education under ground mining e book 04
TRANSCRIPT
-
8/14/2019 Education Under Ground Mining E Book 04
1/112
First edition 2008www.atlascopco.com
Raiseboringin Mining and Construction
-
8/14/2019 Education Under Ground Mining E Book 04
2/112
Atlas Copco Rock Drills AB
www.atlascopco.com
Turning heads and pulling the string
A tough environment demands tough machines.
Machines built for tight places able to squeeze out
the most productivity in the least amount of time.
Machines that are versatile, reliable, cost-efficient and
with the highest rate of penetration and safety on the market.
No other company has the experience, the innovation and
the commitment to the industry like Atlas Copco.
Whatever the rock, wherever you are. Weve got the
raiseborer to fit your application. Count on Atlas Copco,
(We wont string you along)
Committed to your superior productivity.
-
8/14/2019 Education Under Ground Mining E Book 04
3/112
RAISEBORING 1
Foreword
2 Foreword by Marcus Eklind, Product Line Manager,Raiseboring, Atlas Copco Rock Drills AB
Talking technically
3 Rock drillability
7 History of raiseboring
10 The raiseboring concept
13 The raiseboring machine
20 Computer based training for raiseboring
22 Horizontal and low angle boring
25 Development of boxhole boring
29 Down reaming
33 Modern boxhole boring with BorPak
36 Selection of raiseborer drive system
38 Computers improve rock excavation productivity
40 Site preparation
47 Operating the raiseborer
51 Bailing considerations
56 Cutter and reamer design
64 Raiseboring drillstring components
Case studies
67 Boxhole boring at El Teniente
73 Raiseboring for production at McArthur River78 Replacing Norways Tyin hydropower plant
Product specifications
82 Robbins raiseboring machines
91 Pilot bits from Atlas Copco Secoroc
96 Drill string components
99 Power packs
101 Drill pipe handling equipment
102 Transporters
103 Tools
104 Raiseborer system upgrade kits108 Conversion table
Contents
Produced byAtlas Copco Rock Drills AB, SE-701 91 rebro, Sweden, tel +46 19 670 70 00, fax 019-670 73 93.Publisher:Marcus Eklind, [email protected] Production Manager:Elisabeth Nilsson, [email protected]:Mike Smith, [email protected] Senior Adviser:Hans Fernberg, [email protected]
Contributors:Bjrn Samuelsson, Jan Forsberg, Johnny Lyly, Mikael Bergman, Rikard Erlandsson, Roberto Lopez, Sverker Hartwigall [email protected], Steve Brooke, [email protected]
Digital copies of all Atlas Copco reference edit ions can be ordered from the publisher, address above, or online atwww.atlascopco.com/rock.Reproduction of individual articles only by agreement with the publisher.
Edited byMike Smith, tunnelbuilder ltd, United Kingdom. Designed and typeset byahrt, rebro, Sweden. Printed byWelins Tryckeri AB, rebro, Sweden.
Legal notice
Copyright 2008, Atlas Copco Rock Drills AB, rebro, Sweden. All product names in this publication are trademarks of Atlas Copco.Any unauthorized use or copying of the contents or any part thereof is prohibited. This applies in particular to trademarks, model denominations,part numbers and drawings. Information in this publication is provided as is. Atlas Copco Rock Drills AB disclaims any representation or warrantiesof any kind including without limitation warranties of merchantability or fitness for a particular purpose, non-infringement or content. In no eventwill Atlas Copco Rock Drills AB be liable to any party or any damages for any use of this publication. The contents, including illustrations and photos,in this publication may describe or show equipment with optional extras . It may also contain references to products or services that are not availablein your country. This publica tion, as well as specifications and equipment , is subject to change without notice. Consul t your Atlas Copco Customer
Center for specific information.
Front cover: Robbins 34RH C at the Kvarntorp test mine in Sweden
-
8/14/2019 Education Under Ground Mining E Book 04
4/112
2 RAISEBORING
ForewordAgeneration ago, excavating raises was hard and dangerousmanual work, carried out by only the most experienced miners.Mines needed ore passes and ventilation raises, and there
was only one way to excavate them, using drill/blast. WhenJames Robbins built the prototype Robbins 41R raise drill in1962, it was the beginning of a new era. Boring of raises wasfar more attractive than traditional methods. It was faster,cleaner, and, above all, took the operators out of the raisesand placed them in accessible, well ventilated, and safepositions.
From the Robbins 41R to the current model 191RH, theRobbins raise drill has come a long way. Both in the capa-bilities of the machine, and in the technology behind it. Ourraise drills are now capable of boring holes 1,000 m-long,and up to 6 m-diameter. As a result, raiseboring is now thepreferred, and most cost-effective, means of excavatingopenings in underground projects.
Increased automation is a continuous trend in the businessof raise drilling. The reasons for this are simple, and can be
summarized as: reduced labour; faster and smoother operation;quicker response to blocky ground; and data logging anddiagnostics. New control systems ensure that the operator
can select the optimal running parameters to get the mostout of the raise drill, both in performance and economy.Functions such as automatic shutdown and anti-jammingmake it possible to carry on drilling between shift changes,without worrying about spin backs or losing the drill string.
As the hydraulic drives have developed and become moreefficient, the improved control accuracy has made them thefirst choice for most customers. Hydraulic drives offer goodreaming characteristics and are very soft on the drill string.Combined with the new reliable control system, this is prov-ing to be the way forward in most operating environments.
This book is designed as a reference for all raise drillers,describing the methodology in detail, and giving an insightinto the current equipment offering from Atlas Copco. Wehope you find it useful, and we are available to discuss thefiner points with you at any time.
Marcus Eklind
Product Line Manager, Raiseboring
Atlas Copco Rock Drills AB
-
8/14/2019 Education Under Ground Mining E Book 04
5/112
TALKING TECHNICALLY
RAISEBORING 3
Rock properties
Data on unconfined compressive strength
(UCS) is the most commonly available
rock property. However, it is difficult to
use UCS to predict d rilling perfor-mance without additional information.
The average UCS for selected forma-tions is shown in Table 1 (next page).
One simple method to determine theapproximate hardness of a formation isthe Moh scale, if UCS information isunavailable. The Moh scale is used toclassify the relative hardness between
different minerals. Diamond is at the topof the hardness scale, rating a 10, andtalc is at the opposite end, rating a 1.In general, the minerals at the high endof the scale are harder than those on thelow end of the scale. Scratch testing can
be used to estimate the hardness: a fin-
gernail can scratch up to about 2 Mohs,a copper coin up to about 3 Mohs, and
glass up to 6 Mohs. However, care mustbe taken to ensure that the scratch isnot a powder residue left from the itembeing used to scratch. Some commonminerals and rocks are shown with their
corresponding Moh Hardness number
in table 2 (next page).Other factors that influence drilla-
bility are:Abrasiveness abrasiveness of a for-
mation is usually indicated by its silica
content. Abrasive formations accelerate
cutting structure wear, causing slowerdrilling rates as the carbide becomesblunter, and sometimes cone shell ero-sion, which can ultimately lead to lostinserts.
Jointing and bedding formationswith joints or layers are easier to drillthan massive unfractured formations,
since the anomalies provide free faceswhich make failure easier.
Schistocity schists have layers ofmica interbedded with harder, morebrittle rock. These mica layers absorbthe energy of the drilling process, with
the rock acting as a plastic, rather thana brittle material.
Rock failure
The primary failure mode employed bythe rotary drilling method is the tensile
failure of the rock under a compressiveload to form rock chips. In weaker,more ductile formations this primarymethod of failure may be replaced oraugmented by the gouging and scrapingaction of the cutter. Studies have shown
that the action of the cutting element isprogressive, as shown in Figure 1.
As force is applied to the cutting
element, the cutter deforms the rock.As the force increases, a pressure bulb
Rock drillability
Fracturing rockDrillability is the ability to frac-ture or drill rock using mechanicalmeans, and is governed by a num-ber of factors. Some of these arerelated to the rock formation, andothers to the forces applied, andthe geometry of the drilling equip-ment. Rock properties, rock fail-ure mechanisms, and drilling para-meters all relate to drillability, andare helpful in evaluating drillingefficiency, trouble shooting pro-blems, and estimating cutter per-formance.
General rock boring principlesand their practical application arethe basis of modern raiseboring.Two basic principles are used to-gether in full face boring - theseare cratering and kerf breaking.The objective when boring is tocrush the rock until tensile crack-ing occurs, causing chips to breakaway. The art is in the design ofthe cutters and the pressure withwhich they are kept in contactwith the rock. This is where ex-perience counts, and nobody hasmore knowledge about raise bor-
ing than Atlas Copco Robbins.
Figure 1: Cratering is the first stage of kerf breaking.
Zone of triaxial
crushing Radialcracks
-
8/14/2019 Education Under Ground Mining E Book 04
6/112
TALKING TECHNICALLY
4 RAISEBORING
of finely crushed rock forms under thecutter. The pressure bulb transmits pres-
sure to the surrounding rock, causingtensile fractures. As these propagate to
the rock surface, chips form, releasingthe pressure of the pressure bulb.
Rock breakage also relies upon the
interaction of several cutting structureelements and their contact points onthe rock. The placement of the cuttingstructure elements is a critical part ofthe cutter design.
Cutting structures
Atlas Copco uses three types of cuttingstructure geometry for raiseboring appli-
cations: kerfed carbide insert cutters;
rowed cutters; and randomly-placed car-bide insert cutters.
