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By G. L. Simmons.

Many large. low-grade (refractory) sulfide gold resources exist in Nevada and other parts of the world that are not amenable to concentration by conventional flotation practice, Over the past several years Santa Fe Pacific Gold (SFPG) has investigated flotation process options to economically treat low-grade refractory resources of this type at Lone Tree and Twin Creeks. Conventional flotation technology applied to the original high-grade gold resources at Lone Tree and Twin Creeks was initially unsuccessful. Review and analysis of auriferous (gold-bearing) iron sulfide mineralogical characteristics and flotation chemistry provided a fundamental understanding that led to the development of a new flotation process that SFPG refers to as N2TEC. This paper discusses the development of this technology and compares N2 TEC results with conventional flotation practice.

Jan 1, 1997

By Dirk van Zyl

Natural materials can be used successfully in the construction of heap leach pads. The use of these materials usually result in the least expensive approach for such facilities. Sufficient geotechnical experience has been gained in the design and construction of clay heap leach pads so that they can be used with confidence. A number of operators presently use clay pads in their heap leach facilities; these include Alligator Ridge, Ely, Nevada (gold), and Union Carbide, Gas Hills, Wyoming (uranium). This paper describes the construction and field investigation of a clay pad for the heap leaching of agglomerated precious tailings. The project is located in the Mojave Desert, Southern California. The design had to satisfy operational requirements as well as regulatory requirements. The California Water Quality Control Board (WQCB) was one of the agencies which had to issue a permit for the project. Their biggest concern was the discharge or escape of cyanide into the environment. Rather stringent requirements were therefore placed on the pad design criteria, especially in terms of permeability.

Jan 1, 1983

By James E. Lawver

Response surface methodology is a well-known and powerful technique for determining optimum conditions in flotation systems. One disadvantage is the onerous task of the numerical calculations and curve platting. This paper describes a system in which the investigator simply selects the range of several flotation variables after which the design of the experiment, data analysis, generation of response surface equations, and response surface plats are automatically carried out using a digital computer and a computer-driven curve plotter. Several typical response surfaces of important variables in phosphate flotation are presented as examples. An overview of the flow charting of the system is provided in the addendum.

Jan 1, 1978

By Chris Groccia, Damodara R. Chinnasane

Vale is in the process of resuming mining in the lower 810 ore body (810 OB) below 4130L at Copper Cliff Mine – South Side. Production in the lower 810 OB had continued until it was temporarily ceased in 2017 to allow for the execution of activities associated with Copper Cliff Mine Phase 1 project. While mining the stopes in both the lower and mid part of the 810 OB, a seismic response was experienced that resulted in rockbursts and challenging mining conditions. The majority of the rockbursts experienced in the past were associated with stopes mined in a bottom-up mining sequence under a diminishing pillar situation between 3350L and 3540L. The current mining plan is comprised of both top-down and bottom-up mining fronts using a center-out chevron sequence of long hole open stopes to manage induced stresses. Numerical modeling assessments have been carried out to forecast the response of the rock mass due to the planned mining. Seismicity and stress induced damage surrounding excavations are anticipated, and areas requiring extra attention have been identified. A tactical approach is being used to prepare the area for production, including replacement of ground support elements that are damaged or have insufficient residual capacity, and installation of dynamic support in areas anticipated to experience bulking and/or dynamic loading that would exceed the current support system’s capacity. A series of monitoring programs are being put in place to confirm current conditions, and to monitor the response of the rock mass to proactively implement ground control tactics should the need arise. This paper provides a summary of the approach used to forecast, monitor, and manage the behavior of the 810 OB rock mass response to continued mining at depth.

Apr 26, 2022

By J. A. Ehler

Speed and torque control of standard A.C. induction motors can be accomplished using a variety of devices ranging from mechanical, hydraulic, and electrical. Also, the motor can be specified as an A.C. wound rotor or D.C. motor using the associated controls. Normally, any one of these drive types can be adequately used to provide the torque control necessary to accelerate a conveyor belt system. The selection will depend on the economics, experience, and preference of the designer or end user. These drive types will be presented from a functional and performance viewpoint to assist in the understanding of the available technology.

