In-stope bolting for a safer working environment

Transcription

1 text:templte Jounl 2/3/10 9:34 AM Pge 47 In-stope bolting fo sfe woking envionment by P. Henning* nd P. Feei* J o u n l Synopsis Rock fll ccidents continue to be the min cuse of ftl nd seious injuies in the mining industy. Although thee hs been n impovement in the FOG (flls of gound) elted ftl nd seious injuies ove the pst few yes, the te is still too high. New technology hs mde it possible to educe this te significntly. FOG ccidents imply filue of the suppot system o the design of the suppot system in use. In this ppe we del with the ltest technology vilble to ssist the mines to educe the tes of FOG elted injuies nd ftlities. Intoduction Relible nd pemnent ock suppot is the min focus in the mining industy to minimize the isk of FOG elted injuies nd ftlities. To chieve the objectives of the sfety milestones geed by the industy, thee is n eve incesing demnd to impove technology nd systems to combt injuy nd deth of wokes in the mines. Filue o indequte suppot of conventionl now vein stopes still esult in injuies nd ftlities. Stopes e suppoted to ensue sfety of the wokfoce, but injuies nd ftlities still occu fom time to time. This is cle indiction tht something diffeent needs to be implemented in ddition to the mesues ledy in plce to impove the sfety sitution on the mines. Duing 2008, 57 lives wee lost due to FOG elted injuies on SA mines. (DME Annul Repot 2007). This is 57 too mny. 748 people wee seiously injued by FOG. The mines lose evenue due to the esultnt wokplce stoppges. Mining nd engineeing expets undestnd the need to impove sfety on the mines. Becuse of thei constnt esech nd development of suppot systems, new technology becomes vilble to help mines meet thei sfety objectives.. Mines tht ppecited the potentil nd intoduced instope bolting, chieved emkble decline in ockfll ccidents/incidents in thei woking plces. Howeve, the tendency since inception of this pctice hd been to use the sme ock dilling mchine used to dill the woking fce (usully compessed i opeted) to dill the oof suppot holes. As esult, holes e nomlly obliquely dilled due to height constints, thus not yielding the desied hole length nd ngle. A futhe development ws the invention of the emotely contolled Autoock mini stope suppot dill, ig which hs given the industy sense of hope nd optimism towds elizing the 2013 tgets nd milestones. The emotely contolled Auto Rock mini stope dill ig ws intoduced to the mining industy in 2002 nd to dte moe thn 3,000 units e being used ll ove the mining industy of South Afic. The Autoock mini suppot ig lso chieved pestigious Design Excellence Awd fom the SABS in Octobe The dvntge of hving emotely contolled instope mini suppot ig, which is ble to dill suppot holes between 70º nd 90º in low stoping widths, vying fom 800 mm up to 4.5 metes, ws soon elized by the mines. The ig lso fetues igid clmping ods secuing the ig between the hnging nd footwlls of the stope excvtion fo dded sfety until the bolt instlltion is complete. Whee use is mde of esin suppot tendons, the Autoock ig is lso used to spin the esin bolts home, ceting vey effective suppot system minutes fte the instlltion, owing to the high bond stength between the ock nd steel povided by the full column esin. * Minov RSA. The Southen Aficn Institute of Mining nd Metllugy, SA ISSN X/ This ppe ws fist published t the SAIMM Confeence, Hd Rock Sfety, Septembe P p e The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 110 NON-REFEREED PAPER JANUARY

