Fibra plastica

189The Journal of The South African Institute of Mining and Metallurgy JULY 2001

Introduction

De Beers Premier Mine has been looking atupgrading the underground support criteriathrough improved shotcrete mix designs,mechanization of support placement, increasedquality control and increased safety. Thereasoning behind the planned change ofsupport philosophy has been driven in part bythe swing-over of the BB1E undercut to anadvanced undercut with developmentfollowing in a de-stressed zone. Requirementsfrom the Premier Mines C-Cut have alsochanged Premier Mines support philosophy.The B-Cut and C-Cut development willsubsequently require support implementationto follow directly behind the development ofany excavation with the aid of a semi-automatic wet shotcrete machine. However, inorder to facilitate this change in supportphilosophy wet shotcrete has had to proveitself as a competent form of support that isable to marry itself successfully into thedevelopment cycle.

Kimberlite is hygroscopic and the waterused in the shotcrete mix is drawn out of theshotcrete into the kimberlite. This results indecomposition at the kimberlite/shotcreteinterface, weakening the rock strength of thekimberlite and nullifying or reducing theeffectiveness of shotcrete as an interboltsupport medium. The problem has beenaddressed by spraying a sealant onto thekimberlite as soon after development of anexcavation as possible. The sealant preventswater entering the kimberlite. The applicationof the sealant obviously adds time and cost tothe support cycle. If the wet mix shotcrete canbe designed to eliminate a need for the sealantat the interface this would be a considerableadvantage.

Wet shotcrete trialby A.D. Storrie* and P. Bartlett*

Synopsis

An underground wet shotcrete trial was completed last year todetermine the effectiveness of wet shotcrete as an alternativesupport mechanism to dry shotcrete in the kimberlite environment.The wet shotcrete was manufactured at the underground batchplants, transported to site using an agiecar and transferred to theshotcrete pump. The wet shotcrete is pumped to the nozzle wherecompressed air at 7 bar and an accelerator, Meyco SA 160, is addedand enables the shotcrete to be placed successfully onto the tunnelwall. No tunnel guard was previously placed on the sidewall andhangingwall.

Geotechnical testing indicates that the Grace fibre performedextremely well with the energy absorption tests at 7 kg/m3 and 8kg/m3 where both achieved over the mine requirement of 750joules. The Grace fibre and wet shotcrete mix also achieved acompressive strength in excess of 55 MPa, well above the 45 MParequirement for Premier Mine. The recommended wet shotcrete mixdesign is therefore based upon:

Material/ Criteria Quantity/m3 Units

Lafarge 42.5 Duratech 500 kg Condensed silica fume 40 kg Rayton Sand 1.558 Ton Delvocrete stabilizer 10 3.6 litres Glenium 27CH 5.4 litres Meyco TCC 735 5 litres Water 230 litres Meyco SA160 25 litres Fibre 8 kg Cement/Water Ratio 2.35 Water/Cement Ratio 0.43 Flow 615 mm

If the wet shotcrete system is implemented there is a potentialfor Premier Mine to make major savings. In South Africa there aretwo suitable wet shotcrete machines available for the miningindustry, the Spreymec, manufactured by Tamrock and theFermel/Meyco wet shotcrete machine. The Spreymec is a fullyimported machine. The Fermel component is manufactured in SouthAfrica and the Meyco shotcrete components are imported andsupported by MBT (Master Builder Technologists) in South Africa.The Fermel/Meyco machine is assembled in South Africa. PremierMine has allocated some R2,100,000 towards the implementation ofthe wet shotcrete system. If implementation is successful thereshould be an internal rate of return gain of 76% with regard to thisproject. * De Beers Premier Mine

The South African Institute of Mining andMetallurgy, 2001. SA ISSN 0038223X/3.00 +0.00. First presented at SAIMM Colloquium:Shotcrete and membrane support, Apr. 2001.

Wet shotcrete trial

Why wet shotcrete?

Although the dry shotcrete product is a third of the price ofwet shotcrete, wet shotcrete does have major advantages.The wet shotcrete advantages include: -

Rebound of the product is reduced to 510% with wetshotcrete, compared to 1535% with dry shotcrete

With dry shotcrete, rebound of fibre can be as high as35% compared to 510% for wet shotcrete

The dust created when placing shotcrete is significantlyreduced with a wet application compared to a dryapplication

Thicker shotcrete layers can be applied with wetshotcrete when doping products and accelerators areadded. Dry shotcreting does not allow for this benefit

Greater quality control can be achieved when manufac-turing wet shotcrete with effective cube test auditing ofshotcrete at the batching plant and on site. Follow upin situ core testing can also form part of the auditingsystem. With mesh and dry shotcrete used together, itis impossible to conduct core tests or manufacturecubes for compressive strength testing. Ultimately themine is solely dependent on the ability of the batchplant operator and the shotcrete nozzle operator forquality control

Flow testing the wet shotcrete mix at source gives goodquality assurance and control prior to dispatching theproduct for final placement

With dry shotcrete, due to variations in aggregatewetness prior to application, the water dosage is variedproportionally. Although the nozzle operator may beextremely efficient, the chance of error, resulting in theover or under wetting of the shotcrete is greatlyincreased. This deficiency will reduce the strength ofthe shotcrete

Both applications of wet and dry shotcrete lendthemselves to mechanization. The dry shotcrete systemrequires a greater infrastructure. Water pipes to sitewould be required for the final mixing of water withshotcrete on placement. Where possible water is notpermitted in a kimberlite environment due to thedecaying nature of kimberlite when water is added

The placement of wet shotcreting lends itself tomechanization and will therefore result in a reductionof overall cost through increased productivity

Dry shotcrete requires a large workforce to placeshotcrete support. Fewer people are required to place asimilar quantity of wet shotcrete

Less shotcrete is required with a wet application due tothe shotcrete following the profile of the tunnel. Withwelded mesh, large voids between the kimberlitesurface and the mesh are created. An increasedquantity of dry shotcrete is required to fill and coverthis void

A semi-robotic wet shotcrete machine does not exposethe operator to unsupported ground and is thereforeconsiderably more safe than Premier Mines current dryshotcrete operation.

Premier Mines shotcrete requirements

Added to the advantages indicated above, Premier Mine

primarily requires that wet shotcrete must prove itself as avalid and effective form of support in the kimberliteenvironment. The wet shotcrete process must also form anintegral part of the development schedule and cycle. Shotcretestrength requirement of 45 MPa and energy absorption rateof 750 joules is required. The energy absorption of the wetshotcrete is gauged according to the EFNARC plate test,which is designed to determine the energy absorbed from theload/deformation curve as a measure of toughness. This testis designed to model more realistically the biaxial bendingthat occurs underground at Premier Mine.

Wet shotcrete mix designs for Premier Mine

In the Greater Cullinan district there are two sand aggregatesuppliers. The one, Rayton sand, is presently contracted tosupply Premier Mine with sand. The other Richter sand haveno contract with Premier Mine. The grade analysis variesbetween Rayton and Richter sand, with Rayton producing thefiner of the two products, Examples 1 and 2 and Table I.After conducting a series of cube tests, it was identified thatthe coarser Richter sand is more suited to the wet shotcreteprocess, Table II.

