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By J. W. Craven, M. Katom, K. M. McCaffery

At Ok Tedi, ore type and SAG feed size distribution vary widely and frequently. This makes control of the SAG mills by application of the power/pressure relationship difficult. Power logic has traditionally been conservative due to power spikes associated with rapid size distribution changes. A new expert system was installed in early 2000. The system incorporates multiple state fuzzy logic to deal with frequent and radical ore type and size variations, along with monitoring of motor temperatures. A short term power spike no longer warrants immediate radical action. This has resulted in increased mill throughput and improved circuit stability.

Jan 1, 2001

By R. H. Zeng

Many subsidence researchers in the U. S. have developed new empirical function methods to predict subsidence, or attempted to validate some empirical functions developed by foreign researchers for use in the U. S. An attempt is made in this paper to develop a new empirical function to predict a surface subsidence basin due to longwall mining. In the U. S., the emphasis of empirical methods for the subsidence prediction over longwall panels has been in large part on determining the profile functions for the major cross-sections of a subsidence basin. In this approach, the surface monuments are usually laid out along the major cross-sections and thus, the subsidence profiles developed are restricted for subsidence prediction along the major cross-sections. However in practice many monuments or surface structures for which subsidence prediction for damage evaluation is required, are not laid out along the major cross-section of the basin. In such cases, it is difficult to get either the empirical profile function for the cross-sections where these structures are located or to predict their subsidence based on the profile function developed for the major cross-sections. Therefore, there exists a strong need to develop a subsidence basin function with a reasonable degree of accuracy, which can be determined or confirmed by the data of scattered monuments on a surface basin. The same subsidence basin function can also be used for prediction of subsidence for any arbitrary points over a longwall panel. In 1982, He (1) proposed the clastic theory, for which he developed the basic differential equations describing the movement and deformation of overburden due to underground mining, and performed the selection of best solution for the equations. He found that the Weibull dietribution is the optimal solution. The Weibull distribution has three parameters that vary to fit the subsidence profile so well that the profile function derived from it provides a high degree of accuracy in subeidence prediction. However the results