Kerf, or disc cutters use an extension
of the rock failure mechanism described
above. When properly-spaced discs arecombined with sufficient cutter force,
very efficient drilling results, since the
disc maintains continuous contact with
the formation.
Interaction between adjacent discpaths produces shear failure of the rockbetween these paths. Figure 2 demon-
strates the pattern of a kerf type cutteron the rock face.
Kerf cutters tend to spall out 10 -20 cm(4 to 8 in) long banana shaped chips andsmaller, almost circular chips depen-
ding on the formation and the loading.Compared to randomly placed carbideinsert cutters, kerf cutters tend to require
higher thrust and torque to spall outchips, but are more efficient if sufficient
load and torque are available. The kerfcutter concept is shown in Figure 4.
Carbide rowed cutters perform some-
where between the kerf-type cutter andthe random insert-type cutter. The rowed
cutter design has multiple rows of in-serts, but no steel kerfs in which theinserts are located. The lack of kerfsallows more room for cuttings removal,less opportunity for abrasive formations
to wear away the cutter shell, and greater
penetration of the inserts into the for-mation with less power consumption.The staggered insert location and mul-tiple rows tend to decrease the torquerequirements, somewhat similar to therandom cutting structure, and the rows
of inserts allow for rock kerfs to spallout of the formation, although generallysmaller than a pure kerf cutter design.
The patented design of random in-sert cutters employs a random patternof inserts on the cutter shell to provide
Formation UCS (Psi) Mpa Formation UCS (Psi) Mpa
Berea Sandstone 2,500 17 Limestone 20,000 138
Austin Chalk 3,000 21 Marble 20,000 138
Sandstone 9,000 62 Dolomite 24,000 165
Quartzitic Sandstone 9,000 62 Porphyry 40,000 276
Shale 15,000 104 Pink Quartzite 68,000 469
Table 2: Moh hardness numbers for selected common minerals and rock.
Mineral or Rock Moh Hardness Mineral or Rock Moh Hardness
Amphibolite 6.2 Gypsum 1.5
Andalucite 7.5 Limestone 3.3
Andesite 7.2 Magnesite 3.5
Basalt 7.0 Magnetite 4.2
Bituminous Coal 2.5 Marble 3.0
Chert 6.5 Potash 2.2Cryolite 2.5 Pyrite 6.2
Diabase 7.8 Quartz 7.0
Diamond 10.0 Quartzite 7.0
Dolomite 3.7 Ryolite 7.2
Emery 8.3 Salt 2.5
Feldspar 6.2 Sandstone 3.8
Gabbro 5.4 Slate 3.1
Gneiss 5.2 Soapstone 1.0
Granite 4.2 Sulphur 2.0
Graphite 1.0 Zircon 7.5
Table 1: Average UCS for selected formations.
Figure 2: Kerfs on the rock face.
Figure 3: Random pattern on rock face.
-
8/14/2019 Education Under Ground Mining E Book 04
7/112
-
8/14/2019 Education Under Ground Mining E Book 04
8/112
TALKING TECHNICALLY
6 RAISEBORING
Life = Function (force to the powerof 3.33). In the previous example, ifthe 40,000 lb cutter load results in a1,000 hr bearing life, then the 50,000lb force would result in 1,000 hours x(40,000/50,000) 3.33 = 475.7 hr.
The actual load applied to each cuttermust be used for this application, andthe load must be broken down into axialand radial load in the bearing, for a clo-ser estimate.
The reduced life is even more pro-
nounced when the cutters are consid-ered as a system. For example, the abovecalculation may be accurate when onecutter is considered, but what if thereare 10 cutters in the system? If the oddsare that there will be one failure in 100,or 1%, in that period of time, the chancesof failure increase as the number of cut-
ters increases.In addition, too little force may also
be detrimental to the life of the cuttingstructure on the cutter. If the appliedload is insufficient to fracture the for-
mation (minimum of 80% of the UCSassuming a 1 square inch contact area
per cutter), the inserts will wear rapidly.
This failure is enhanced in abrasiveformations.
Rotary speed and torque
Rotary speed generally affects drilling ra-
tes linearly. For example, a 10% increasein rotary speed should produce a 10%increase in drilling rate. The traditional
approach to rotary speed recommen-dations has been to limit the peripheral
speed of the head to under 350 ft/min.These limitations have been set due toconcerns over gauge wear on the head,drill string wear, and drill string failure,
all of which have occurred at high peri-pheral speeds. Higher rotational speedsare incorporated into smaller raiseboring
machines, but caution must be exercisedwhen using high rotational speeds onlarge diameters.
The relationship between rotary speed
and bearing life is also linear, but is
negative, leading to a 10% decrease inbearing life as a consequence of a 10%increase in rotational speed.
Increases in penetration rate due toincreases in rotational speed are not as
dramatic as penetration rate increases
due to increased cutter load, but shouldnot be discounted. Often, the increased
speed is within the capability of thedrilling machine, with the consequencebeing increased power consumption.
Insofar as drilling torque is con-cerned, capacities of equipment oftendictate the load that can be applied to thecutters. Several factors influence torque
requirements, such as load per cutter,reamed diameter, formation, and angle
of the raise. Additionally, the torque re-quirements tend to fluctuate radically,with peak torque more important thanaverage torque.
All things being equal, the torque re-
quired increases as the load per cutterincreases, as the diameter of the raise
increases, and as the angle of the raiseincreases away from vertical.
Formation can be more difficult toclassify in regards to torque require-ments. However, in general, the softerthe formation, the deeper the insert pe-
netrates, and the higher the torque re-quirement. This relationship can bealtered considerably if the rock failsreadily through shear, as in some verti-
cally jointed formations. Broken andblocky formations can also produce
large spikes in the required torque asthe formation tries to unravel.
Steve Brooke
Penetration Rate Vs. UCS
0 1 2 3 4
0 10000 20000 30000 40000 50000 60000 UCS
Penetration
Rate
n = 1.4
n = 1.6
n = 1.2
n = 1.8
Figure 5: Random pattern on rock face.
CrateringCratering is the term used to describethe crushing action in the rock di-rectly beneath the contact area of thecutter edge, which is usually a chiselshaped tungsten carbide insert. As in-creased loading is reacted into the rock
by the cutter, it is crushed to a f inepowder and compressed. The induced
stresses initiate radial tensile cracksin the rock mass, which break backto the free surface. As penetration ofthe cutter edge into the rock continues,the cracks expand, and chips splitaway. This allows the crushed fines to
escape and new tensile cracks to form.In this way, continuous production ispossible by simply keeping the rotating
bit pressed against the face.
Kerf breakingKerf breaking occurs when radiatingcracks beneath the cutter edge reachan adjacent kerf and form a chip be-tween the two cutter kerfs. Kerf brea-king is applied to the entire rock face
by a reamer dressed with either singlerow disc cutters or multi-row buttoncutters. These are mounted on the rea-
mer at spaced intervals outward from
its centre. As it rotates and is thrustforward into the rock face, the cuttersroll against the surface of the rock andcrush kerfs in concentric paths. Once
the critical depth of penetration to spa-cing ratio is reached for the particularrock type being bored, chipping occurs
between the kerfs, and the rock face
can be systematically excavated.
-
8/14/2019 Education Under Ground Mining E Book 04
9/112
TALKING TECHNICALLY
RAISEBORING 7
Market share
The history of raiseboring is reallythe history of Robbins raise drills. Asthe industry pioneer, the company hasmanufactured 350 raise drills of theapproximate 600 that have been pro-duced in total to date, giving it a +60%
market share. In all, some 35 models have beenintroduced, with reaming diameters of0.6 m to 6.0 m.
Of the models produced, the 73RMis the most sold, with a reaming diameter
of 1.8 m-3.1 m.Nearly all of these Robbins raise
drills are st ill available for work. So,despite always requiring high capitalinvestment, raise drills have given anexceptional return to their owners whileretaining solid residual value. This sumsup the raiseboring story.
Apart from mechanizing the singu-larly most dangerous job in mining,
these machines have proved to be awise investment all round.
Built for life
When James Robbins built the first raise
borer in 1962, lit tle would he havethought that it would still be working45 years later. However, the fact is that
the very same 4 ft-diameter machine,
the original Robbins 41R as shown inFigure 1 with pinned drill tubes andsteel cutters, was recently reported asworking in Morocco.
By 1966, rapid development on thepart of Robbins had established industry
standards for tungsten carbide cutters,and a f loat box to reduce stresses inthe main bearing and drill string of the
raiseboring machine. Connectors usingAPI-standard 7-inch tapered threadswere introduced to connect the drilltubes on the second machine built byRobbins and was in use in various sizes
unti l the DI-22 thread was invented in1969. This proved to be a well func-tioning and reliable connection.
In 1967, Robbins upped its gamewith the introduction of the Robbins
History of raiseboring
Forty five years onIt is now 45 years since Atlas Cop-co Robbins built the worlds firstsuccessful raiseboring machine,and launched a worldwide revo-lution in underground mining andconstruction that is still gainingmomentum. New products, concepts andtechniques, such as automation,computerization and horizontalreaming are creating exciting newopportunities for the user under-ground. The latest innovation is the ap-
plication of Atlas Copcos CAN-buscontrol technology to raiseborers,using components that are com-mon to other new generation pro-ducts such as Rocket Boomer andSimba drill rigs that may alreadybe at work on the mine. In this way, mechanization forone-man operation is facilitatedwithout having large inventoriesof spares, and with very short lear-ning curves for all concerned.
