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By Morgan M. Sears

The LaModel program is widely used to calculate stresses and displacements on thin tabular deposits, particularly when multiple seams or complex mining geometry is encountered. The program itself allows the user to create multiple mining steps to show a progressive sequence of mining. However, LaModel considers each individual step as an independent steady-state condition, and any previous loading conditions of the materials are not tracked. It also does not consider any sort of dynamic stress change during the mining process. In certain circumstances, especially in multiple-seam situations, modeling a scenario of the seam of interest without considering the previous mining sequence in the off seams can potentially lead to inaccurate results. The primary objective of this paper is to present a situation where a potentially dynamic, unstable mining condition was encountered. It was not evident until the previous loading conditions in the off seams and the impact of dynamic stress changes in the active seam were considered. It is important to make the mining community aware of these potential modeling scenarios where the path-dependent nature of the mining sequence is of key importance. This paper presents a case history where room-and-pillar retreat mining was being conducted in a relatively deep cover stress regime where multiple seam interactions were present from both undermining and overmining. Mining in the active seam was being conducted with roomand- pillar mining techniques consisting of a series of parallel production panels being successively developed and retreat mined along a set of Mains. In this situation, the traditional global LaModel analysis without any path-dependent adjustments did not fully identify the area of poor conditions that were encountered. This paper explores the impacts of mining in the active seam on the lower seam which, in turn, has a negative impact on the active seam. This provided a solid foundation for the subsequent analysis of the three seams simultaneously. Based on the calibrated model, it is likely that retreat mining in the active seam resulted in increased stresses in the underlying seam that conceivably resulted in additional convergence and, most likely, additionally convergence of the pillars under the panel being developed. This in turn could have caused active subsid- The LaModel program is extremely useful for analyzing multiple-seam mining scenarios. As multiple-seam situations become even more prevalent, the potential for encountering a path-dependent mining scenario also increases. To successfully model path-dependent mining scenarios, the ground control engineer will be required to make sound judgments on the condition of pillars in sub-adjacent seams. These engineering judgments should be based not only on the current state of stress, but also on any prior or future states of stress. This means considering the stresses from over or undermining as well as stresses applied to the sub-adjacent seams from actively mining the seam of interest.

Jun 25, 2024

By Terrence Chatwin, Michael Sweeney, Steve Accardo

Sutter Gold Venture excavated an exploration decline into a mineralized zone in the Sutter Creek gold mining district. Delays in obtaining the conditional-use permit resulted in 7 to 10 million gallons of water accumulation in the decline containing elevated dissolved arsenic. Sutter received a permit to land apply the water after reducing the arsenic concentration to 0.05 mg/L. Initially the water was treated by co- precipitation arsenic with ferric hydroxide. Operational difficulties of this treatment system resulted in Sutter pursuing alternative treatment methods. The activated alumina adsorpting was selected due to its flexibility and ease of operation. Operating and maintenance data and costs will be presented.

Jan 1, 1995

By J. E. Carr

A bewildering number of continuous thickeners and clarifiers are used in mineral industries and other heavy industries. General types are: 1. Conventional Thickeners (Fig. 1). 2. Thickeners with Flocculating Feedwells (Fig. 2). 3. Solids Contactors (Fig. 2). 4. Tray Thickeners (Fig. 3). 5. Lamellas (Fig. 4). 6. Conventional Thickeners with Lamellas 7. High Flow, Fluid Bed Thickeners (Fig. 5). These units must be adapted to varied applications. They must provide operating flexibility to meet process needs. Such factors multiply the decisions which must be made prior to the selection of a thickener. The seven types of thickeners listed above, with their variations, share design concepts which limit their application and which can be used to evaluate their performance. Some of these are listed: 1. Feed velocities must be limited and/or controlled. 2. Natural or reagent flocculation is necessary. 3. Horizontal settling area is the basis for capacity. 4. Overflow velocities must be limited and/or controlled. 5. A controlled underflow is necessary. Applying these needs to the basic process concepts is thickener selection. The basic function of a thickener in the minerals industry is the separation of a thickened sludge containing fine solids from water. To this primary separation function are frequently added others to give a list as follows:

Jan 1, 1977

By K. Zabrusky

"Wireframe construction is an integral part of resource estimation. Wireframes control domaining of samples and data for geostatistical analysis and grade estimation. They may also provide 3D representations of lithology and grade domains. Thus, the way in which a wireframe is constructed has implications throughout the resource estimation process. Proper construction technique and understanding of wireframing processes should be a high priority in a model workflow. Herein is presented an overview of two main categories of wireframes: implicit and explicit. Construction differences between these two types are highlighted. Factors affecting the choice between the two wireframe types will be discussed, including data quantity, data distribution, and sampling technique. Deposit geometry also plays an important part in wireframe construction. The role of geologic knowledge, cross section orientation, and deposit type in regards to wireframe construction will be discussed. The effect of wireframe type on resource estimation will be examined. Finally, best practices for creating meaningful solids that contribute to a reasonable grade estimation are outlined. INTRODUCTION Wireframes are essential to many types of resource estimations. They provide a way to delineate a deposit into various domains. Domaining can be done by lithologic or geologic units, structures or structural zones, or by grade. Domaining is important for geostatistical analysis and grade estimation of a deposit. The purpose of domaining is to analyze and estimate like data with like. Grade distribution patterns may vary by lithology or by proximity to or existence within structural zones. Properly constructed wireframes are therefore a fundamental necessity to a properly executed geostatistical analysis and resource estimation model. The choices made in construction of wireframes have a trickle-down effect on the entire model and should be made according to best practices for the deposit type at hand.TYPES OF WIREFRAMES Explicit The term “explicit wireframe” is used in this paper to indicate wireframes that are constructed by the modeler. This usually involves the modeler drawing the wireframes “by hand”, e.g. still utilizing some sort of computer aided drawing software, but with the modeler making all decisions about the size, shape, and positon of the wireframe. These wireframes are drawn based on some type of key variable that the modeler determines is important to their system. Often, this key variable may be a lithologic unit that controls mineralization, an observable structural zone, or a grade cutoff. Explicit wireframes are generally constructed as a series of shapes drawn on 2D planes or cross sections that are then connected into a 3D shape. Figure 1 shows an example of an explicit wireframe that was drawn based on a grade cutoff on 2D sections (Figure 1a), then joined into a 3D shape (Figure 1b)."

Jan 1, 2015

By E. McCullough, S. Gaillard

"Diesel particulate matter (DPM) remains a health concern in many underground metal/nonmetal mines, and has been regulated by the Mine Safety and Health Administration since 2002. While the NIOSH 5040 standard method for DPM monitoring is required to demonstrate regulatory compliance, the FLIR Airtec DPM Monitor can serve as complementary engineering tool. It is a handheld instrument that offers near real-time measurements. As part of an ongoing field study, the Airtec has been used to survey elemental carbon concentrations (a proxy for DPM) in an underground stone mine. Via “spot-checking” and more prolonged area monitoring, this effort was aimed at determining spatial and temporal DPM variation in several key locations. INTRODUCTION Diesel particulate matter (DPM) is the solid fraction of the exhaust emissions from a diesel engine. It is largely made up of elemental and organic carbon (EC and OC, respectively), which can be measured as proxies for estimating mass concentrations of DPM. The National Institute for Occupational Safety and Health (NIOSH) considers DPM to be a health hazard and potential carcinogen [1]. It is believed to cause and/or exacerbate respiratory illness upon inhalation, deposition, and retention in lung tissue [2]. Since DPM exists in both the micro- and nano-particulate ranges, it can surpass typical auto-immuno defense mechanisms that keep larger particles out of the respiratory system [2]. Relative to other occupations, the DPM exposure potential for underground miners is high because these individuals work in enclosed environments where diesel powered equipment is frequently used [3,4]. A variety of engineering and administrative controls have been devised to reduce DPM exposures in underground mines, and increased airflow is often a key component of control strategies. In large-opening mines, which are most common in the metal/nonmetal sector, DPM abatement via increased ventilation can be especially complex due to moving and controlling the large air quantities [5]. The Mine Safety and Health Administration (MSHA) has regulated DPM exposure in metal/nonmetal mines since 2002. The final rule limits personal exposure to total carbon (TC, which is the sum of EC and OC) to an eight-hour time weighted average (TWA) of 160 µg/m3. To demonstrate compliance, operators must use the NIOSH 5040 Method [6]. However, the Airtec DPM Monitor (FLIR Systems, Inc., Nashua, NH) was developed as an engineering tool to provide near real-time measurements of both EC and TC for tracking personal exposures [7]. The portable Airtec works by capturing DPM on a filter and successively measuring laser extinction on the filter as DPM accumulates; the EC fraction of the DPM is dark, and so as it accumulates the filter becomes darker and absorbs more laser light [8]. The laser extinction value is directly correlated to EC, but since EC and TC are generally observed in consistent proportions (i.e., TC = EC*1.3), the Airtec is also programmed to display TC as a TWA [9]. There have been multiple studies conducted to validate the Airtec and the instrument has been adopted by some mine operators as a tool for their health and safety programs [3,8]."