Jan 1, 1998

By Gregory M. Rumbaugh, Todd Kostecki, Christopher Mark

From 2015 to 2021, five massive pillar collapses occurred at four underground stone mines in the eastern United States. These events resulted in powerful airblasts that damaged mine infrastructure and mobile equipment, seriously injured miners, and disrupted underground travelways. Each of these pillar collapses propagated through the overlying strata, causing a subsidence basin on the surface. Pillar collapses are particularly hazardous for miners because they can occur with little warning and can affect miners that are far from the pillar collapse area. The following case studies show that certain factors may increase the likelihood of a pillar collapse. For instance, each of the five events involved the collapse of at least twelve benched pillars with width-to-height ratios (w/h) of 0.8 or less. This study elaborates on

By William C. Ellis

Underground water is part of a continuing hydrologic cycle, which involves all elements of water occurrence. All groundwater of economic importance is in process of movement through a porous rock stratum from a place of intake or recharge to a place of disposal. Groundwater moves and is contained in fractures in the rock and/or in intergranular spaces of porous formations. Where there have been no water developments by man, groundwater is in a state of approximate equilibrium and the forces of replenishment and discharge are in balance. Thus, groundwater, unlike other mineral resources, is constantly being replenished in most areas at a rate which is measurable and which is important in the planning of its utilization. As illustrated by Figure 1, replenishment of groundwater supplies results from the direct penetration of rainfall through the soil to the water table, by seepage from surface streams or ponds, and/or by subsurface movement from an adjacent groundwater body. Under natural discharge conditions, water is commonly consumed by transpiration of trees and other types of vegetation, by flows from springs, by evaporation from shallow depths below the surface, and seepage into streams that traverse the area.

Jan 1, 1964

By Heinz Petry

In deep strip mines the job of moving overburden may be so much bigger, and more costly than the removal of coal or ore that the operation is often called dirt mining. Constant improvement in stripping machines and techniques of using them is needed to offset rising costs and to increase production in mines that are now operating, and to make it economically possible to work deeper or thinner deposits.

Jan 1, 1962

By P. Mousset-Jones

The USBH Mining Systems and Ground Control Generic Research Center funded a project leading to the improved planning of airflow and refrigeration in underground mines experiencing hot working conditions. The project was broken down into approximately five phases: 1. Visiting some of the known hot mines in the U.S. and sending out a questionnaire to determine other mines which might be experiencing hot working conditions in the future. 2. Choosing two mines in which to conduct measurements to determine the insitu rock thermal conductivity and diffusivity, and comparing these values with laboratory determined values. 3. Investigating computer programs available for mine climate simulation, and testing these programs with case study examples from the two mines where the rock thermal properties were measured. 4. Considering improved ways of estimating the wetness factor and experimenting with the use of heat flux meters to more directly measure the rock heat inflow into the airstream. 5. Applying the results of these investigations to simulating the climate for future mine development and production areas at the two- mines. The project is approximately two thirds completed. At the time of writing, the insitu measurements at one of the mines are still being recorded. This paper will be describing the procedures and results of the insitu rock thermal property measurements, and give a brief description of some of the simulated results obtained for a mechanised cut and fill stope case study from the Homestake Gold Hine in South Dakota.