Figure 1: The Robbins 41R, first of a long line of raise drills.
-
8/14/2019 Education Under Ground Mining E Book 04
10/112
TALKING TECHNICALLY
8 RAISEBORING
61R, capable of reaming a 6 ft-diameter
hole. This became the most-sold ma-chine in the world, reaching volumesof 50-60/year in the early-1970s. The61R became the 63R, as shown in Figure2, and is now the 73RM and the currentmarket leader with the biggest volume
sales to date.
From 1971-73, larger machines suchas the Robbins 83R were developed tosatisfy a demand for bigger diameterboreholes. All machines built before1973 were equipped with two-speed AC
motors, but from then onwards, DCdrive and hydraulic drive became thenatural choice.
The first boxhole borer appeared in1974, giving miners the option of exca-vating raises where there is limited orno access to the upper level. The raise-
borer is set up at the haulage level anda full-diameter raise is bored upward,
with the cuttings gravitating down thehole for removal. Within ten years, theRobbins BorPak was launched, facili-tating boxhole boring without a drillstring, making the operation vastly more
efficient and easy to set up.
Improved methodology
Since Robbins introduced to the mi-ning industry the first machine builtexclusively for raiseboring, the advan-tages over older methods have becomeincreasingly evident.
Foremost among these is safety, asworkers are not required to be in theraise during the excavation process. The
inherent dangers of rock falls, fumes,and the handling of explosives areeliminated.
The second advantage is speed ofoperation. Even early on, Robbins raise
boring machines achieved milestonesby reaming 150 ft (46 m) raises in softgranite at two-week intervals. These had
previously taken several months usingthe older methods.
Before long, bored raises exceeding1,000 ft (305 m) became common. Raisediameters of over 20 ft (6 m) have nowbeen bored in medium to soft rock.
Single passes in hard rock are ap-proaching 3,280 ft (1,000 m) in length.Raiseboring machines have proved su-perior and more economical when com-pared to the drill and blast methods ofraise excavation. They have also opened
new opportunities for mine planning,offering more opportunities for lessdevelopment investment and earlierproduction.
Another advantage is that, becausethere is no blasting, the rock is not shat-tered. The result is a smooth interiorraise surface, which allows for moreefficient movement of ore and air, andprovides maximum wall stability.
Finally, mechanization with raise bo-ring machines requires less manpoweroverall. Skilled conventional miners,always in short supply, are not neededto operate a raiseboring machine. Lesstotal manpower, less rock to handle,
less construction time, and increasedsafety all add up to earlier profits.
Figure 2: Robbins 63RM was predecessor to the worlds most sold raise drill, the Robbins 73RM .
Figure 3: Atlas Copco Jarva raiseborer.
-
8/14/2019 Education Under Ground Mining E Book 04
11/112
TALKING TECHNICALLY
RAISEBORING 9
Acquisitions
In the late 1970s, Robbins boughtIngersoll Rands raiseborer division,with its well-regarded tungsten insertcutters, which to this day are acknow-
ledged as the best available. Robbinsimmediately switched from Reed cut-ting tools to those of its own manufac-ture, and has since supplied them withevery raiseborer produced. IngersollRand had itself built some 30 raise bo-ring machines prior to the takeover byRobbins. Another acquisition by Robbins
was that of Drillco Texas when it wasunder Chapter 11 administration.
In 1980, Atlas Copco bought theJarva Company, based in Solon, Ohio.
Four very advanced raiseboring ma-chines were built in 1982-1983 as shown
in Figure 3, with variable speed drives
and computer control as shown in Fi-gure 4. These machines are today ope-
rated by Dynatec in North America.
Future trends
The current trend is towards compute-rization of the raiseboring operationusing Atlas Copcos patented Rig Con-
trol System (RCS). This is CAN-busba se d, with a si ng le power cableservicing all of the electric units, andanalog or digital switches controllingthe use of the electrical power. Thedigital signal is superimposed on thepowerline, and a computer listens tothis, and sends out instructions in the
same manner. Two tiny wires have beenadded to cope with the signalling, and
sometimes two powerlines are required.
The CAN-bus system is very reliable,flexible and easily expandable. Newunits can be added anywhere on themachine, without adding another cable.It has become very popular in the forest
and textile machine industries, and mostcars, trucks and construction vehiclesare, or will be, equipped with this system
in the future.RCS gives the operator greater con-
trol over the machine, with some of themore mundane aspects of the boringprocess computerized, leaving him free
to concentrate on the more complexaspects. The result is that a single ope-rator can now control all functions on a
raiseborer, including rod changing.
Marcus Eklind
Figure 4: The control console of the Atlas Copco Jarva raiseborer.
-
8/14/2019 Education Under Ground Mining E Book 04
12/112
TALKING TECHNICALLY
10 RAISEBORING
Raiseboring process
In raiseboring, the machine is set up atthe surface or upper level of the twolevels to be connected as shown in Fi-gure 1. A small pilot hole is then dril-led down to the lower level using a drillbit attached to a series of cylindricaldrill pipe pieces, which form the drillstring. Upon completion of the pilot hole,a reamer with a diameter larger thanthe pilot hole is attached to the drill
string at the lower level. Using the rea-
mer, the small pilot hole is reamed back
to the machine on the upper level. Thecuttings excavated by the reamer fallto the lower level and are removed by
any convenient method.
Applications
Raiseboring machines have been usedin both mining and civil projects forholes in the range 0.6-6.0 m-diameterand up to 1,000 m-long. Some specificapplications of bored raises are:
Mining: materials transport; ventilation;
manriding; mineral production.
Civil:hydro penstocks and surge cham-
bers; redirection and retrieval of hydro
water; petroleum, pressurized gas, and
nuclear waste storage; road and rail tun-nel ventilation; stormwater storage and
drainage; access for pipes, hoses, andcables; water inlets and outlets for fishfarms.
Horizontal and low angleraiseboring
Standard raiseboring machines are ca-pable of boring raises at angles f romvertical to 45 degrees from horizontal.Raises from 45 degrees to horizontal
The raiseboring concept
ParticularterminologyThe raiseboring concept involvesterminology that is a little diffe-rent from normal mining language.Raiseboring, also called raise dril-ling, is the process of mechanicallyboring, drilling, or reaming a ver-tical or inclined shaft or raise be-tween two or more levels. All le-vels may be underground, or onelevel may be at the surface. During the early developmentof mechanical raise excavation,
different approaches were pursuedand, in several cases, systemswere developed. The most suc-cessful method became known asraiseboring. Today, raiseboring is acceptedas the world standard for mecha-nical raise excavation, and thename of Atlas Copco Robbins issynonymous with the technique.
Figure 1: Raiseboring process.
Figure 2: Low angle raiseboring.
-
8/14/2019 Education Under Ground Mining E Book 04
13/112
TALKING TECHNICALLY
RAISEBORING 11
have been completed with the additionof only a few accessories and minoradjustment of the standard machine asshown in Figure 2.
Other methods of vertical
boringOther methods of mechanical raise andshaft excavation have been developed in
addition to raiseboring. These methodsare described in the sections below andare as follows: boxhole boring; blindshaft boring; down reaming; pilot down
- ream down; hole opening; BorPak.
Boxhole boring
Boxhole boring is used to excavate rai-
ses where there is limited or no accessto the upper level. Here, the machineis set up at the lower level and a fulldiameter raise is bored upward.
While boring upward, stabilizers areperiodically added to the drill string toreduce oscillation and bending stresses.
The cuttings are carried by gravity down
the hole, and are deflected from themachine and removed at the lower level.Boxhole boring can be completed withor without a pre-dr illed pilot hole, asshown in Figure 3.
Blind shaft boring
Blind shaft boring is used where thereis access to the upper level of the pro-posed raise, but limited or no access to
the lower level. With this method, theraise is excavated from the upper leveldownward using a down reaming sy-stem connected by a drill string to themachine above. Weights are added to the
reamer mandrel as shown in Figure 4.
Stabilizers are located above andbelow the weight stack to ensure verti-
cal boring. A reverse circulation sy-stem, or a vacuum system, is typicallyused to remove the cuttings out of theshaft.
Down reaming
Down reaming begins by drilling aconventional pilot hole, and then en-larging it to the final raise diameter by
reaming from the upper level to the lo-wer level as shown in Figure 5. Larger
Figure 3:
Boxhole boring.
-
8/14/2019 Education Under Ground Mining E Book 04
14/112
TALKING TECHNICALLY
12 RAISEBORING
diameters can be achieved by conven-tionally reaming a pilot raise, and then
enlarging it by down reaming.During reaming, the cuttings gravi-
tate down the pilot hole, or reamed hole,and are removed at the lower level. Toensure sufficient down reaming thrust
and torque, the down reamer is fittedwith a non-rotating gripper and thrustsystem, and a torque-multiplying gear-
box driven by the drill string. Upper and
lower stabilizers ensure proper kerf cut-
ting, and reduce drill string oscilla-tions.
Pilot down, ream down
This method, also known as hole open-ing, is used to enlarge an existing pilot
hole with a small-diameter reamer. Theoperation is similar to pilot hole drill-ing, the only difference being that a small
reamer is used instead of a pilot bit.The small reamer is designed to use theexisting pilot hole to guide the drilling.Stabilizers are used in the drill stringbehind the reamer to prevent it frombending. Pilot down, ream down holeopening is only used when a standardreaming system is either impracticalor impossible, as shown in Figure 6.
