World record for raiseboring - Atlas Copco

A prime example of fine raiseboring technology: Perfectly straight and smooth walls,bored at precisely the required diameter.STAKESSwedishiron minersstage world’s biggestraise boring projecting raises ranging from 90–360 m long andup to 5 m in diameter.Weighing in at 33 tonnes, the Robbins91RH C is an enormously powerful machine.It has a pulling power of 6 800 kN and a continuoustorque of 450 kNm.The rock consists of several differentformations including granite with a com-pressive strength of 220–350 MPa as wellas quartz porphyry with a strength ofup to 350 MPa.During upward reaming, the machineis also assisted in these hard rock condi-tions by the superior cutting capability ofthe Secoroc Magnum V cutters that aremounted in the cutterhead. Designed andmanufactured by Atlas Copco Secoroc inTexas, USA, they are designed for maxi-mum cutting efficiency in collaborationwith these raiseboring rigs’ massive rota-tion and feed forces.Groups of fourAlthough the Robbins 91RHC is capableof boring raises up to 1 000 m long, theyare being used here to bore a large numberof short ore passes in groups of four.These will be installed between the differentlevels, ultimately linking up the new levelat 1 365 m.Net penetration when boring pilot holesis 0.95 m per hour and each machine isaveraging 10 m per day, depending on therock formation and shaft length. Each raisewill take several months to complete.Bergteamet’s Project Manager at theKiruna site is Håkan Johansson, one ofthe raiseboring specialists who last yearassisted in the dramatic rescue of thetrapped Chilean miners and where raise-boring was one of the methods used toreach them.MINING & CONSTRUCTION – 1 / 2011 7