Mining practice in the Kimberley Division of Consolidated Mines Limited by J. V. CLEASBY*. B.Se.. A.R.S.M. (Fellow). H. J. WRIGHT*. B.Se.. M.Se.. (Fellow). and M. T. G. DAVIES*. B.Se. (Visitor) SYNOPSIS T his paper highlights the changes that are taking place at De Beers Consolidated Mines Limited in mining methods, mechanization, and employment practices. De Beers has four underground mines in Kimberley itself (Dutoitspan, Bultfontein, De Beers, and Wesselton), and two open-cast mines outside Kimberley (Finsch and ). Emphasis is placed on the new method envisaged for Koffiefontein when it becomes an underground mine. The paper also includes notes on chemical drilling and on winding practices.

SAMEVATTING Hierdie referaat laat die klem val op die veranderinge wat by De Beers Consolidated Mines Beperk aan die gang is wat betref mynboumetodes, meganisering en indiensnemingspraktyke. De Beers het vier ondergrondse myne in Kimberley self (Dutoitspan, Bultfontein, De Beers en Wesselton) en twee oopgroefmyne buite Kimberley (Finsch en Koffiefontein). Die nuwe metode wat vir Koffiefontein beoog word wanneer dit 'n ondergrondse myn word, word veral benadruk. Die referaat sluit ook aantekeninge oor chemiese boorwerk en oor wenasgebruike in.

INTRODUCTION tains the head office of the De 1891. Finsch Mine was a more Beers Company, and the - recent discovery by A. T. Fincham The Kimberley Division of De sorting and trading companies for in 1961. Beers Consolidated Mines Limited goods produced in Southern Africa, The 'Big Hole' remains as a is composed of four underground which are newly housed in a building monument to the Kimberley Mine, mines in Kimberley itself (Dutoits- specially designed for the purpose. which was closed in 1913, and today pan, Bultfontein, De Beers, and were first discovered is a great South Mrican tourist Wesselton) and two open-cast mines in the Kimberley area at Hopetown attraction, second only to the Kruger outside Kimberley (Finsch and in 1866 on the banks of the Orange National Park. De Beers have built Koffiefontein). Fig. 1 is a map of River. This and later finds triggered a museum at the edge of the 'Big the Kimberley district showing the the start of the great 'diamond Hole', which preserves buildings, location of these min'3s. Finsch is rush'. In 1870 the mining equipment, shops, and goods 150 km west of Kimberley and (now closed) and Dutoitspan pipes from the early Kimberley days. Koffiefontein is 80 km south of were discovered, followed by those Finsch and Koffiefontein Mines Kimberley. Kimberley also con- at Bultfontein, De Beers, and Kim- are both open-pit bench mines and berley (now closed) in 1871, Koffie- are fully self-contained, with their *De Beers Consolidated Mines Limited. fontein in 1880, and Wesselton in own treatment plants, housing, ser-

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. Outoitspan Mint . . W llon Mint

N01 TO SCALE. Jag.rslontein Mint . Fig. I-Map showing the location of the mines of De Beers Consolidated Mines Limited in the Kimberley area

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 247 B

24T ,UHE Of SECTION 1 1 l05m.Level

24M

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24M , B 50 o 50 'QOm""

Fig. 2-Plans and section showing the downward taper of the upper part, and the irregularity of the lower part, of a typical Kimberley pipe

vices, etc. The four mines in Kim- Wesselton, De Beers, and Dutoits- generally sharp, indicating that berley feed ore by conveyor to a pan pipes (Fig. 2). earlier intrusions were completely central treatment plant and enjoy From surface to approximately consolidated prior to the intrusion joint services. These mines utilize 100 m, the wallrocks around the of later material. At Finsch and the block-caving method of mining, Kimberley group of pipes consist of Koffiefontein Mines only one major which has almost entirely replaced black and grey shalcs of the Karoo phase of intrusion is apparent at the the previous method of chambering. System, containing numerous and present levels of exposure, but, as The combined tonnage of ore pro- generally concordant dolcrite sills. in the Kimberley pipes, included duced by the Kimberley Mines is The shales overlie a variable thick- fragments of earlier indi- 15000 t per day, Koffiefontein ness (300 to 1000 m) of Ventersdorp cate a more complex intrusive 12 000 t per day, and Finsch 13 000 t lavas with intervening quartzite history. per day. horizons. The Ventersdorp rock rests Most varieties of kimberlite are uncomfortably on Basement characteristically hygroscopic, GEOLOGY granite-gneiss. The Ventersdorp swelling and crumbling when wet The Kimberley pipes are approxi- System is not present at Koffie- owing to the absorption of water by mately circular or oval in shape, fontein, where Karoo shales, with clay minerals in the rocks. This and are deeply eroded volcanic intervening dolerite sills, rest directly characteristic makes wet drilling of necks, which, at the present land on granite-gneiss at a depth of kimberlite extremely difficult, and surface, have average diameters approximately 250 m. The wall- additional complications arise from ranging from approximately 230 to rocks at Finsch consist of 130 m the generally incompetent, low- 500 m. The upper parts of all the of banded ironstone separated from strength characteristics of kimber- pipes decrease in area with increas- the underlying dolomite, limestone, lite, compounded by the abundance ing depth, the average dip of the dolomitic shale, and chert of the of structural discontinuities (shear contacts being approximately 80°. Dolomite Stage by a sequence of planes and fractures). These features At depths of more than 500 m, this passage beds approximately 25 m make kimberlite difficult to support regular decrease in area is not thick. The passage beds consist of but are an advantage during block- always maintained, and the pipes colourful, rhythmic alternations of cave mining operations since they assume highly irregular forms. The thin dolomitic, siliceous, and iron- facilitate collapse and break-up of contact between the pipe and the rich layers. ground within the caves. wall-rock varies in inclination rapidly Several stages of intrusion have The occurrence of diamonds in over short vertical intervals, and a resulted in the presence of separate these pipes and separate intrusions marked effect of the kimberlite columns of kimberlite and kimber- within individual pipes ranges from intrusion by structures in the wall- lite breccias within the four Kim- approximately I part in 8 million rock is evident. This irregularity berley pipes. Internal contacts be- to less than I part in 100 million. at depth is most pronounced at the tween these separate phases are The distribution of diamonds is

248 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY extremely complex. At any level irregularly over successive depth axial hole of the drill steel effectively in the pipes, the grade of separate zones. In general, however, both allays dust, water alone cannot be intrusions may be similar or may the grade and the average size of used during the drilling of kimber- vary by a factor of five or more. diamonds decrease with depth. lite because it coagulates the dust Similarly, pronounced changes in particles into a thick clay that CHEMICAL DRILLING horizontal grade may occur within causes the drill steel to stick in the a single intrusive phase. Vertical The problem of dust during drill- hole. In addition, the roof, side- variations of grades within indi- ing operations has long been one walls, and footwall are weakened by vidual intrusions may be relatively of the biggest single mining hazards. water and therefore become difficult limited, may change in more or Unlike other mining operations, to keep safe. Fortunately, however, less linear fashion, or may vary where water flushing through the there is no free silica in kimberlite,

