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By A Rantala, K Aberkrom, O Haavisto, P Blanz

More complex ore bodies with lowering grades increase the challenges of maintaining high throughput, energy efficiency and required particle size for optimal downstream processing in grinding circuits. Continuous and often rapidly changing characteristics of the mill feed requires constant focus to operate the circuit at optimal level. Modern process instruments, on-line analyzers, monitoring and process control systems provide attractive and managed options to increase the circuits’ capability to respond to the challenge, often in phases and in rather short time period. Furthermore, well instrumented and performing base level automation in the grinding circuit enables advanced process control (APC) strategies that utilize measurements from the whole circuit to stabilize and optimize production. In this paper alternatives for incorporating process measurements and controls to typical grinding circuits are proposed. The expected benefits to throughput, availability, energy efficiency and particle size stability are described in recent case examples.CITATION:Rantala, A, Blanz, P, Aberkrom, K and Haavisto, O, 2015. Increasing grinding circuit robustness with advanced process control, in Proceedings MetPlant 2015, pp 129–141 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By Wilbert J. Huff

This is the sixth of a series of annual reports describing the work of the Explosives Division, Bureau of Mines, United States Department of the Interior.3/ It deals particularly with the activities of the division from July 1, 1940 to June 30, 1941. The studies outlined in this and preceding reports of the series have been conducted under the direction of the author and the respective unit leaders, to whom specific credit is given.

Jan 1, 1942

By Wilbert J. Huff

This is the sixth of a series of annual reports describing the work of the? Explosives Division, Bureau of Mines, United States Department of the Interior.3/ It deals particularly with the activities of the division from July 1, 1940, to June 30, 1941. The studies outlined in this and preceding reports of the series have been conducted under the direction of the author and the respective unit leaders, to whom specific credit is given.

Jan 1, 1942

By V. S. S. Yadavalli, J. Hager, R. Webber-Youngman

"This article investigates the complex problem of a budgeting process for a large mining operation. Strict adherence to budget infers that financial results align with goals. In reality, the budget is not a predetermined entity but emerges as the sum of the enterprise’s operational plans. These are highly interdependent, being influenced by unforeseeable events and operational decision-making.Limitations of stochastic simulations, normally applied in the project environment but not in budgeting, are examined and a model enabling their application is proposed. A better understanding of budget failure in large mines emerges, showing that the budget should be viewed as a probability distribution rather than a single deterministic value.The strength of the model application lies with the combining of stochastic simulation, probability theory, financial budgeting, and practical scheduling to predict budget achievement, reflected as a probability distribution. The principal finding is the interpretation of the risk associated with, and constraints pertaining to, the budget.The model utilizes a four-dimensional (space and time) schedule, linking key drivers through activity-based costing to the budget. It offers a highly expressive account of deduction regarding fund application for budget achievement, emphasizing that ’it is better to be approximately right than precisely wrong’."

Jan 1, 2015

By Michael Kaplan

An investigation was conducted of the use of a mechanical rock splitter as the primary means for rock fragmentation in underground hard rock mining systems. Analyses and scale model tests showed that reasonably sized splitters that could be mounted on the booms of conventional drill jumbos were capable of fragmenting over a ton of rock per cycle. Detailed drill-split mining systems were developed for entry development, room and pillar, bench mining, and cut and fill mining. Economic analyses of these systems showed them to be generally competitive with conventional drill-blast methods. Except for bench mining, drill-split offered substantial cost savings over drill-blast. The investigation also included a technical evaluation of the mechanical splitter, an analysis of health and safety, and a determination of the potential applicability of drilling and splitting.

Jan 1, 1979

By Louis W. Cope

Mongolia is known in western countries as the location of rich dinosaur fossil fields. However, the country is even richer in mineral resources. The Ministry of Industry and Trade reports 6,000 mineral occurrences of 80 metals and minerals. Mongolia has already attracted much foreign investment in the mining sector. Mining is the country’s largest industry. It is responsible for 17 percent of the gross domestic product, 65 percent of industrial output and 57 percent of export earnings.