190 JULY 2001 The Journal of The South African Institute of Mining and Metallurgy

Example 1Rayton sand grading analysis

SOILS & MATERIALS TESTINGP.O. BOX 227, MARAISBURG, 1700

SIEVE ANALYSISValues are expressed as a percentage

of the total sample

Client PREMIER MINELocation SHOTCRETE MIX DESIGNS (RAYTON SAND)Data 2000/06/09 Test No 459bJob No 20179 Checked By EB

GRADING ANALYSIS - SHOTCRETE AGGREGATES

TEL: (011) 674 1325FAX: (011) 674 4513e mail: [email protected]

Sieve TotalSize Passing(mm) (%)

37.50 100.0026.50 100.0019.00 100.0013.20 100.009.50 100.006.70 99.964.75 99.343.35 93.592.360 79.411.180 60.850.600 40.090.425 20.930.30 11.650.15 3.100.075 1.33

100

80

60

40

20

0

Perc

enta

ge P

assi

ng

0.01 0.1 1 10 100Particle Size (mm)

With Master Builder Technologists, one of the worldleaders in shotcrete technology, provided the additives inconjunction with Azalcons cementitious material andPremier Mines already established concrete deliverables. Tothis end wet shotcrete testing at Premier Mine was basedupon the following:

Lafarge 42.5 ordinary Portland cement Azalcon HT33 is a cementitious type hydraulic

hardening material consisting of selected fly ash,Portland cement special activators and additives

Delvocrete admixture is used to stabilize the hydrationprocess by forming a protective barrier around thecement particles

Glenium 27 CH admixture is added to reduce the water/cement ratio required in the shotcrete mix

Meyco TCC 735 admixture is added to enhance thequality of shotcrete in a plastic and hardened state.This ensures improved hydration characteristics andreduces the concrete shrinkage and increases binding,density and compressive strength

Meyco SA160 accelerator is added to accelerate theearly strength of the shotcrete while at the same timelimiting the decrease in final strength

Condensed silica fume 90 (CSF), an extremely finematerial and is a by-product from the silicon metalindustry and is used as a cementitious compound inthe shotcrete matrix. CSF acts as a filler and helps thehydration process and increases shotcrete density andstrength and reduces shotcrete rebound, permeabilityand the amount of water that can bleed from theshotcrete. CSF can be used in powder form, however, aslurry format is recommended for health reasons

Rayton sand Richter sand Synthetic Industry HPP S 50 Fibre, a 50 mm-length

monofilament polypropylene is manufactured withwaves throughout. The waves are designed to improvethe bonding between the concrete matrix and the fibre

Grace Concrete Products, Grace Structural Fibre, a 50mm-length synthetic polymer blend of polypropyleneand polyethylene. During the mixing process withconcrete the fibre fibrillates and deforms, creating agreater bonding area between the concrete matrix andthe fibre. The fibre has a tensile strength of 550 MPaand Modulus of Elasticity of 4.3G Pa.

The development of a successful wet shotcrete forkimberlite

Premier Mine has looked at various types of shotcreting inthe past with varying degrees of success.

The Azalcon wet shotcrete trialDuring 1999 a wet shotcrete trial with Azalconscementitious material, HT33, resulted in failure. The failurewas due in part to the use of an unskilled workforce inconjunction with an incorrect starting up and closing downprocedure with the wet shotcrete machinery. Due to thenature of the kimberlite and its ability to absorb water,Premier Mines policy has demanded that no washing downof surfaces be undertaken before placing shotcrete orimpermeable membrane. This hindered the trial considerablyby creating a dust interface between the shotcrete and thekimberlite and in turn contributed to the failure of theshotcrete as a form of support. The water content was notlocked within the shotcrete rapidly enough to prevent thekimberlite from absorbing the water and allowed thekimberlite surface to decay into a clay type surface. Thealready partially decayed nature of the kimberlite alsoresulted in the tunnel guard membranes, inability to renderitself effectively to the kimberlite to form a good bond. Toplace wet shotcrete an air pressure of 7 bar is preferred;during the trial an average mine air pressure of 4 bar wasachieved. This shortfall in compressed air resulted ininsufficient compaction of shotcrete onto the kimberlitesurface. All these factors contributed to the ultimate failure ofthe wet shotcrete trial, Figure 1.

Wet shotcrete trial


Example 2Richter sand grading analysis

SOILS & MATERIALS TESTINGP.O. BOX 227, MARAISBURG, 1700

SIEVE ANALYSISValues are expressed as a percentage

of the total sample

Client PREMIER MINELocation SHOTCRETE MIX DESIGNS (RICHTER SAND)Data 2000/06/09 Test No 458Job No 20179 Checked By EB

GRADING ANALYSIS - SHOTCRETE AGGREGATES

TEL: (011) 674 1325FAX: (011) 674 4513e mail: [email protected]

Sieve TotalSize Passing(mm) (%)

37.50 100.0026.50 100.0019.00 100.0013.20 100.009.50 100.006.70 99.474.75 90.843.35 70.372.360 55.931.180 43.680.600 37.550.425 30.400.30 18.990.15 5.720.075 2.57

100

80

60

40

20

0

Perc

enta

ge P

assi

ng

0.01 0.1 1 10 100Particle Size (mm)

Table I

Sand density details

Description Rayton Sand Richter Sand

Loose Bulk Density 1.555 1.692Compacted Bulk Density 1.672 1.881Apparent Relative Density 2.629 2.644

Wet shotcrete trial

Although the Azalcon trial was unsuccessful valuablelessons were learntit was important to build upon thisknowledge. For the Azalcon trial a worm and stator pumpwas used, Figure 2 and Figure 3. This worm and statorsystem is suitable for small contractor type operations butdoes not lend itself to a more automated and controlledenvironment. To develop Premier Mines understanding ofwet shotcrete a more professional approach had to be taken.To achieve a more professional approach shotcrete specialistshad to be utilized. Local aggregates with the best-knownadditives had to be used to develop various shotcrete mixdesigns before the underground trial began. To give thefuture trial the best chance of success the services of MasterBuilder Technologists, providers of shotcrete additives andshotcrete expertise were utilized. Geopractica, consultinggeotechnical engineers were used for the duration of the trial.Machinery, which lends itself to mechanization, automationand to Premier Mines environment had also to be utilized forthe duration of any future shotcrete trial.

The wet shotcrete pre-trialFollowing initial laboratory wet shotcrete design testing atGeopractica four mix designs were identified for theunderground pre-trial on a reduced scale; two linear metresper design, Table III. HPP S 50 fibre was used in all four-mixdesigns. Past experience with earlier wet shotcrete trials hadproved unsuccessful, it was therefore considered prudent toconduct the pre-trial before any major expense had been laidout.

The equipment utilized for the trial was also considered tobe of major importance. Without going to the major expenseof a completely automated wet shotcrete machine withonboard compressor, shotcrete pump and accelerator pump itwas necessary to utilize the complete range of machinery, a450 CFM diesel compressor, a Putzmeister shotcrete pumpwith an onboard accelerator pump, Figure 4. Premier Minesbatch plants, although suited to mixing concrete whilstutilizing a larger aggregate, are not ideally suited to mixingwet shotcrete. The concrete paddle bushes are well worn andtherefore have little resistance. This resistance is needed to

mix the sand at the extremities of the batching plant bowl.The result of this is that ninety per cent of the wet shotcreteis mixed by the batch plant whilst the remainder is mixed bythe agiecar, Figure 5. Although the bowl and paddleshortcomings would cause difficulties if allowed to continuewith a wet shotcreting production phase, the batching plantdid not pose a major difficulty for the trial as a concretetechnologist was present for the duration of the trial.