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JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 249 and thus the dust hazard is much in the shank of the drill steel to Jeto bottom-dump skips are used smaller than in some mines. Most allow the water tube to penetrate at De Beers and Bultfontein Mines, of the drilling in kimberlite has into the steel for approximately and Sala bottom-dump skips at hitherto been dry, but mining regu- 58 mm (Fig. 3). The head of the Wesselton Mine. lations introduced in 1965 called drill steel has two holes drilled The man and material winders for a dust count of less than 500 adjacent to the T.O. insert that on the Bultfontein and De Beers particles per millilitre. Attempts intersect the axial hole to ensure main shafts (and, from 1976, the were made as far back as 1949 to proper wetting and reduce blockages. Wesselton main shaft) are automatic suppress the dust, and various types Encouraging results have been elevators with a payload of 5000 of dust-extraction filters, mobile achieved with standard non-vented kg and a speed of 7,5 m/s, and are dust cars, and chamber dust cars rock drills. Special permission was designed for a maximum winding were used with a fair measure of obtained from the Mines Depart- depth of 975 m. In operation, they success. However, it was eventually ment for an experiment, the ad- are identical to an automatic eleva- found that greater efficiency could vantages being tor in a building, no driver or opera- be obtained from the use of a (1) less leakage due to increased tor being required. The station chemical dispersant introduced into pressure on the seal, gates and conveyance doors are a small amount of flushing water. (2) no air blowing onto the face operated manually, but are electric- During the development phase, from the front-head release ally interlocked to ensure that they experiments on various chemicals ports, thus reducing dust forma- are closed before the conveyance were conducted, but it was eventu- tion, and moves, and mechanically interlocked ally found that a dispersant called (3) no 'fogging' in the event of a to prevent them from being opened Dispex N40 was the most effective faulty seal or water tube. except when the conveyance has and economical. It was also possible Because Dispex N40 is a decked at its destination. to drill both soft and hard kimberlite dispersant, any dirt in the pipes The conveyance is called to a with Dispex, and the overall pene- and mixing tanks is loosened, station by the pressing of a call tration rates were faster as a result. causing blocked water tubes and button as in a building. During shift The number of dust particles per thus rock-drill breakdowns. How- times and material-handling times, millilitre at the drilling face with ever, this is avoided by ensuring the call buttons are made inoperative the chemical method is 85, compared that the inline filters on the pipe by the turn of a key switch, with 244 for dry drilling with dust- column are kept in good condition and control is then limited to the extraction units, and 500 as the and are cleaned regularly. Dispex conveyance control panel only, which permissible standard. The cost is N40 also affects the machine lubri- means that the person in charge approximately RO,Ol per metre. cant, which has necessitated the retains complete control. A valve having the following addition of an additive to reduce Owing to the depth and speed of characteristics is necessary to con- its detergent action. wind, the use of trailing signal trol the mix of water and Dispex cable is unpractical, and a radio- WINDING PRACTICE to the machine: type 23-channel signalling system (a) an adjustable flowrate but with The shafts, for the sake of con- is installed, with the signal generator a set drilling position, venience, can be divided into the mounted in the conveyance and (b) a set drilling position that categories of main shaft for the powered by a battery. A signal- cannot be easily or inad- hoisting of rock, men, and materials, receiving set is installed in the vertently altered by the machine and service shafts for the hoisting headgear. This set receives, filters, crew, of men and materials. Each main and amplifies the signals received (c) a closed position to prevent shaft is equipped with a rock and feeds them to the control waste of solution during de- winder and a man and materials system. For safety, a minimum lays, and winder, and each service shaft with number of two signals is required (d) a flushing action that alters a man and materials winder. to be correctly received before the the set flowrate only while The rock winders are conventional control panel is activated. In the flushing is required. drum winders with Ward Leonard case of an emergency, the emer- It was found that Newman Hen- controls designed for depths up gency stop button in the conveyance der control valves modified to inject to 1200 m and a speed of 17 m/so is pressed, which cuts the carrier sufficient chemical solution to give They are on automatic operation, signal and thus prevents any other the desired consistency of sludge at i.e., the skips are automatically signals from being transmitted. average penetration rates (Fig. 3) loaded from weight-batched flasks. A feature of these elevators is the were the most suitable. Winding-engine drivers are used accurate decking achieved, the maxi- The drilling fluid is mixed in and only for start-up, shut-down, and mum variance being about 25 mm. reticulated from a mixing tank that re-set operations, apart from rope, This is maintained by the mounting is calibrated and set to give a winder, and shaft inspections. For of magnetic switches at each station. 0,5 per cent concentration of Dispex. these purposes they are drawn They are activated by a vane on The 'chemical' rock drill has a from a drivers' pool at the Bult- the conveyance that can be ad- longer hard-chromed water tube, fontein Mine or from the Wesselton justed to very close tolerances. which requires a recess and a seal Mine man and materials winder. For shaft inspection, the machine

250 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MIN ING AND METALLURGY is controlled from the inspection mounted on the bridle to facilitate was installed with the skip having a platform mounted above the con- loading and unloading. payload of 3 t. veyance, the speed being limited to The man and material winders Further progress in automation is a pre-adjusted inspection speed. The on the service shafts are all auto- being planned for Koffiefontein Mine, same applies to rope inspection, matic elevators with a payload of where a new shaft is nearing com- which is controlled from the bailie about 2700 kg and a speed of pletion. This will be equipped with Because of the difficulty of slinging 2,5 m/s at a maximum length of three fully automatic winders, which long materials above or below an wind of 360 m. In operation, they will not be equipped with the norm- elevator cage, the conveyance for are identical to the machines on al driver's control console, and these machines has been built to the main shafts, except that they no winding engine drivers will be accommodate materials up to 7 m are controlled by a trailing cable. required or be on call. long inside the conveyance. An For the development phase on these The rock winder will be a thy- air-driven chain hoist is permanently shafts, a skip and cage combination ristor drive, three-rope Koepe with

OV~R.URJ:J ""

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SECTION ACROSS SCRAPER DRIFT

Fig. 4- The general layout of a block cave

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 25t a sheave of 5 m diameter. In opera- 'Creep Down', and 'Stop', that can Weight Problems tion, it will be completely automatic, be plugged in at any station. In The general layout of the 580 m i.e., when switched on, it will hoist addition, it will be possible to block-cave section, Bultfontein Mine, ore continuously provided that it despatch the load to a specific is shown in Fig. 5. Early practice is available in the underground station. was to carry out undercutting by storage bins and the headgear bins The gradual automation of winders pillar wrecking with long holes, are able to receive it. For shaft over the past thirteen years has which required prior installation of inspection, it will be controlled at resulted in a significant reduction the concrcted drifts to permit inspection speed only, from the in the complements of winding removal of the broken ground from platform above the skip. For rope engine drivers, bankmen, onsetters, the undercut horizon. This resulted examination, it will be controlled and cage assistants. Automated in serious abutment damage to at examination speed from a position machines are safer as the controls the drifts as the undercut area in the headgear, the bank, or the operate only within predetermined increased in size. It was planned shaft bottom (for tail ropes). Con- limits that cannot readily be by- to bring the southern half of the trols are also provided for skip passed. Although the maintenance block into production initially in inspections and starting up after of automated winders is more com- 1960, followed by the northern half an unscheduled stop. This machine plex than that of manually operated some three years later. However, will be licensed as an elevator machines, very little difficulty has installation of the completed drifts despite the fact that it is powered been experienced in training artisans in the northern half continued by 3850 kW and has a payload of for this duty. ahead of the undercutting in the 23 t. BLOCK-CAVING PRACTICE southern half, and by the time The man and materials winder undercutting was completed in the will be an automatic elevator with The introduction of block caving southern section up to Drift No. 8, the same general specification as is described in a paper published serious abutment damage was the existing main-shaft elevators. It in 1960, by W. S. Gallagher and occurring as far as Drift No. 13 is designed for a maximum length W. K. B. Loftus. Fig. 4 shows a in the northern section. of wind of 1000 m. general layout of a block cave. The The third winder is a heavy- present paper deals with the subse- Initially, the undercut floor was materials winder, which is capable quent weight problems encountered carried 6 m above the drift floor, of raising or lowering a load of 30 t in the Bultfontein 580 m block but subsequently this distance was at a speed of 1,25 m/so Its duty is cave, changes in layout and design increased to 7,4 m to lessen abut- very much the same as that of a to overcome the weight problem, ment damage. However, initial pro- crane. It will be operated from a and brief descriptions of the subse- duction difficulties led to the tops pendant control, with control but- quent layouts at all four of the of the cones being sliped off by tons for 'Up', 'Down', 'Creep Up', Kimberley Mines. long holes to reduce the distance

