
provides some contrast between an initial flight 20a, which has
shorter cutting arms 10, and a latter flight 20b, which has longer
cutting arms 10. FIG. 8 provides additional perspective as to how
flights 20 are stacked for a cutting system and shows the
difference in lengths between an initial cutting arm 10a and a
terminating cutting arm 10b.
[0052] FIG. 9 shows an LRFD system 22 incorporating a helical drag
bit in accordance with an embodiment of the invention. The system
22 is comprised mainly of down-hole components including a bit
system 24, bailing bucket 26, down-hole electric motor/gearbox 28,
debris accumulation cup 30, sheath 32, pilot bit 34, and auger 36.
Lifting and lowering of the LRFD in the borehole are accomplished
by a tripod frame and winch system on the surface.
[0053] As shown in FIG. 10, comminution of the rock or soil is
performed by several helicutter components (e.g., flights 20) that
work in series. The individual action of each helicutter relies on
the reaction force capability of the remaining stationary
helicutters with frictional contact with the rock or soil mass,
allowing the system 22 to self-advance, step-by-step, through a
broad range of substrate materials. The individual component action
also reduces instantaneous power requirements. In FIG. 10, Step 0
depicts the drill system 22 prior to the beginning of a drilling
cycle. Step 1 involves the advancing of the pilot bit 34 into the
rock or regolith under the influence of the weight of the drilling
system 22 and minimal rotational reaction force.
[0054] Still referring to FIG. 10, a sheath 32 covers the helical
auger 36 pilot shaft and permits the conveyance of pilot cuttings
to a bailing bucket 26 located above the helicutters system 24.
Once extended to maximum reach, shown in Step 1, (can be about 0.3
m in one embodiment of the invention, or less if working in highly
fractured rock, rubble or sand) the pilot bit 34 rotates in place
to allow the helical auger 36 (inside a sheath 32) along its shaft
to transfer cuttings away from the pilot hole area. The sheath 32
then retracts to engage the first helical flight 20. The first
helical flight 20 is then rotated and thrust forward in a
prescribed ratio by the sheath 32 as shown in Step 2. The flight 20
creates a thread like spiral groove in the pilot hole wall created
by the pilot bit 34. In Step 3, the sheath 32 drive tube is
retracted from the first flight 20 to engage the second helical
flight 20. Step 4 depicts the stage where the second flight 20
reaches its end of stroke. In a consecutive manner, the remaining
helical flights 20 are individually advanced to the bottom,
deepening the thread groove in the rock.
[0055] The purpose of the auger shaft is to drive the pilot bit 34
and convey the rock cutting debris to a bailing bucket container.
Table I summarizes cutting properties, in various substrates, of an
exemplary embodiment of the invention, as depicted in FIG. 10.
1TABLE I Media State Density (g/cm{circumflex over ( )}3) Comments
Limestone Pulverized 1.700 Flowed with some clumping Sandstone
Pulverized 1.630 Flowed well Sand Granular 1.500 Flowed with some
grinding
[0056] FIG. 11 shows a hole created using a device in accordance
with an embodiment of the invention, which comprises helical spiral
threads 19 at a specified pitch in rock 15. The helicutters
incorporate a basic drag bit approach to shearing a helical groove
19 in the rock 15. Based on the pitch 18 of the helical spiral, a
traceable thread groove 19 is created in the rock 15 that allows
for development of downhole reaction forces and the extraction of
rock samples that have not seen excessive thermal loading. By
modifying the pitch 18 of the cutter arms 10, individual cutter arm
10 thickness, rake, and back angle, cutter arm 10 section geometry,
and number of cutter arms 10 per flight 20, several drilling
parameters can be modified across a broad range. The parameters
affected by this include axial force, torque and efficiency for a
given RPM.
[0057] As shown in FIGS. 1b, 2b, 3a, and 6-8, special attention is
given to the internal design of the cutter hub 38. Engagement
between a flight 20 and a sheath-driver is made possible through
key grooves in the internal surface of the hub 38 and key posts of
the sheath-driver. In order to engage a flight 20 to the driving
shaft, the driver is threaded into the cutter hub 38. Once the
driver reaches the set position inside the hub 38, a cam system is
activated by the reverse rotation of the pilot bit 34, lifting the
driver to engage its posts into the hub 38 grooves. Engagement
between the cutter arm flights 20 and the sheath-driver is designed
to smoothly lock and unlock the hub in the cutting mode, while
transmitting the cutting torque with a high strength margin.
