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By C. A. Vining, J. R. Nopola

"Evaporites, such as salt and potash, pose unique problems to ground-support designs not encountered in other rock types. Evaporites are subject to continual creep and no amount of ground support can successfully arrest this process. Common ground-support techniques that are useful for most rock types may reduce the effective life of bolts in evaporite mines and can create unseen hazards. A different approach to ground support must be applied to provide long-term support in areas where high creep rates are present. The goal of effective ground-support designs in these situations is not to contain the rock and prevent it from moving; rather, the ground-support design must be able to move along with the rock and contain any fully detached slabs until additional remediation measures can be undertaken. The most appropriate ground-support designs will consider both the expected movement of the rock and the duration that the area needs to remain accessible.INTRODUCTIONEvaporites, such as salt and potash, pose unique problems to ground-support designs not encountered in other rock types. The factors that must be considered in design stem from the deformation behavior of salt, which can fail in a brittle manner, akin to most rocks, but can also deform in a slow, ductile manner, resembling the stretching and elongation of steel. The deformation behavior of salt has been well established in technical circles where it has been studied for decades (Hardy and Langer, 1984). Much of the research in salt mechanics is related to repository science, specifically at the Waste Isolation Pilot Plant (WIPP) in southwest New Mexico. RESPEC has been continually involved in the WIPP from the initial design considerations (Gnirk, Grams, and Zeller, 1977) to the current day (Keffeler, 2016) and has been able to leverage cutting-edge research of salt mechanics into practical solutions for mining operators. While a detailed description of salt mechanics is not provided in this document, Fossum and Fredrich (2002) include a fine overview of salt mechanics. The following list paraphrases their chapter on basic facts about salt to provide some context for the reader unfamiliar with salt mechanics:"

Jan 1, 2018

By J. V. Belke

There are many aspects of a grinding mill supply and installation that can result in the mill not operating as intended, resulting in unplanned shutdowns, poor reliability and headaches for all concerned. One of the largest aspects, both in criticality and physical mass, is the mill foundation; if not properly specified, designed and constructed the mill operation will be compromised. The mill foundation starts with the design specification and loading diagram supplied by the mill builder. The importance of understanding these documents and how to apply them is critical for the start of any mill project. When designing mills with a GMD the foundation must be properly modeled to ensure that all interactions of the mill and motor structures, foundation and subsurface strata behave in the intended fashion. All of the previous efforts can be laid to waste if the construction of the mill foundation is poorly handled. Mill foundations are typically the most massive concrete structure at a processing plant and can easily cause nightmares for inexperienced contactors. This paper explores some of the more important facets along the lifecycle of the grinding mill foundation.