V!:-rri7!:PS:>O"'P """'-"1

Fig. S- The layout of the S80 m block cave, Bultfontein Mine

252 DECEMBER '1975 JOURNAL OF THE SOUT H AFRICAN INSTITUTE OF MINING AND METALLURGY F~OO R from floor of drift to top of cone back A , I.!'.:'~C.!'!-/:/'~-, ----- to approximately 6 m. A section of ) " 0' " "'I : @l the cone layout is shown in Fig. I ;,,...,. , I -s;a.. . "."..,," . 6(A). L_- ;:." . 1 ! <';,,''.','" . {. ,.:.." vI ~(, . Soon after the southern section :"\ --- "3,7- --0- attained its full production of 4320 tjd, the central area, shown SECTION ACROSS DRIFTS dotted in Fig. 5, collapsed. Con- certed and continued drift-repair efforts over several years failed to B regain this area, as pressures and weight were excessive. As short lengths of drifts were regained, excessive pressure crushed the con- crete lining of the drifts almost overnight, and finally all regaining /.3.7"" work in this area was abandoned. In 1964 work was started to SECTION ACROSS DRIFTS bring the northern half of the 580 m level into production as the ore C reserves in the southern half were nearing depletion. All the drifts in the northern half had to be recon- structed as they had deteriorated severely since initial installation. Then, when undercutting of this ,-.:, --- 7-- -:- section was started, it was decided to leave a pillar, not undercut, in SECTION ACROSS DRIFTS the centre, approximating to the Fig. 6 area that had collapsed in the southern section. This proved to be a costly decision.

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Fig. 7

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 253 As full production of the northern lining as strong as possible to large lumps that block the top of the section was being reached, the withstand the peripheral stress on cones on the undercut floor horizon central pillar became a focus of the drifts. and require the 'action' crews to intense pressure. The ends of the In the first category, it was ob- enter the drawpoints either to drill drifts adjoining the pillar were viously desirable to site the undercut and blast the lumps, or to place pushed back laterally, sometimes horizon as high as possible above large pack blasts to displace the at the rate of a few millimetres per the drift horizon commensurate with lumps. Cone geometry could also day, and intense top and side pres. practical production requirements. be varied. They could be sited so sure on the drifts occurred approxi. Also, if the undercut could be stoped as to converge over the drifts, mately halfway between the pillar prior to the installation of the leaving a pillar between the drifts and the rock contact. Determined drifts, undercut abutment damage (Fig. 6C) or be located between efforts to advance to the pillar in to the drifts could be avoided. It was drifts so as to leave a pillar over order to undercut it failed. At the decided to increase the undercut the drifts (Fig. 6B). The latter same time, a large number of drift. floor height from 6 to 10 m, as it problem was submitted to the De- repair crews made little progress was felt that 10 m was the limit of partment of Mining of the University in repairing the damaged drifts. Ore height at which 'action' work could of the Witwatersrand, who carried reserves on the southern section be effectively carried out. 'Action' out photo-elastic stress studies with were running out, and call product. work is the name given to the opera- plastic two-dimensional models of ion could not be achieved on the tion of breaking or bringing down the two layouts. These studies northern section. The call production was then reduced from 4320 to 2540 tjd, and plans were made for a rescue operation. Installation of Sub-level Caves It was decided to construct small block. cave sections below the central collapsed area of the southern section on the 595 m level, and below the pillar area of the northern section on the 610 m level, to recover the lost ore reserves in. these areas. On the south side it was decided to make use of existing ventilation level development for the undercut horizon on the 585 m level, with the drifts on the 595 m level, and to elevate the ore by incline to the ,/)/"!",c T/O,.., ~,.:: ..I., .-:>PG' 580 m level haulage. tC"'~C6 .~J)VANCI!: Because of the intense pressure exerted by the pillar on the north side, it was decided to site the sub. cave lower down, with the undercut on the 600 m level and the drifts on the 610 m level, 30 m below the ;;- 580 m level drifts. There the ore . would be conveyed horizontally to an existing ore pass, No. 10, in POlAN OF STOPE PANELS the country rock. The plan and section view of the sub. caves is shown in Fig. 7. At the same time, some radical re. thinking took place in the design and procedures for block caving.

Summary of Changes in Design and Procedures The approach to the weight prob- lem was two-pronged: firstly, to design a system where the weight on the drifts would be minimized, SECTION ACROSS STOPE FACE and, secondly, to make the drift Fig. 8-A typical stoping layout

254 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY clearly indicated that stresses on Because of the weak nature of the to carry Granby cars was completely the margins of the drifts would be kimberlite, drifts were initially de- impracticable. In addition, in the much lower where the cones con- veloped as pilot tunnels 1,4 by conventional block-cave system, all verged over the drifts (Fig. 6C), and 2,1 m across the pipe and then sliped lumps of ore that could pass through this layout was adopted. for concreting to 3,5 by 3,3 m. the drawpoints (1,2 by 1,2 m) Stoping of the undercut operation Sliping was carried some 10 to 12 m could be handled by the scraping could be carried out by breast- ahead of the finished concrete, and tramming equipment, and were stoping panels of suitable width which permitted a 5 m long concrete eventually reduced in size by the and scraping the broken ground shell, I m thick, to be poured on an large underground crusher, so back to ore passes situated in the existing concrete floor together with avoiding the necessity of costly country rock. As the kimberlite in a further 5 m concrete floor ahead grizzly blasting. If this feature was the Kimberley mines is compara- of it for the next shell. The inside to be retained, and this was most tively weak and incompetent- dimensions of the finished drift were desirable, conventional conveyor crushing strengths vary from 15 1,72 by 1,83 m. Special attention belts could not be used for the to 85 MPa with 55MPa being con- was paid to obtain smooth-blasted transport process. sidered a reasona ble average--it periphery in the sliped portion, It was decided to equip the was considered advisable to limit and roof-bolt support was in- transport tunnels with heavy-duty face lengths to about 30 m, and to stalled to prevent fall out. Panzer or armoured conveyors, as induce early caving behind the face Drifts were sliped to a normal used in longwall coal mining in by drilling and blasting 5 m hanging- arch shape, and the concrete filling Europe. Although expensive in initial wall wrecking holes at 50° into the was also arch-shaped. Special efforts cost, these proved to be extremely hangingwall. Stope width was 1,7 m. were made to obtain a complete successful for the purpose required. Fig. 8 shows a typical stoping concrete fill to the roof of the They were robust and could handle layout. Special attention had to excavation. The shuttering was all the large lumps delivered by be paid to dense mat pack and prop changed from the early monolithic the scraper scoops, as well as being support close to the face to prevent type to a simple shuttering of small economical to operate. The Panzer hanging collapse at the face, and plates supported on standard rigid conveyor on 610 m level is shown to complete removal of support arches. The monolithic type became in Fig. 13. behind the face where hangingwall very difficult to install because of wrecking was carried out. Under- early distortion due to normal wear Production from the Sub-level cutting by stoping was completely and tear. Although arch-shaped Caves successful and eliminated all abut- drifts were considered desirable in Production commenced from these ment damage to drifts. In addition, earlier practice, they could not be two sub-level caves (595 m and pressure on drifts prior to con- attained because it was not always 610 m) some 18 months after the creting was considerably reduced as possible to control the profile of start of the whole operation. the undercutting tended to de-stress the sliped excavation in the weak Initially, six drawpoints in each the drift horizon. kimberlite, nor was it possible to drift in line were opened for pro- In the second approach to the fill to the roof with concrete that duction. Drawpoints were 5 m problem, pneumatic placing of the was pneumatically placed into the apart, and thus the width of the concrete was replaced by pumping, shuttering. Fig. 11 is a view of producing strip was 30 m. No to avoid segregation of the concrete shuttering in place ahead of com- problems were encountered. After and to enable a concrete of lower pleted concrete, but with the front pulling from the strip for about water-cement ratio, and hence masking removed. Fig. 12 shows a two months, during which a cushion greater strength, to be transported. completed drift. of broken ground built up above the Samples of the aggregates were One further problem had to be producing drawpoints, the strip was submitted to the Portland Cement overcome in the design of the two slowly moved across the pipe, by Institute, who designed the requisite sub-level caves: the transport of the first closing the rear drawpoint and mix for pumping, to achieve a ore from the 595 m drift to the then opening the next drawpoint minimum 28 day strength of 44 580 m haulage for the one cave, and in front of the strip. Mter a further MPa. Strict quality control was from the 610 m drifts to No. 10 two months of production in this maintained on the supplies of pass in the country rock for the position, the process was repeated, aggregates by sieving analyses, and second cave section. As the transport so that gradually the producing on the quality of concrete by slump tunnels in both cases were situated strip was moved across the whole and cube tG3ts. A double-acting in the weak kimberlite, and the cave area. This rescue operation concrete pump is shown in Fig. 9, finished tunnel would require a proved to be completely successful. and diagrammatic sections of a I m thick concrete lining, there was No damage occurred, and the pro- batching plant and the supply of obviously a limit to the size of the duction from these small layouts aggregates and cement are given in raw excavation that could be sup- reached 1600 tjd, when the total Fig. 10. Aggregate supplies were ported and adequately controlled production from the mine was stored above the pump and fed prior to concreting, and hence to suspended for a few years because to paddle mixers by modern auto- the finished size of the concrete of a recession in diamond sales. mated weight-batching equipment. tunnel. Obviously, a finished tunnel It was evident that all the ore re-