[0058] The average power consumption in drilling a 63 mm diameter
hole with 1.89 m of advance through sandstone is about 225
Watt-hrs/m. Power consumption on the order of about 100 Watt-hrs/m
is achievable, according to one embodiment of the invention, using
the system 22 of the invention. Power consumption in sandstone
averages about 385 MJ/m.sup.3, while power consumption in limestone
averages about 300 MJ/m.sup.3.
[0059] In one embodiment of the invention, system 22 mass has been
shown to be about 45 kg for one prototype that was used in the
laboratory. Many of the articles of the system 22 are preferably
removable. Taking this into account it has been shown that total
system 22 mass can be reduced to about 16 kg, in accordance with an
embodiment of the invention.
[0060] In accordance with an embodiment of the invention rock chips
of greater than 1 cm.sup.3 can be recovered from holes with the
ability to know the location from which samples were derived to
within 15 mm.
[0061] Instead of plunging an entire shaft deep into a substrate,
an alternative strategy may be considered for an alternative
embodiment of the invention using a detached, self-driven
underground autonomous tethered drill system 22 like that shown in
FIG. 9. In contrast to prior drilling systems and methods, such a
system 22 may be lightweight so that it needs only enough power to
accomplish the drilling task while propelling itself downward,
trailing a thin cable for power and communication. An auxiliary
thin wire rope connected to a surface winch may be linked to the
system 22 for lifting and clearing of scientific samples and the
rest of the drill process cuttings. The elimination of drill-string
from the drilling process can dramatically reduce the weight of
main system 22 components, along with reduction of power
consumption for drilling task. While drill-string systems are
limited by the ultimate depth they may achieve, autonomous tethered
system 22 may reach almost any desirable destination.
[0062] In an alternative embodiment shown in FIGS. 12 and 13, each
cutting arm 10 terminates in a scoring cutting blade 40, positioned
orthogonally relative to the axial arm length 14, at a tangent to
the drag bit body's 12 outer circumference. The scoring cutting
blade 40 serves to cut a relatively smooth bore extension to
enlarge the hole 17, as opposed to the spiral or interlocking
trench 19 formed by the above-described first embodiment. Upon
removal, the debris from this second embodiment of the helical drag
bit can resemble a coil, spring, or "slinky," or the debris may
break-off in pieces for removal.
[0063] This embodiment provides a new approach to thread stripping
(and thus sample removal). As shown in FIG. 12, cutter flights 20
were fitted with tungsten carbide scoring cutting blades 40 that
can cut a kerf in the top and bottom of each rock thread 19 at the
deepest point of the helical groove. Successive scoring cutting
blades 40, shown in FIG. 13, cut the kerf deeper and deeper until
the whole rock thread 19 is excavated and captured into the bottom
of the bailing bucket as a sample
[0064] The embodiment illustrated in FIGS. 12 and 13 achieves a
low-energy drilling bit and provides a superior device for
enlarging a pilot hole 17. The bore extension cut with the
invention does not require the "snapping-off" of the spiral cut as
does the device of the '027 patent. This embodiment can be utilized
with the system 22 of FIG. 9, where thread scorers 40 are advanced
breaking off the rock ridges as scientific samples. For a final
hole diameter of about 80 mm (practical range of finished hole
diameter can be 50 mm to 250 mm) the chips formed by thread
breaking can be about 2 to 3 cm in length. Chips can be captured in
a bailing bucket 26 along with pilot cuttings from the pilot auger
shaft that can be captured in a separate bailing bucket
compartment. Following a complete drilling cycle the bucket can
then be lifted to the surface by a winch wire-line system.
[0065] The helical drag bit may be used as a geo-tech device for
measuring the properties of drilled substrates 15 (e.g., rock),
like that shown in FIG. 11, by measuring the torque required to
advance the helicutter. Such an embodiment of the invention has the
advantages of enabling in situ direct rock compression strength
measurements to be made in the field during drilling and also of
eliminating the bounce anomaly associated with prior art
compressive strength testing techniques, thereby providing
on-the-spot, reliable geo-tech measurements.
[0066] The compressive strength of rock substrate 15 through which
the helical drag bit is traveling is measured, in part, based on
(i) the cutting arm 10 design of the helical bit and (ii) torque
required to turn the helical bit through the rock 15. Although each
successive arm 10 can have an increasingly larger axial length 14,
the cutting depth generally is the same for each, and the average
cutting depth of all arms 10 can be used for measurement
calculations. The torque on the helical drag bit and each arm 10 is
a known variable, which can be controlled or measured.