Table II

Geopractica mix design concrete cube test results

Design Sand Cementitious Cementitious CSF Glenium Delvocrete Meyco TCC 735 Water Days Compressive Flow

type type content (kg) 27CH (litres) stabilizer 10 (litres) (litres) Liters Strength (MPa) (mm)

1 Richter HT33 660 0 0.00 0.00 0.00 240.00 35 26.80 18.60 23.60 6051 Repeat Richter HT33 660 0 0.00 0.00 0.00 240.00 28 18.80 20.10 23.70 5802 Richter HT33 590 0 2.00 0.00 0.00 197.00 35 29.00 34.70 32.90 6253 Rayton HT33 793 0 0.00 0.00 0.00 277.00 35 28.00 31.10 43.30 5904 Rayton HT33 716 0 1.80 0.00 0.00 237.00 Flow too wet5 Richter HT33 534 0 2.67 0.00 0.00 177.00 35 32.70 29.40 25.80 6006 Richter HT33 495 0 2.20 0.00 0.00 180.00 35 26.30 26.20 19.30 6056 Repeat Richter HT33 495 0 2.20 0.00 0.00 180.00 28 34.90 34.30 34.60 6607 Rayton HT33 523 0 2.67 0.00 0.00 190.00 35 29.50 31.30 5907 Repeat Rayton HT33 526 0 2.67 0.00 0.00 185.00 28 36.10 30.10 31.30 6058 Richter 42.5 OPC 505 40 5.00 3.60 5.00 203.00 32 40.90 44.20 34.10 6009 Richter 42.5 OPC 505 40 5.40 3.60 5.40 192.00 32 47.60 47.30 50.40 58510 Richter 42.5 OPC 475 38 5.00 3.60 5.00 190.00 32 37.00 48.00 42.50 60510 Repeat Richter 42.5 OPC 475 38 5.00 3.60 5.00 190.00 28 44.80 41.80 43.90 63011 Rayton 42.5 OPC 450 36 5.40 3.60 5.00 225.00 32 39.40 37.90 35.20 58512 Rayton 42.5 OPC 500 40 5.40 3.60 5.00 230.00 32 43.00 44.50 41.10 61513 Rayton HT33 617 0 0.00 0.00 0.00 225.00 28 30.50 28.40 32.00 595

Figure 1Azalcon wet shotcrete hangingwall photographs

Wet shotcrete fall of ground

Wet shotcrete stalactite formations on tunnel hangingwall

Shotcreteslabbing0.75m2

The sidewall and hangingwall were previously coatedwith tunnel guard; an impermeable membrane. Over a shorttime a layer of dust had built up over the tunnel guard. Thisdust was removed prior to the placing the wet shotcrete usinga water and compressed air mix.

Wet shotcrete trial


Table III

Mix design cube test results, costs and selectionDesign Sand Sand Cementitious Cementitious Condensed Glenium Delvocrete Meyco Meyco HPP fibre Total

type type silica fume stabilizer TCC 735 SA 160

Content Cost/ Cost/ Cost/ 27CH Cost/ Cost/ Cost/ Cost/ Cost Cost

Cube (R) Content cube (R) kg Cube (R) (litres) Cube (R) (litres) Cube (R) (litres) Cube (R) (litres) Cube (R) (kg) Cube (R) Cube

1 Richter 1334 40.02 HT33 660 336.60 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R874.011 Repeat Richter 1334 40.02 HT33 660 336.60 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R874.012 Richter 1520 45.60 HT33 590 300.90 0 0.00 2.00 21.64 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R865.523 Rayton 1094 32.82 HT33 793 404.43 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R934.644 Rayton 1275 38.25 HT33 716 365.16 0 0.00 1.80 19.47 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R920.275 Richter 1630 48.90 HT33 534 272.34 0 0.00 2.67 28.85 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R847.486 Richter 1661 49.83 HT33 495 252.45 0 0.00 2.20 23.80 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R823.476 Repeat Richter 1661 49.83 HT33 495 252.45 0 0.00 2.20 23.80 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R823.477 Rayton 1598 47.94 HT33 523 266.73 0 0.00 2.67 28.88 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R840.947 Repeat Rayton 1608 48.24 HT33 526 268.26 0 0.00 2.67 28.88 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R842.778 Richter 1635 49.05 42.5 OPC 505 167.47 40 130.40 5.00 54.09 3.60 47.95 5.00 68.89 25.00 129.70 7.50 367.69 R1,015.239 Richter 1662 49.86 42.5 OPC 505 167.47 40 130.40 5.40 58.42 3.60 47.95 5.40 74.40 25.00 129.70 7.50 367.69 R1.025.8810 Richter 1696 50.88 42.5 OPC 475 157.52 38 123.88 5.00 54.09 3.60 47.95 5.00 68.89 25.00 129.70 7.50 367.69 R1,000.5910 Repeat Richter 1696 50.88 42.5 OPC 475 157.52 38 123.88 5.00 54.09 3.60 47.95 5.00 68.89 25.00 129.70 7.50 367.69 R1,000.5911 Rayton 1618 48.54 42.5 OPC 450 149.23 36 117.36 5.40 58.42 3.60 47.95 5.00 68.89 25.00 129.70 7.50 367.69 R987.7712 Rayton 1558 46.74 42.5 OPC 500 165.81 40 130.40 5.40 58.42 3.60 47.95 5.00 68.89 25.00 129.70 7.50 367.69 R1,015.5913 Rayton 1409 42.27 HT33 617 314.67 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 25.00 129.70 7.50 367.69 R854.33

Shotcretewet mixingtrough

Worm andstator feedbox

Shotcretefeed

Worm and stator pump and mixing unit

Staterclampsholdingsteelsleeveand wormscrewthread

Connectionto hose

Feed trough and worm and stator

Figure 2Azalcon wet shotcrete equipment

Shotcreteandcompressedoutlet

Shotcreteintake

Compressedair intake

Azalcon wet shotcrete nozzle

Shotcreteintake

Shotcrete,acceleratorandcompressedoutlet

Compressedair intake

Acceleratorintake

Shotcrete intake

Figure 3Azalcon wet shotcrete nozzles

Wet shotcrete trial

The wet shotcrete was transported to site in one cubicmetre increments using the Premier Mine agiecars. The wetshotcrete was then transferred into the shotcrete pump. Thewet shotcrete was then pumped to the nozzle via a 50 mmrubber hose. At the nozzle, compressed air was delivered at apressure of 7 bar in conjunction with an accelerator to placethe wet shotcrete. Once the wet shotcrete had been placed,penetration with a finger became impossible after twominutes. After five minutes it became impossible to force anail through the wet shotcrete. A driving force behind thesuccess of all four-mix designs was the use of the SA160accelerator, which helped to lock the water in the shotcreteand give high initial shotcrete strength. All four wet shotcretemix designs were successfully applied to the sidewall andhangingwall, Figure 6.