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER1975 255 Fig. 9-A double-acting concrete pump

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256 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY Fig. I I-Concrete shuttering with front masking partially removed

Fig. 12-View of a completed block-cave drift JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 257 to embody the successful features of the sub-caves. As the schist country rock on the 700 m level was less competent than the kimberlite, it was decided to use Panzer conveyors in concrete-lined tunnels in the kimberlite as ore conveyors, instead of trolley locomotive traim in the country rock. Accordingly, the arch- lined haulages in the country rock were concrete lin0d to form circular access tunn'31s, the existing con- ventional access tunn01s were waste filled, and Panzer conveyors were installed in concrete-lined drifts in the kimberlite 10 m below the pro- duction drifts, with short passes equipped with chain-link doors feed- ing down from the production drifts. Production drifts 15 m apart were installed across the pipe from the now-circular concrete-lined access tunnol, after the undercut had been stoped. The drift layout is shown in plan in Fig. 14, and Fig. 15 shows the plan view of the Panzer transfer level. Fig. 16 shows a section through the tramfor pass. Initia] production from this cave had just commenced when the production of the mine was suspended, as mentioned above. However, no serious problems are envisaged when production is again commencod from this section.

760 m Layout, Dutoitspan Mine The main development of the Fig. 13-View of a Panzer conveyor on 610_m:level.:Bultfontein Mine 760 m block cave layout at Dutoits- pan was being carried out slightly s~rves lost in the centre of the 580 m granite gneiss, soon changed to a ahead of that of the 700 m at level would be successfully recovered. very incompetent chlorite-talc Bu]tfontein. This was also a con- It should be noted that effective schist as the haul ages and accom- ventiona] layout. The country rock draw control, which is essential panying access tunnels on each side on the south side was a competent for optimum recovery of ore reserves, commenced to encircle the pipe. granite-gneiss, whereas that on the can be achieved only where weight Both haulages and access tunnels north side was a weak schist, can be controlled and severe drift were supported with yieldable steel although stronger than the Bu]t- damage avoided. arches, the haulages with 29 kg/m fontein schist. The north-side haul- age, access tunnels, and winch Change in Basic Design of the sections and the access tunnels with 16 kg/m sections, each spaced chambers had been supported with 700 m Block Cave 0,6 m apart. As this development yieldable arches. Although these Whilst the construction phase of proceeded, despite keeping the steel excavations appeared to be reason- the sub-level caves was in progress, arch support right up to the face, ably stable, it was decided to rein- development of a conventional block- it became increasingly evident that force them with concrete after the cave layout on the 700 m level, these excavations would not remain experience with the Bultfontein 700 Bultfontein was proceeding. The sufficiently stable to serve as extract m layout. The haulage was lined haulage from the main shaft to the tunnels for the 700 m production. with a 0,75 m thickness of concrete pipe had been completed, and the It was at this stage that the design inside the arches, permitting just haulage tunnel together with the ac- of the 595 m and 620 m sub-caves sufficient clearance for the operation cess tunnel round the pipe was being and the operation of the Panzer of 6 t Granby cars, but not the developed in the country rock. conveyors were seen to be entirely 6 t trolley locomotives. These trains However, the country rock from successful. Accordingly, the design would be hauled by battery loco- the shaft to the pipe, a competent of the 700 m layout was changed motives. The winch chambers were

258 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY :Z(f~

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Fig. I4-Plan of 701l~m block cave,:Bultfontein Mine

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S'cP,s-r Fig. IS-Plan of 710 m Panzer transfer level, Bultfontein Mine also concrete-lined inside arches, level shows the lobes to have coal- facilitate any future automation but not the access tunnels. The esced into one pipe body again. of the trains. latter were heavily injected with Initially, the layout was designed The general layout in the cave Colgrout. The layout is shown in with a single haulage tunnel be- system itself was not changed. Fig. 17. tween the pipe and the main shaft, However, the following innovations but the necessity for hauling large were introduced. 785 m Layout, Wesselton Mine tonnages ultimately (about 8300 t/d) (a) Pozzolith was used as an addi- The drift and haulage layout is required the addition of the line tive to the concrete. This re- shown in Fig. 18. As can be seen, connecting the shaft with the north- sulted in an increase of the the pipe was split into three lobes, ern part of the pipe, thus completing final minimum 28-day strength but it is of interest that primary the haulage loop and making it from 44 to 54 MPa. sampling development on the 930 m uni-directional. This would also (b) On completion of the con-

JOURNAL OF THE SOUTH ,AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 259 ",,'V'?,,' .In"'.I",,')'u,,,;' .1/"'" """/<1 ~(/./'."",""".I' """'. 1(.~ ,', --(J..""',.,.._a/~"~'-"'~"'"- ~'-"'~ '. ""

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260 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY , ..."."., 7>

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Fig. If-Layout of proposed 745 m block cave, De Beers Mine