Jan 1, 1985

By Iain Weir-Jones

The efficient operation of an open pit mine presupposes that the slopes are maintained at an angle which closely approaches that of the ultimate stability of the slope. In order to do this in a safe manner, it is essential that the data relating to the behavior of the slopes be monitored and made available, through an instrumentation system, to the appropriate personnel so that soundly-based engineering decisions may be reached with the minimum of wasted effort. In addition to simply detecting potential failures, the system should also define what type of failure is developing; i.e., rotational, wedge, or dilational failures. Providing this data is the prime function of a stability monitoring system. Therefore, in an operating open pit mine, the instrumentation system must provide information which will have a direct bearing upon both the safety and the economics of the operation, as well as provide data which is pertinent to initial design, or to the re-design of slopes where developing instability is found to be a problem.6 It is possible to excavate pit slopes which will remain stable under extremely adverse conditions; however, such slopes would usually be so flat that they would tend to render the operation of a pit uneconomical which might otherwise be mined at a profit. On this basis, all practical pit slopes must be considered to be, to some ex- tent, unstable; if they are not, the design is too conservative and the mine is not returning its maximum profit. To reduce the problem to its fundamentals, one can simply state that the ideal pit slope design produces a slope which stands with zero maintenance for the entire life of the pit and then collapses into the final excavation as soon as the personnel and equipment have been removed. Such a design is impossible to achieve, but the fact remains that an efficient slope would hover on the edge of failure for the life of I the pit. As one retreats from this position, the profitability of the mine decreases because of an unduly conservative design.

Jan 1, 1975

By Walter Hoecker

The dissolution of gold in cyanide_ leaching has been we11 published with the genera1 acceptance that gold is oxidised by oxygen and stabilized by complexation with cyanide [1]. The dissolution of gold is essentially an electrochemical process. The rate of the anodic gold dissolution is controlled by the cyanide concentration. - (2) While the cathode reduction of oxygen is controlled by dissolved oxygen concentration - (3) There are a number of factors influencing the concentration of oxygen, and if 1owered substanth.lly will effect the efficiency of the leaching plant. These include: "' salinity "' temperature "'partial pressure "'oxygen consumption rate The use of pure oxygen for· cyanidation is only beneficial if oxygen is rate limiting, Conversely a slurry saturated with air (typically 5 - 8 ppm) may not be enough for maximum leach rate. The diagram below shows the maximum dissolved oxygen levels obtainable with pure oxygen and air. DISSOLVED OXYGEN (MAXIMUM) IN WATER At steady state, the rate of the cathodic reaction must equal the rate of the anodic reaction. Thus the rate of gold dissolution is dependent on both the· cyanide and oxygen concentrations. - (4) Using an average of Do/Den =· 1.5 [2] (where Do and Den are the oxygen and cyanide diffusion coefficients) the table below illustrates the maximum effective oxygen concentrations for given cyanide levels in clean water [3].

Jan 1, 1992

By A. S. Kane

According to the 1966 Bureau of Mines Mineral Year Book only three states reported production of lignite in that year. These state: were North Dakota, Montana, and South Dakota; although it is known that there is production of lignite in Texas, California and, perhaps, Arkansas. In the year 1966 North Dakota produced 3,543,000 tons of lignite, Montana produced 328,000 tons of lignite, and South Dakota produced 10,000 tons of lignite. In view of the fact that North Dakota produces approximately 95 per cent of all the lignite reported in the United States, in discussing lignite mining, my remarks will be confined to lignite mining as conducted in North Dakota and will be confined to the production of lignite by stripping methods, as this is the predominate method used today. The first lignite mining in Worth Dakota, undoubtedly, was done by people settling in the western part of the state where wood was scarce and where lignite is exposed in the banks of creeks and ravines. The first production records were kept in 1884 and indicate that 35,000 tons of lignite were mined that year. The growth of the lignite industry has been very slow during the intervening period, but in 1966 production started to increase, and it is now indicated that production in the next few years may approach 6,000,000 tons per year. Ninety-seven per cent of the lignite produced in the lignite area of the Midwest is utilized in the generation of electric power, and it is anticipated that this use will predominate during the next two decades.