Feb 23, 2014

By Richard R. Klimpel

Introduction Froth flotation is one of the most common unit engineering operations in use today. Its aim is to upgrade the quality of coal by removing ash/pyrite and separating selected minerals from undesired gangue materials. Flotation has been successfully practiced at the industrial scale for more than 50 years. Its use is increasing due to the ever decreasing feed grades of the coals and minerals being processed. Flotation has also shown itself to be a flexible process that lends itself well to many solid/solid separations. Thus, with surprisingly little equipment modification, separations can involve very different particle sizes and densities, and relative weight ratios of materials to be separated. In addition, the flotation process is economic, especially when compared to size reduction, its associated precursor process. Flotation also lends itself to continuous operations with a given equipment configuration. The operation must exhibit an ability to vary feed rate of solid to the process by as much as 50% without a total collapse of separating efficiency. In addition, the mechanical flotation cell is scaleable from 2.8 to 57 or 85 m3 (100 to 2000 or 3000 cu ft) with surprising ease relative to other unit engineering operations over the same relative size increase. The separating medium used is water. Most of the chemicals required - pH regulators, frothers, collectors, activators, and depressants - are all relatively inexpensive and common. They are not usually used in large quantities. Froth flotation is certainly one of the most versatile and forgiving unit operations in the chemical, mining, and agricultural industries. The problem with the industrial flotation process is that it is fairly easy to get reasonable results and relatively difficult to get excellent results. Why is it so difficult to fine tune the froth flotation process? There are some obvious reasons and a few not-so-obvious factors. The obvious category would certainly contain the tendency of natural feed materials (ores and raw coals) to have variable physical, metallurgical, and surface properties. This occurs even when special care is taken to minimize such differences with blending. There is another obvious reason for difficulty. An inherent broadness of the feed particle size range to flotation results from using any of the common industrial-scalefine grinding devices - ball-, rod-, or autogenous mills. Research has been done into the chemical reagent and equipment aspects of flotation. It has shown strong interactions (limitations) of chemical reagents and equipment on larger and smaller particles. The point is that current flotation practice works best on average- or medium-sized feed particles. The greater the amount of large or small particles, or of both large and small, the more difficult it is to achieve excellent flotation results. Other reasonably obvious factors include: • variations in mineral type and liberation sizes; • water chemistry variations such as those involving Ca", C03, or Fe", or various soluble metal cations; • the presence of stray organic materials such as returning soluble reagents or partially degraded reagents in reuse water; • the lack of reliable on-line instrumentation for monitoring and control; • frequent equipment malfunctions of all types; • excessive feed rates for installed plant capacity; • poor operator interaction with the process; and • poor reagent dosage control. There are less obvious, but real limitations to flotation. These are inherent in the design and operating characteristics of the most common cell design in use today - the mechanical flotation cell. Individual performance attributes of the chemical reagents used, along with their manner of use, also carry limitations. The bulk of this paper will deal with chemical reagents and their use. Chemical reagents In 1979, the author and his co-workers were asked to invent and implement, at the industrial scale, new flotation reagent chemistry. After reviewing some of the literature (Sutherland and Wark, 1955; Klassen and Mokrousov, 1959; M. Fuerstenau, 1962; D. Fuerstenau, 1976; and Leja, 1982), a series of carefully controlled plant scale tests were set up. These tests were designed to understand existing reagent scale-up from the laboratory to the plant. They were to quantify at the plant level the effect of some of the more important, controllable chemical reagent factors (frother and collector type, frother and collector dosage, pH effects). This is a learning experience that all researchers involved in flotation theory should experience. It quickly became apparent that: • because a factor is important

Jan 12, 1988

By Brain W. Lawrence

Sublevel stoping generally is a large-scale open stoping method. It sometimes is referred to as long-hole or blasthole stoping. This method usually is applied to strong ore bodies that require minimal support and are surrounded by strong country rock. The ore body should be fairly regular in shape and well-defined. The dip of the footwall normally should be sufficient to allow broken ore to gravitate freely, although the method has been adapted successfully to mine some of the flatter ore bodies. Sublevel stoping is not dependent on the width of the ore body. Widths of less than 6 m (20 ft), however, make the utilization of long-hole drilling techniques more difficult. The main criteria for sublevel open stoping are competent ore and stable host rock, regular ore boundaries, and a footwall dip that exceeds the angle of repose of broken ore. Basically, the method entails providing access to the ore body at various subintervals between the main haul- age levels in order to drill and blast the intervening ore. Stope drilling is carried out from drilling drifts on the sublevels, and the ore is blasted in slices towards an open face, which generally is vertical on the downholes and may be inclined towards the open face for the up holes. The blasted ore gravitates to the bottom of the stope and is collqcted through drawpoints. Fig. 1 illustrates a typical sublevel stoping mine. The method requires extensive ore body development with relatively high capital expenditures. How- ever, much of the development is in ore, and production costs are comparatively low. Productivity rates are in the 13.6 to 27.2 t (15 to 30 st)/manshift range. The drilling, blasting, and loading operations are performed independently, and equipment utilization is high. Large outputs can be obtained with few units and limited personnel. Dilution with waste rock may occur if ore boundaries are irregular or if caving occurs, but 100% of the ore within the stope usually is recovered. Pillar recovery sometimes is a problem. It is at this point that most of the waste dilution occurs. At the time data was gathered for this report (1973), the sublevel open stoping method was used by more than 21% of the metallic ore mines in the US (9 out of 42 mines producing 1088 + t/day (1200 + stpd) and provided more than 12% of the total metallic ore production from these mines. DEVELOPMENT Access to a sublevel open stope mine is gained by a slope or shaft that is normally sunk in the footwall of the ore zone, away from any possible effects from blasting or other production operations in the stoping process. Main level interval is selected and usually varies from 45.7 to 121.9 m (150 to 400 ft), depending on the vertical extent of the ore body, the number of drawpoints required to maintain output, and the eventual stope height. The main haulage drifts are located at the bottom of the stope horizon, either directly in ore or in the footwall, with access crosscuts at intervals. Raises are driven up through the ore to connect to the level above and provide access and ventilation to the sublevel drilling drifts, which are driven horizontally in the ore for the length of the stope. Depending on the drawpoint system to be used, the stope is either undercut by a raise-and-cone system, from a scram or slusher drift, or simply provided with a drilling drift from which access is made at intervals to the main haulage level. A raise driven either at the end or in the middle of the stope (if stope access is from both ends) provides a start for opening up a vertical slot across the stope to establish a free or open face for long-hole drilling and blasting. Sublevel stoping has proved to be a relatively safe and economical system.