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 261 creting of a drift, grout was (e) Klockner-Ferromatik Hydraulic horizontal ore storage has been injected into the roof of each Props were introduced as face provided on the same level as the shell to ensure a complete fill support, instead of mat packs. underground crusher, and the ore between the concrete and the Three rows were installed 1,5 m will be reclaimed from below the kimberlite. apart, and props were 1,5 m horizontal storage bins by a Panzer (c) All block-cave haulages in the apart. These were successful conveyor that feeds onto an in- Kimberley mines had been and saved timber and labour. clined Panzer conveyor, delivering equipped with 6 t Granby cars However, in friable ground, the ore into the crusher. This crusher and 6 t trolley d.c. locomotives. especially near the rock con- treats the ore from the existing It was decided to equip the tacts, mat packs had to be production levels on the 500 and Wesselton haulage with 10 t used as well. 620 m levels. If conventional storage Granby cars and 10 t a.c. (f) A light two-boom drill rig has in passes above the crusher had trolley locomotives. recently been introduced and been adopted for the new layout, (d) In the stoping operation, the is being used to complete the an additional crusher and access 5 m wrecking holes drilled into haulage loop. cross-cut from the shaft would have the hanging and blasted 8 to 1Om (g) A complete investigation was been required. The 745 ID level has behind the face were discon- made into full automation of been estimated to be the economic tinued. Instead, the stope was the haulage (driverless trains cut-off level of this section of the carried 1,9 to 2,0 m wide, and and remote control of filling pipe. 1,5 m holes were drilled at 50° and tipping). However, the cost The 745 IDhaulage from the shaft into the hanging behind the of automation is not economic was commenced with a two-boom face. These were designed, not at present wage levels. medium drill rig (Fig. 20). After to 'wreck' the hanging, but to initial training of crews and teething break an additional 1,0 m from 745 m Layout, De Beers Mine troubles, the development has settled the hanging and so increase the This is the most recent of the down into a smooth operation. The stope width. This led to more block-cave systems, and the pro- rig is operated by three .:Bla.cks,. sta ble face conditions and would posed layout is shown in Fig. 19. who also carry out the complete induce earlier caving. A feature of this layout is that cleaning operation with a front-end

Fig. 20- Twin-boom pneumatic drill rig used at De Beers Mine

262 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY loader and Granby cars. On a three-shift operation, the 3,5 by 3,4 m haulage is advanced 5 m per day. It is also intended to carry out the development around the pipe, haulage, access tunnels, and drifts in kim berlite with the smaller drill rig at present in use at Wesselton.

Research Investigations The Mining Department of the cv University has taken a keen interest in a number of aspects for improving the block-caving system, during the course of which they developed a sophisticated and effective stress- MWAD'J, ,'RAPA TAlAlA CONGO strain measuring instrument. As mentioned for the Bultfontein sub- level caves, stress distributions 0 around drifts for different cone con- D \"\ figurations were measured using the ~G V(/'eJ photo-elastic stress technique. The results led to the adoption of a PREM'ER ZARR'!SA FINSCH lETSENG KOFFIEFONTEI configuration that has proved highly successful. 8 rP0 At present the Rock Mechanics ~~~WEOCELTON Department of the University is JA,ERS

Fig. 22-Aerial view of Finsch Mine

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 263 which would be cut by a mechanized years. It became obvious that Koffie- plant have been reduced, the rig. The technique of finite element fontein would not be mined through- number of men employed on second- analysis is being used to compare out its life as an open pit, and ary breaking being reduced from this proposed configuration with the major planning exercises were initi- four to one. existing successful one. ated to cater for the eventual drop Selection of Equipment down to an underground mining General Statistics operation. Nevertheless, in the opera- During the past decade there has tion of the open pit, the equipment, been a tendency to move towards Output per White final slope angles, and the ultimate larger-capacity equipment. The pri- underground shift 318 t open-pit bottom require constant mary advantages in this escalation Output per Black re-assessment. This extremely in size have been a reduction in the underground shift 20 t interesting phase in Koffiefontein's number of units required during Output per man (Black life will extend until about 1981, any specific phase of the life of the and White) 19 t when the transition from open-cast pit, and an increase in the rated Output per case of to underground mining will be duty of units such as drill rigs. Thus explosives 250 t complete. the number of operators has tended Output per winch per to decrease, the maintenance re- shift 100 t Equipment quirements have tended to become Cost per centare stoped R17,00 easier, and the traffic density in Cost per cone developed R300,00 The equipment currently used at the pit has fallen. Cost per metre of Finsch and Koffiefontein is as However, larger units have some concrete drift R250,00 shown in Table 1. Cost per tonne, including TABLE 1 treatment and general EQUIPMENT USED AT FINSCR AND KOFFIEFONTEIN MINES expenses R2,60 Finsch Koffiefontein Drilling 4 rotary drill rigs 6 rotary drill rigs 2 rotary percussive drill rigs OPEN-CAST MINING AT Loading FINS CH AND KOFFIEFONTEIN 1 6 yd3 electric shovel 4 6! yd 3 electric shovels 3 4,5 yd 3 electric shovels 4 10 yd 3 front-end loaders 1 10 yd 3 front-end loader Finsch Mine has now .been in Hauling production for almost eleven years, 10 70 t haul units 11 70 t haul units during which 43 000 000 t of waste 7 50 t haul units 5 35 t haul units rock have been removed and Service and Sundry 24 000 000 t of diamondiferous ore 1 crawler mounted dozer 1 crawler mounted dozer 2 rubber-tyred dozers 3 rubber-tyred dozers have been treated. The pipe is roughly 3 graders 2 graders circular and is approximately 500 m 2 water carts 2 water carts in diameter with a surface area of 1 padding truck 1 padding truck 1 explosive truck 1 explosive truck 17,9 hectares. The size of the Finsch 1 Anfex truck 1 Anfex truck pipe relative to other major pipes 1 hydraulic breaker mounted on a can be seen in Fig. 21. hydraulic excavator. The mining layout is a series Where possible, standardization of disadvantages such as a reduction in of 12 m benches, which were origin- equipment has been attempted, the flexibility of the operation, and ally cut at an extremely shallow although in certain instances this the mismatching of the larger units angle but which have gradually been has not been possible owing to with permanent or semi-permanent steepened to an angle of 45 o. The poor delivery dates. equipment such as the treatment shape of the pit is polygonal, An interesting development has plant and the shovel fleet. It is roughly approximating the shape been the recent introduction, at extremely important, therefore, to of the pipe (Fig. 22). To eliminate Koffiefontein, of a hydraulic impact consider the entire system in which the number of corners inherent in breaker mounted on a hydraulic a unit will operate, and not the unit a zig-zag roadway, an 18 m width excavator (Fig. 24). One of the in isolation. spiral roadway has been laid out major problems at Koffiefontein has The present selection techniques at a gradient of 8 per cent (I in been the poor fragmentation of the are based on three broad factors: 12). To date, the pit has reached dolerite and the soft kimberlite, (I) operational effectiveness or 'Will a depth of 148 m below the surface. resulting in a disproportionate it work in the situation?' Koffiefontein Mine was re-opened amount of secondary blasting. Until (2) operational efficiency or 'How in January 1970 after having lain recently, this duty was carried out much will it cost?' dormant for 40 years. Since then, by rotary percussive drill rigs and (3) distributor service or 'Will spare 37000000 t of waste have been has been expensive in terms of men parts and technical advice be mined, and II 000 000 t of ore have and materials, and disrupting to available from the distributor/ been treated (Fig. 23). Initially, the pit cycle because of blasting and manufactured' . Koffiefontein was regarded as a the consequent dozing of fly rock. To effect this type of technique, the marginal proposition, but more re- The introduction of the hydraulic units under consideration are studied cently viable reserves have been impact breaker has boon very im- by three departments: the Mining, proven for a life in excess of twenty pressive. Delays in the pit and Engineering, and Operations Re-

264 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY Fig. 23-Aerlal view of Kofflefonteln Mine