2 text:templte Jounl 2/3/10 9:34 AM Pge 48 In-stope bolting fo sfe woking envionment Conventionl now eef suppot systems On most of the mines whee the conventionl stoping method is pplied, the stopes e tempoily suppoted with mechnicl pops o jcks. These e usully emoved befoe the blst, leving the spce between the wok fce nd the pemnent suppot unpotected. Mny pesons hve been seiously injued duing the emovl of tempoy suppot nd some hve been ftlly injued. Duing the blst, this excvtion is futhe incesed, ceting unsfe hngingwll conditions fo the clening shift enteing the woking fce. Timbe, cementitious pcks o pestessed elongtes e then used fo pemnent suppot: Tempoy suppot followed by pemnent suppot hs the following dwbcks: Low poductivity Suppot medium must leve pth fo the mechnicl scpe Bulky nd dds to logisticl poblems Pesons exposed to unsfe hngingwll conditions Suppot cnnot be instlled ight up to the wok fce Suppot hs low stiffness Suppot t isk of being blsted out FOG still occus. In-stope bolting s now eef suppot system The instlltion of oof bolts s tempoy nd lso pimy suppot in stopes nd gullies in conjunction with pcks, pestessed elongtes nd pops guntees dded sfety on the wok fce Resin nchos, end-nchoed bolts, cemented o fiction bolts cn be used Suppot holes cn be dilled fom emote, sfe position using n Autoock mini suppot dill ig Suppot tendons cn be instlled ight up to the fce pio to the blst esulting in: FOG ccidents/incidents dsticlly educed. Good suppot e covege leds to impoved hngingwll conditions Suppot density cn esily be incesed to consolidte geologicl fetues Impoved sfety t the wok fce Impoved stoping width contol ese of undecutting nd suppoting of bows Single suppot cycle eplces two cycles, i.e. tempoy suppot stys in s pimy o pemnent suppot. Fce e left cle fo people nd equipment to mnoeuve. No obstuction of scpes o mechnicl clening plnts. Reduced timbe equiement depending on the gound conditions. Reduced timbe equiements will hve the following dvntges: Less mteil to tnspot Lowe costs Lbou sving Highe speed of constuction With bolting instlled, thee is educed isk of potentil pesonl injuy due to FOG becuse of enhnced sfety, which potects wokes between the stope fce nd the pemnently suppoted e, defined s the citicl isk e (CRA) both duing dilling nd clening opetions. Since intoducing instope bolting, mines hve shown significnt impovements in thei FOG csulty tes. Mines not mking use of in-stope bolting should seiously conside implementing the system to ssist with the eduction of FOG incidents in ode to sfegud thei people. Quite often you will he the emk, In-stope bolting is too expensive. We hve mined without it fo yes, why should we conside it now? The sme mine cn then ffod millions of nds when woking plces e stopped becuse of unsfe woking pctices. Why the need fo in-stope bolting? The immedite skin of ock ound the excvtion is wekened by the blsting, exposue, nd stess The depth of fctuing (penettion) into the solid depends on numbe of fctos, nd in genel cn be up to 5 m fo some stoping opetions Hoizontl clmping foces e induced in the ock mss tht tends to knit the ock togethe in moe coheent bem Key blocks e lwys pesent nd dislodging of one o moe of these could led to n uncontolled fll of gound Fctuing might in some cses teminte on dominnt geologicl stuctues such s bedding plnes o joints. since the ltte e ssocited with diffeent mode of ock mss behviou nd chcteistics It is impotnt to know tht the fce is not ecognized s suppot. The eson fo this is tht the fce nd hngingwlls e fctued due to the position of the stess fctues ceted by the dvncing fce nd hngingwll convegence. These spects e best illustted in Figue 1. Tke note tht it is simplified model of the ctul fctue pofile ound undegound excvtions. Suppot mechnism of oof bolting in stopes Due to the fce to pemnent suppot distnce, inelstic closue is llowed to occu, (seption of bedding plnes). Figue 1 Section view of typicl undegound stope envionment 48 JANUARY 2010 VOLUME 110 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