[0067] As shown in FIG. 9, the drill system 22 incorporating the
helical bit can be in communication with a computer 42 or other
device having software for calculating the compressive strength of
the rock 15 based, in part, on the helical drag bit design and the
torque on the drill. The bounce anomaly is corrected because the
helical drag bit is designed to have opposing arms 10. Because the
arms 10 of the helical drag bit are always in opposition during use
and have increasing lengths, there is no opportunity for bounce and
the arms 10 are always cutting, making for balanced forces on the
helical bit.
[0068] The geometry of a helical flight 20 provides symmetry of
forces such that the normal force on each cutter is balanced by the
cutter arm 10 on the opposite side of the flight 20. Every rotation
of the helical flight 20 results in a prescribed advance into the
rock 15 and the cutting depth is defined by the initial hole 17
diameter, the pitch 18 of the cutter arms 10 surrounding the
central hub 38 and the geometry of the individual cutter arms 10.
Ultimately the system 22 can interpret lithologic changes based on
measuring torque. Drilling in three different lithologies and
across small bed separations has shown a direct correlation between
measured torque and the compressive strength of the rock 15 via the
following equation: 1 q u = Tc K SE w d r
[0069] In the above equation: q.sub.u is the unconfined compressive
strength of the substrate; Tc is the torque per cutter; K.sub.SE is
a coefficient of proportionality between specific energy (SE;
SE=K.sub.SE.multidot.q.sub.u) and the unconfined compressive
strength (q.sub.u) of the substrate; w is the cutter width; d is
the depth of the cut; and r is the radial distance of the cutting
edge (measured from the center of rotation).
[0070] In accordance with an embodiment of the invention, the
helical drag bit is used as a geo-tech device in a similar manner
as discussed above in relation to the system 22 shown in FIG. 9. A
pilot hole 17 is bored in a substrate 15 to fit the body 12 of the
helical drag bit. Then the helical drag bit can be used for
geo-tech measurements by spirally cutting the sidewalls of the
pilot hole 17 while the forces acting on the helical bit are
measured to calculate substrate properties.
[0071] Another embodiment of the invention uses the helical drag
bit in the mining and excavating industries, as well as in any
scenario where a particulate substrate 50 (e.g., rock or concrete)
requires support and stability control. In mines, for example, it
is required that an underground opening be reinforced with a
supporting/stabilizing rock bolt 52. The invention can be used to
achieve at least a 40% increase in holding capacity and pull-out
strength for rock bolts 52 within rock 50. Additionally, use of the
helical drag bit system in forming rock bolt holes reduces the dust
and noise compared to prior methods. The helical drag bit system
produces relatively large rock chips instead of small particles,
which reduces dust formation. Also the helical drag bit system
operates at a relatively low rpm, which reduces drilling vibrations
and thereby noise.
[0072] As shown in FIG. 18, after boring a relatively smooth pilot
hole 54, the helical drag bit can be used to spirally (or
helically) cut the interior sidewall of the hole in an "optimal
hole geometry" 56, thereby texturizing the hole 54 in a manner like
that shown in FIG. 11. The texturized hole 54 allows resin to
spread over a greater surface area inside the hole 54 with a
complex (spiral or interlocking) geometry, and thereby achieve a
better grip between the rock 50 and bolt 52.
[0073] The optimized hole geometry can be configured to the
physical and chemical properties of the resin/grout and surrounding
rock and rock strata. The optimal hole geometry can modify the
mechanism of the pullout force transfer between the grout and rock.
In accordance with this embodiment of the invention, it is possible
to form right or left handed grooves in the optimal hole geometry.
For example, left handed grooves used with a right handed rock bolt
rotation can improve resin/grout redistribution.
[0074] This technique is not limited to providing supporting and
stabilizing means for the roof walls of mine openings. The
technique can be used in a variety of particulate substrates in a
variety of orientations where a bolt-like device would be
advantageous. For instance, the helical drag bit can be used to
form bolt holes 54 in retaining walls or in concrete surfaces, and
in both vertical and horizontal orientations.