Jan 1, 1986

By Maurice Grieves

GC. Waterman Mr. Grieves' paper on "Shaft Sinking Today--A Boring Business Tomorrow" in the Dec. 1981 issue of MINING ENGINEERING is an excellent description of recent improvements in speed and costs of shaft sinking. However, shaft boring techniques are not a recent development. In 1935-36, the Idaho Maryland Co. (gold), Grass Valley, CA, bored the vertical 1.5-m-diam Idaho No. 2 ventilation and supply shaft to a depth of 346 m. The equipment was designed and perfected by Branner Newsome and was, I believe, described in "Transactions." Pickands Mather later bored a 1.8-m-diam shaft to a depth of about 305 m using Newsome's design. The Idaho No. 2 shaft cut through hard gabbro, diabase dikes, soft serpentine, very incompetent ankeritized serpentine and a strong fault zone. The completed shaft did not require timber support; the fault zone was cemented. Equipment consisted of a rotating 1.5-m or 3-m core barrel with a slotted bottom which cut a 76-mm kerf. The cutting agent was chilled steel shot introduced into the slot as needed. The driving mechanism and core barrel were lowered into the shaft, the former secured to the wall and the inshaft "engineer" operated the motors which controlled core barrel rpm and advance. After an advance of 1.5-3 m the equipment was lifted out of the shaft, a half(?) stick of powder cut off the drilled core, and it was hoisted to the surface with a cable attached to an eye bolt at the tope of the core. A "shift" consisted of three men: hoistman, equipment operator (down the shaft), and a surface laborer. Advance was variable as equipment and techniques were perfected. Near the end of the job advance was, as I remember, 1.5-3 m per shift. Costs were, as I recall, about $115/m. Up to 4 m cores were lifted out in one piece and swung to the dump by a stiff leg derrick. The Newsome equipment was relatively inexpensive to build and operate and his method should be (more than?) competetive with the methods described by Grieves. W.E. Hawes The author, in mentioning the South African developments of the cactus grab, ignores the parallel development of the Cryderman mucker in this hemisphere. Perhaps a slightly longer history of blind hold drilling would have been in order. Blind shaft boring got a major boost at the Nevada Test Site, as part of the nuclear weapons development, when it was essential to be able to quickly assess depth for weapons testing. One of the early civilian attempts to utilize this technology occurred when Kerr McGee drilled the shaft at the Section 19 Mine at Ambrosia Lake, NM. This twin masted drill rig belonged to a subsidiary of Kerr McGee, not Shaft Drillers. This was a difficult hole, due to bentonitic shales that decomposed. Later advances in drilling fluids eliminated this problem. The Conoco project referred to is not entirely correct, and needs minor amplification: The depth of the development (not pilot) shaft drilled was 684 m, at a diameter of 3.05 m, with a 2.16 m ID hydratatic casing being installed to a depth of 669 m. Conoco Inc., not Challenger, executed the drilling, however Conoco did use Challenger Drilling Company's Rig 14-S. Rig 14-S is unique in that it is specifically designed for shaft drilling, rather than being an oil field rig used for this service. All work was planned and directed by Conoco personnel. Deviation of the aforementioned shaft from vertical was 31 cm. Two smaller shafts (pilot shafts) were drilled with the same rig. These smaller ones were drilled 1.8 m in diameter, to depth of 665 m and cased with .91-m-diam casing, to depth of 650 m to be used as pilot holes for 5.5 m diameter shafts. The total elapsed time for all drilling, casing, cementing, and rig moves was 50 weeks. The constraints mentioned of vertical accuracy, torque, wall collapse, rig set up time, lining time etc., pumping out, etc., may not be as serious as the author implies. First, vertical accuracy: The record achieved by Conoco indicates that with reasonable care, good accuracy can be obtained, primarily by having a fair amount of weight in tension, rather than on the drill bit. Second, the amount of torque that can be applied to the drill stem has been greatly increased by the introduction of larger diameter drill stems, such as the new Hughes rig uses. Third, risk of collapse of shaft walls is minimal with the proper mud program. Basically, the walls are supported by the weight of the mud and it is not removed until some type of casing is installed and grouted in. Here in the real challenge of blind drilling shafts to devise a more economical method of lining bored shafts than using steel casing. The remaining issues were minor at Conoco, provided adequate planning and scheduling takes place. An excellent paper, "Shaft Drilling--Crownpoint Project" by Hassell H. Hunter, presented at the Fifth Uranium Symposium in Albuquerque in Sept. 1981 contains details of this project. A combination of blind boring, with enlargement by either mechanical means (boring machine, or tunneling type shield) or slabbing down, with muck removal through a larger bored shaft would seem to be the future trend in shaft development. The economics, especially for wet conditions, favor this concept over conventional sinking, as has been demonstrated at Kerr McGee --Churchrock, UNC--Churchrock and Conoco at Crownpoint.

Jan 3, 1983

By C. A. Young

Cyanide is a fast-acting, highly toxic substance but, at the same time, is deemed essential for sustaining life as well as our standard of living. In this manuscript, the facts about cyanide are presented beginning with a brief history and definition and ending with a discussion on cyanide alternatives. Other topics include speciation, physical characteristics, toxicity, manufacturing, cyanogenics, cyanide cycle, separation, destruction, and markets including those outside the mining industry. Emphasis, of course, is placed on gold production by leaching and how it is influenced by ore type, mineral characteristics and economics as well as its advantages and disadvantages.

Jan 1, 2001

By D. W. Rich

An environmental management system (EMS) is a key part of a company?s environmental stewardship. Procedures and practices to continually improve environmental performance can provide great benefits in operating the company. Managing site environmental quality data is a key component of this. An environmental data management system (EDMS) is an important element of the EMS for mining and other projects, providing project staff with the information that they need to make decisions that can have a significant impact on public health. Improvements in computers, data communications, and transfer formats have made it much easier to implement an integrated EDMS program for gathering, managing, selecting, and displaying data from the field and the lab. Software now lets users define sampling plans, create files for field data entry, and print Chains of Custody. Laptop and handheld computers facilitate field data entry and may provide automated communication back to the office. Most labs can now create usable electronic data deliverables. QC checks and limit comparisons can be largely automated. The result is organized data that can be efficiently used for reporting, graphing, and mapping, to better understand project issues.