BorPak
The BorPak system is used for blind holeboring. It comprises a guided boringmachine, a power unit, a launch tube/transporter assembly, a conveyor, and an
operator's console. The BorPak operates
like a microtunnelling machine, climb-
ing up the raise as it bores. Cuttings pass
through the centre of the machine, fal-ling down the raise and launch tubeonto a conveyor. This revolutionary ma-
chine has the potential to bore from 3.9to 6.6 ft (1.2 - 2.0 m) diameter holesat angles as low as 30 degrees. Like araiseboring machine, the BorPak offershigh speed drilling, but eliminates theneed for a drill string. It also pro-vides the steering flexibility of a raiseclimber. BorPak is especially attractive
when f lexibility and mobility are ata premium, or when the job requiresdrilling a series of short raises.
Roberto Lopez
Figure 4: Blind shaft boring.
Figure 5: Down reaming.
Figure 6: Pilot down, ream down.
-
8/14/2019 Education Under Ground Mining E Book 04
15/112
TALKING TECHNICALLY
RAISEBORING 13
Derrick assembly
The derrick assembly supplies the ro-tational and thrust forces necessary toturn the pilot bit and reamer as well asto raise and lower the drill string. Thisassembly consists of several major com-
ponents. These are: base plates; main-frame; columns; headframe; hydrauliccylinders; and drive train assembly.
Base plates
The base plates, left-hand and right-hand, provide the structure for suppor-ting the weight of the derrick assemblyas well as for positively transferring theforces required for raiseboring into thederrick mounting system.
The base plates are normally set ona level concrete foundation pad and an-chored by rock bolts passing throughthe pad into the rock formation below.
In some instances, the base plates aremounted to a steel beam system, whichin turn is secured to concrete founda-tion pads and the rock formation.
Mainframe
The mainframe is the major load bear-ing structure of the derrick assembly.It is mounted and secured on the baseplates with removable turnbuckles andexpansion pins. Each turnbuckle con-
sists of two threaded eyes screwed intoa turnbuckle body. The turnbuckles
establish and maintain the requiredboring dip angle. After the boring angle
is confirmed, the expansion pins are
tightened to provide linkage between themainframe and turnbuckles, and the base
plates and turnbuckles, for the positive
transfer of boring forces.Removable pivot brackets mounted
at the rear of the mainframe allow thehydraulic cylinders of the transportersystem to be attached to the mainframefor derrick erection and takedown.
These brackets also serve as rests for
the derrick assembly when loaded onthe transporter. The mainframe is equip-
ped with a worktable. This is designedwith a hollow centre to allow passage
of drill string components from the drive
train assembly into the pilot hole. Theplane of the worktable top surface re-
mains perpendicular to the axis of thedrill string at all dip angles.
All worktables are equipped with, orare used in conjunction with, a work-table wrenching system. This reacts themachine torque into the mainframe for
threaded connection makeup and break-out. The wrenching system is also usedto hold the drill string and the cuttingcomponents securely in the hole whenadding or removing parts.
The worktable also provides moun-
ting for various accessories necessaryfor raiseboring machine setup and
The raiseboring machine
Thrust and rotationThe raiseboring machine (RBM)provides the thrust and rotationalforces necessary for raiseboringas well as the equipment and in-struments used to control and mo-nitor the raiseboring process. The RBM is composed of fivemajor assemblies described in thesections below. These are: derrick;hydraulic system; lubrication sy-stem; electrical system; and con-trol console supplied with eachmachine.
Figure 1: Derrick assembly layout .
-
8/14/2019 Education Under Ground Mining E Book 04
16/112
TALKING TECHNICALLY
14 RAISEBORING
operation, such as the pilot hole starterbushing, the outlet housing of the blo-oie system, the drivehead installationand removal tools, and the ram assem-bly, if fitted.
Columns
Chrome plated cylindrical columns pro-vide torque transfer from the drive train
assembly into the mainframe. These co-
lumns are connected at their bottom to
the mainframe, and at their top to theheadframe. They pass through machined
bushings in the crosshead, and guidethe crosshead as it travels up and down.
Headframe
The headframe is mounted atop the
derrick assembly columns, linking themtogether. This dampens column vibration,
and shares the boring torque betweencolumns. The headframe is most com-monly secured to the columns by use of
a bolted crown gear coupling system.
Hydraulic cylinders
The hydraulic cylinders supply the thrust
required for raising and lowering thedrill string in relation to the raise bo-ring machine. These same cylinders also
supply the thrust necessary for bothpilot hole dril ling and raise reaming.Extra thrust capacity is often providedin the design of these cylinders to dealwith special circumstances.
Drive train assembly
The drive train assembly supplies to the
drill string and cutting componentsthe rotational power necessary for raise
boring. General descriptions of the three
major components making up the drivetrain assembly are given below. Theseare: crosshead; main drive motor; andgearbox.
Crosshead
The crosshead is a moving platform towhich the main drive motor system andgearbox are mounted.
Driven by the hydraulic cylinders and
guided by the columns, the crossheadraises and lowers the drill string andtransfers torsional forces into the raise-
borer columns.Most Atlas Copco Robbins raise bo-
ring systems utilize the crosshead as areservoir for the gearbox lubrication oil.Other lubrication system components,
such as the lubrication motor and pump,can also be housed in the crosshead.
Figure 2: Exploded view of derrick assembly.
Main Drive
DC Hydraulic AC
Headframe
Mainframe
Hydrauliccylinder
Machineworktable
Turnbuckles
Turnbuckles
Expansion pins
Expansion pins
Gearbox
Columns
Hydraulic cylinders
Drivehead
Crosshead
Baseplates
-
8/14/2019 Education Under Ground Mining E Book 04
17/112
TALKING TECHNICALLY
RAISEBORING 15
Main drive motor system
The main drive motor system of thederrick assembly supplies the rotationalpower necessary for raiseboring. Fourtypes of main drive motor systems canbe used with Atlas Copco raiseboringmachines. These systems are: AC, DC,hydraulic and VF.
The AC system has the simplest de-sign, lowest cost, and highest reliabilityof all raise drill drive motor systems.It features fixed speed and fixed tor-que, and is best suited to competentground, where minimum motor stallingwill be encountered.
DC drive is variable speed and va-riable torque, and is best suited for lar-ger raise diameters in mixed ground
conditions.Hydraulic drive, employing variable
speed and good torque limiting control,is suited for use in all ground condi-tions and has high reliability.
The VF drive system, developed in-house by Atlas Copco, combines thesimplicity of the AC drive motor sy-stem with exact motor speed, torque,and positioning control.
The VF system circuitry controls the
speed, torque, and position of its AC
motor by first converting the incoming
AC mine power to DC, and then con-
verting it back to an AC signal. The
frequency and voltage of the AC signal
outgoing to the AC motor can be ad-justed, enabling precise speed, torque,and positioning control.
Gearbox
The gearbox mounts directly to the maindrive motors at its input end, and re-duces motor input speed to a speedcompatible with raiseboring at its out-
put end.Most gearboxes use a planetary re-
duction system. This shares the load
among three planetary gears, reducingthe diameters of the individual gearsrequired, and allowing a more compact
drive train assembly.Gearbox reductions must include ra-
tios capable of providing high torqueand low speed for raise reaming, andhigh speed and low torque for pilot holedrilling. It is not uncommon to have amulti-speed gearbox with a var iable
speed motor.The output end of the gearbox is
attached by a splined connection to thefloating box, which connects it to the
Figure 3: Cross-sectional view of the drivehead.
Splinedconnection
Axialfloat
Floating box withpatented sphericaldesign and replaceablethreaded insert
Driveheadcapscrew
Swivelingaction
Figure 4: Pilot drilling and reaming.
-
8/14/2019 Education Under Ground Mining E Book 04
18/112
TALKING TECHNICALLY
16 RAISEBORING
drill st ring. The splined connection,while enabling the rotational power ofthe drive train assembly to be transmitted
into the drill string, also allows the floa-ting box to drift axially when threading
or unthreading drill string components.Axial free f loat permits the threa-
ding of the floating box to follow thethreading of the stationary drill string
component, greatly reducing the chancesof thread damage during connectionmake-up or breakout. Periodic heightadjustment of the drive train assembly
in relation to the drill string componentis necessary, which can be carried outby the operator.
Spl ined connect ion f loa t ingboxessupplied with newer raiseboring
machines are equipped with a spheri-
cal design patented by Atlas CopcoRobbins.
This provides a swivelling action in
addition to free float. This preventsbending, stresses from damaging thegearbox and accommodates slight drillstring misalignment.
The floating box can be housed in-ternally within the gearbox, or mountedto the output end of the gearbox as aseparate component. When mounted se-
parately from the gearbox, the assembly
housing the floating box is referred to as
the drivehead.The drivehead is connected to the
output end of the gearbox by spindlebolts or a single threaded capscrew. Ifa single capscrew is employed for thisconnection, drivehead installation/re-moval tools are required when instal-ling or removing the drivehead fromthe gearbox.
Hydraulic system assembly
The hydraulic system supplies hydrau-
lic power for raiseboring. This assemblycomprises the hydraulic power unit and
all interconnecting hose assemblies.The hydraulic power unit is on a
skid-mounted structure containing a hy-
draulic reservoir. These are used as mo-
unting platforms for the majority of thecomponents making up the hydraulicsystem. Included in these componentsare the motors and pumps used to po-wer the hydraulic system along withvarious valves, filters, and manifolds.
Lifting eyes are provided on thehydraulic power unit for hoisting andpositioning.