[0075] An embodiment of invention incorporates use of a rock bolt
52 to complement the superior hole geometry characteristics
achieved with the helical drag bit of the invention. Such a bolt
52, however, is not limited to use in a rock 50 substrate and is
not limited to a particular size. The bolt 52 can be used in any
particulate substrate and can range in length from mere centimeters
to meters.
[0076] In one embodiment, shown in FIG. 15, the rock bolt 60 can
have a mechanical anchor 62 at the end of the bolt 60. The anchor
62 will engage the helical threads 64 located at the end of the
associated pilot hole 54. The mechanical anchor 62 adds another
level of holding capacity and pull-out strength to the bolt 60,
thereby providing additional safety. The bolt 60 with the
mechanical anchor 62 can be used with or without resin. This is not
a self-drilling bolt embodiment.
[0077] In another embodiment, the bolt (e.g., bolt 52 of FIG. 14)
is self-drilling. The helical cutter will be incorporated into the
bolt itself. The bolt can screw itself into rock 50 with or without
the need of a well-defined pilot hole 17. The self-drilling bolt
can be used with or without (if no pilot hole is used) resin,
depending on the depth of the grooves 19 of the optimal hole
geometry.
[0078] In another embodiment, shown in FIG. 16, the rock bolt 70 is
itself a helical anchor, being either fully threaded or partially
threaded. The helical anchor bolt 70 has threads 72 that can
loosely or tightly match the spiral cuts 74 made by the helical
drag bit. In this embodiment, a threaded portion of the rock bolt
70 fits into the spiral cut portions 74 of the hole 54 in the rock
50. This bolt embodiment gains added holding strength and pull-out
capacity by allowing the rock 50 itself to directly support the
bolt 70. Again, such a bolt 70 could be used with or without resin.
Additionally, this embodiment is particularly useful for concrete
support and stabilization. The rock bolt 70 can also be configured
relative to the optimized hole geometry 56 so as to be removable
and reinsertable upon demand. A fully threaded bolt 70 will have
maximum anchorage capacity. A partially threaded bolt 70 can serve
to reduce roof layer separation by anchoring to the most competent
portion of substrate.
[0079] FIG. 18 shows an embodiment similar to that shown in FIG.
16. The rock bolt 70 of FIG. 18 has partial threads 72, which in
this embodiment refers to the non-continuous design of the threads
72. The helical groove 74 cut into the rock bolt hole 54 using the
helical drag bit system can be slightly smaller than the threads 72
of the rock bolt 70. Such a design promotes the further cutting of
the rock 50 by the threads 72 of the rock bolt 70, which is
facilitated by the prior cutting of the groove 74 by the helical
drag bit system. The threads 74 provide additional holding capacity
for the rock bolt 70. Grout, or another adhesive, may be used with
this embodiment and the additional cutting of the rock 50 by the
rock bolt threads 72 effectively spreads the grout throughout the
hole 54.
[0080] As discussed above in reference to FIG. 14, the pitch of the
helical drag bit and the cross-section of the individual cutters
can be optimized in view of the properties of the surrounding rock
50 and of the resin grout is used. The ultimate displacement of the
rock bolt 52 before pullout occurs can be controlled by the pitch
of the grooves 56. The force transfer mechanism between the grout
and the rock 50, as well as the bolt 52 and the rock 50, can be
controlled by the changes in the cross-section of the grooves 56 of
the optimal hole geometry. The pitch may be adjusted in real time
to suit the rock properties as measured in situ during the
advancement of the helicutters.
[0081] Another embodiment of the invention is shown in FIGS.
19a-19d. FIG. 19a shows a cross-section of rock 102 having a rock
bolt hole 104 formed therein. In this embodiment, the helical drag
bit system is not necessarily used since the rock bolt 100 itself
has the capability of forming a groove for holding itself in the
hole 104. FIG. 19b shows a rock bolt 100 having protuberances 106
along at least a portion of its length, preferably at the tip end
which will ultimately be positioned nearest the end of the rock
bolt hole 104. These protuberances 106 are not mere irregularities
or deformities in the rock bolt 100 such as may be found in typical
rebar, for example, but are designed to excavate the rock 102
around the rock bolt hole 104. The rock bolt 100 is moved into the
rock bolt hole 104 in a direction 108. As shown in FIG. 19c, as the
rock bolt 100 is forced into the hole 104, the protuberances 106
will gouge or cut the wall of the rock bolt hole 104, producing a
rough groove 110 along the hole 104. FIGS. 19c and 19d show the
groove 110 in a direction along the plane of the drawing; however,
the groove 110 will preferably enlarge the hole 104 only with
respect to the size of the protuberances 106, which are preferably
isolated and discrete along the shaft of the rock bolt 100 (FIGS.
