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Coincidentally, the porphyry resource tonnage at Resolution is comparable to that at Chuquicamata, at around 1, million mt, albeit at about twice the copper grade. The company pointed out that this package, developed by Gemcom, has been in use for 25 years now, during which time it has been used for a wide variety of block-cave scenarios. The author of the monograph, Dr. The orebody geometry, mining geometry, material fragmentation and flow, economics and mining history, and sequencing can all have an effect, as can the impact of dilution from various sources.

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In situations where a new lift is being designed beneath an existing block cave, there is the possibility that resources may be increased through the presence of residual ore from the level above, and Dr. Diering is of the opinion that the quantification and categorization of this type of material will play a more important role in the future. With the trend toward the establishment of block caves at greater depths over relatively small footprints and in competent rock-mass environments, they noted that operators are also planning higher cave columns in order to maximize the profitability from the extraction level.

The ability for a cave to propagate vertically in such environments is less predictable, they added. With its production level at a depth of 1, m, Newcrest Mining developed Ridgeway Deeps beneath the existing sublevel caving mine. The transition took place in , although as a analysis note from Credit Suisse suggested, the move here did not go completely to plan. Nonetheless, Newcrest was not deterred but has transferred the experience gained to the design of its newest operation in New South Wales, Cadia East.

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Panel Cave 1 at Cadia East came on stream in January , with Panel 2 scheduled for production next year. And, of course, Newcrest now has the in-house expertise to be able to evaluate other deposits for block caving, including its huge Wafi-Golpu prospect in Papua-New Guinea.

Hydraulic Fracturing Helps Fragmentation With near-surface opportunities for block caving becoming fewer, more recent developments are commonly encountering new challenges in terms of natural orebody caveability. Deeper rocks are stronger, less fractured and so less amenable to caving on their own—hence the need to give nature a helping hand.

Hydraulic fracturing offers a means of doing so, effectively preconditioning the orebody by enhancing existing weaknesses while creating others. As well as pre-conditioning the orebody, the fractured area is de-stressed, making it much more predictable as to how the orebody will cave. ConMico has developed a hp portable high-pressure hydraulic fracturing rig that is completely self-contained apart from power and water supplies.

Supplied to Codelco for use mainly at El Teniente, but also at its other block-cave mines, the rig is just more than 4 m long and 2. Fracturing begins at the back of the hole, with the packer being moved toward the collar, section-by-section, until the entire hole length within the ore zone has been treated. Working at such pressures, the packers themselves are fairly sophisticated pieces of equipment, according to the commercial director for Australian-based Inflatable Packers International IPI , Howard Kenworthy.

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  • According to Kenworthy, only pure water is injected, which typically fractures a radius of 25 m around the hole. The company claims that these packers are exceptionally durable, and can be used in any hole orientation, both up-holes and horizontally. The standard packer systems are either or mm-diameter for working in NQ [76 mm] or HQ [96 mm] holes, with fracturing intervals from mm and a pressure bypass safety feature.

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    As well as hydraulic fracturing, Codelco also uses confined blasting as a preconditioning mechanism. For example, one described studies on the relationship between preconditioning and fragmentation at El Teniente, which it said, showed a clear and direct relationship between the preconditioning intensity and fragmentation 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 productivity and operating costs.

    Block Caving Geomechanics | Angus & Robertson

    Equipment for the Job With its very regular spacing of production-level drifts and drawpoints, it is not surprising that block caving has been used as a test-bed for automated loading and hauling. 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 , with full production under way from the first block cave two years later. Even then, with the mine owned by North Ltd. That the mine has only been able to achieve that proportion 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 hammers are one solution, with the Australian company Transmin having developed its Rocklogic control system for this application.

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    First used at Ridgeway Deeps, it provides remote operation and collision-avoidance capabilities for rockbreakers. Atlas Copco noted that this was the first time that a mt-capacity loader had been used in that particular area of the mine, where 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.

    References Publications referenced by this paper. A model for cave propagation and subsidence assessment in jointed rock masses. Sainsbury B-A. Predicting rock mass cavability in block caving mines C. A practical manual on block caving. DH Laubscher. Block caving geomechanics international caving study I, — E Brown.

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    A new approach to studying complete rock engineering problems John A. Hudson , John Paul Harrison. Brady , Erik Thorson Brown. An application of rock engineering systems for estimating TBM downtimes O.