Jan 1, 1982

By Bétournay. M. C.

Advantages ?Safety ?Health ?Rapid, continuous development, productivity ?Stope dilution reduction Disadvantages ?High cost and long time for equipment development ?Hard rock mining condition limitations ?Size of equipment ?Equipment set-up time, down time ?Performance does not meet financial return targets ?Drill and blast retains advantage in cost, productivity, capital investment, application flexibility ?Stress accumulation issues in deep mining, ground support and material handling issues in weaker rock

May 1, 2009

By M P. Sandy, R M. Stephenson

Portals to access underground mines are important infrastructure and their design requires careful consideration. Portals are generally expected to last for the life of the mine. Typically, the exposure of personnel and equipment is high, with many hundreds of movements through the portal per day. Consequently, the risk associated with geotechnical instability must be extremely low. Portals are often established from a boxcut. In areas where the weathering profile is well developed, the design and execution of the boxcut can involve significant effort, with the objective of minimizing the volume of the boxcut, whilst ensuring that conditions at the design depth are suitable for establishing a stable portal. Properly designed site investigations are a critical part of this process. Currently available portal design guidelines have not been updated for decades, however the equipment and ground support systems have changed significantly in recent years. Many mine portals have since been constructed in a relatively short time frame with success, often in challenging ground conditions using some of the more modern approaches to ground support. This is beneficial because delays in establishing a portal will generally delay other critical path activities, and lead to cost overruns.

Mar 15, 2021

By F. T. Cawood

This article is a continuation of a series of publications by the authors on the international debate on resource nationalism, with specific reference to South Africa. Previous outcomes have shown that mine nationalization is not a solution for South Africa, and that maintaining stability of the current mineral and tax regimes is fundamental. It will not be wise to replace existing law and policy instruments until there is a better understanding of the distinction between fact and public perception about the impact of the current system. The new scheme of state custodianship linked to a mining royalty that effectively targets economic rents provides for effective resource use. The methodology in this article is to consider how South Africa's mineral tax regime can be tweaked to achieve optimal management and benefit from mineral extraction and associated rents by avoiding changes feared by investors. The major finding is that the current suite of instruments can be considered a suitable platform for optimal management of resource rents. However, it will be necessary to first investigate ways of improving the mineral beneficiation intent of the royalty structure, and secondly investigate whether the mineral rent portion of the royalty formula can be ring-fenced for the purpose of establishing a sovereign wealth fund.

Jan 1, 2013

By Susan G. Bilhorn

A number of studies have been conducted in active and inactive mine environments using continuous monitoring and data acquisition systems to detect various parameters. In addition to the information obtained for research purposes, these monitoring systems can provide a means to remotely collect required information (such as radon daughter concentrations and air velocity) and control various conditions (such as fan operation and air door position) in numerous working sections of an active mine. Selection of detector locations and placement, which are critical to obtain the information and control desired while not inhibiting mine operations and influencing the detector readings, are covered in this paper.

Jan 1, 1984

By Stephen C. Tadolini, Thomas E. Marshall, Cecil Banta, L. J. Prosser, Anthony T. Iannacchione

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) endeavors to provide national and world leadership in the prevention of work-related illness, injury, and death. This is accomplished by using a scientific approach to gather information, assemble and create knowledge, then translate the knowledge and results into products and services. These products and services are then delivered to all personnel who can effect prevention. Obviously, the development and use of instruments to monitor mine roof conditions provides an opportunity to execute that mission. In the late 1990’s, based on observations at a number of underground limestone mines, only a few used roof monitors. Subsequently, NIOSH introduced the Roof Monitoring Safety System (RMSS) as an aid to roof inspection beyond traditional visual and sounding techniques. Initial expectations were that by gaining roof movement information, ultimately roof sag rates could provide indications of eventual failure. During this investigation, RMSSs were installed in 13 underground limestone mines in six states and this paper analyzes the data obtained at three of these mines. This paper also provides an overview of the system, data, analysis, and applications relevant to the RMSS.