20a-20c). Upon complete insertion of the rock bolt 100 into the
rock bolt hole 104, the rock bolt is partially rotated 112 so that
groove 110a is formed semi-annularly with respect to the rotation,
the rock bolt 100, and the rock bolt hole 104. This groove 110a
provides support for the protuberances 106, which locks the bolt
100 into the hole 104.
[0082] FIG. 19e shows an alternative embodiment, where a rock bolt
100 of the same basic configuration as shown in FIGS. 19c and 19d
is inserted into a rock bolt hole 104, but instead of being forced
straight into the hole 104, the bolt is rotated 112 while being
forced into the hole 104 in the direction 108. This rotation 112
and forward motion 108 of the bolt 100 and protuberances 106
creates a spiral-type groove 111 along the wall of the rock bolt
hole 104. The rotation 112 may be continued throughout insertion of
the rock bolt 100 to create a groove 111 as shown in FIG. 19f. This
spiral groove 111 will support the protuberances 106 and will hold
the rock bolt 100 in the rock bolt hole 104, particularly if grout
is used.
[0083] The protuberances 106 of the rock bolt 100 shown in FIGS.
19a-19f can be of several designs, including but not limited to
those shown in FIGS. 20a-20c. FIG. 20a shows a rock bolt 100 having
rounded protuberances, similar to those as shown in FIGS. 19a-19f.
FIG. 20b shows a rock bolt 100 having rounded protuberances 106
that increase in radial length from a first protuberance 106 toward
the tip end 114 the rock bolt onward. This configuration allows for
easier gouging/cutting of the grooves 110 or 111 shown in FIGS.
19c-19f. FIG. 20c shows a rock bolt 100 having angular
protuberances 106, which may be in the form of blades or may be
pyramid-shaped. This angular shape of the protuberances 106 allows
for easier insertion into and gouging/cutting of the rock bolt
hole. As stated above, other protuberance 106 shapes and
configurations are possible.
[0084] Protuberances 106 may be formed in a number of ways,
including, but not limited to, formation during stamping of a rock
bolt as a part thereof. Protuberances 106 may also be formed by
attaching them to a rock bolt by brazing or welding. Additionally,
recesses or holes may be formed in a rock bolt for insertion of
protuberance 106 there into. As stated above, other ways of forming
the protuberances 106 are possible.
[0085] FIG. 17 shows a graph, which compares rock bolt pullout
strength using prior art hole geometries (i.e., standard tests 1
and 2) to rock bolt pullout strength using an optimized hole
geometry (i.e., single and double passes) in accordance with an
embodiment of the invention. Tests were performed in the same rock
material. The graph plots the load in pounds force required to pull
a rock bolt along its axis to a given displacement. As shown in the
graph, rock bolts used in combination with the optimal hole
geometry show improved bolt pullout performance.
[0086] Embodiments of the invention can also be used to reduce dust
and noise when drilling rock bolt holes 54. Cutter arm 10 depth can
be carefully designed to reduce torque requirements per cutter arm
10 or by increasing depth, to increase the size of chips. In one
study, all drilling cuttings were collected from two different
helical cutter flights 20. The cuttings were sieved to separate
fines from larger chips using a 0.015 mesh. With a change of only
0.05 inch cutter arm 10 depth, significant differences in drill
cuttings characteristics were identified with no detrimental effect
on drilling. Table II illustrates the differences in the cuttings
characteristics.
2 TABLE II Flight 1 Flight 2 Avg. Torque 55 N-m 41 N-m Thread
cuttings mass for 2.85 m of drilling 204 gm 146.4 gm Mass of
particles < 0.015 mesh 153 gm 127.6 gm Mass of particles >
0.015 mesh 51 gm 18.8 gm
[0087] The processes and devices described above illustrate
preferred methods and typical devices of the invention; however,
other embodiments within the scope of the invention are possible.
The above description and drawings illustrate embodiments, which
achieve the objects, features, and advantages of the present
invention. However, it is not intended that the present invention
be strictly limited to the above-described and illustrated
embodiments. Any modifications, though presently unforeseeable, of
the present invention that comes within the spirit and scope of the
following claims should be considered part of the present
invention.
* * * * *