Jan 1, 2006

Nuclear power currently produces about 20% of the electricity in the US, with 104 nuclear power plants located in 31 states. The commercial US nuclear industry contributes over $4 billion annually to US workers in salaries and wages. 25,000 new jobs need to be filled in the next 5 years. There are over 30 new power plants under consideration by US utilities. The operating reactors use uranium oxide fuel enriched to about 4% U235 and fission is the process used to generate heat to form steam to drive the turbine generators. Nuclear energy is an important element in the US generation portfolio and represents the largest producer of nearly emission-free electricity. Most, if not all, of the operating plants will secure an extended 20 years of operation or more. The last plant constructed was ordered in 1978. New smaller, modular reactors are under design to provide less expensive, expandable generation options.

Jan 1, 2011

By R. Hart

In this paper, problems that have been experienced with the rockpass system at Kloof Mine No. 3 Shaft are described. Actions that have been taken to overcome the problems are also described. These include the use of slugshots to remove hang-ups, the abandonment and waste filling of passes, and design criteria adopted for an alternative pass system.

Jan 1, 2006

By M. Mortada

Nonsteady-state flow of slightly compressible liquids in porous media of non-uniform properties has been the subject of a number of recent studies. Most of these studies considered one-dimensional flow in systems with cylindrical geometry and with the properties of the porous medium varying with radial distance only. A. Houpeurt' studied the problem in its general form by examining the solutions of the differential equation, In Eq. 1, the permeability k and the porosity + are arbitrary functions of radial distance. Houpeurt concluded that, except for special forms of the functions k and the problem is not well suited for mathematical treatment, but lends itself to high-speed digital computation. Carslaw and Jaeger' discussed the solution of Eq. 1 for the case in which the permeability varies as a power of the radial distance. P. Albert3 studied analytically the pseudo steady-state solutions in systems of finite radial extent and non-uniform properties. He also obtained some numerical solutions for nonsteady-state flow using a high-speed computer. William Hurst4 examined the interference pressure drop due to a point sink located in an infinite system consisting of two permeability regions in series. In this case, the permeability changed at a radial distance r from the point sink. INTERFERENCE BETWEEN OIL FIELDS IN A NON-UNIFORM AQUIFER The interference pressure drop for oil fields located in an extensive aquifer of uniform properties is discussed in a number of places in the literature. This work considers the interference pressure drop for oil fields located in a non-uniform extensive aquifer comprising two regions of different properties as shown in Fig. 1. Region I of the aquifer extends from which is the radius of Oil Field A, to ar,,, where a>1. It has permeability k,, porosity +, and effective compressibility c,. Oil Field B is located in Region II which extends from ar, to infinity and has different properties from those of Region I, but the same formation thickness h. Region II has permeability k2, porosity and effective compressibility c2. The choice of this type of aquifer should not imply that it is of frequent occurrence. It is chosen primarily to illustrate the effects of non-uniform aquifer properties on oilfield interference. It is of interest to point out that a non-uniform radial aquifer in which both the permeability and the porosity are inversely proportional to the radial distance can be treated in a manner similar to a linear aquifer of uniform properties. The situation where only the permeability varies as the inverse of the radial distance is also amenable to analytical treatment. Both aquifers behave quite differently from a radial aquifer with uniform properties so far as the water influx and the interference pressure drop are concerned. METHOD OF SOLUTION The expression for the interference pressure drop in Oil Field B due to a constant rate of water influx in Oil Field A is developed in the Appendix. This is accomplished by the simultaneous solution of two partial differential equations describing the pressure in Regions I and 11. The two differential equations are solved subject to the following conditions: (1) at r,, the pressure gradient is constant; (2) at ar the pressure and

