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any hole orientation, both up-holes and horizontally. The standard packer sys- tems are either 89- or 70-mm-dia- meter for working in NQ [76 mm] or HQ [96 mm] holes, with fracturing intervals from 750 mm and a pressure bypass safety feature. With Codelco's block-cave operations well-established in harder, primary ore zone, it is not surprising that the com- pany has made significant investment in gaining a better understanding of the rela- tionships between orebody preconditioning and fragmentation once caving has start- ed. As well as hydraulic fracturing, Codelco also uses confined blasting as a preconditioning mechanism. Four of the papers presented at this year's Caving 2014 conference in Santiago, Chile, specifically addressed aspects of preconditioning. For example, one described studies on the relationship between preconditioning and fragmenta- tion at El Teniente, which it said, showed a clear and direct relationship between the preconditioning intensity and fragmenta- tion performance. In another paper, the authors reported on simulations on the effects of a number of variations of hydro-fracturing, confined blasting or combined systems on predicted secondary fragmentation, hang-ups and oversize in the drawpoints, as well as pro- ductivity and operating costs. Equipment for the Job With its very regular spacing of produc- tion-level drifts and drawpoints, it is not surprising that block caving has been used as a test-bed for automated loading and hauling. And, while the world's main sup- pliers of LHDs and mine trucks have been developing systems that can fulfill the requirements, one of them, Caterpillar, has gone a stage further with its transfer of technology from coal mining to the hard- rock environment. If one mine can be said to have been at the forefront of underground transport automation, it must be Northparkes in New South Wales. Underground mining began in 1995, with full production under way from the first block cave two years later. Even then, with the mine owned by North Ltd. and Sumitomo, the first flirtations with LHD automation were in the air, as an article in a 1998 edition of World Mining Equipment explained. Teleremote operations were then just being introduced on the mine's fleet of six Tamrock 450E electrically powered LHDs. With Rio Tinto's acquisition of North Ltd., and Sandvik building on Tamrock's foundations to develop its Automine load- ing system, Northparkes has been very suc- cessful, proving ground for the concept and the technology. According to Sandvik, that success led to Rio Tinto adopting Automine for its Argyle block cave. Newcrest also uses it at its Ridgeway Deeps mine, while Sandvik has delivered 14 LH517 LHDs, all equipped for autonomous operation, for Cadia East. Meanwhile, Northparkes' reliance on its surface-operated LHDs is continuing to pay off. The mine handled a record of just more than 6 million mt of ore last year, and in December its automated loaders handled a record 80% of the total tonnage produced during part of the month. That the mine has only been able to achieve that propor- tion despite a long involvement with automation projects is a reflection on the complexity involved, with the LHDs being controlled during loading by the operator in the control room, then traveling autonomously to the dump and back to the next scheduled drawpoint. One of the critical aspects of any block cave—poor fragmentation—can pose real problems, both in drawpoints and at the ore dump. Pedestal-mounted hydraulic ham- mers are one solution, with the Australian company Transmin having developed its Rocklogic control system for this applica- tion. First used at Ridgeway Deeps, it pro- vides remote operation and collision-avoid- ance capabilities for rockbreakers. Atlas Copco recently reported on a yearlong trial of its semi-autonomous LHDs at Codelco's Andina block-cave oper- ation. With two ST14s being equipped for teleremote loading and autonomous haul- ing, dumping and return, communication between the loaders and the control room used the mine's WLAN system and an overland fiber-optic link—with the control room being located some 80 km away from the mine itself. Atlas Copco noted that this was the first time that a 14-mt-capacity loader had been used in that particular area of the mine, where 10-mt units were the norm. In addition, the four operators chosen for the trial were the youngest ever to operate heavy equipment at a Codelco mine, the company selecting them for their hands-on ability with software and joystick controls. The project has encompassed three phases, starting with the installation of the control room and some underground haulage slashing to provide adequate space for the ST14s to operate. This was followed by operator training and produc- tion ramping until round-the-clock opera- tion was achieved. The final five-month period focused on testing the performance of the semi- autonomous loading system in a real production environment. By the end of 36 E&MJ; • JULY 2014 www.e-mj.com B LO C K C A V I N G ConMico's 300-kW (400-hp) self-contained rig for hydraulic fracturing in block-cave orebodies. EMJ_pg32-37_EMJ_pg32-37 7/2/14 8:35 AM Page 36