3 text:templte Jounl 2/3/10 9:34 AM Pge 49 In-stope bolting fo sfe woking envionment J o u n l In-stope bolting knits the stess/blsting induced fctues, jointing nd othe geologicl discontinuities mentioned bove, thus limiting wedge type fllouts/ seption long stess/blst induced fctues. (Figue 5 6.) Clssifiction of ccidents Figue 2 Sectionl view showing typicl stope closue Flls of gound occu within the fce e s esult of poo Although thee hs been 22.2% decese in the fll of gound ftlity te fom 0.09 in 2006 to 0.07 im 2007, Figue 7 shows tht fll of gound ccidents e still the lgest contibuto to the cuse of ftlities in ou mines. A totl numbe of 76 lives wee lost s esult of fll of gound ccidents in Thee hs been decese in ock elted ftl ccidents subsequent to the implementtion of peconditions nd instope oof bolting. Howeve, thee is n lming incese in ftl ccidents, othe thn the ock elted ftlities, in the gold secto. FOG emins the biggest thet to the sfety of the people woking undegound. Although thee hve been consideble impovements ove the pst few yes, thee is lot tht cn still be done to impove the sfety sitution on the mines. DME gives lot of cedit fo the impovement in FOG sttistics to the implementtion of in-stope bolting on the mines. Figue 3 Digmmtic section depicting the effect of noml stope design Figue 5 Genel ccidents clss contibution Figue 4 Section view of typicl in-stope oof bolting instlltion The Jounl of The Southen Aficn Institute of Mining nd Metllugy Figue 6 Flls of gound ccident tes VOLUME 110 NON-REFEREED PAPER JANUARY blsting pctice in conjunction with bedding plne seption nd geologicl fetues. In most cses the pope instlltion of good bolting system will contol flls of gound in the CRA. By instlling ock bolt, it ssists in einfocing the hngingwll bem being ceted by the effective length of the ock bolt. If one einfoces the bem, it deflects nd ects lmost elsticlly, contolling the inelstic closue. Seption long the stess induced fctues is minimized s the bolting esults in the clmping of these fctues. P p e

4 text:templte Jounl 2/3/10 9:34 AM Pge 50 In-stope bolting fo sfe woking envionment When mking use of esin bolts fo suppot, the Autoock ig cn lso be used to spin the esin bolts home, which povides n ctive suppot system within minutes of the instlltion. Bolt instlltion is completed befoe the ig is moved to the next suppot hole position. (Figue 11.) Advntges of using n utoock ig fo in-stope bolting (Figue 14 nd 15.) Impoved sfety/hnging wll conditions Impoved poductivity Suppot holes cn be dilled between 70º nd 90º in stoping widths vying fom s low s 800 mm with the smlle dill igs up to 4.5 metes with the lge units Figue 7 Lbou pecentges pe commodity Some sttistics of mines tht implemented in-stope bolting Elndsnd mine implemented in-stope bolting in Mch Totl FOG ccidents pe- nd post-implementtion of in-stope bolting e shown in Figue 8. In-stope bolting begn t Modikw Pltinum Mine in August Since then thee hs been mked eduction in the numbe of injuies s esult of FOG ccidents/incidents. (Figue 9.) Both sfety nd poductivity hve been impoved. Rockbolts e instlled within 0.5 m of the fce, impoving hngingwll supppot in font of the fist line of elongtes. Significnt sfety impovements e nticipted becuse mine pesonnel e t educed isk fom flls of gound. Oe dilution is lso significntly educed, esulting in win-win sitution. Figue 8 FOG ccidents pe- nd post-implementtion of in-stope bolting t Elndsnd mine In-stope bolting mking use of n uto ock emotely opeted mini stope suppot dill ig Genel fetues of n utoock dill ig Potble 750 model weighs only 45 kilogms Requie only one peson to opete in low stoping widths Opete fom the compessed i nd wte lines vilble in the stopes Cn opete fom i pessues s low s 3 b; (i pessues fom 4 6 b ecommended fo optimum pefomnce Opeto exposed to educed noise, owing to emote opetion Opeto not exposed to the sevee hnd vibtions expeienced with hnd held jck hmmes Built in clmping ods secue the Autoock between hnging nd footwll of stope duing dilling. This enhnces dilling ccucy. Although the clmping ods offe some suppot, tempoy suppot is still equied to comply with the mine stndds whilst opeting the ig Figue 9 FOG ccidents/incidents t Modikw Pltinum Mine Figue 10 Bolts tht cn be used with in-stope bolting 50 JANUARY 2010 VOLUME 110 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