Despite all the wet shotcrete mix designs adhering to thesidewall and hangingwall successfully, the Azalcon HT33product did not flow easily from the batching plant into theagiecars. The HT33 mix designs also started to cure andhydrate after a very short period. Once the HT33 wetshotcrete had been transported from the 630 m Levelbatching plant to the test site on 615 m Level, less than fiftyper cent of the HT33 mix was able to flow from the agiecarunaided. Water had to be placed into the agiecar kettle inorder to increase the fluidity of the mix. The adding of watertherefore changed the design of the shotcrete and reduced thestrength proportionately.


Dosingpump

450 CFM compressor

Wet shotcrete pump and dosing machine

Figure 4450 CFM compressor, shotcrete and dosing pump

Poormixing ofsand,cementand water

Batch plant shortcomings

Batch plant quality control

Figure 5Batch plant shortcomings and quality control

Lafarge 42.5 OPC with Rayton sand

Wet shotcrete placement

Figure 6Lafarge 42.5 OPC with Rayton sand, wet shotcrete placement

From the four mix designs tested underground, coresamples were taken, Table IV. However only cores takenfrom Rayton sand with OPC test cores gave satisfactoryresults. The cores taken from the remaining three panelswere of poor quality due to the thickness of panels placed.The Rayton sand with OPC mix design results were howeverextremely good and recorded results averaging over 40 MPa.Despite the HT33 mix designs costing on average R120.00per cube less than OPC per cube metre, it was decided toremove HT33 from further trial.

The wet shotcrete trial

For the wet shotcrete laboratory tests, Rayton and Richtersand and Lafarge OPC were used in conjunction with Graceand HPP S 50 fibre. The wet shotcrete materials for twoduplicate EFNARC panels was manufactured in a mechanicaldrum mixer and placed into moulds. The standard panels, 1 m x 1 m and 100 mm thick were compacted using atamping rod and by dropping from a height of 10 mm, 70times. The panels were cured for five days prior to cutting tothe correct size and placing into a curing bath until testing.

For the underground trial Rayton sand, Grace and HPP S50 fibre were used with Lafarge OPC. To ensure that therewas as little interruption to the mines concrete operation, nochanges to the underground batch plant system wererequired in order to cater for Rayton sand shotcrete designfor the underground shotcrete trial. A concrete technologistwas employed at the batch plant to manufacture the wetshotcrete and to ensure that the correct standard wasachieved. The machinery and process for the trial mirroredthe lines of the previous trial. Four production level draw-points were earmarked and sprayed with ten linear metres ofwet shotcrete, each draw-point with a different quantity ofHPP fibre or Grace fibre. Due to the 4 m x 4 m dimensions ofthe tunnel a scissors lift was utilized to give the nozzleoperator the height to ensure that there was only 1 mbetween the nozzle and kimberlite surface. After cleaning thekimberlite surface with a mix of water and compressed air,shotcrete was placed successfully in all four draw-points.However, once the troughs were opened via blasting to minestandard, it became apparent that the required shotcretethickness was not achieved, Figure 7. Following thisdevelopment it also became apparent that no hand-heldnozzle placement of shotcrete should be undertaken unless100 mm plugs were used to guide the nozzle operator.

Geotechnical results for the wet shotcrete trial

The Richter sand results indicate: From cube tests, the HPP S 50 fibre with Richter sand

performed better in compression than the Grace fibrewith Richter sand, Table V and Figure 8

The Richter sand with HPP S 50 fibre energyabsorption test results indicate an ability to sustain agreater load before failure than that achieved withRichter sand with Grace fibre, Table VI

With the Richter sand being a more rounded aggregate,less water is required than with Rayton sand. TheRayton sand is coarse and consequently has anincreased surface area; this increases the waterdemand

Despite the Richter shotcrete design demanding moresand compared to the Rayton shotcrete design, for asimilar quantity of cement per cubic metre, thewater/cement ratio for the Richter design is less butdelivers an increased compressive strength over andabove the Rayton designs which require more water

The Grace fibre has a lower density compared to theHPP fibre so for a given mass, one cube, Grace fibrerequires a greater volume. The increased volume ofGrace fibre and its fibrillating nature demands that, fora given flow, a greater volume of water is requiredwhen compared to the HPP fibre. This increased waterdemand ensures that the wet shotcrete remainspumpable, however, in turn the increased water/cement ratio reduces the strength of the shotcrete mix

Due to the Richter design formulated with HPP S 50fibre and due to the shape and size of the aggregate,

Wet shotcrete trial


Figure 7Wet shotcrete support after opening up the trough at aproduction drawpoint

Table IV

Wet shotcrete mix design core testing

Design Sand type Cementitious Core Core Core Core Failure Measured compressivetype number diameter (mm) length(mm) age (days) load (KN) strength MPa

1 Richter HT33 9 104 55 28 173 20.410 104 49 28 195 23

10 Repeat Richter 42.5 OPC 4 104 103 28 133 15.695 104 100 28 109 12.86

12 Rayton 42.5 OPC 1 104 102 28 371 43.762 104 101 28 320 37.743 104 101 28 417 49.18

13 Rayton HT33 6 104 96 28 91 10.737 104 75 28 82 9.67

Remaining wetshotcrete, 30mm thick

Kimberlitehangingwall

both are able to key and develop a good mechanicalbond. Indications suggest that the finer Grace fibre isless able to key sufficiently well to Richter sand, a well-rounded aggregate. If the cement content wereincreased the bond between the Grace fibre wouldincrease while at the same time improving the ductilityof the fibre reinforced shotcrete. It is not recommendedto increase the cement content due the increased costattached.

The Rayton results indicate: The Rayton sand cube results were relatively

inconclusive due in part to the variation in watercontent while mixing, however the results did showthat both the HPP and Grace fibre performed well at 7kg/m3, Table VIII and Figure 10

The Grace fibre performed extremely well in the energyabsorption tests at 7 kg/m3 and 8 kg/m3 where bothachieved over 750 joules, Table IX and Figure 11

Wet shotcrete trial


Table V

Richter sand and fibre reinforced wet shotcrete cubetest results from laboratory trials

Design Fibre Content Days Compressive Average10 strength (MPa) (MPa)

Grace 6 7 37.17 37.1728 44.48 45.38

47.7642.7846.49

Grace 7 7 30.46 32.5834.69

28 40.97 41.9839.7642.8444.35

HPP S 50 6 7 30.76 34.8738.97

28 49.79 48.7647.5948.89

HPP S 50 7.5 7 39.17 39.0738.97

28 47.09 48.0949.09

HPP S 50 9 7 39.97 40.2340.48

28 39.37 47.4950.2951.348.99

45.38

48.76

41.98

48.0947.49

6 7 8 9Fibre content (kg/m3)

Grace 50 mm laboratory HPP S 50 mm laboratory

50.00

48.00

46.00

44.00

42.00

40.00

38.00

Com

pres

sive

stre

ngth

(MPa

)

Figure 8Richter sand wet shotcrete cube results graph

Fibre Type HPP S 50 6 Kg/m3Test No. 1220 13

Side A (mm) Side B (mm) Side C (mm) Side D (mm) Min Max Average

100 95 90 100 100 102 100 100 90 102 98

Energy Absorption = 775 J ITASCA Corrected Energy absorption = 883 J



100 100 100 98 98 99 99 102 98 102 100


Fibre Type HPP S 50 7.5 Kg/m3Test No. 1220 15


102 103 102 103 104 105 104 102 102 105 103


Fibre Type HPP S 50 7.5 Kg/m3Test No. 1220 16


105 103 100 100 100 102 102 105 100 105 102




104 105 105 104 103 100 100 104 100 105 103




100 101 101 100 100 101 101 100 100 101 101


Table VI

Richter sand laboratory energy absorption testresults

1000

900

800

700

600

500

400

300

200

100

0

Ener

gy a

bsor

ptio

n ra

te (jo

ules)

6 7 7.5 8 9Fibre content (kg/m3)

Grace 50 mm laboratory HPP S 50 mm laboratory

728 757

650

810

903

Figure 9Richter sand laboratory energy absorption graph

In comparison to the HPP S 50 fibre, Grace fibres, goodperformance could be as a result of the finer matrix ofthe Rayton sand while at the same time being a coarseaggregate and providing a large surface area. Thislarge surface area increased the well-fibrillated Gracefibres ability to bond with the aggregate and cementmore effectively. The HPP fibre was unable to matchthe bond achieved between Rayton sand and Gracefibre.