Design of individual hydraulic sy-stem assemblies varies according to thetype and size of machine. The servicemanual should be consulted for spe-cific hydraulic system setup, operation,
and maintenance procedures.
Lubrication system
The lubrication system assembly en-
sures proper delivery of lubricating oilto the high-speed bearings and otherselected components of the drive trainassembly gearbox. This assembly iscommonly made up of the lubricatingoil reservoir, with level gauge, thermo-
meter, and breather; pump drive motor;and lubricating oil pump, filter, heatexchanger, and flow meter.
Most Atlas Copco Robbins raise bo-ring machines employ the crosshead ofthe drive train assembly as the lubrica-
tion reservoir, and as the housing forthe lubrication pump drive motor and
Figure 5: Hydraulic power unit.
Figure 6: Electrical power unit.
-
8/14/2019 Education Under Ground Mining E Book 04
19/112
TALKING TECHNICALLY
RAISEBORING 17
pump. Some machines are designed with
the lubrication system reservoir and com-
ponents located separately from the der-rick assembly, usually to permit the der-rick to be tilted to bore raises at lowdip angles without affecting the levelof the lubrication oil reservoir and thefunctionality of the lubrication system.
Electrical system
The electrical system assembly com-prises the electrical power unit and allelectrical power and control cables.The electrical power unit consists of anenclosed cabinet containing the powerand control distribution hardware andcircuitry for the entire raiseboring sy-stem. Lifting eyes are provided on thiscabinet for hoisting and positioning.
Power and control cables are inclu-ded in the electrical system assembly.
Most of these cables are of the quick-coupler type, with all the plugs and
receptacles identified for ease in making
proper connections during systemsetup.
Because of varying site power sup-plies, and differences in main drivemotor systems and machine options, the
design of electrical system assembliescan be quite diverse from machine tomachine. The service manual suppliedwith each raiseboring machine should
be referenced for specific electrical sy-stem setup, operation, and maintenance
procedures.
Control console
The modern rig control system fromAtlas Copco features a Control Area Net-
work (CAN) for digital communicationbetween all modules connected to theBus wire.
The entire system features various
I/O (In/Out) modules for communi-cation with all machine sensors and
meters, a master module for computing
and processing of operational data, and
a display module for presentation ofcalculated data.
The I/O modules are positioned inthe thrust pack and the drive pack, aswell as on the derrick assembly. Thecomputing module is usually placed inthe drive pack, which is located in asafe, dry place for power supply and
convenience to major components.The display module is part of the
control panel, itself a robust assemblyenclosed in a waterproof envelope, spe-cially designed for outdoor and under-ground use.
Manufactured and delivered to over400 units since 1998, this proven, stan-dardized control system is modular, with
all major parts interchangeable withother similarly-controlled Atlas Copco
products.
Jan Forsberg
Figure 7: Robbins 73RH C with RCS control panel.
-
8/14/2019 Education Under Ground Mining E Book 04
20/112
TALKING TECHNICALLY
18 RAISEBORING
Robbins 73RM-DC in TasmaniaHenty Gold Mine, owned by Gold Fields Tasmania Pty,
is located on the west coast of Tasmania, in the middle
of an environmental protection area with many re-
strictions. The mine needed more fresh air, and opted
for a raise bored ventilation shaft from surface.
Pilot and reamThe pilot hole was pre-drilled by a subcontractor in threestages to HQ 14 in using DTH equipment. A Robbins73RM-DC raiseborer was then employed by SkanskaRaiseboring of Sweden to develop the 689 m-long,2.44 m-diameter vertical ventilation shaft.
Crawler transporterSome ten 20 ft containers were used for transportationof the equipment to site.
The rig was mounted on an air powered crawler tran-sporter capable of 1.5 km/h and positioned on a specially-designed steel frame over a 10 m-deep concrete lined
pre-sink of 4.5 m-diameter. All drill tubes were inspected
with a magnetic particle inspection kit before the projectstarted.
One month of boringSkanska had three operators and one supervisor on site.Set up took seven days, and take down five days. Drillpipe was high strength, with 10 in outside diameter in 5ft lengths. Thread lubrication was Best o Life 3010 fromDallas, Texas, US. Pipe changes took 5-6 minutes, usinga side loading pipeloader and crane.
Boring took place over a 31-day period, during whichaverage penetration rate was more than 22 m/day. The2.44 m (8 ft) reamer was dressed with 14 cutters, 7 four-row and 7 five-row. The raiseborer developed thrust of100 - 280 t, the equivalent of 7-20 t on each cutter, witha torque of 350 and 7-8 rev/min. The drillstring wasstabilized using a stinger and two 13.625-in stabilizers,and no cutter changes were necessary during the boringoperation.
Satisfied customer
The machine gave close to 100% mechanical availability,delivering the raise in half the expected time, allowing
ventilation the equipment to be installed earlier thanexpected.
The mine had to bring forward extra resources formucking, in order to keep pace with the raise drilling.There were no accidents or incidents, and no reportableenvironmental impacts, such as oil leakage, and the cus-tomer expressed satisfaction with the project.
Side loading pipeloader in operation.
Robbins 73RM-DC under installation.
Reaming the Henty ventilation shaft.
-
8/14/2019 Education Under Ground Mining E Book 04
21/112
TALKING TECHNICALLY
RAISEBORING 19
Most popular modelWith 35 units delivered worldwide since 1980, the Rob-bins 73RM has become the most popular raiseboringmodel today. The 73RM is used to develop raises andshafts in the crucial 1.8 m to 3.1 m-diameter (6-10 ft)range.
The two medium-sized Robbins 73RM-VF raise bo-rers now at work developing ventilation shafts in the ar-duous conditions at Norilsk, Russia are an example. TheVariable Frequency drive governs the speed of the mainmotors, and consequently the speed of the pilot bit andthe reaming head, by means of frequency conversion ofmotor current.
Variable frequencyWith VF control, the machine and the drill string areautomatically protected from over-torque. Using full tor-que at minimum cur rent and low speed gives smoothstart-up and stop procedures at constant torque, withreaming performed in the 0 8 rev/min range (0 50 Hz),
and pilot hole drilling in the 0 30 rev/min range. At con-
stant power, reaming is performed in the 8 16 rev/minrange (50 100 Hz), and drilling in the 30 60 rev/minrange, where the torque drops as the speed increases.
Overcoming geologyThe ability to vary the reamer head speed is particularlybeneficial for operation under widely varying geologicalconditions, whether working in hard or soft rock, or solid to
fractured. Also, the reaming head speed can readily be adaptedto various reaming head diameters.
Variable speed cont rol was previously achieved byeither a hydraulic or DC electrical motor drive. Theadvantages of the Atlas Copco Robbins AC drive, whichis fully torque vector controlled, are superior efficiency,reliability and reduced operational costs.
In all, the final outcome is higher productivity andbetter cutter economy.
Variable frequency drive for Norilsk
One of two Robbins 73RM-VF machines delivered to Norilsk Mine, Russia..
-
8/14/2019 Education Under Ground Mining E Book 04
22/112
TALKING TECHNICALLY
20 RAISEBORING
Expert knowledge
The course is based on the skills andexperience gained by key Atlas CopcoSecoroc personnel over many years and
conveys expert knowledge in the useof modern rock drilling products.
CBT Rock Drilling Tools version 4.0was released after six years of patientdevelopment. Computer based training
transfers knowledge about raiseboring
and drill str ing products, and their use,
in a simple and efficient way.Aided by 3-dimensional animations,
photographs, film sequences and inter-
active lessons, the training course ex-plains how the markets leading raiseboring and drill str ing products canincrease both productivity and profit.
With version 4.0, CBT now includestraining on all Atlas Copco Secorocproducts, with:
1. Three separate packages divided intoTophammer, DTH and Raiseboring.
2. Separate libraries for drilling equip-ment and applications in all packages;
3. Updated product training section ontophammer equipment i ncludingtroubleshooting, bit grinding and careand maintenance;
4. Product training section on in-the-
hole equipment including trouble-shooting, bit grinding and care and
maintenance;5. Product training section on consum-
ables for raiseboring equipment, in-
cluding care and maintenance;6. Focus tests on each lesson;
Computer based trainingfor raiseboringLatest versionAtlas Copco Secoroc recently in-troduced version 4.0 of its Com-puter-Based Training (CBT) pack-age as being of paramount im-portance in achieving the highestlevel of competence in rock dril-ling tools among distributors andcustomers, as well as its own salesforce. Correct understanding ofhow to choose, use and maintainthe rock drilling tools affects profi-
tability for all, and adds to com-petitiveness. Atlas Copco Seco-roc believes that the CBT packagefor rock drilling tools is the mostcomprehensive interactive train-ing tool available in the industrytoday.
Main menu. This is the first picture shown when you start the CBT. From this main
menu you can choose which of the courses you would like to enter.
Course menu. View picture for the course Raiseboring. Under the text Introduction you find two
buttons, Learning objectives will explain what you are expected to learn. Introduction will give
you an overview by running pictures and a speaker talking. Under Lessons you choose chapters.
-
8/14/2019 Education Under Ground Mining E Book 04
23/112
TALKING TECHNICALLY
RAISEBORING 21
7. a new section of product selection
exercises.
Complete training
The whole Secoroc CBT Rock DrillingTools package comprises approximately50 hours of lessons and tests. With arecommended maximum of four hours
of lectures per day, the total length of acomplete training course on rock dril-ling tools can be estimated at threeweeks.