By M. J. Beus, B. Stewart, S. Iverson

Synopsis U.S. Mine Safety and Health Administration (MSHA) accidents statistics have identified ore-pass hazards as a significant safety problem in U.S. underground metal mines. The statistics show that nearly 75% of injuries are directly or indirectly related to pulling or freeing of ore-pass chutes, the use of hand tools in ore passes, fails of broken rock in ore passes and structural failures of chutes or gates and ore-pass walls. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) are investigating hazards in and around ore passes in hard rock mines. Risk assessment methods, such as fault-tree analysis, have been employed to identify the most probable causes of orepass failures, define research priorities and analyse the factors that result in malfunctioning and unsafe ore passes. Static and dynamic loads are being measured in a laboratory setting with the use of a reduced-scale orepass mock-up. Field tests are being initiated in mine ore passes to determine static and dynamic loads. Data from the test ore passes are being compared with data from the mine to characterize true system behaviour. Computer modelling with the use of closed-form solutions, finite-element analyses and a newly developed particle flow code predicts static and dynamic leads from the flow and the impact of ore and waste in the ore pass. Preliminary results indicate that dynamic impacts from ore and waste rock might be considerably greater than expected. The total static load is substantially less than is typically used fur the structural design of chute and gate support members. It is suggested that damping factors, normal and shear stiffness and mass frictional characteristics have a significant effect on particle flow and resulting impact loads. This is being verified with the use of results from laboratory tests, field tests and particle flow analyses. Ore passes are vertical or steeply inclined openings in a rock mass through which ore and waste are transported and where they mar also be stored. A typical underground mining system is shown in Fig. 1. The arrows indicate the locations of ore passes and loading pockets and their relative configurations. The control of material flow is potentially one of the most hazardous operations in underground mining. According to MSHA data. most of the ore pass-related accidents in the U.S.A. are associated with the loading-unloading cycle and removal of blockages from ore passes. In particular, attempts to free ore hang-ups have resulted in multiple fatalities. The hazards are obvious; there is uncertainty as to when the ore will break loose and miners are unable to escape falling rock to a safe location. Although ore passes and chutes and gate systems for underground metal and non-metal mines roust meet the requirements specified in the U.S. Code of Federal Regulations (CFR). Parts 57 and 75, recent structural failures of ore-pass linings and gates have underlined the lack of adequate ore-pass design standards available to both MSHA enforcement staff and mine engineers. Because of the importance of an ore pass to the safe operation of a mine design criteria need to be assessed and new guidelines developed. Researchers at the Spokane Research Laboratory of the Nationals Institute for Occupational Safety and Health (NIOSH) are investigating hazards in and around ore passes in hard rock mines and studying design criteria for ore passes. The near-term goal is to conduct laboratory and field experiments and computer modelling to evaluate the ore-pass design criteria currently used. Literature searches, field site

By Frank S. Wartman

"The experimental flotation work described in this paper was undertaken to test the conclusions derived from a previous microscopic and chemical study of several samples of converter slag. That study3 resulted in the conclusion that approximately 90 per cent of the copper content of a converter slag wad in either the sulphide or metallic form, and that if the slag were cooled slowly the copper-bearing material would be in particles of such size that they would be freed from silicate and magnetite grains by grinding the slag to pass a 150-mesh sieve. If this were true, it should be possible to separate the copper-bearing grains from slowly cooled, converter slag by the flotation process.Many attempts, of which the author has seen no published account, have been made to treat slags, especially converter slags, by flotation. In every case these trials have been made with chilled slags, in which, as shown in the preceding report, the copper-bearing material is top finely disseminated, to be freed by any reasonable degree of grinding.The flotation tests described in this paper have shown that it is possible to recover by flotation about 30 per cent of the copper content of a converter slag containing 3 per cent copper and to obtain flotation concentrates which have a copper content of 35 per cent.Acknowledgment is made to G. L. Oldright, supervising engineer of the section of nonferrous metallurgy, U. S. Bureau of Mines, for valuable assistance and direction; to W. A. Sloan for chemical analyses; and to Alfred P. Towne for assistance in experimental manipulation."