Jan 1, 2009

By Edward Thomas

Yucca Mountain Overview The U.S. Department of Energy?s Yucca Mountain Project is a geologic repository project designed to receive, handle, package, transport, and emplace spent nuclear fuel and high level radioactive waste. The planned repository would be located in Yucca Mountain on the western edge of the Nevada Test Site, about 90 miles northwest of Las Vegas, Nevada, and would include both surface and subsurface areas. Yucca Mountain rock formations consist of successive layers of volcanic rocks (called tuffs) approximately 14 to 11.5 million years old, formed by eruptions of volcanic calderas to the north. With the volcanic rock the potential for methane emission is not an issue and the subsurface repository is a non-gassy (methane) classification. This paper will provide a summary of the development ventilation system design that provides fresh air for subsurface construction activities, and the emplacement ventilation system design that removes heat generated by the waste packages. The subsurface layout, illustrated in Figure 1, contains 108 emplacement drifts, one Performance Confirmation(PC) observation drift, nine intake/exhaust shafts, and three access ramps. The existing Yucca Mountain facilities, shown in bold lines in Figure 1, include a 7.8 km long, 7.62 m (25 ft) diameter U shaped tunnel that is formed by the North and South Ramps at both ends of the Exploratory Studies Facility (ESF) drift and a 1.5 km long, 5.0 m (16.4 ft) diameter Enhanced Characterization of the Repository Block drift (ECRB) that were constructed from 1994 through 1998. These drifts were used for site characterization activities and have been incorporated into the subsurface repository configuration. The unexcavated perimeter access main and exhaust main drifts are typically 7.62 m (25 ft) diameter TBM excavations and the emplacement drifts are 5.5 m (18 ft) diameter TBM excavations. The turnouts leading into the emplacement drifts are to be excavated by either mechanical, or drill and blast methods and serve as the launch chambers for the emplacement drift TBM excavations.

By W. Hustrulid

In the mid-to-late 1800’s the U.S. mining industry was on the threshold of nearly a century of golden times. Nearly every state had a prosperous and growing mining sector. The importance of the industry was reflected in the creation of the state school of mines. Today, with the depletion of readily available mineral reserves, much of the U.S. metals mining industry is considered to be in a sunset phase. The same is true with the mining schools that serve the industry. However, the United States is still a major consumer of the world’s minerals and requires a dependable supply of both minerals and minerals professionals. In his 2002 Jackling Lecture “You Can’t Make a Silk Purse Out of a Sow’s Ear” the author presented a list of concerns, propositions and recommendations. In this follow-up paper, the author further explores the subject through the presentation of a detailed case example focusing on the iron mining industry of Minnesota and minerals education at the University of Minnesota.

Jan 1, 2004

By Alix Thierart, Yann Rouillard, Bernard Catalano

Bessac's presence in Singapore started in 2014 with the construction of the Thomson metro line, which includes 18 miles of twin-bore tunnels and 22 stations split into 17 construction packages. Bessac joint venture was allotted the T219 lot. The works include the construction of a new 660-foot (200-meter) long transfer station, two parallel 19-foot (5.8 m) ID tunnels and a pedestrian underpass. The urban context and the very soft ground stratum imposed to utilize unusual tunneling techniques, from upgrading a slurry TBM to a high-density slurry TBM to launch with very low cover and canopy pipe roofing completed with a MTBM without retrieval shaft.