CBT enables efficient training when-ever the need arises. For instance, a new
employee can start the learning process
right away, and learn about how the pro-duct is manufactured, its characteristics,wear limits and much more.
A modular structure enables usersto study lesson by lesson, or in a se-lective way at their own pace.
With personal computers, learning
can take place whenever and whereverthe individual chooses, including inthe field. The training package tea-ches you to find the right tool for any
given rock drilling application at any
time of the day. Similar to its experi-ence with CBT version 2.0, Atlas Copco
Secoroc has found good market accep-
tance of version 3.0, which has been ad-vising key customers and technicalschools on its use, as well as its ownsales team.
The new version of CBT 4.0 is ex-pected to even further cont ribute tothe added value in Atlas Copco Secoroc
sales service, inproving profitabilityand competitiveness for all involved in
raiseboring and rock drilling.
Bjrn Samuelsson
Chapter.In this section you choose the lesson you want. In the lower right
corner you find four buttons. X will finish the actual step. Number two will
take you back one step. The third button allows you to scroll through the course.
Lesson.There are three buttons for presentations. Video camera
button: running pictures and speaker text. Photo camera button: pictures
from more important or difficult parts. Text button: pictures and text.
Step player.When pressing the step player button you will find film
sequences or animations. At the end of every lesson you can also go through
a test, Focus test, to check your knowledge.
Product selection exercises.At the end you also have the possibility
to go through some real exercises, where you will have the background for a
specific rock excavation and from that choose the suitable equipment to do the job.
-
8/14/2019 Education Under Ground Mining E Book 04
24/112
TALKING TECHNICALLY
22 RAISEBORING
Modifications
There are many different applicationsthat require horizontal or low angledrifts. Raiseboring is a non-explosivemethod, so the vibration effect on sur-rounding rock, and on buildings closeto the drill site, are kept to a minimum.Hydropower projects, urban sewerage
projects, and service drifts in mines area few examples where horizontal raise-boring has advantages over dr ill/blast
methods. The latter methods are noteven an option in the 0.7-1.2 m-diameter
range, because men and equipment are
simply not available to safely work such
small openings.The raiseboring method does not
change when the angle is lowered tohorizontal. However, transporting therock cuttings from the face becomesa challenge, because gravity does nothelp in the same way as for steeperholes. Hitting the target with the pilotbit also requires more skills than in a
vertical raiseboring application, be-cause of the downward pull of the drill
string.However, most types of raiseboring
machines can be modified to pull hori-
zontal and low angle raises. These modi-
fications generally include an alteredgearbox lubrication routing, a modi-fied base plate, and the addition of arear support for the guide columns.
Handling rock cuttings
A reamer used in a horizontal applica-tion employs scrapers to remove cut-tings from the rock face. These clean
Horizontal and low angle boring
New applicationsRaiseborers have been adapted tosome unusual situations wherehorizontal or low angle holes havebeen required. These have beenwell documented at projects whereraise bored holes were planned,such as at Venda Nova in Portu-gal. However, recent legislationfollowing a tunnel fire at Guadar-rama in Spain completely changesthe picture. At the Guadarramatwin railway tunnels, the TBMswere well ahead of the cross pas-sage development when a fire oc-
curred near the face. As a result,the fire crews were denied accessto the face along the parallel tun-nel, and had to stand off. All fu-ture twin tunnels in Spain will nowhave to develop cross passagesclose to the face. Because thesetunnels are mainly TBM- driven,and blasting would be risky to hu-gely expensive equipment, thecross passages will have to be de-veloped mechanically. Horizontalraiseboring is possibly the onlycurrently available alternative.
Low angle raiseboring.
Robbins raise drill in front of the face.
-
8/14/2019 Education Under Ground Mining E Book 04
25/112
TALKING TECHNICALLY
RAISEBORING 23
the lowest point on the face prior toeach gauge cutter passing through, sothat the reamer is not forced upwards by
the cuttings. This will avoid unwantedbending stress in the drill string.
A large volume of water is also re-quired to keep the rock face clean andfree of cuttings. This can be introducedthrough the drill string, and either piped
from the back of the reamer, or throughholes drilled in the stem directed at the
gauge cutters.Additional flushing water can be
pumped from the machine to the faceon the outside of the drill string. A sea-ling system around the drill string, eq-uipped with an intake valve, is neces-sary with this method. This is similar
to the blooie system, which uses air asthe f lushing medium for pilot hole dril-ling. On raises with angles steeperthan 3 degrees from horizontal, largevolumes of flushing water, up to 3,000lit/min, should be sufficient to removethe cuttings.
Raises larger than 1.8 m-diametercan generally be mucked using a smallloader, while short holes can be muckedby hand. Water and scrapers are nee-ded to keep the rock face clean.
For smaller diameter raises close tohorizontal, mucking methods are more
innovative. The following methodshave been used successfully on recentprojects.
A pulley with steel cable is attached
on a swivel on the back of the reamer.The cable passes through the reamer,and a pair of air-powered winches isused alternately to pull out a scraper,which cleans the cuttings from the raise.Water and scrapers are needed to keepthe rock face clean.
Alternatively, a steel container is at-
tached to the back of the reamer with a
swivel. The scrapers on the reamer liftthe cuttings into the container, fromwhere a slurry pump and pipeline con-vey the cuttings out of the raise. Thismethod occasionally requires people in-
side the raise to extend pipe, route po-wer to the pump, and remove any over-size cuttings.
Another method is to use a non-rotating sealed plate pulled on a swivel
behind the reamer. A pipe is connected
to the sealed plate, and a pan is mountedjust below the pipe connector on thereamer side. The reamer scrapers liftthe cuttings onto the pan, and a mix-ture of air and water supplied throughthe drill string cleans the face. The in-
creased pressure inside the sealed areaensures that cuttings are blown out
through the pipe, which has to be ex-tended as reaming progresses. A cablethat attaches to the back of the sealedplate is used to winch the reamer outof the raise when necessary.
Horizontal piloting
The weight of the drill string causes de-
viation of the pilot hole in a horizon-tal application, so great care has to betaken throughout the piloting sequence.If the thrust is too high on the pilot bit,
it will divert the pilot hole upward. Iftoo low, it will divert the pilot holedownward.
Stabilizers installed along the pilothole will counteract some of the drill
string weight, as will a balanced amountof bailing medium, although too littlebail ing may cause the d ril l str ing tostick.
The accuracy of the pilot hole ismost affected by the machine set-upand collaring, for which an experienced
operator is a necessity. An accurate, but
more expensive and time consuming,
approach to a horizontal pilot hole isto drill it in three stages. First, a guidedcoredrilling machine drills an accurate
small-diameter hole. This is reamedby DTH to pilot hole size, following
Steel container collects cuttings behind the reamer.Collaring of the reamer showing the scrapers.
-
8/14/2019 Education Under Ground Mining E Book 04
26/112
TALKING TECHNICALLY
24 RAISEBORING
which the raiseboring drill string is
installed.
Challenge at Venda Nova
A consortium of three Portuguese com-
panies, Somague, Moniz da Maia Serra& Fortunato (MSF) and Mota, was for-med to complete the civil works of the
Venda Nova project situated on the ri-ver Cavado in Ruives-Vieira do Minho,
in north Portugal as shown in the mapalongside.
The project required the drill/blastexcavation of 300,000 cu m of rock toprovide a 2.8 km inlet tunnel, a 1.4 kmdischarge tunnel, a powerhouse cavern,a 625 m-long ventilation tunnel, a1,210 m access tunnel, and a 130 mwater intake. There are also two raise-bored shafts of 415 m and 110 m.
The consortium chose Atlas Copcoequipment for the main operations usingRocket Boomer drill rigs, Secoroc rocktools, Swellex rock reinforcement, anda Robbins raiseborer.
Somague is the leading company inPortugal for drilling, mining and civil
works, and its relationship with AtlasCopco goes back some 40 years.
Rock conditions at the Venda Novasite are mainly favourable. The host rock
is granite, with some areas of schist and
zones with fractures and faults.One of the most challenging aspects
of the project was the development ofthe shorter of the two raise bored shafts.The 110 m escape and ventilation shafthas a decline of only 26 degrees, fromthe turbine hall to the existing ventila-
tion and escape system.Drillcon Iberia Lda, a subsidiary ofDrillcon AB of Sweden, used an AtlasCopco Robbins 73R raiseboring ma-chine to develop the shaft in fairly hardgranite of 170 MPa. The raiseborer wasmounted on a concrete platform in theescape tunnel, from where the pilot hole
was drilled down to the turbine hall.The tunnel was then reamed upwards,back to the escape tunnel.
A Secoroc RRL 3.5 m reamer wasflown in from Australia specially for theproject, as pictured below. The cuttersperformed perfectly, and the mucking
was very easy, using water pressure toassist with flushing the muck out during
reaming. A total of 18 new cutters wereused on the reamer: nine 5-row cutters,and nine 4-row cutters.
The deviation on the finished holewas 40 cm, which is less than 0.5 %.
Atlas Copco assisted the contractorswith every step of the raiseboring pro-cess, from training drillers on the Rob-
bins unit, to helping install new cutters
on the reamer. When the hole was fin-
ished, Atlas Copco personnel were onhand to demonstrate servicing of thereamer, maintenance of the cutters, andregreasing.
Drillcon have another two Robbinsraiseborers in Portugal, stationed atNeves-Corvo copper-zinc mine, where
they drill approximately 2,500 m/year.