Fig. 24-Hydraulic rock breaker used instead of secondary blasting JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 265 search Departments. made to sub-divide the mining used the 'ratio of areas' rule, which The Mining Departm~".,is re- sequence into four main stages. propounds that quired to comment on the operation The first stage involved mining (i) the instantaneous stripping ratio of each unit. Where possible, per- within the ore body, and thus no is equal to the l'~ip of the sonnel are sent to look at each unit stripping was involved. The second respective plan areas of waste under operational conditions to pick stage required waste stripping to stripping and ore mining, and up information on performance and be carried to final pit limits, the (ii) thus, if the surface waste strip- general characteristics. The slope angle being kept fairly shal- ping limits are fixed, the instant. Engineering Department is required low (approximately 22°). During this aneous stripping ratio is the to comment on the probable main- stage it was envisaged that work same whatever pit slope is tenance costs based on previous would be carried out to determine taken. experience, interpolation of results the final slope angle. The stripping As the area of the orebody was achieved by others, and a knowledge ratio was fixcd at 1,37 to 1, which known and the economic stripping of stores holding and workshop was comiderably highcr than the ratio (the value of the imtantaneous facilities. The Operations Research minimum stripping ratio and stripping ratio when the cost of Department is required to analyse allowed a margin for error. The open-cast mining is equal to the the information and simulations third stage necessitated the mining cost of underground mining) could received from manufacturers and back of the waste benches to the be calculated, then the total sur- identify any significant differences final limits set by the slope angle, face area of waste stripping could in unit performance or cost. and stage four was the mining be determined. The final slope angles o The most important selection in back of the flat ore benches to the were assumed to be 45 in waste and o the future will be that of haul units. maximum safe ore slope angle. 35 in ore, and the ultimate open-pit depth was estimated to be 275 m. The shovel fleet is relatively young so The mining pattern has followed The significant factors in the that, unless the decision is taken to the original plan fairly closely, but purchase shovels with larger bucket during the past two years the major determination of final open- pit depth capacity, it will probably not re- disadvantage of mining to an average are the final slope artglegoitnd the quire replacement. Similarly, the stripping ratio, that of a detrimental relative costs of open-pit and under- ground mining. Costs are a con- drill fleet is young, with an a1/:erage cash flow, has become accentuated age of 2000 hours. The ha1l1 fleet, by spiralling rates of inflation. This stantly changing variable and however, requires continual replace- disadvantage is compounded by necessitate continuous updating of the pit- bottom calculatiom. ment, and an exercise is currently indications that the final safe slope Currently, work is under way on being carried out to determine the angle may be as steep as 60 o in a detailed examination of the pro- truck best suited to the operation. the ironstone. Thus, the stripping perties of the country rock in an The boundaries of the system in ratio has been gradually reduced attempt to obtain more accurate which these haul units will operate to the present ratio of 1 to 1 and yd3 (approximately 9 t) are the 4t could be reduced further when cur- estimates of the final slope angles electric shovels and the 450 t/h rent investigatiom determine the that can be achieved in the waste treatment plants, limiting the choice final slope angle. cuts. The major areas of investiga- to the 50 to 70 t range. tion are the detailed mapping of the As this ratio is reduced and the joint planes and core drilling to cash flow enhanced, there will, of establish the nature of passage beds Development of a Stripping course, be a price to pay in loss of that are known to exist between the Philosophy flexibility in the mining sequence ironstones and underlying dolo- and the possibility that ore pro- mites. When Finsch Mine was originally duction could be lost if waste planned, considerable thought was stripping were held up. Another Economic Open-pit Depth at given to the rate at which waste disadvantage will be the requirement Koffiefontein stripping should be effected. The of an increasingly large haul fleet choice lay between the two extremes as the pit deepens. The mining sequence at Koffie- of mining each waste bench to its The final decision will probably fontein was complicated by an final limit before commencing the be a compromise that will follow the already-existing excavation, and the mining of the underlying bench, or lead given by the original planning slope angle of the excavation was, stripping at the instantaneous strip- team. However, it should be possible in effect, the failure angle of the ping rate, which means mining only to reduce insurance margins because country rock. Thus, the open-cast enough waste to liberate the ore of improved knowledge of the pro- mining of Koffiefontein was planned required. The problem was made perties of the country rock, and in three distinct phases or cuts more difficult by the fact that the experience in the mining operation. (Fig. 25). final slope angles, and thus the The dimensions of the first cut ultimate pit configuration, could Economic Open-pit Depth at were a minimum, commensurate only be guessed. To gain experience Finsch with haul road requirements and in the necessary mining techniques the configuration of the original and to allow time to establish the Initial exercises to determine the open pit to enable ore production final slope angle, the decision was ultimate depth of the open pit to commence at the earliest possible

266 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY 12.

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date.The first waste cut was com- is reached. This would cause mass- update the exercises when signifi- menced in January 1970 and was ive dilution of the ore in the under- cant changes in parameters are completed in February 1972. The ground mine and the possible failure encountered. removal of 17000000 t of waste of underground drives due to the Other areas of inve3tigation at exposed 12 500 000 t of ore. The impact of rimrock falling onto the present being pursued are the de- second waste cut, which dovetailed workings below. velopment of an automated product- into the first cut, commenced in A possible method of dealing ion reporting system that will in- October 1971 and was due to be with the shale band would be to clude the maintenance of the earth- completed in May 1975. This cut seal it, but this would pose the moving fleets, and the development was to remove 18 000 000 t of waste problem of access to the band in of a computerized ore-reserve to expose a further 11 000000 t of the near vertical pipe. If current system. ore. The third waste cut, which was investigations indicate that the waste started in September 1974, will be benches could be carried at a steeper UNDERGROUND MINING AT completed in December 1977 and angle than the present 450, it would KOFFIEFONTEIN will remove 24 000 000 t of waste be possible to adjust the mining Initial exercises indicated that to expose 9 000 000 t of ore. pattern below the 76 m level to the economic open-pit bottom at Work is currently being carried out allow the shale band to be carried Koffiefontein will be the 240 m to determine the critical slope angle in the deeper waste' benches. This level, which will be reached in for the Koffiefontein pit. The prob- would also allow access to the 1981. In mid-1973, initial planning lem is not the normal slope-stability adjacent granites, which might re- for the change-over from open-pit problem in that, in most stability quire anchoring. The determinant to underground mining began, one calculations, the slope is allowed in this problem will be the economics of the first steps being the considera- to fail when open-pit operations of deepening the pit versus the cost tion of various mining methods for have ceased. At Koffiefontein, the of rim failure. the Koffiefontein pipe. slope must remain stable while the Block caving and sub.level pipe is being mined underground. Future Developments in Open- pit Desi~n stoping, which are the main methods Thus, it could be required to stand used in the Group, were considered for up to 30 years after the closure To date, all the calculations for first. Block caving is a relatively of the opencast operation. pit design and pit bottom have been simple mining method and allows a The problem is further compli- done manually. The results achieved moderate degree of mechanization, cated by the fact that an unstable for any set of parameters are and its use at Koffiefontein would shale layer was detected during the adequate, but, owing to the com- mean that any future refinements sinking of the main rock shaft. plexity of the calculations, only two could be used in the Kimberley According to present planning, this or three of the many variables are Division. Unfortunately, the rela- shale layer will be intersected in taken into account, and the exer- tively large area of the Koffiefontein the near vertical side of the pipe, cise tends to be updated at in- pipe and the high daily tonnage call and slaking tests indicate that the frequent intervals. mean that the amount of pre- shale will weather and fail. This To overcome some of these prob- production construction would be failure could cause failure of the lems, a computerized open-pit de- immense. A total of 74 scraper drifts overlying and underlying granites, sign system is to be introduced. would be required, and, to utilize this which would cause erosion of the The system will be used to re- number of winches, the pipe would rim of the pipe until the natural valuate the work already done at have to be bisected with a central angle of repose of the country rock Finsch and Koffiefontein, and to access tunnel. To improve loco-