Apr 1, 1931

By P E. H Gregg, R B. Stewart

Restoration trials established in 1985 included a treatment where pasture seed was sown directly into fertilised tailings. After seven years, accumulated soil data was used to compare physical and chemical changes in the plots with the original tailings control area nearby.   A known amount of annual fertiliser additions over the seven year period allowed nutrient balances to be calculated. Losses of S and P were relatively high at 72% of applied S and 28% of applied P. Calculations show that at least 240 kg N/ha/yr was fixed by clovers and this is likely to be under-estimated given that the calculation did not allow for leaching losses.

Jan 1, 1993

By Chelsea Woodward

The Spokane Research Laboratory of the National Institute for Occupational Safety and Health has demonstrated a prototype hydrogen-fueled mining vehicle as an alternative to diesel equipment in underground mines. Safety and control systems were added to allow a 70-kW rubber-tired hydrogen vehicle, originally developed by the U. S. Bureau of Mines and Hydrogen Consultants, Inc. (now Hydrogen Components, Inc., of Littleton, CO), to be tested. This work began in late 2000 and culminated with a Mine Safety and Health Administration fire safety review and field tests at the Stillwater Mine in Nye, MT, in 2004.

Jan 1, 2006

By M. P. Hay

"For a model to be successful it must address the concerns and needs of a target audience. Further, the model must demonstrate the same patterns of behaviour as the real system, and need only be complex enough to meet this objective. If the model is too complex it can become unusable to those who need it most.With this in mind, SUPASIM has been developed for the practical metallurgist requiring only laboratory flotation rate data as input. Some 35+ successful plant simulations have been completed since 1985. The approach of SUPASIM is to characterise an ore, organise information in an understandable way and add structure to the complex flotation situation and hence support the metallurgist to interpret the relationship between variables and optimise the flotation process.The paper describes the basis on which the model was developed and sets out to provide an insight into interpreting laboratory flotation kinetics and their physical meaning in a production plant and the influence floatable gangue has on float performance and plant design. A case study illustrates how the ratio of slow floating mineral to gangue can influence circuit design and improve recovery on a plant scale.INTRODUCTIONThere is an enormous amount of useful data in the results of a laboratory scale rate test. Each variable of fraction and rate, for mineral, metal and gangue has a physical meaning in the plant. The link between float kinetics and the plant in respect of recovery, grade, pulp density, pulp flowrate, residence time, number of stages of cleaning and circuit configuration has been established by the author in the process of developing SUPASIM."

Jan 1, 2005

Phosphorus Phase Analysis of Medium-Low-Grade Rare-Earths-Bearing Phosphate Ores

Sep 13, 2010

By Aly M. Mohammad

The Delaware River Tramway will link civic and retail developments in Philadelphia, Pennsylvania and Camden, New Jersey. Twin 300-foot towers will anchor the cables at either side of the river. Four high capacity drilled shafts designed by the Geotechnical Department of DMJM+HARRIS support each of the towers. At the Philadelphia tower, each 6-foot diameter shaft extends 130 feet deep and terminates with a 30-foot rock socket. The shafts are situated within the footprint of an existing relieving platform, which complicates the typical construction sequence. Also, the subsurface conditions at the site provide a unique challenge in both the design and construction of the drilled shafts. During the construction of the four-drilled shafts for the Philadelphia tower, a 6000-ton Osterberg load test was performed on the first shaft to verify design assumption and confirm the shaft capacity. The results of the test were utilized to establish load transfer characteristics and develop foundation design parameters suitable for the site conditions. By doing so the Design Engineer was able to reduce the length of the rock sockets on the remaining production shafts by approximately 5 feet per shaft. As a result, the test provided a significant cost saving to the Owner by eliminating 15 feet of rock drilling from the construction costs. This paper presents a description of the unique design and construction methods adopted for the foundations, also on the Osterberg load test including equipment used, number and locations of strain gages, and interpretation of results. The results and findings presented in this paper could benefit both the design and construction industries because it provides a comparison between geotechnical design assumption and actual field measurements; which has always been a challenge particularly for rock formation.