The new Venda Nova plant and tun-
nel system came into operation in 2004to provide much needed generating ca-
pacity for the national grid. Venda Novawill also act as a pumped storage sta-tion serving its companion dam Para-dela further downstream. When elec-tricity demand is low, water that haspassed through the powerhouse for stor-age at Paradela can be pumped backthrough 4 km of tunnels to the VendaNova Lake, to provide extra power atpeak periods.
Mikael Bergman
Secoroc RRL 3.5 m reamer as supplied toVenda Nova in Portugal.
Checking the raiseborer drillstring in the 110 m shaft.
Location map for Venda Nova Dam worksite.
Venda Nova
Dam worksite
-
8/14/2019 Education Under Ground Mining E Book 04
27/112
TALKING TECHNICALLY
RAISEBORING 25
Four decades of evolution
Raiseboring started in Germany, prima-rily in the Ruhr coalmines, where theypiloted from a lower level to a higherlevel and reamed down with successively
bigger reamers. The first machine to drill
down and ream up using the techniquethat is now known as conventional raise
drilling, was the Robbins 41R-1101 built
in 1962 for the Homer Wauseca Mine.The raise was 40 in-diameter and 200ft-long. The drill pipe was 5 in-diameter
and 4 ft-long, with oil drilling standardAPI tapered thread. This pipe was torq-
ued up so much during reaming that itbelled on the box ends and welded at the
shoulder, and each length had to be cutoff as it was removed. The pilot hole was
drilled using a Mission DTH hammer, and
Security designed and built the reamer.
Since those early days, some 600 raise-
boring machines have been sold world-
wide.The first Robbins 34R units were
made for Falconbridges Kidd Creekmine in Timmins, Ontario, Canada,
and have been in continuous use sincethey were commissioned.
The mine uses the machines to bore
1.2 m-diameter slot raises, and for down-
reaming 710 mm-diameter holes, which
are used for dumping backfill into empty
stopes.The Robbins 34R has a number of
special advantages: it is small, compact
and powerful; it can operate with as little
clearance as 3.4 m while drilling or rea-ming; and the hydraulic drive provides
variable speed control which helps theoperator to maximize machine per-formance in varying rock conditions.
In addition, with a number of auto-matic features, the Robbins 34R can be
operated by one person. These features
include a sensor that automatically shuts
down the boring cycle at the end of a
cylinder stroke, or at a pre-determinedlevel of torque.
Development of boxhole boring
Safe and efficientThe boxhole borer concept emer-ged in the early 1970s, and thecurrent models of dual-purposeraiseborers are a combination ofthe engineering skills and experi-ence gained since then. Boxholeboring has come a long way sincethe early machines employed onthe South African gold mines,and creditable advances are beingconsistently achieved at minesaround the world, without pilotholes and with minimum site pre-paration and setup time. Most of
the machines ever built are stillworking, releasing miners fromthe thankless task of manual rais-ing, to the benefit of all. Boxholeboring has contributed greatlyto improved safety undergroundwhile providing a far superiorraise at less cost.
Figure 1: The Robbins 34R raiseboring machine was the predecessor to the versatile Robbins 34R.
-
8/14/2019 Education Under Ground Mining E Book 04
28/112
TALKING TECHNICALLY
26 RAISEBORING
Since those first two machines, theRobbins 34R torque and thrust has been
increased, and the model renamed the34RH-HT (High Thrust).It used to be necessary to bolt such
machines down securely on a concretepad, to cope with their high torque andthrust. Such pads were costly and time-
consuming to install, and have sincebeen replaced by a drilling platform that
uses leveling jacks combined with stinger
cylinders in the derrick columns, elimi-
nating the need for pads.
From raiseboring toboxholing
The advantages of raiseboring are: more
economical and much faster advancerates than drill/blast; more stable exca-
vation and considerably safer and better
work environment; smooth wall need-ing 300% less power for air ventilation;
cost/metre decreases as raise lengthincreases, allowing more flexibility inmine design and planning; and a signi-ficant reduction in labour requirements.
The common boxhole raise is an ore
pass raise driven from the haulage way
below to the ore body above. At thebottom of the raise, in the haulage, is achute base with guillotine gate to con-trol feeding of ore by gravity into haul-
age cars. The raise going up from thischute box or base is therefore knownas a boxhole.
The Robbins 34RH-HT can drill box-
holes, for which the machine is set upat the lower level and a full-diameterraise is bored upward. During boring,
Figure 2: The Robbins 34RH raiseboring machine has demonstrated its versatility at projects around the world for more than 25 years.
Figure 3: Boxhole boring can be carried out with or without a predrilled pilot hole, or in a combination of both.
-
8/14/2019 Education Under Ground Mining E Book 04
29/112
TALKING TECHNICALLY
RAISEBORING 27
stabilizers are periodically added to the
drill string to reduce any oscillation and
bending stresses. The cuttings are car-ried by gravity down the hole, and de-flected from the machine for removal at
the lower level. Boxhole boring can becarried out with or without a predrilled
pilot hole, or in a combination of both,where a shorter pilot hole is predrilledto ensure straightness and orientation,followed by single pass/blind reamingand piloting in one step.
Boxhole borer development
Originally, the South African gold mines
utilized drill and blast techniques forthe 8-10 boxholes needed in each stope.
In the highly stressed footwall of these
very deep mines, this proved dangerous.In 1972, the West Driefontein Gold
Mine asked the Robbins Company and
Calweld Corporation to develop a box-hole borer. The raises were to be 90 m-
long, 5 ft-diameter, and from vertical to
60 degrees inclination. The result wasthe Robbins 51R, first produced in 1973,
featuring 24 in non-rotating drill string
and in-the-hole motor and drive system.
The thrust was 350,000 lb and the tor-que was 95,000 ft lb. The drill pipe was
4 ft-long with 3 radial fins for stabi-lization. The rig weighed only 28,000lbs and could be transported through a2 m x 2 m drift.
The 51R was later rebuilt as a 55R,which was the prototype of the 52R.The 52R was more compact, used 24 in-
diameter f langed pipe, had many hy-draulic and drive train improvements, a
built-in water spray, and non-rotary drill
string with in-hole cutterhead drive.Some 22 units of 52R with hydraulic and
electric drive were built, many of which
are still operating.In 1982, Robbins launched a project
to design a new machine, the 53R withderrick drive and rotary drill string. The
machine was designed so that site pre-paration work was limited to only a basic
pad. The reaming torque was 80,000lbs ft and thrust was 620,000 lbs.
The Robbins 53R was ready forSouth African gold mining, and the first
machine went to Vaal Reefs 8 Shaft in1984, where the first 42 m-long hole was
pre-piloted. All subsequent holes weredrilled blind, achieving penetration
rates of 2 m/hr to 2.5 m/hr with a 5 ft-diameter head, which in 25,000 psiquartzites was considered excellent. As
a result, the Robbins 53R became popu-
lar in the South African gold fields. The
muck chute was improved, and furtherwork was done on stabilizers.
Dual purpose machines
The Dual Purpose 34R is a low profile,
small diameter machine developed onthe basis of the 32R. The High ThrustHT version was developed in the 1980s
with 47,500 ft lbs torque and 289,000lbs thrust. It allows quick conversionfrom raiseborer to boxholer. It is alsoused around the world at places suchas: Brunswick Mine, Canada; ToyohaMine, Japan; Leinster Mine, Australia;
Western Metals (ARD), Australia; andEI Teniente Mine, Chile.
An important advantage with thedual-purpose machine is that bothboxhole boring and raiseboring can becarried out. The conversion betweendrilling modes is relatively quick andeasy. The 34R is turned upside downand a f loat box spring is added, whereas
Figure 4: The Robbins 51R raiseboring machine, first produced in 1973.
Figure 5: Robbins 53RH set up underground.
-
8/14/2019 Education Under Ground Mining E Book 04
30/112
TALKING TECHNICALLY
28 RAISEBORING
the 53R has top and bottom chucks into
which the swivel is attached.Dual-purpose machines are espe-
cially useful in South African boxholesituations where mine layout allowsbox hol ing and conventional ra ise-bor ing from the same place, givingmultiple holes from one location.
Standardization on one machine type
results in signif icant savings in ma-chines, parts inventory, operator train-ing, maintenance training, proceduresand documentation.
Boxhole reaming
Initially, the reamer for boxhole boring
machines was installed overhead, a cum-
bersome procedure which also entailed
extra time and expense for the prepara-tion of each drilling site.
Accordingly, it was decided to extend
the width and depth of the machine toaccommodate the reamer and stabilizers.
The drill pipe wrenching system wasintegrated in the machines worktable,and was split into two halves, so that hy-
draulic cylinders opened it wide enough
to allow the passage of the reamer. This
feature increases the footprint of the ma-
chine, but does not increase its height,and produces a more functional system.
The remote controlled, hydraulicallyoperated slide-opening worktable ena-bles the entire drill string, includingboxhole stabilizers and reamer, to pass
through the worktable of the machine.Depending on model and frame widthof the 34RH-HT, reamers of diametersfrom 692 mm to 1,060 mm can passthrough the worktable.
Over the years, Atlas Copco engi-neers have designed many reamers,
both standard and specialized. Concern
about the possibility of ground squeez-ing during boxhole boring was over-come by fitting a set of gauge housings
and cutters, which are installed on theunderside of the reamer. In the event of
the ground squeezing during boringoperations, the RCC Duro cutters would
cut their way out as the reamer is with-
drawn from the completed boxhole.All Robbins 34R units are designed
so that the machines full torque andthrust are available in either the push-
ing or pulling mode. The 34RH-HT wasmodified to use stronger 10 in (254 mm)
drill pipe, to better stabilize the reamer,
and to transmit the full torque and thrust
of the machine.