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 267 motive utilization, the simple china- The Long-hole Chambering of approximately 3000 t capacity. man boxes would have to be replaced Method ]'rom these passes, short belts will with ore passes in the kimberlite. A feed the ore to the measuring flasks Production levels will be developed further problem would be that the (Fig. 28). at 30 m vertical intervals, beginning ventilation requirement of 190 m3fs just below the open-pit bottom. would need large-section tunnels Feasibility Test Each level will consist of an access that would be difficult to keep open tunnel driven around the rim of the Before the adoption of the long- under the pressures developed by a pipe in the country rock (Fig. 26). hole chambering method to mine cave. Finally, rain falling in the From this access tunnel, 18 parallel the Koffiefontein pipe, a feasibility open-pit catchment area, without drilling drives will be developed test was set up in the Koffiefontein any overburden to soak up this at 18 m centres across the pipe. At open pit to determine moisture as in the Kimberley under- right angles to these drives, a slot (a) the viability of developing com- ground mines, would percolate will be developed across the other petent 3,4 m by 3,4 m drives in through the broken kimberlite and axis of the pipe. This slot will break kimberlite, cause serious ground-handling pror- through to the level above and will (b) the viability of developing a lems. provide a free breaking face for the breaking slot, The second method considered blasting of a fan pattern of long (c) the type and make of units was the sub-level stoping method holes (Fig. 27). The fan is designed best suited to the operation, and used with success at the Premier to form a continuous cone along (d) the timing of the various sec- Mine, which lends itself to a large the line of the drive that will tend tions of the production cycle. pipe and also to large production to funnel the broken ground to the During the test a variety of tonnages. However, the method is 'low point' to facilitate loading. It equipment was used to drive a fairly labour-intensive and would has been estimated that each fan 3,4 by 3,4 m tunnel for a distance tend to preclude a high degree of blast will liberate approximately of 50 m under a 17 m lip. Thereafter, mechanization. In addition, the 3600 t of ore (25 per cent of one a slot was established at the end of Koffiefontein kimberlite is much day's production). the tunnel, and a series of fans was softer than at Premier, which would The broken ground will be trans- drilled and blasted into the slot from result in excessive wear at the ported by rubber-tyred load-haul- the tunnel, the broken ground being brows of the grizzley levels and dump units via the drive to the rim loaded and trammed away via the necessitate extensive support and access tunnel and will be tipped tunnel. maintenance of these brows. into one of eight ore passes, which The long-hole chambering method A third mining method known as will be vertical raise-bored passes was found to be acceptable because long-hole chambering has been prac- developed from the 52 level via of the following. tised at Wesselton Mine for about all the production levels to the (a) The construction period re- five years. The method is a refine- 28 level. Ore transport on the main quired for initial production ment of the extremely labour- haulage level will be by 20 t cars falls well within the economic intensive chambering method, and pulled by electric locomotives. The life of the open pit. has been brought to a greater degree ore will be tipped into primary (b) A very rapid build-up to full of efficiency by the use of modern crushers sited near the main shaft production can be achieved. trackless-mining equipment. and will gravitate into storage passes (c) The method is highly mechan-

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268 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY '] ~

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Fig. 27-Diagrammatic view of production drilling and blasting-Koffiefontein proposed underground-mining method

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 269 -.','0-,' !: ~_u , , "~~~:" ,r / 1\ --~ "'... !! ,...,rlf ~- OPG" ..,,"',' .s' IM- li &0",. 'i

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Fig. 28-Section through the mine-Koffiefontein proposed underground-mining method

ized and is not labour-intensive, hydraulic drifters have been ordered. of air per rated horsepower of the (d) The method is flexible. If pro- Hydraulic drifters were chosen in production units. With the provision duction experience indicates preference to pneumatic machines of a 30 per cent safety margin, the that the vertical interval be- because of their superior efficiency total volume of air required will tween loading levels is too and to improve environmental condi- be 425 m3Is. The intake air will be small, the level spacing can be tions at the drilling face. They will split into two main streams: ap- increased without any disrupt- also avoid expensive and inefficient proximately 140 m3/s will be brought ion to the production effort. compressed-air reticulation systems. into the 28 level, which will be the (e) No return ventilation shaft is The rigs will be able to drill an top production level connected to required, all the return air elliptically shaped tunnel 28,5 m2 the shaft, and the remaining 285 m3/s being exhausted into the open in area from a single set up. The will enter the mine via a special pit. booms are equipped with a parallel airway on the 52 haulage level and (f) The effect of rain can be holding device, and the rig has the will then be carried up two 3,7m minimized by leaving the wet ability to drill fans and roof-bolt diameter raise-bored airways to broken ground, and drilling and holes. Six diesel-powered load- the 28 production level and sub- blasting fresh dry ground. (This haul-dump units fitted with 5 yd3 sequently to the underlying levels is a major consideration, and buckets have been ordered to handle as they come into production. Each possibly the overriding one.) the loading and hauling duties during drilling drive on the production (g) Pressure problems on drives the development phase. levels will be equipped with a plug- and tunnels should be minimized Production fan drilling will be in fan so that a quantity of 8,5 m3/s as the deeper tunnels lie in the carried out by means of electric can be exhausted from each opera- country granites and there drill rigs carrying hydraulic drifters. ting end. The return air will be should never be more than 90 m On the top level it will be necessary exhausted to the open mine via of ground overlying the drives to blast up to nine fans per day raise- bored ventilation passes and in kimberlite. owing to a low initial recovery of the worked out areas. blasted ground. This requirement All the water that falls into the Operation will drop to four or five fans per open pit will run into the drives All production and development day on underlying levels. To facili- developed on the upper production loading, hauling, and drilling, except tate inter-level movement, all levels levels. It is intended to concrete the hauling duty on the main including the main haulage level the footwall of these drives, and haulage level, will be effected by will be connected by a figyre-8 the water will be led from the drives self-propelled rubber-tyred units. For ramp, which will also serve as a to the rim tunnel and via a water the initial development phase, four major intake airway. pass that connects with all levels electrically powered rigs equipped Ventilation calculations have been to the main sumps on the 58 level. with twin hydraulic booms and based on the provision of 0,05 m3/s The sumps have been designed with