It is therefore recommended that Premier Mine adopt thewet shotcrete mix design shown in Table VII.

Wet shotcrete financial requirements

The wet shotcrete material costs are considerably higher thanthose for dry shotcrete, Appendices 1A and 2A. However,less wet shotcrete material is required due to effectivecontouring to the tunnel profile, reduced rebound of shotcreteand reduced operational placement costs and increasedproductivity compared to dry shotcrete. Other major costsavings are achieved through the reduction of tasks. Theintroduction of fibre reinforced wet shotcrete eliminates theneed for welded mesh and tunnel guard. This task reductiontherefore translates to a reduction of manshifts required toimplement the support types, Appendices 3A and 4A. From2001 to 2005 some 22,000m3 of wet shotcrete support willbe required compared to 36,000m3 for dry shotcrete.

There is a potential for Premier Mine to make majorsavings by introducing wet shotcrete. In South Africa thereare two suitable wet shotcrete machines available for themining industry, the Spreymec, manufactured by Tamrockand the Fermel/Meyco wet shotcrete machine. The Spreymecis a fully imported machine and is manufactured in Finland.The Fermel component is manufactured in South Africa andthe Meyco shotcrete components are manufactured inSwitzerland but supported by MBT (Master BuilderTechnologists) in South Africa. The Fermel/Meyco machine isassembled in South Africa.

Premier Mine has allocated some R2,100,000 towards theimplementation of the wet shotcrete system. If implemen-tation is successful there should be an internal rate of returngain of 76% with regard to this project, Appendix 5A

Conclusions

The fibre reinforced wet shotcrete has proven itself as a

competent form of kimberlite support and requires no weldedmesh or tunnel guard. The wet shotcrete system is also ableto place 5 m3 of wet shotcrete per hour compared to 4 m3 pershift with dry shotcrete.

Although the dry shotcrete materials, mesh and tunnelguard is considerably less expensive to purchase it isextremely labour and time intensive. The dry system is alsoonly as good as the personnel placing the shotcrete. Eachshotcrete design is determined by the nozzle operator and is

Wet shotcrete trial


Table VII

The recommended wet shotcrete design for Premier Mine

Material/ Criteria Quantity/m3 Units

Lafarge 42.5 Duratech 500 kgCondensed silica fume 40 kgRayton sand 1.558 tonDelvocrete stabilizer 10 3.6 litresGlenium 27CH 5.4 litresMeyco TCC 735 5 litresWater 230 litresMeyco SA160 25 litresFibre 8 kgCement/Water ratio 2.35 Water/Cement ratio 0.43 Flow 615 mm


(b) Grace 6 7 21.74 21.7428 32.76 35.2228 37.67

Grace 7 7 31.56 31.5628 53.70 55.9628 58.21

Grace 8 7 39.37 38.2737.17

28 57.01 51.2347.2949.39

HPP S 50 6 7 26.25 26.3526.45

28 38.27 38.3438.5738.17

HPP S 50 7.5 7 40.68 40.1440.7838.97

28 59.71 56.0050.2958.01

HPP S 50 9 7 32.96 34.5032.2638.27

28 66.72 60.5455.0059.91

Table VII

Rayton sand, fibre/wet shotcrete cube results: (a) underground trials, (b) laboratory trials


(a) Grace 7 14 54.70 52.9655.6048.59

28 59.01 57.6454.9059.01

Grace 8 30 39.76 38.6840.06

28 42.4537.4735.3736.97

HPP S 50 7.5 14 38.17 49.7353.4057.61

28 62.72 61.4553.1068.53

HPP S 50 9 28 41.35 46.1041.0537.3748.9353.9154.01

Wet shotcrete trial

therefore open to abuse and is impossible to monitor orquantify. Alternatively the wet shotcrete quality isdetermined by the batch plant operator and should bemonitored, audited and policed by the concrete technologist.The use of a semi-automatic wet shotcrete rig is also safe tooperate, as the operator is not exposed to the area to besupported. The wet shotcrete rig also only requires onequalified operator, an artisan or fitter grade and two helpersto assist with the final preparation of the tunnel.

From the Premier Mine wet shotcrete trial, the largetunnel dimensions proved too big for a hand-held wetshotcrete system. The hangingwalls were difficult to sprayand therefore not completed to the required thickness. A wetshotcrete rig with a semi-automatic robotic arm is thereforerecommended to place the shotcrete as required. From thetrial, it was determined that a greater emphasis must beplaced the importance of the manufacture of concrete and thepersonnel supporting the concrete system. Premier Minetherefore requires a dedicated concrete technologist to ensurethat a standard concrete quality is achieved. Wet shotcrete rigand batch plant operators also need to be trained andeducated on the importance and urgency related to concretemanufacture, delivery and application of concrete. Ultimatelythere needs to be a change in mindset on the importance ofgood quality concrete. Without this support and urgency, it isnot recommended that the mine transfer to the wet shotcretesystem. However, for the future of the mine, both B and CCut, it is imperative that the mine transfers to the wetshotcrete system.

Once Premier Mine has implemented a wet shotcretesystem that fulfils the demands required and has gained thenecessary experience, the shotcrete mix designs must beadjusted to reduce the cost of materials. However, at thisstage it is important to gain a good wet shotcrete databasefrom which to build any future improvements.