Jun 23, 2024

By N. K. Mendiratta

Diethylenetriamine (DETA) is known to be an effective pyrrhotite depressant in pentlandite flotation. It has been reported recently that its performance becomes more consistent when the reagent is used in conjunction with sulfur dioxide (SO2). In the present investigation, the effects of DETA and SO32- ions on the changes in the hydrophobicity of pyrrhotite electrode have been studied at pH 6.8. The results show that both DETA and SO32- can reduce the water contact angles of pyrrhotite; however, the contact angles can be reduced to zero only in the presence of the SO32- ions. This finding may be attributed to the ability of the SO32- ions to reduce the polysulfides formed on pyrrhotite by superficial oxidation, which may in turn provides an explanation for the robust performance of DETA/SO2 combination.

Jan 1, 2001

By D. P. Tao, J. G. Groppo, R. Killmeyer, W. W. Wen, B. K. Parekh

Economical dewatering of ultra-fine (minus 74 m) clean coal slurry produced in column flotation to a 20 percent or lower moisture level will be an important step in successful implementation of the advanced fine coal cleaning processes. The main objective of the present study was to evaluate efficiency and effectiveness of three dewatering techniques, namely, hyperbaric, vacuum and screen bowl centrifuge, in dewatering of ultra-fine (D50 ~ 25 m) clean coal slurry produced by the `Ken-Flote' columns operating at the Powell Mountain Coal Company, St. Charles, Virginia. he hyperbaric filter using 3 bar pressure and 165o cake formation angle, provided a filter cake with 23.6percent moisture with a throughput of 800 Kg/m2-h and air consumption of 868 Nm3/t (460 scfm/t). The vacuum filter with 30 percent submergence provided a filter cake with 27.8 percent moisture with a throughput of 122 Kg/m2-h. The screen bowl centrifuge provided a dewatered product containing 32.9 percent moisture at a feed rate of 450 Kg/hr, however, the solids capture was only65 percent. Addition of 1 Kg/t of a cationic surfactant provided filter cakes with 19.1 percent, 23percent, and 34 percent moisture using hyperbaric, vacuum, and centrifuge, respectively. Similarly, addition of 0.5 Kg/ton of copper chloride lowered filter cake moisture to 20.7 percent and 24.8percent, using hyperbaric and vacuum. With the centrifuge no improvement in filter cake moisture was noted. However, use of 80 Kg/ton of `orimulsion' in the centrifuge provided dewatered product containing 26 percent moisture, and the solids capture increased from 65 to 95 percent. The dewatered product appeared dry and was easily handleable.

Jan 1, 1999

By Faruk Oksuz, Cary Hirner, William A. Rochford

Grouting is a frequently utilized remedy in the planning and implementation of ground improvement and tunnel rehabilitation practice. The state-of-art grouting application used for Chicago’s McCook Reservoir project offers a unique alternative to the tunneling industry for pre-excavation grouting as well as tunnel rehabilitation, rescue and post-excavation ground improvements. The McCook Reservoir project included a computerized grouting control and data collection system for a precise and highly effective groundwater cutoff in fractured dolomites. By using balanced and stabilized grout mixes, the effective permeability of the rock mass was reduced over two orders of magnitude to less than 0.1 Lugeon by installing a double line grout curtain. The stable grout mix designs allowed high pressure and effective grouting at depths up to 125 m (410 ft).

Jan 1, 2005

By Jim Rozek, Robert A. Gee

The Epping to Chatswood Rail Line project is the largest publicly funded infrastructure project in New South Wales. Construction commenced in November2002 with opening scheduled for 2008. The work includes 13 route km of twin TBM driven 7.2 m diameter lined running tunnel, three cross-overs and three new underground stations. The new stations have platform caverns of 20m span with similarly proportioned concourse caverns alongside. The ground is bedded sand stone and shale with high horizontal stresses. Predicted stress-relief induced ground movements during staged excavation led to innovative use of rock anchors for permanent support.