270 DECEMBER 1975 JOURNAL Of THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY a total capacity of 25 million litres, each year (approximately three In addition, works committees are and the main pumps will be capable weeks depending on rank) and are being formed to be followed by a of delivering 1 500 000 litres per therefore a permanent and stable co-ordinating works committee. The hour. The system will be able to force, allowing the Company to first committee has been elected, and cope with a 100 mm cloudburst spend far more time and money on the representatives have been trained over the open-pit catchment area. their training and development. to undertake their duties. Works Thus, the method will be highly Supervisors can become acquainted committees, as opposed to liaison mechanized, electric power and diesel with their workers as people, know. committees, were chosen because power being dominant. Compressed ing their names, their familyba.ck- more relaxed discussion will take air, for a change, will play a very ground, and their problems. This place when the representatives dis- minor role, being used only for main- is assisted by their knowledge of cuss matters within an all-Black shaft chute operation and other English or Mrikaans, which in body, and the resolutions that are minor work, for which it will be most instances is fluent. presented to management are more supplied by small individual com- It is intended to extend the con- likely to be their true feelings. It is pressors. cept of local labour at Kimberley, too early to expect these men to and a start has been made at Koffie- discuss their problems openly while MANAGEMENT AND LABOUR fontein, where a township exists. At sitting in awe of senior ;management. Improved methods of mining and Finsch, where there is no township, To improve communication 'down higher productivity in general call the problem is greater, but con- the line' to all employees, a system for higher standards of labour, sideration is being given to con- of briefing groups is to be established. supervision, and management, and veying local labour from a township Starting at the senior manager, each it is considered to be of value to 20 km away, or building a new man briefs the next level below him record the steps being taken in this township on the mine once approval on matters of importance and direction. from the Bantu Administration can interest at meetings held once a A management training pro- be obtained. month. The intention is that, if gramme was instituted in 1973, Localization, of course, creates employees are given correct and starting with top management, and new problems. Housing in the town- motivating information, 'grape vine' this has now progressed as far as ships very often is not up to a sources will be avoided together second-line supervisors (i.e., miners reasonable standard, and it has with the disputes and problems and artisans). Upon completion at been found necessary to start a that arise from misunderstanding. this level, the first-line supervisors building programme. De Beers is It is now accepted in industrialized (i.e., team leaders) will be trained. shortly to build 250 houses, which countries that communications up The value of using the same course have 3 bedrooms, a full bathroom, and down the line cannot be achieved material for all levels of manage- and all facilities. Since they have satisfactorily by the same system, ment is already apparent in that to be built in the township, private and that representatives of the all levels have clear objectives and ownership is not at present allowed; union or works committee, either understanding of the company they have to be given to the Bantu directly or via a consultative com- policy. Managers now feel free to Administration, but it is possible mittee, provide the essential 'up innovate within the policy para- to reserve occupation for Company the line' communication while a meters, making productivity schemes employees only. It is envisaged separate system such as the briefing more readily accepted and applied. that this building programme will group concept should provide the For senior staff, a more intensive have to be extended and that 'down the line' communication. and advanced management training houses at Koffiefontein will also be Other problems encountered dur- scheme is now being introduced that required. ing localization were absenteeism specifically deals with objectives, Localization emphasizes communi- and job expectation. organization, and motivation. This cation problems in that the accepted The former was a short-lived training will also be given to more hostel machinery falls away. Two although serious problem. Intensive junior managers. It is also planned main steps have been taken to counselling was required to instill to parallel this programme with overcome this problem. Blacks who a sense of responsibility into those training in social skills and inter- have graduated in the personnel who felt that taking a day off for personal relationships so that more field have been trained to take one of many reasons (drinking being value will be obtained from the senior positions in which they deal a particular problem) was not group management sessions. with their own people, including serious. It was here that the Black Great benefit is being obtained in training, selection and manning, graduates were particularly good Kimberley from the use of local welfare, and assistant personnel offi- at improving the attitudes of the Black labour rather than migratory cer positions. The division now absentees. After 18 months of labour. At present 1150 out of the employs eight graduates and, localization, the avoidable absentee 2550 Black workers are local men although they are essentially a part rate is less than 1,0 per cent, a who live in the Kimberley town- of management, they provide an remarkably low figure. ships, and these men are conveyed extremely effective and useful line The local men are in general, by the Company to and from work of communication with the Black relatively well educated, and they ex- each day. They take normal leave employees. pect more job satisfaction, not being

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY DECEMBER 1975 271 happy in menial or purely manual of pay and allowed a 30 per cent it seems to be essential that more work. Consequently, re-organization reduction in the complement. The non-Whites must be trained. of work and mechanization become introduction of rigs and larger CONCLUSION essential. They are also more aware loaders into development with a The mining industry will un- of differences in rates of pay and crew trained to do all the jobs also doubtedly present very great chal- the evaluated level of work, and increased productivity. This multi- lenges in the future. Working costs it was necessary to question the pay training of the workers is proving a are increasing at an astronomical rate for certain jobs. An added great success in all areas of the mines pace, and commodity prices, in complication is that the Company and plants. So far, 440 men out of general, are not rising as fast and is in a competitive market and has a trained total of 1000 have received in some cases are falling. Better to compete with the South African training in more than one job. methods, and increased efficiency Railways and other industry and To date 70 artisan aides have been and productivity are the only business in Kimberley. Of course, trained and introduced into the answers to this problem, and this this is not an unhealthy situation work situation. Acceptance of the in most cases means more mechaniza- provided the men are allowed to be aide is improving, and some aides tion and better utilization of the productive. are doing really productive work, labour resources available. The training of workers to do allowing the artisan to concentrate In conclusion, thanks are extended more than one job has significantly on the more highly skilled jobs. to De Beers Consolidated Mines improved productivity. In the block There is no doubt that the engineer- Limited for permission to publish caves, for example, a machine opera- ing field offers great scope for in- this paper. Thanks are also due to tor who drilled hang-ups and large creased productivity, and, with the Messrs Vertue, Clements, and Michie rocks in the drawpoints was also present shortage of artisans and the of De Beers Consolidated Mines trained to drive the scraper winch. large number of new mining and Limited who assisted in its compila- This put him into a higher category industrial projects in the pipeline, tion.

Company Affiliates

The following members have been Gardner-Denver Co. Africa (Pty) Ltd. Rooiberg Minerals Development Co admitted to the Institute as Com- Goldfields of S.A. limited. limited. pany Affiliates. The Grootvlei (Pty) Mines Limited. Rustenburg Platinum Mines limited Harmony Gold Mining Co. limited. (Union Section). AE & Cl Limited. Hartebeesfontein G.M. Co. Limited. Rustenburg Platinum Mines limited AfroxjDowson and Dobson Limited. Highveld Steel and Vanadium Corpo- (Rustenburg Section). Amalgamated Collieries ofS.A. Limit- ration limited. St. Helena Gold Mines Limited. ed. Hudemmco (Pty) limited. Shaft Sinkers (Pty) limited. Apex Mines Limited. Impala Platinum Limited. S.A. Land Exploration Co. limited. Associated Manganese Mines of S.A. Ingersoll Rand Co. SA (Pty) Ltd. Stilfontein G.M. Co. limited. Limited. Kinross Mines Limited. The Griqualand Exploration and Fi- Blackwood Hodge (S.A.) Limited. Kloof Gold Mining Co. limited. nance Co. Limited. Blyvooruitzicht G.M. Co. Ltd. LefHI'ings Ho1dings limited. The Messina (Transvaal) Develop- Boart & Hard Metal Products S:"A. Leslie G.M. Limited. ment Co. limited. Limited. libanon G.M. Co. limited. The Steel Engineering Co. Ltd. Bracken Mines Limited. Lonrho S.A. limited. Trans-Natal Coal Corporation Limic- Buffelsfontein G.M. Co. limited. Loraine Gold Mines Limited. ed. Tvl Cons. Land Exploration Co. Cape Asbestos (Pty) Ltd. Marievale Consolidated Mines Limit- & Tsumeb Corporation limited. Compair S.A. (Pty) Limited. ed. Union Corporation Limited. Consolidated Murchison (Tv') Gold- Matte Smelters (Pty) limited. Vaal Reefs Exploration & Mining Co. fields & Development Co. limited. Northern Lime Co. Limited. Limited. Deelkraal Gold Mining Co. Ltd. O'okiep Copper Company Limited. Venterspost G.M. Co. limited. Doornfontein G.M. Co. limited. Palabora Mining Co. Limited. Vergenoeg MiningCo. (Pty) limited. Durban Roodepoort Deep limited. Placer Development S.A. (Pty) Ltd. Vlakfontein G.M. Co. Limited. East Driefontein G.M. Co. Limited. President Stern G.M. Co. Limited. Welkom Gold Mining Co. limited. East Rand Prop. Mines limited. Pretoria Portland Cement Co. limIt- West Driefontein G.M. Co. limited. Envlrotech (Pty) Ltd. ed. Western Deep Levels limited. SaaiplaasG.M. Co. limited. Prieska Copper Mines (Pty) Limited. Western Holdings limited. Fraser & Chalmers S.A. (Pty) limited. Rand Mines limited. Wlnkelhaak Mines limited.

272 DECEMBER 1975 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

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