Muck collection
To prevent the cuttings from covering the
machine as they fall down the bored raise,
a muck collector is installed betweenthe bored hole and the machine.
Atlas Copco have designed a muckcollector that connects to the head frame
of the Robbins 34RH HT, with exten-sion bars that can be adjusted to raiseor lower the muck collector by pushing
it with the drive head.The muck collector unit is f itted with
a rubber seal, which assists in contain-ing muck and dust. This is designed intwo halves, to be opened by remote-controlled hydraulic cylinders for thereamer and stabilizers to pass. It also fea-
tures a cone-shaped seal to clamp aroundthe drill pipe to prevent muck and water
from entering the drive box area of themachine.
The collector also incorporates amuck chute, which deflects the muckaway from the machine to the rear endin a 90-degree working range. Further-
more, this remote controlled and hy-draulically operated muck collector isfully integrated into the derrick assem-
bly, and remains on the machine, even
during transportation.The design of the 34RH-HT conti-
nues to evolve, as customer require-ments change, resulting in 360-degreedrilling, no concrete pad requirement,reamer and stabilizer installation under
the head frame, and an integral muckcollector.
Close cooperation between AtlasCopco engineers and customers is re-sulting in the continued development of
this most versatile raise drill.
Roberto Lopez
Figure 6: The remote controlled and hydraulically operated muck collector is fully integrated into the
derrick assembly, and remains on the machine even during transportation.
-
8/14/2019 Education Under Ground Mining E Book 04
31/112
TALKING TECHNICALLY
RAISEBORING 29
Down reaming, one step
In the working sequence below, the rea-
mer needs to either pass through themachine work table or be assembled tothe drill string in a pit underneath theraiseborer. The raise is piloted
Drill string is pulled
The reamer is attached and collared
As the raise advances, stabilizers areattached to the drill string, usually in
a pre-determined pattern After breakthrough the drill string is
pulledThe diameter limitations on the above
method are set by the raiseborer thrustbearing load limit, the pilot hole size,and the chosen reamer connecting pro-
cedure as shown in Figure 2.
Down reaming, two ormore steps
The down reaming sequence, when theraise is done in several steps, is the same
as described above. When the first reamer
completes and is removed from theraise, the second, larger reamer is col-lared into the top of the hole. The front
of this reamer follows, and is stabilized
in the raise using drill string stabilizers
of the same diameter. Weight stacks have
historically been used on the reamer to
increase the thrust capacity in the down-
reaming system, as shown in Figure 3.
Down reaming
Increased safetyDown reaming is a type of raiseboring where a pilot hole is rea-med from the machine to a lowerlevel. This can be done in one orseveral steps to final diameter. Thecuttings are transported throughthe pilot hole to a lower level. Thismethod is mainly used for small-diameter slot-raises and backfilldrifts. Very occasionally the downreaming method is used for largediameter raises, usually in steps.Down reaming is more complexand more costly than raise rea-
ming due to the necessity to sta-bilize the reamer and drill stringwhen reaming. Removing cuttingsfrom the face requires more effortthan a standard raisebored shaft.Down reaming is mainly usedwhen the lower level is unsafe orif access to the lower level is fi-nancially not viable. One advan-tage for the down reaming me-thod is that all work is done atmachine level further increasingsafety over competing methods.
Figure 1: Part of the down reamer used on the San Giacomo project in Italy.
Figure 2: Down reaming, one step.
Pilot down Ream down
-
8/14/2019 Education Under Ground Mining E Book 04
32/112
TALKING TECHNICALLY
30 RAISEBORING
Reamer, guide andstabilizer design
Down reamers should be equipped witha front guide. It should stabilize thereamer in the pilot hole while allowingthe cuttings to pass th rough into thepilot hole. Cuttings pass the front guidebetween the wear ribs. Some designslead the cuttings from the face through
the centre of the guide.In raise reaming, a f lat reamer pro-
file is best. This is not the case in downreaming. The cutters should be on anangle towards the pilot hole, so thatgravity can help the cuttings flow down-
wards. To prevent recutting, raises withlower angle than the reamer profileshould be avoided. If the down-reamed
hole has a lower angle than the reamerprof ile, than the cuttings have to bescraped, flushed or lifted into the pilothole, since the lowest point of the face is
not the pilot hole. The cuttings are flu-shed into the pilot hole by water pipeddown the drill string to the reamer, and
out to the reamer gauge. A rear guidering will further stabilize the reameraction, keeping carbide breakage to aminimum.
To centre and prevent side loading
of the drill string, rotating or non-rotating stabilizers are installed on evenspacing. The rotating stabilizer is of asimple design that works well in lowload applications. It is bolted onto thewrench flats on the drill string. The non-
rotating stabilizer consists of a specialdrill pipe with four arms mounted on a
bearing bushing. This design runs qui-
eter, and can be more heavily loaded.
Raiseboring machines to
be used for down reamingMost standard raiseboring machinesare equipped with a smaller bearing on
the pushing (pilot) side compared withthe main bearing on the pulling side(reaming).
Exceptions are the Atlas Copco Rob-
bins 34R H and 53RH Raiseborers.These machines are designed for raisereaming, down reaming and boxholeboring.
Roberto Lopez andMikael BergmanFigure 3: Down reaming, large diameter.
-
8/14/2019 Education Under Ground Mining E Book 04
33/112
TALKING TECHNICALLY
RAISEBORING 31
Robbins 34RH set up for down reaming at Brunswick Mine.
Secoroc RDI 720 reamer in the hole.
Brunswick Mine has a partnership with Atlas Copco
Construction & Mining Canada that encourages
new product test ing and innovative change. For the
Brunswick operation, the change from 2-cutter to3-cutter RDI 720 down reamer in their slot reaming
programme has been a great success.
Falconbridge Limited Brunswick Mine has extracted and
processed ore from the world's largest underground zincmine for more than 40 years. Located in northern NewBrunswick, Canada, approximately 30 km southwest ofBathurst, the mine produces 3.6 million t/y of zinc, lead,copper and silver ore, and has produced 110 million t ofore to date.
The Brunswick orebody comprises massive sulphides,
with zinc, lead, copper and silver being the principal
metals produced. The host rocks and the mineralizationhave undergone four significant deformation events, re-
sulting in intense folding and faulting.Production is carried out on five main levels to a depth
of 1,125 m, and two shafts provide access. The mine em-ploys approximately 800 people.
Regular programmeFrom the first test r un three years ago, the Robbins34RH has down reamed 3,700 m of slot-raises. The minesregular programme is 3 to 4 slot raises a month. Thebench height is normally between 20 m and 45 m. The
slots are drilled on a slight angle from vertical.The down reaming working sequence is as follows: cleanthe drill site down to bare rock and pour a concretedrill pad at the site; erect, anchor and align the machineon the drill pad at the required angle; drill the 9 in-diameter pilot hole to break through, and retract thedrill str ing; install the down reamer through the drilltable, and down ream the hole to break through; attachrotating stabilizers to the wrench flats on the first rodabove the down reamer and on the wrench flats ofevery fifth rod; pull the dr ill string and down reamerout of the hole, once the hole is complete; and move theequipment to the next prepared drill site.
Viable alternativeDown reaming provides a viable alternative to conven-tional reaming when the lower level breakthrough siteaccess is restricted due to the mine planning sequence. AtBrunswick mine, as the advantages of the RDI 720 down
reamer were understood, a large number of the slot raisesthat were scheduled for conventional reaming were swit-ched to down reaming.
Unlike in conventional reaming, the complete down-reaming operation can be handled at machine level, andsecuring of the lower level is no longer necessary.
-
8/14/2019 Education Under Ground Mining E Book 04
34/112
TALKING TECHNICALLY
32 RAISEBORING
This, of course, is a big advantage in underground benching,
sub level stoping, or any other underground mining methodwhere an open face needs to be created to safely blast the
initial excavation of a new production area.
Stable reamer actionThe RDI 720 down reamer has improved the speed ofthe operation in all aspects. Since the three-cutter designprovides more stable reaming action compared to its two-cutter counterpart, the reamer can be loaded higher, androtated faster, without transmitting excessive stress or
vibration back into the drill string. At Brunswick, thismore than doubled the penetration rate, while increasing
cutter life and reducing machine down time.With this higher productivity, the mine has reduced its
need for contracting additional raiseboring services from
external sources to keep up with the ongoing slot raisedemand.
Historical down reaming problems, low cutter life and
low penetration rate virtually disappear with the three-cutter design, and the customers save money by doingthe work themselves.
RDI 720 down reamer.
RDI 720.
-
8/14/2019 Education Under Ground Mining E Book 04
35/112
TALKING TECHNICALLY
RAISEBORING 33
Innovation at work
BorPak gets its name from the expand-
able packer unit that absorbs the torqueand thrust of the rotating cutterhead.Cuttings gravitate down a guidance tube
and onto a conveyor. Operated from apanel outside the raise, BorPak impro-
ves worker safety and lowers labourcosts. A hydraulic power system advan-
ces the cutterhead, and steering is con-
tinuous, using a laser as a guide. Safetygrippers prevent the unit from slidingdown the raise between strokes or in theevent of power failure.
Atlas Copco engineers will workwith clients to design BorPak to spe-cific requirements of the job. The sy-stem can be fully automated, and iscapable of around-the-clock operation.
Site preparations are m