Recommendations

Premier Mine has two choices:

To continue with the tunnel guard, mesh and dryshotcrete placement system

Alternatively, it is recommended that Premier Minepurchases the Fermel/Meyco wet shotcrete rig which is


61.4555.96

60.54

6.00 7.00 7.50 8.00 9.00Fibre content (kg/m3)

Grace 50 mm Underground HPP S 50 mm Underground

Com

pres

sive

stre

ngth

(MPa

)

70.00

60.00

50.00

40.00

30.00

20.00

10.00

0.00

57.64

38.68

Grace 50 mm Laboratory HPP S 50 mm Laboratory

Figure 10. Rayton sand wet shotcrete cube test results (Compressivestrength/fibre content)

Fibre Type Grace 50 mm 7 kg/m3Test No. 1102 A


100 100 110 100 100 95 110 105 95 110 103


Fibre Type Grace 50 mm 7 kg/m3Test No. 1102 B


110 120 105 105 105 100 100 100 100 120 106


Fibre Type HPP S 50 mm 7.5 kg/m3Test No. 1106 a


110 115 130 120 130 115 125 105 105 130 119


Fibre Type HPP S 50 mm 7.5 kg/m3Test No. 1106 b


125 130 125 115 110 120 120 125 110 130 121


Fibre Type Grace 50 mm 8 kg/m3Test No. 1121 A


90 100 95 90 90 85 80 90 80 100 90


Fibre Type Grace 50 mm 8 kg/m3Test No. 1121 B


120 110 115 110 110 110 105 110 105 120 111

Energy Absorption =1058 J ITASCA Corrected Energy absorption = 942 J

Fibre Type HPP S 50 mm 9 kg/m3Test No. 1123 a


115 115 115 125 115 110 120 120 110 125 117


Fibre Type HPP S 50 mm 9 kg/m3Test No. 1123 b


90 105 95 95 90 100 95 85 85 105 94


35.22

56.00

46.10

51.23

38.34

523595

1099

735

460 527

1380

982

691606

6.0 7.0 7.5 8.0 9.0Fibre content (kg/m3)

Grace 50 mm LaboratoryGrace 50 mm Underground HPP S 50 mm Underground

HPP S 50 mm Laboratory

1600

1400

1200

1000

800

600

400

200

0

Ener

gy a

bsor

ptio

n ra

te (J

oules

)

Figure 11. Rayton sand ITASCA energy absorption tests resultsTable IX

Rayton sand laboratory energy absorption test results

TYPE 5UNDERCUT INTERSECTION (per metre of tunnel)

considerably less expensive than the Spreymec and iswell supported by wet shotcrete specialists. However,before the implementation of the wet shotcrete systemcan commence the following is required.

- The batch plants must be upgraded to such anextent that a good mixing process is achieved andall weighing or measuring systems are accurateand easy to read whether or not any wet shotcretesystem is to be introduced

- The batch plant operators must receive extensiveon-the-job training in the manufacture ofconcrete and in plant maintenance, (this wouldneed to be well supported by Management).Those who were considered unsuitable tomanufacture concrete after a one-week training

period must be replaced with operators that aremore competent

- The wet shotcrete rig must be operated by aartisans or a fitter. Once identified, the operatormust receive a two-week induction course on amine where the machine is operational. Theoperator must also receive extensive training fromthe supplier of the machine at Premier Mine onhow to use, clean and maintain the rig

- After a two-month period the supplier of the wetshotcrete rig must audit the operation and givemore training where necessary.

Acknowledgements

The Premier Mine Projects Department is grateful to the

Wet shotcrete trial


CAPITAL SUPPORT TUNNEL TYPES FOR DRY SHOTCRETE

TYPE 1PRODUCTION TUNNEL (per metre of tunnel)

Description Rate Unit Unit Cost Cost Efficiency Manshifts

1,8 m gewis 4 each 36.31 145.22 0.09 0.36welded 12 m2 17.92 215.00 0.11 1.32meshtunnelguard 12 m2 35.95 431.34 0.03 0.36(2 layers)shotcrete 12 m2 56.25 675.00 0.26 3.12(100 mm)footwall 1.2 m3 265.34 318.40 0.73 0.88

total 1,784.96 6.04

TYPE 3PRODUCTION TROUGHS (per metre of tunnel)

* All the above costs are material costs only* Scribing materials for contact arch support excluded* D.A.S. to be used for roadways in rim tunnels


1,8 m gewis 4 each 36.31 145.22 0.09 0.36welded 12 m2 17.92 215.00 0.11 1.32meshtunnelguard 12 m2 35.95 431.34 0.03 0.36(2 layers)

total 791.56 2.04

TYPE 6WASTE ROCK SUPPORT


1,8 m gewis 4 each 36.31 145.22 0.09 0.36welded 12 m2 17.92 215.00 0.11 1.32meshshotcrete 4.4 m2 56.25 247.50 0.26 1.14(100 mm)

total 607.72 2.82

TYPE 7CONTACT ARCH SUPPORT (Extraction Level)

TYPE 2PRODUCTION DRAWPOINT (10 metres)

TYPE 4UNDERCUT TUNNEL (per metre of tunnel)


1,8 m gewis 4 each 36.31 145.22 0.09 0.36welded 12 m2 17.92 215.00 0.11 1.32meshtunnelguard 12 m2 35.95 431.34 0.03 0.36(2 layers)Shotcretel 12 m3 56.25 675.00 0.26 3.12(100 mm)

total 1,466.56 5.16

TYPE 8CONTACT ARCH SUPPORT (Undercut Level)


6 m anchors 5 each 204.44 1,022.20 1.21 6.05bullnose 40 each 108.93 4.357.20 0.24 9.60ropeinstallationtunnelguard 0 m2 35.95 0.00 0.03 0.00(2 layers)Shotcretel 0 m3 56.25 0.00 0.26 0.00(100 mm)

total 5.379.40 15.65


1,8 m gewis 0 each 36.31 0.00 0.09 0.00welded 0 m2 17.92 0.00 0.11 0.00meshtunnelguard 0 m2 35.92 0.00 0.03 0.00(5 metres)yielding 11 each 5.510.00 60,610.00 1.97 21.67archestekseal 83 m3 224.00 18,592.00 0.02 1.66footwall 0 m3 265.34 0.00 0.73 0.00concrete

total 79,202.00 23.33


1,8 m gewis 0 each 36.31 0.00 0.09 0.00welded 0 m2 17.92 0.00 0.11 0.00meshyielding 5 each 5,510.00 27,550.00 1.97 9.85archestekseal 42 m3 224.00 9,408.00 0.02 0.84footwall 6.6 m3 265.34 1,751.21 0.73 4.82concrete

total 38,709.21 15.51

TYPE 9REHABILITATION on average per 5 m


site 1 each 0.00 0.00 3.00 3.00preparationstrip 5 m 0.00 0.00 2.00 10.00slipe 5 m 290.00 1,450.00 2.00 10.00lash 5 m 0.00 0.00 0.25 1.25tunnel 0 m2 35.95 0.00 0.03 0.00guard1,8m gewis 40 each 36.31 1,452.20 0.09 3.60welded 0 m2 17.92 0.00 0.11 0.00meshtendon 20 each 34.00 680.00 0.18 3.60strapsshotcrete 0 m3 56.25 0.00 0.26 0.00100 mm

total 3.582.20 31.45

TYPE 9ARMCO


tunnel 14.1 m2 68.50 965.85 0.03 0.42guard1,8m gewis 4 each 0.00 0.00 0.09 0.36welded 14.1 m2 60.00 846.00 0.11 1.55meshARMCO 0.2 m 25,000.00 5,555.56 25.00 5.56erectconcrete 5.6 m3 265.34 1,474.08 0.22 1.22back fill(25 MPa)shotcrete 12 m2 34.00 408.00 0.26 3.12100 mmfootwall 1.2 m3 265.34 318.40 0.73 0.88concrete

total 9.567.89 13.11


1,8 m gewis 40 each 36.31 1,452.20 0.09 3.60welded 120 m2 17.92 2,150.00 0.11 13.20meshtunnelguard 120 m2 35.95 4,313.40 0.03 3.60(2 layers)shotcrete 120 m2 56.25 6,750.00 0.26 31.20(100 mm)6m anchors 23 each 204.44 4,702.12 1.21 27.83bullnose 10 each 108.93 1,089.30 0.24 2.40ropeinstallationcamelback 10 each 108.93 1,089.30 0.24 2.40ropeinstallationfootwall rail 2 m 697.50 1,395.00 0.22 0.44footwall 12 m3 265.34 3,184.02 0.73 8.76concrete

total 26,125.34 93.43

Appendix 1A

following for permission to publish Premier Mine General Manager, Mr Hans Gastrow Premier Mine Mining Manager, Mr Malcolm Lotriet General Manager Mining, Mr Tony Gutherie General Manager Geotechnical Engineering, Mr Alan

Guest.