5 text:templte Jounl 2/3/10 9:34 AM Pge 51 In-stope bolting fo sfe woking envionment Tble I Chcteistics of bolts used fo in-stope bolting Chcteistics End ncho/ock stud Resin/full column gouted Hydo Bolt Split set Equipment equiements T- spnne/pneumtic Spinning dpto/gout pump 25 Mp pump, Pushe dolly toque wench hoses nd couples Instlltion time 60 seconds 60 seconds 60 seconds with pump 60 seconds+ in good woking ode Full column suppot No 100% Appox 85% Appox 85 % Active suppot Yes if popely Active when 2 speed esin system is Yes if popely Yes poviding hole tensioned used nd tensioning is done befoe the inflted dimete is coect setting time of the 5/10 esin Typicl pek lod 10.5 tons tons 10.7 tons 5 tons- slip in excess Instlled elibility 70% 90% 80% 85% depending on pope instlltion Sensitivity to unde size Not genelly Sensitive when ovesized holes e Decese pefomnce Will incese. boehole di. (e.g.) bit we sensitive dilled. Recommendtion is to dill 28 mm due to ptil infltion Difficult to instll holes with 20 mm esin bolts Undegound esilience Dmged plte,thed, Excellent Good: vlve Good if not popely tensioned dmge unlikely She yield bility mm Low 7 mm mm mm End nchoing nd Ancho on shell only Good with 2 speed esin nd if Fiction nchoing ove No end nchoing citicl bond length tensioning of bolt is done length of bolt fiction only Comments Expensive. Ineffective if not Low cost, vey stong nd ely Vey expensive coosion Coosion- dependent on tensioned popely stength when esin is used. coectly dilled holes J o u n l P p e High speed dilling. When mking use of the esin bolt option, the hole is dilled nd the esin bolt instlled in ppoximtely 6 minutes, povided tht sufficient compessed i is vilble nd the dill bit is in good condition Why use n Autoock dill ig to dill suppot holes nd instll oof bolt suppot? See ccident sttistics detiled in Figues 12 nd 13. Implementtion of Autoock on the mines (is shown in Figues 14 nd 15.) Figue 11 Auto ock dill ig Cost-effective suppot system Compessed i, hydo poweed o electic dill cn be fitted to the Autoock dill ig Povides qulity suppot system when used with n ppopite bolting system Any type of suppot tendon cn be instlled using n Autoock mini stope dill ig Suppot holes fo the instlltion of cble nchos cn be dilled in low stoping width by mking use of coupling dill steels Ese of opetion. RDOs tined to opete the Autoock dill ig within 3 dys Conclusion Ntully, thee hs lwys been esistnce to chnge in the mining industy. In-stope bolting is seen s lot of ext wok nd the implementtion of it difficult nd costly execise. Cn the vlue of peson s life be clculted in nds nd cents? If in-stope bolting is effectively pplied in evey mined pnel in South Afic, lives will be sved. To implement this on ny mine will cost some money, time nd effot. It will lso demnd commitment nd discipline. A cultue must be ceted mongst ll employees to wok sfely nd cete sfe woking envionment. In-stope bolting will be the best investment ny mine cn mke to sfegud the lives of thei people. The utho would like to thnk the DME fo mking vilble the nnul epot nd the pemission to use the ccident sttistics in this ppe. Specil thnks to M. B.B. Nel nd J. vn Vuuen nd A. Kolesky fo the infomtion tht mde this ppe possible. Refeences DME nnul epot 2007/2008 NEL, B.B. In-stope Roof Bolting VAN VUUREN, J.J. Impoving Stope Suppot. Senio Rock Enginee Rock Mechnics Technology Ltd. MURRAY & ROBERTS CEMENTATION MINING TRAINING ACADEMY Sfety Sttistics. The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 110 NON-REFEREED PAPER JANUARY

6 text:templte Jounl 2/3/10 9:34 AM Pge 52 In-stope bolting fo sfe woking envionment Figue 12 RDO ccident nlysis Figue 13 Rock dilling ccidents Figue 14 Autoock dilling 90 º suppot holes in pltinum mine stope in the Rustenbug e 52 JANUARY 2010 VOLUME 110 NON-REFEREED PAPER Figue 15 Dilling of suppot 70º towds the stope fce, t deep-level gold mine in the West Rnd, in vey bd gound conditions The Jounl of The Southen Aficn Institute of Mining nd Metllugy