Jan 1, 1968

By D. Lauriski, E. D. Thimons, A. C. Smith, D. C. Fredley

The National Institute for Occupational Safety and Health (NIOSH) and Northwest Barricade LLC (NWB) conducted a study to evaluate the effectiveness of a novel fire blocking gel for use in underground coal mines to extinguish or retard the growth of a coal fire. The gel agent was subjected to controlled laboratory testing to assess its ability to delay coal ignition. It was then evaluated to determine if manual fire hose application could be used to apply the agent to mine roofs and ribs to provide a safe egress for mine rescue teams from a fire area. The gel agent was also evaluated in a water sprinkler system to determine its potential for use in conveyor belt fire suppression systems. The agent was then tested in live-fire exercises to examine its effectiveness in retarding and extinguishing a deep-seated coal fire and wood fire. Lastly, the ability of a mine rescue team to quickly and safely apply the gel agent to a mine entry during a simulated mine fire exercise was determined.

Jan 1, 2011

By Randall J. Weege

Nickel laterites throughout the world are similar in their gross aspects, but vary significantly in detail. The deposits occur in two separate and distinct geologic settings --those formed over ultramafic rocks which were mechanically emplaced, and those formed over ultramafic rocks that were intruded as melts. The source of the primary nickel in the parent rock may occur both as ionic replacement in silicate lattices and as nickel sulfides. Factors controlling the degree of laterization and nickel enrichment are dependent upon the parent rock characteristics as well as chemical and climatic conditions. Two chemically and physically distinct zones (oxide and saprolite) are commonly present in the laterized rock, but one or the other may be extremely thin or absent. Cobalt and copper may be present in recoverable amounts. Geologic, geophysical and geochemical methods are all utilized in exploring for these deposits. These methods are compared, evaluated and illustrated in the paper. Drilling patterns and ore reserve calculations are also discussed. In contrast to many ore deposits, processing costs are much higher than mining costs. The most efficient processing method is directly dependent upon the chemical composition of the ore. This variation in the chemical and physical characteristics of nickel laterites requires a detailed test program of the metallurgical response to representative samples and blends of ore. Detailed laboratory and bench-scale metallurgical tests are necessary prior to a full scale pilot plant test.

Jan 1, 1978

By Dmitriy A. Malovichko

The general theory for the description of seismic sources is briefly discussed. The effect of excavations on seismic radiation is considered. Expressions for seismic source mechanisms in terms of the geometrical and mechanical parameters of source processes are provided for the following cases: fault slip and shear failure in a confined environment, dynamic stress fracturing around a tunnel, rock fall, landslide and sudden subsidence. A classification of seismic events in mines based on source mechanisms is introduced. The classification separates blast-, slip- and crush-type events. Various approaches of analysis of source mechanisms involving forward modelling and inversion are discussed. The following examples demonstrating the utility of source mechanisms in mining are presented: forensic analysis of damaging seismic events, assessment of the increase in the depth of failure for dynamic stress fracturing around tunnels and its duration, examination of the rockmass deformation regime, assessment of deformation around tunnels using crush-type events, identification and parameterisation of weak geological structures, stress inversion from slip-type events. Finally, the requirements for seismic data to ensure high quality source mechanism solutions are briefly reviewed and future challenges in the interpretation and utilisation of seismic source mechanisms in mines are speculated on.

Apr 26, 2022

By R. J. Hamilton

Considerable success has been achieved in recent years in reducing concentrations of respirable dust in UK coalmines; thankfully this has been reflected in significant improvements in pneumoconiosis statistics. However, continuous increases in mechanisation and in rates of working, accompanied by more stringent dust regulations, necessitate the introduction of improved and often more sophisticated methods of dust control. The increased application of exhaust ventilation and air cleaning techniques seems likely to be the most important step forward in dust control in coalmining during the next few years. A typical drivage in a UK mine is not more than 16 ft (5 m) wide and is supported by steel arches. In the past the majority of such roadways were driven by the conventional means of blasting and loading. Since the main purpose of ventilation was to clear blasting fumes and to provide adequate scouring of firedamp, not surprisingly it was usual to have 'forcing' ventilation. Present systems of operation are making increasing use of heading machines and it is not surprising that well over half of all drivages are now ventilated by exhausting methods. (1) The great majority of coal getting in the UK is from longwall faces, usually in seams of less than 6 ft (1.8 m) thickness. Although this method of min¬ing has many advantages in terms of safety and productivity, dust control is made more difficult because of the need for men and machines to work in the same ventilation stream. Much emphasis has been placed on improving the design and methods of opera¬tion of longwall machines to reduce dust production, and improved ventilation has provided greater dilution, and in consequence, reductions in dust concentration. On all machines water is now fed through internal galleries to the cutting elements. Unfortunately, one of the difficulties associated with mining thin seams is that there is some unavoidable cutting in the roof or floor and in many seams there are faults to be traversed and dirt bands which must be removed with the coal. Under these conditions it appears that the use of exhaust ventilation and air cleaning offers the most promising way of achieving satisfactory dust conditions.