The Projects Department is also grateful to the followingfor their contributions

Geopractica Consulting Geotechnical Engineering Master Builder Technologists South Africa Grace Concrete Products South Africa Azalcon.

TYPE 1PRODUCTION TUNNEL (per metre of tunnel)

Wet shotcrete trial


CAPITAL SUPPORT TUNNEL TYPES FOR WET SHOTCRETE

TYPE 3PRODUCTION TROUGHS (per metre of tunnel)

* All the above costs are material costs only* Scribing materials for contact arch support excluded* D.A.S. to be used for roadways in rim tunnels


1,8 m gewis 4 each 36.31 145.22 0.09 0.36shotcrete 12 m2 149.29 1,791.49 0.03 0.36(100 mm)

total 1,936.71 0.72

TYPE 4UNDERCUT TUNNEL (per metre of tunnel)


1,8m gewis 4 each 36.31 145.22 0.09 0.36shotcrete 12 m2 149.29 1,791.49 0.03 0.36(100 mm)

total 1,936.71 0.72

TYPE 6WASTE ROCK SUPPORT


1,8 m gewis 4 each 36.31 145.22 0.09 0.36shotcrete 4.4 m2 149.29 656.88 0.03 0.13(100 mm)

total 802.10 0.49

TYPE 5UNDERCUT INTERSECTION SUPPORT

TYPE 7CONTACT ARCH SUPPORT (Extraction Level)

TYPE 2PRODUCTION DRAWPOINT (10 metres)

TYPE 8CONTACT ARCH SUPPORT (Undercut Level)


1,8 m gewis 0 each 36.31 0.00 0.09 0.00yielding 11 each 5,510.00 60,610.00 1.97 21.67archestekseal 83 m3 224.00 18,592.00 0.02 1.66footwall 0 m3 265.34 0.00 0.73 0.00concrete

total 79,202.00 23.33


1,8m gewis 0 each 36.31 0.00 0.09 0.00yielding 5 each 5,510.00 27,550.00 1.97 9.85archestekseal 42 m3 224.00 9,408.00 0.02 0.84footwall 6.6 m3 265.34 1,751.21 0.73 4.82concrete

total 38,709.21 15.51

TYPE 9REHABILITATION on average per 5 m


site 1 each 0.00 0.00 3.00 3.00preparationstrip 5 m 0.00 0.00 2.00 10.00slipe 5 m 290.00 1,450.00 2.00 10.00lash 5 m 0.00 0.00 0.25 1.251,8m gewis 40 each 36.31 1,452.20 0.09 3.60tendon 20 each 34.00 680.00 0.18 3.60strapsshotcrete 0 m3 149.29 0.00 0.03 0.00100 mm

total 3.582.20 31.45

TYPE 9ARMCO


1,8m gewis 4 each 0.00 0.00 0.09 0.36ARMCO 0.2 m 25,000.00 5,555.56 25.00 5.56erectconcrete 5.6 m3 265.34 1,474.08 0.22 1.22back fill(25 MPa)shotcrete 12 m2 149.29 408.00 0.03 3.12100 mmfootwall 1.2 m3 265.34 318.40 0.73 0.88concrete

total 9.567.89 13.11


1,8 m gewis 4 each 36.31 145.22 0.09 0.36shotcrete 12 m2 149.29 1,791.49 0.03 0.36(100 mm)footwall 1.2 m3 265.34 318.40 0.73 0.88concrete

total 2,255.12 1.59


1,8 m gewis 40 each 36.31 1,452.20 0.09 3.60shotcrete 120 m2 149.29 17,914.95 0.03 3.55(100 mm)6 m 23 each 204.44 4,702.12 1.21 27.83anchorsbullnose 10 each 108.93 1,089.30 0.24 2.40ropeinstallationcamelback 10 each 108.93 1,089.30 0.24 2.40ropeinstallationfootwall rail 2 m 697.50 1,395.00 0.22 0.44footwall 12 m3 265.34 3,184.02 0.73 8.76concrete

total 30,826.89 48.98


6m anchors 5 each 204.44 1,022.20 1.21 6.05bullnose 40 each 108.93 4,357.20 0.24 9.60ropeinstallation

total 5,379.40 15.65

Appendix 2A

Wet shotcrete trial


Life of mine base case support requirements for dry shotcreteB-Cut LOM for 2001 SBPBase manpower case for dry shotcreteDate 23 March 2001

Year 2001 2002 2003 2004 2005 2006

615 Level support metresTunnel metres-blue 315 227 266 0 0 0Tunnel metres-waste 88 96 0 0 0 0Contact metres 10 5 5 0 0 0Manshifts 1,887 1,450 1,380 0 0 0630 Level support metresTunnel metres-blue 118 89 237 71 0 0Tunnel metres-waste 160 160 0 0 0 0Draw point metres 124 86 276 76 0 0Trough metres 61 61 183 71 0 0Contact metres 22 28 5 5 0 0Manshifts 2,494 1,977 4,389 1,295 0 0717 Level support metresTunnel metres-blue 640 922 502 0 0 0Tunnel metres-waste 401 237 0 0 0 0Contact metres 50 95 25 0 0 0Manshifts 4,512 5,574 2,629 0 0 0732 Level support metres 0Tunnel metres-blue 93 358 240 384 136 0Tunnel metres-waste 54 828 0 0 0 0Draw point metres 109 271 228 371 105 0Trough metres 91 193 132 203 71 0Contact metres 9 91 10 5 25 0Manshifts 1,940 7,637 3,871 6,205 2,001 0747 Level support metresTunnel metres-blue 48 115 135 0 0 0Tunnel metres-waste 373 142 26 0 0 0Draw point metres 10 95 133 0 0 0Trough metres 0 61 112 0 0 0Contact metres 19 11 0 0 0 0Manshifts 1,474 2,128 2,359 0 0 0

GRAND TOTAL 2,794 4,169 2,514 1,186 337 0

Total manshifts required 12,307 18,765 14,629 7,500 2,001 0

B-Cut LOM for 2001 SBPBase material case for dry shotcreteDate 23 March 2001

Year 2001 2002 2003 2004 2005 2006

615 Level support metresTunnel metres-blue 315 227 266 0 0 0Tunnel metres-waste 88 96 0 0 0 0Contact metres 10 5 5 0 0 0Material cost (R) 553,422 410,605 409,460 0 0 0630 Level support metresTunnel metres-blue 118 89 237 71 0 0Tunnel metres-waste 160 160 0 0 0 0Draw point metres 124 86 276 76 0 0Trough metres 61 61 183 71 0 0Contact metres 22 28 5 5 0 0Material cost (R) 854,939 747,371 1,327,097 421,126 0 0717 Level support metresTunnel metres-blue 640 922 502 0 0 0Tunnel metres-waste 401 237 0 0 0 0Contact metres 50 95 25 0 0 0Material cost (R) 1,375,840 1,863,935 832,986 0 0 0732 Level support metresTunnel metres-blue 93 358 240 384 136 0Tunnel metres-waste 54 828 0 0 0 0Draw point metres 109 271 228 371 105 0Trough metres 91 193 132 203 71 0Contact metres 9 91 10 5 25 0Material cost (R) 625,402 2,725,369 1,207,697 1,853,657 770,010 0747 Level support metresTunnel metres-blue 48 115 135 0 0 0Tunnel metres-waste 373 142 26 0 0 0Draw point metres 10 95 133 0 0 0Trough metres 0 61 112 0 0 0Contact metres 19 11 0 0 0 0Material cost (R) 489,569 671,209 692,748 0 0 0