Jan 1, 2005

By William C. Cooley

SUMMARY A review is presented of the state of development of high pressure water jet equipment and of large impact hammers for rock tunneling. Information from the U.S.S.R. is based on published literature and three personal visits. Applicable papers which were presented at the International Symposium on Jet Cutting Technology in Coventry, England in April 1972 are reviewed. Data are presented on continuous jet systems, pulsed water cannons, and hydraulic-powered impact hammers with respect to the specific energy of rock breakage and potential application in tunneling machines. INTRODUCTION It has been estimated that the cost of underground excavation during the period 1970-1979 in 15 countries of the Organization for Economic Cooperation and Development will be over $54 billion, an increase of 104% over the period 1960-1969. It is expected that 55% of the tunneling construction will occur in hard rock (Ref. 1). Present tunneling machines are generally limited to soft and medium-hard rock. When used in hard rock, the cost of replacing mechanical cutter bits is high. Therefore there is a need for improved rock fracture methods which can be applied economically in tunneling machines for hard rock. Water jets and mechanical hammers are two

Jan 1, 1997

By Arnold Hammons

Automated temporary roof support (ATRS) systems have been incorporated into roof bolters since the 1970?s. During roof bolting, many injuries have occurred from large pieces of draw rock falling inby the ATRS beam and tipping back into the operator?s area. Other injuries have occurred due to smaller, sharp rocks falling onto the operator?s hand and arm during initiation of roof bolt drilling. These injuries are attributed to weak immediate roof, sometimes called roof skin failure. Even though ATRS systems support the roof and provide a measure of protection against roof skin failure, additional hazards sometimes do exist immediately inby and outby the supported roof. Design innovations such as the ATRS mounted rocker pad deflector systems have been designed to improve the roof bolter operator safety. This paper will inform the reader of the hazards, machine evolution through different design solutions, and the current state of the art in preventing roof skin failure injuries when roof bolting.

Jan 1, 2009

By L. B. Phelps

The nation is confronted with thousands of acres of abandoned coal lands. In Pennsylvania alone, these lands have been estimated to cost $15 billion to reclaim (Pennsylvania Bulletin, 1985). One way to deal with this problem is to provide a mechanism by which the active mining industry can undertake to remine certain of these abandoned mine areas. Remining is classified as reaffecting previously mined areas in order td extract the remaining coal reserves while improving the environmental quality of these lands through land restogation and abatement of pollutional discharges. However, there currently is a disincentive for operators to plan to extract reserves on these abandoned mine lands which have preexisting pollutional discharges. Therefore, they presently avoid them. This is because of the "potentially unlimited liability of post- mining treatment for any discharges that would remain after mining? (Pennsylvania Bulletin, 1985).

Jan 1, 1987

By O. N. Sikazwe

The Nchanga Cu-Co ore deposit of the Zambian Copperbelt, is hosted in Neoproterozoic siliciclastic-carbonate sedimentary rocks, and it consists of two orebodies: the Lower Orebody (shale) and the Upper Orebody (arkose). Refractory Cu ores present in the Upper Orebody comprise 150 Mt with average 0.87% Cu, and are characterized by inadequate recovery of copper by leaching. This materials characterization study, conducted on refractory ore samples from the Upper Orebody using optical microscopy, QEMSCAN®, and microprobe, has shown that copper occurs mainly in biotite, phlogopite, malachite, pseudomalachite and goethite. QEMSCAN® has quantified the abundance of each phase and total Cu deportment in each phase.

Jan 1, 2008

By C. J. Pritchard

As productivity improvements reduced the number of continuous miner sections from seven to three while maintaining full productive capacity, a decision was made to test an advancing tailgate ventilation system on the shortwall mining section. Having the shortwall mine its own return air system has freed the third mining section for more productive, less costly mining. The advancing tailgate has provided effective ventilation across the face and gob with acceptable pressure losses. The tailgate development continuous miner section has been since transformed from a low productivity part-time function to a high productivity development/retreat panel and is available for long term mine development duties also.