Jan 1, 1980

By R. R. Klimpel

This paper discusses the effect of water chemistry, reagent type, and other environmental factors on the performance of sulfide mineral size reduction and froth flotation processes. Two specific problems will be discussed: 1) the importance of appropriately utilizing the electrochemical window that is created in the grinding process to enhance sulfide mineral recovery by froth flotation; and 2) the impact of steel grinding media versus autogenous grinding on the efficiency of sulfide mineral flotation with varying thiol collectors and water sources.

Jan 1, 1996

By A. K. Bakshi

Mineral suspensions show Newtonian flow properties at lower solid concentration, but change into non-Newtonian regime as the solids content is increased. For Newtonian fluids viscosity is independent of shear rate, but for non-Newtonian fluids it varies with rate of shear. Therefore, measurement of viscosity at a shear rate, different from the process will be futile unless the slurry is Newtonian. This is especially true for hydrocyclone operation, where the rate of shear is different at different points within the hydrocyclone. In this case, it is very important to determine the flow type of the suspension before attempting to establish any correlation between viscosity and process efficiency. A new technique to distinguish such changes in flow type has been developed. This involved a co-axial cylinder type viscometer which measured apparent viscosity at a low shear rate, and a vibrating sphere type viscometer which measured the apparent viscosity at a high shear rate. Special precautions were taken to allow measurements of viscosity of rapidly settling mineral suspensions. Because the vibrating sphere viscometer operated at a much higher shear rate than the rotating viscometer, the two instruments together could determine the shear-rate dependency of the viscosity. Ground silica of 80% passing 65~m size in water was used to prepare slurries at concentrations ranging from 1O-70wt% solids. Viscosity of each slurry sample was measured simultaneously by both the viscometers and the results were compared with each other. With this technique, it was found that all the silica slurry samples were in the Newtonian flow regime.

Jan 1, 1995

By Katerina Adam

During wet grinding the electrochemical interactions between grinding media and pyrrhotite not only accelerate the media wear but also adversely affect the flotation response of the sulfide mineral. A possibility of remedying the adverse effect on its floatability by applying electric potentials to grinding media was examined. Flotation tests, Auger electron spectroscopy and x-ray photoelectron spectroscopy were used to study the surface properties of pyrrhotite. Although anodic polarization of the steels increased the metal loss by corrosion, the flotation recovery of pyrrhotite was increased. In the case of cathodic polarization, the flotation recovery improved in a narrow range of overpotentials. At higher cathodic overpotentials, however, the floatability of the mineral was progressively lowered although the corrosive wear of grinding media might be reduced.

Jan 1, 1984

By Tegner C. Johnson

Just a few years ago my company was referred to as the Marion Steam Shovel Company. We still make shovels, both two and eight crawler types. The eight crawler stripping shovel appears to have been replaced by the walking dragline for overburden removal and in some cases for the mineral as well. The walking dragline appeared in the coal fields in the early 1930's. It owes its popularity today to the fact that it can cope with overburden depths in excess of 100 feet and with blasted sedimentary rock, all at an 0 & 0 cost of ± 10¢/BCY.

Jan 1, 1974