Jan 1, 2002

By Karl A. Higgins

In 1976, Prof. G. G. Meyerhof published a famous article in the Journal of Geotechnical Engineering titled ?Bearing Capacity and Settlement of Pile Foundations?. This article presents the authors opinions on calculating pile capacities in clays and sands, group capacities and pile settlement. A portion of the article presents correlations of shaft friction and end bearing to the Standard Penetration Test (SPT) N-value. Subsurface exploration via the Standard Penetration Test is the most widely used exploration tool in the United States, so correlations of pile capacity to N-value are significant to the practice of geotechnical engineering. Meyerhof?s SPT-N correlations are relatively simple calculations compared to other pile capacity computation methods presented in the article or found in other text books (such as the a-method, b-method, Nordlund, Vesic, Meyerhof?s semi-empirical, others) and therefore are popular amongst practicing geotechnical engineers. At the time these correlations were published by Prof. Meyerhof, utilization of dynamic testing with the Pile Driving Analyzer (PDA) was not widespread in geotechnical engineering practice. Prof. Meyerhof?s correlations appear to be based upon conventional static pile load testing of instrumented piles. Dynamic pile measurements to estimate a pile?s static capacity provides certain advantages over conventional static load testing, namely the determination of unit shaft friction values at discrete intervals along the pile, and the unit end bearing support value. The author has compiled a database of driven, displacement piles tested with dynamic methods (ref. ASTM D4945, Test Method for High-Strain Dynamic Testing of Piles). The data was collected between 2002-2010 and is comprised of displacement piles driven into coastal plain sediments in the mid-Atlantic states of Virginia, Maryland and the District of Columbia. In layered soils, dynamic testing in particularly helpful as it reveals the differences in unit shaft friction for varying soil types. One hundred ninety (190) piles are included in the database, with a corresponding 1,373 discrete shaft friction and 190 end (toe) bearing measurements. The pile type typically consisted of 12 and 14 inch square, prestressed, precast concrete piles; however, a significant number of piles were steel HP 12 or 14 inch sections. The database was sorted based upon soil type, and then correlations of shaft friction and end bearing were derived in the same or similar manner as Meyerhof?s original 1976 publication. The new correlations are compared to Meyerhof?s original values.

Jan 1, 2011

By Mario Terceros H., Bengt H. Fellenius

"ABSTRACTFour strain-gage instrumented bored piles were constructed in a sedimentary, dense to very dense, fine to medium sand in Santa Cruz, Bolivia. Two of the test piles were the normally used bored pile constructed with bentonite slurry and two piles were Bauer Full Displacement Pile (FDP). One of each pair was equipped with the Expander Body, an inflatable steel cylinder that on pressure-grouting provides an enlarged pile toe. Head-down static loading test were performed on three of the piles and a bidirectional test was performed on the fourth pile, a standard pile with Expander Body and a bidirectional cell placed immediately above the EB. The latter pile was tested in 3 phases. First by activating the cell, second, by a head-down test, and, third, by a repeat bidirectional cell test. The static loading tests proved the shaft resistance of the FDP pile to be about twice that of the standard bored pile and that the Expander Body more than doubled the toe stiffness. The strain-gage records showed that the standard bored piles had multiple bulges and neckings, which affected the evaluation of the axial stiffness and load distribution of the piles. The testing programme was used for a prediction event with 60 persons, ahead of the tests, submitting predictions of the load-movement curves for the test piles and also a capacity appraised from the curves.1. INTRODUCTIONOn April 23 - 26, 2013, the First International Conference and Seminar on Deep Foundations was held in Santa Cruz, Bolivia under the auspices of INCOTEC SRL, the UAGRM University, and the Bolivian Association of Civil Engineers and Chamber of Construction. To coincide with the conference, a research study on construction and static and dynamic testing of four instrumented bored piles was undertaken. To ""add spice"" to the conference, a prediction event was organized on the test programme. This paper presents the soil conditions at the site, the type and construction of the test piles, the outcome of the prediction event, and the results of the static tests.2. SOIL CONDITIONSGeotechnical studies comprising SPT and CPT tests with routine laboratory analysis were performed on recovered soil samples. Three SPT boreholes were put down at three of the locations of Pile TP1, TP2, and TP3, at 5.0 m distance from each other. The SPT procedure consisted of manual hoisting of the weight by three crew members pulling on ropes over a pulley supported by a tripod and letting the weight fall by gravity. The groundwater table lies at 3.5 m depth.Figure 1 shows diagrams of the SPT N-indices and the distribution of water content in the three boreholes. The SPT-indices show the soil density to be compact. The average water content is about 15 %, plus-minus a few percent."