By Panagiotis (Takis) Katsabanis, Lyall Workman, Jack Eloranta

The reduction of metallic ores to concentrate consumes a great deal of electrical energy. In the past two decades, a number of case studies have demonstrated a beneficial relationship between powder factor and grindability. However, changes in mill performance cannot be attributed to changes in feed size alone. Blasting energy and the distribution of that energy appears to affect subsequent comminution beyond crushing. This experience has prompted researchers to attempt to duplicate and quantify the mechanisms involved. To date, published reports indicate a measure of success. However, the blast engineer and the mill engineer still lack the tools and basic understanding necessary for full drill to mill optimization.

Jan 1, 2015

By J Lyall Workman, Peter N. Calder

"Presplitting is a technique mines and quarries may use to produce high quality final pitwalls. Damage from backbreak can be minimized, thereby insuring the final pit walls standat the designed angle. Thus costly excess waste removal is avoided. Safety in the pit isenhanced. Control blasting is an essential component of procedures to maintain the stabilityof final pit walls prone to failure."

Jan 1, 1993

By C. Cunningham

The process of initiating opencast blasts through long cables is onerous. An obvious alternative is to replace these with radio controlled firing apparatus. Such devices appear from time to time and with the advance of telecommunications, more are likely to appear. However, there are two crucial and seemingly intractable obstacles to overcome: firstly, the problem of malfunction of the system, which can either fire prematurely or go into a state of suspense in which it is unknown whether firing might unexpectedly occur, and secondly, the problem of terrorism, as such a system could provide the capability for an off the shelf remote bomb. The issues of accessibility and electronic reliability when linked to explosives in a mining environment have to be demonstrated to be adequately covered before serious consideration should be given to these systems, up to now largely confined to military applications.

Jan 1, 2003

By W. M. Colwell

When it comes to the analysis of gold bearing ore, there are literally dozens of variables that contribute to the final "true value" of a given sample. Initial sample selection, splitting size and method, inherent nugget gold, pulverization method, and analytical method variations are but a few. However, it seems that the inherent nugget gold particle is targeted as the primary reason for intra and inter-laboratory variations in assay. The following study will show that this is not always the case. A series of tests were undertaken for the Aurora Partnership-Aurora Project to solve inter-laboratory variations in the analyses of blasthole cuttings. Initial concern was centered on the probability that free gold occurrence was resulting in erratic results for the mine's cyanide shake assays and outside laboratory fire assays. Comparison of fire assay and cyanide shake assay was sporadically consistent with previously demonstrated extraction percentage for the cyanide method. The goal was to delineate the factors that ensure consistency in analyses; implement, where needed, Good Laboratory Practices; and reestablish acceptable analytical method correlation.

Jan 1, 1993

By Robert J. Russell

The importance of grinding as a unit operation in all industry has caused much effort to be expended toward improving the facility with which grinding can be done. Endeavor has continued nearly 100 years to formulate laws governing crushing and grinding. This has not been without controversy. However, grinding is an experimental science and our useful knowledge originates in experience. The recorded experience is grinding history. Today, many types of size reduction equipment, each with variations, are available to industry. Frequently, more than one type of grinding equipment will meet a requirement of grinding. However, an economic evaluation of installation and operating costs generally indicates a preferred type. The selection of grinding equipment requires' a consideration of the purpose in grinding, the characteristics of the material to be ground, equipment available for grinding, and the manner in which it can be applied best.

Jan 1, 1960

By Earl M. Frizzell

This paper addresses considerations for the use of artificial support of pit walls in surface mines, a new project of the Bureau of Mines. Results to date indicate that a polymer-coated cable with embedded grit could provide good anchorage for stabilizing benches and highwalls, and an electronic method of recording discontinuities in the field is being reviewed and developed for application to mining. The objectives of the work in progress are to define the engineering parameters and evaluate the concepts for artificial supports in order to provide safe working environments when pit slopes are steepened to increase ore recovery and reduce overburden handling.

Jan 1, 1986

By R. P. H. Willis, A. G. du Plessis, R. B. Wilson

This paper reviews issues to be considered in choosing primary access and transportation options for platinum and other mines. It proposes appropriate criteria and a methodology for deciding on the optimum primary access option for any particular orebody. Also included are generic parameters that can be used to facilitate the process of choosing the optimal access option.