Jan 1, 1989

By H. D. Brenk

"The German Federation of International Mining and Mineral Resources (FAB) is a federation of German companies that are active in international mining and mining related business. The FAB presents a platform for the exchange of information about the worldwide mining commodities in the dialogue with German and foreign institutions. The expertise of the member companies in mining and related activities is based on a long term operation and consulting experience in Germany and abroad. This forms the basis for the special international competitiveness "Made in Germany". The FAB is particularly engaged in the following topics and tasks and acts as a focal point for: • international project developments with the German mining industry, • sustainable mining, consulting and equipment services, • geological and environmental technologies, • project financing and • intermediation of contracts, project enquiries, professional symposia and events. The FAB acts as a contact- and coordination site for international business partners, organizations and governmental authorities. Together with the federal government the FAB organizes bilateral working group meetings in the commodity and mining sector. Project enquiries are being distributed from the FAB among their member companies."

Jan 1, 2011

By Ravi Ray, Kostas Kaklis, Zach Agioutantis

"Modern underground mining is becoming more complex and geotechnically challenging. The engineer uses numerical, analytical, and data-driven methods (empirical and/or experimental) or their combination to overcome these challenges. Each method has its advantages and disadvantages. Nevertheless, given the amount of innovation and experience involved in developing each of these techniques, it will be prudent to use all their benefits rather than favoring one technique over the other. Pillars are the most important support element in an underground mine. A holistic geo-mechanical solution needs to be determined to design mine pillars using a proper sequence and exact mix of the three methods. A combination of these methods, in sync, can encompass the several advantages of the three methods while eliminating their disadvantages. This paper presents a conceptual three-tier solution to the pillar design problem, to improve its design pedigree, using a proper combination of numerical, analytical, and data-driven methods. At the focus of this proposed method lies the Ground Reaction Curve (GRC) concept.INTRODUCTIONAlthough the stability analysis of underground excavations is a challenging problem, its understanding has improved tremendously over recent years through the use of improved tools and techniques. The trial and error method was replaced with more scientific methods like the empirical and analytical methods that are still in use today. Empirical methods were developed based on large data sets obtained from experiments and observations (e.g., coal pillar strength equations). Analytical methods were developed based on mechanical understanding of stability (e.g., safety factor for vertical pillar loading, Convergence Confinement Method). Improvement in computing power and numerical techniques led to the development of several numerical methods (e.g., finite difference, finite element) suitable for geo-mechanical analysis.Each of these methods have certain advantages and limitations. Nevertheless, the user is often puzzled over the proper method selection and over the proper sequence of using them. This exercise becomes more challenging when different methods are combined, where, for example, one has to estimate the pillar strength based on empirical equations (e.g., Mark-Bieniawski coal pillar strength equation), determine the factor of safety based on an analytical approach (e.g., tributary area load divided by pillar strength), and analyze pillar-strata interactions using numerical analysis (see Esterhuizen, Mark, and Murphy, 2010b).Challenges increase when current pillar design methods are designed as passive structures to balance the fixed dead weight of the overburden. This classic suspension design approach does not recognize the self-stabilizing capacity of the overburden (Frith and Reed, 2018). A practical solution to address these issues is the use of numerical analysis. However, one should always keep in mind that the numerical modelling approach may have certain practical limitations."

Jan 1, 2019

By J. O. Marsden, C. Green

In 2003, a high-temperature pressure leaching circuit to treat copper sulfide concentrates was commissioned at the copper/molybdenum operation at Bagdad, AZ. In late 2007, a medium-temperature pressure leaching circuit was commissioned at the Morenci mine in Arizona. The Morenci circuit was shut down in mid-2008, following a fire in the autoclave circuit. The onset of the global financial crisis in late 2008 resulted in significant changes to the operating profile in the Southwestern United States with respect to concentrates production, concentrates treatment, acid production and acid consumption. As a result of these changes, the Morenci concentrator was shut down, and the pressure leaching circuit remained offline. In late 2014, the increasing acid requirements in the Southwestern United States prompted a reevaluation of the Morenci concentrate leaching facilities. As a result, the pressure leaching circuit was restarted in high-temperature (200 °C) mode in May 2015 and has operated successfully for three years since recommissioning. This paper describes the current pressure leaching circuit configuration and the factors leading to the successful application of copper sulfide concentrate leaching at this location.