Jan 1, 2014

By R. Ramírez, N. Aslin, G. Ríos, T. Bravo, A. R. Almansa

Lacy copper has been an on-going concern at Atlantic Copper for at least 10 years and was first reported to Glencore Technology in mid-2010. Over the past 12 years, many of the plates were replaced due to age and general deterioration however; plate passivation and lacy copper issues have persisted. After analyzing all the possible causes of this phenomena, it was found that the problem is caused by a degradation of stainless steel as a consequence of the deposition of Sb oxides. These deposits act as passivating agents of stainless steel, which reduces the density of copper nuclei, causing defective copper deposit, with low thickness and ductility. After doing several tests for reducing/removing the phenomena, the over-riding factor was found to be the anode-cathode overlap. An adequate overlap eliminates the problem of "lacy copper". This was verified during an eight month trial with anodes extended 2.5cm in length. Longer anode not only avoids the appearance of lacy copper, but also recovers cathodes that already have lacy copper. On the other hand polishing of plates only gives rise to a temporary solution that requires on-going polishing, to avoid the re-appearance of lacy copper. INTRODUCTION The electrolytic copper refinery of Atlantic Copper in Huelva (Spain) was commissioned in 1970 with an initial capacity of 40,000 t of cathodes per year. In 1975 the copper refinery was expanded to 108,000 t/year. From 1994 to 1996, a new expansion together with the implementation of ISA permanent cathode technology led to a capacity of 215,000 t/y. Since 1995, a progressive increase in the current density up to 350 A/m2 has been accomplished, which together with an increase in the number of cells from 1,120 to 1,204, has led to the present cathode production capacity of 290,000 t/y A lack of copper deposition in the lower part of the steel permanent cathodes was first reported in 2010. This phenomenon is known as “Lacy copper” because of the appearance of the copper deposit as it can be seen in Figure 1. The occurrence of this phenomena was relatively low and was assumed to be originated by an excessive anode scrapping. Nevertheless, in December 2015 Lacy Copper was observed in a significant amount of copper cathodes giving rise to the following issues: Increased tramp copper – housekeeping and maintenance problems Poor appearance of cathode deposit and untidy looking bundles

Jan 1, 2019

Reliable estimation of in situ stress is a major step in the analysis and design of underground excavations in rock, particularly for evaluating the stability of underground structures to prevent failure or collapse. In the last ten years, the Western Australian School of Mines (WASM) has studied and developed an AE stress measurement technique using orientated core named the WASM AE method. It allows the determination of a representative and detailed knowledge of the in situ stress field during the early stages of a project (such as mine feasibility studies), even in areas where development access is not yet available. The method has been used for in situ stress measurement at more than 80 mine sites worldwide with over 200 individual stress measurements carried out to date. This paper describes the sample collection, sample testing and reconciliation of results for very deep measurements carried out at the Craig-Onaping mine complex in Sudbury Canada. The results constitute the deepest measurements undertaken to date at the WA School of Mines and indicate that the main principal stress is horizontal and oriented parallel to a common regional sub trend in a NE/SW direction.

May 1, 2009