Jan 1, 2004

By D. J. H. Walker, W. H. Gibson

The inclination of any pit wall composed of stacks of benches is limited by the overall quality and structural complexity of the rock mass in which the slope is situated. For a bench stack angle that satisfies the stability criteria, various combinations of bench height, bench face angle and berm width can be used in the slope design. The bench face angle and berm width geometries must be chosen to fit the bench stack angle but must provide a berm that will be capable of catching the volume of failed wedge material from the bench faces above. Other considerations for bench height and berm width are equipment size, ore selectivity and blasting design. This paper studies the effects of different slope configurations on slope performance as it relates to wedge stability, volume of rock safely contained on berms, and rockfall. Optimisation of the geometry is carried out based on the need to minimise the volume of failed material which limits the effectiveness of the berm. This will reduce the number of rocks that can continue to fall further, reaching geotechnical safety berms or pit ramps, that put safety of personnel and equipment at risk. For general study it is most effective to investigate and compare the performances of each of a wide range of geometrical combinations of bench height, bench face angles and berm widths that fit a variety of different bench stack angles. These analyses were conducted for a predetermined bench stack height and three different bench stack angles.

Jan 1, 2006

By I. M. Stewart

In a proposed rulemaking regulating asbestos, nonasbestos varieties of Tremolite, Anthophyllite and Actinolite would be excluded from the regulations controlling permissible exposure to asbestos fibers. This proposed rulemaking is perceived as improving the scientific basis of the regulation of asbestos because it recognizes that there are no scientific data, either mineralogical or health related, which support the regulation of nonasbestos Tremoiite, Anthophyllite and Actinolite in the same manner as asbestos fibers. However, the proposed regulation, while representing a major advance in the treatment of AT A for regulatory purposes, does not provide an adequate analytical method for distinguishing between asbestos and nonasbestos particles, nor an adequate description of the regulated minerals. This paper addresses those topics, recommending that OSHA include an appropriate mineralogical definition, and implement a discriminate counting procedure to distinguish asbestos from nonasbestos particles.

Jan 1, 1992

By Edward A. Vitunac

The emerging importance of pneumatic conveying systems for bulk materials is becoming recognized by more persons responsible for materials management as consultants, at the corporate level and at the plant level. They have learned that the economic advantages of a pneumatic system are frequently decisive when compared to alternate methods. Included in these advantages are relative simplicity, ease of installation, flexibility, ease of maintenance, cleanliness, safety and ease of automation to the degree desired. In general, installed costs favor a pneumatic system when compared to competing mechanical systems if the transporting distances are long or to and from many points. In addition, supplemental use such as cooling, heating, or drying may supply the incremental value required to justify its selection. (1). The main disadvantages of a pneumatic system is the greater horsepower required per unit weight of material conveyed and material limits in abrasiveness and density. In addition, there is a tendency to increase material breakage at changes of direction and at any obstruction such as the imperfect butting of one, piece of pipe to another in the conveying line. Classification of the material at the discharge may also cause problems in dusting and segregation. Materials weighing less than 4 pounds per cubic foot tend to cause feeding and collecting problems although they can be conveyed easily. Material between 4 and 20 pounds per cubic foot can be handled with less problems but flow rate is hard to predict. The 20 to 60 pounds per cubic foot range offers best results; whereas, over 60 pounds per cubic foot, materials tend to drop out of the air stream and settle in the pipe line unless careful provisions are made to prevent it. (2).

Jan 1, 1967

By Don Conrad, Tom Friend, Bill Wiehagen, Lynn Rethi

On-the-job training (OJT) is a very common method of teaching job skills. Much of the training is done by experienced workers. This paper discusses small investments that can help improve the effectiveness of OJT. Effective OJT involves some structure and planning in the transfer of responsibility for task performance from the trainer to the novice. Assisting the OJT trainer could involve helping develop up-to-date job analyses and offering strategies for teaching and evaluating job skills. The scope of this paper addresses (1) organizational considerations supporting structured OJT, (2) general strategies for structuring OJT, (3) a typical approach for conducting OJT, (4) characteristics and duties of OJT trainers, and (5) limitations of OJT as a teaching method. Health, safety, and operational skills can be connected through training. Haul truck operator training is used to illustrate some of the concepts discussed in this paper.

Jan 1, 2002