GRAND TOTAL 2,794 4,169 2,514 1,186 337 0

Material cost (R) 3,899,172 6,418,490 4,469,988 2,274,783 770,010 0

Appendix 3A

Life of mine base case support requirements for wet shotcreteB-Cut LOM for 2001 SBPBase manpower case for wet shotcreteDate 23 March 2001

Year 2001 2002 2003 2004 2005 2006

615 Level support metresTunnel metres-blue 315 227 266 0 0 0Tunnel metres-waste 88 98 0 0 0 0Contact metres 10 5 5 0 0 0Manshifts 423 287 268 0 0 0630 Level support metresTunnel metres-blue 118 89 237 71 0 0Tunnel metres-waste 160 160 0 0 0 0Draw point metres 124 86 276 76 0 0Trough metres 61 61 183 71 0 0Contact metres 22 28 5 5 0 0Manshifts 967 747 1,869 548 0 0717 Level support metresTunnel metres-blue 640 922 502 0 0 0Tunnel metres-waste 401 237 0 0 0 0Contact metres 50 95 25 0 0 0Manshifts 1,430 2,249 747 0 0 0732 Level support metres 0Tunnel metres-blue 93 358 240 384 136 0Tunnel metres-waste 54 828 0 0 0 0Draw point metres 109 271 228 371 105 0Trough metres 91 193 132 203 71 0Contact metres 9 91 10 5 25 0Manshifts 795 2,653 1,616 2,583 837 0747 Level support metres 0Tunnel metres-blue 48 115 135 0 0 0Tunnel metres-waste 373 142 26 0 0 0Draw point metres 10 95 133 0 0 0Trough metres 0 61 112 0 0 0Contact metres 19 11 0 0 0 0Manshifts 350 785 959 0 0 0

GRAND TOTAL 2,794 4,169 2,514 1,186 337 0

Total manshifts required 3,965 6,721 5,459 3,130 837 0

B-Cut LOM for 2001 SBPBase maretial case for wet shotcreteDate 23 March 2001

Year 2001 2002 2003 2004 2005 2006

615 Level support metresTunnel metres-blue 315 227 266 0 0 0Tunnel metres-waste 88 96 0 0 0 0Contact metres 10 5 5 0 0 0Material cost (R) 1,066,774 710,182 708,712 0 0 0630 Level support metres 0Tunnel metres-blue 118 89 237 71 0 0Tunnel metres-waste 160 160 0 0 0 0Draw point metres 124 86 276 76 0 0Trough metres 61 61 183 71 0 0Contact metres 22 28 5 5 0 0Material cost (R) 1,069,323 930,230 1,777,295 571,602 0 0717 Level support metresTunnel metres-blue 640 922 502 0 0 0Tunnel metres-waste 401 237 0 0 0 0Contact metres 50 95 25 0 0 0Material cost (R) 3,496,601 5,653,124 1,939,961 0 0 0732 Level support metresTunnel metres-blue 93 358 240 384 136 0Tunnel metres-waste 54 828 0 0 0 0Draw point metres 109 271 228 371 105 0Trough metres 91 193 132 203 71 0Contact metres 9 91 10 5 25 0Material cost (R) 835,480 3,402,887 1,578,833 2,440,855 964,446 0747 Level support metresTunnel metres-blue 48 115 135 0 0 0Tunnel metres-waste 373 142 26 0 0 0Draw point metres 10 95 133 0 0 0Trough metres 0 61 112 0 0 0Contact metres 19 11 0 0 0 0Material cost (R) 588,866 866,990 951,710 0 0 0

GRAND TOTAL 2,794 4,169 2,514 1,186 337 0

Material cost (R) 7,057,043 11,563,414 6,956,511 3,012,458 964,446 0

Appendix 4A

Wet shotcrete trial


Premier Mine support costing requirements

One manshift in support (R) 332Wet shotcrete machine cost (R) 147.31LHD rates assuming 80% support utilizationScissor lift rates assuming 70% support utilizationRoco rand rates assuming 10% support utilization

Wet shotcrete versus dry shotcrete budgetRayton sand, wet shotcrete machine with 7kg/m3 Grace fibre wet shotcrete versus dry shotcrete

Discounted cash flow (with capital cost included in the first year)

Dry shotcrete costs

Requirements 2001 (6 months) 2002 2003 2004 2005

Dry shotcrete requirements (m3) 5,298 15,675 9,435 4,466 1,260Support requirements (m2) 22,205 65,439 39,353 18,661 5,250Wet shotcrete requirements (m3) 3,345 9,891 5,953 2,819 795

Total manshifts required 6,154 18,765 14,629 7,500 2,001Labour cost (R) 2,042,964 6,230,085 4,856,961 2,490,140 664,168Material cost (R) 1,949,586 6,418,490 4,469,988 2,274,783 770,010

LHD (R) 602,297 1,781,948 1,072,556 507,710 143,243Running cost Roco rand (R) 24,150 71,451 43,007 20,358 5,744

Scissors lift (R) 161,803 478,708 288,135 136,393 38,481Total cost (R) 4,780,800 14,980,682 10,730,646 5,429,384 1,621,646

Year 2001 (6 months) 2002 2003 2004 2005Wet shotcrete capital cost (R) (2,100,00)Wet shotcrete cost (R) (3,980,523) (14,158,214) (8,987,722) (4,155,636) (1,272,125)Dry shotcrete cost (R) 4,780,800 14,980,682 10,730,646 5,429,384 1,621,646Total cost (R) (1,299,723) 822,468 1,742,924 1,273,748 349,521

NPV @ 15% R1,539,755IRR 76.02%

Wet shotcrete costs

Total manshifts required 1,982 6,721 5,459 3,130 837Labour cost (R) 329,058 2,231,477 1,812,352 1,039,292 278,021Material cost (R) 3,528,522 11,563,414 6,956,511 3,012,458 964,446Running cost (R) 122,944 363,323 218,859 103,886 29,659Total cost (R) 3,980,523 14,158,214 8,987,722 4,155,636 1,272,125

Discounted cash flow

Year 0 2001 (6 months) 2002 2003 2004 2005Wet shotcrete capital cost (2,100,000)Wet shotcrete cost (3,980,523) (14,158,214) (8,987,722) (4,155,636) (1,272,125)Dry shotcrete cost 4,780,800 14,980,682 10,730,646 5,429,384 1,621,646Total cost (2,100,000) 800,277 822,468 1,742,924 1,273,748 349,521

NPV @ 15% R1,265,842IRR 37.89%

Appendix 5A

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