Jan 1, 2016

By Kapila Pathirage, Michael S. Schultz, Gregory Sanders, Ulf G. Gwildis

Adequate understanding of the subsurface conditions along the alignment of a planned tunnel is key for managing project risk. For achieving this understanding, geotechnical borings are conducted during design. Where their spacing cannot reduce the risk of encountering differing site conditions (DSC) in-between borings to an acceptable level, supplemental exploration methodologies or data evaluation approaches may be required to bridge the data gap. This paper compares the exploration design approaches of recent tunnel boring machine (TBM) and microtunnel boring machine (MTBM) projects in the quaternary deposits along the Eastern Seaboard, the glacial geology of the Pacific Northwest, the sedimentary rocks of the South, and metamorphic rocks in western Germany, describing their respective effectiveness of managing DSC risk.

Dec 1, 2022

By J. Iannicelli

Kaolin tailings ponds play an important role in reclamation of land and water. Discharges impounded from kaolin plants include oversize fractions consisting of coarse kaolin, mica, quartz as well as magnetically extracted contaminents, acid filtrates, and plant washdown streams. Tailing ponds perform an essential function in sedimentation of particulates, blending and reoxygenation of liquid waste, and neutralization and clarification of discharge water. During the past fifteen years, most kaolin firms have segregated their coarse filler waste to allow for possible reclamation for production of delaminated coating clay. This excess coarse filler fraction constitutes a reserve for future coating clay production.

Jan 1, 1985

An open pit production planning method for stage mining is presented in this paper. The method brings solutions to the four most important parameters in stage mining : 1) the number of stages, 2) the size and geometry of each stage pit, 3) the mining sequence of the benches in the stage pits, and 4) the time of transition from one stage to the next. The method can also simultaneously optimize the ultimate pit, mine life, and production rate in each stage.

Jan 1, 1996

By Douglas G. Hubert

To put coal in its proper perspective as a source of energy for electric power production, we must first compare it to other energy sources. A report of the Atomic Industrial Forum dated February 1958 records a number of authoritative though widely varying predictions. The most optimistic of these states that by 1968 there will be a total U.S. capacity of about 6000 megawatts of nuclear power, if growth continues at the present rate. Other sources indicate over 200,000 megawatts of total electrical capacity in utility plants by 1968. This is only 3% nuclear. Therefore, 97% of our total power production will be from non-nuclear energy. Fig. 1 shows the distribution of energy sources of electric utility product- ion in the U.S. as reported by the Federal Power Commission in 1954. Note that less than one quarter of the total is hydro and about one half of the total is coal. For 1957, the Edison Electric Institute reports that of the total steam- electric generation in the U. S., 68.6% was by coal, 7.9% was by oil and 23.5% was by gas. This is an increase for coal and a decrease for oil and gas in those three years. Thus we can conclude that two-thirds of the steam-electric power in the U. S. is now generated by coal. Fig. 2 shows the major markets for coal for 1947 vs 1957. The greatest in- crease has been in the electric utility market, where it has more than doubled in the ten years. One-third of the total coal produced goes to the utilities which now represent coal?s major market. Utilities used 160 million tons of coal in 1957, and the estimated quantity for 1967 is 275 million tons, and for 1977 is 525 million tons. It is predicted that 85% of steam-electric power will be generated by coal in 1975.

Jan 1, 1959

By J. W. Scott

The problems involved in installing, maintaining, and operating large vibrating screens have been summarized and discussed, based on a survey of current use of such screens in selected North American mineral processing applications. Practical, effective solutions for the more serious common problems are described, along with some recommendations on design practice for specifying, selecting, and installing large screens.

Jan 1, 1983

By A. B. Cortes

This research work discusses the development of a two-dimensional model that represents the flow that occurs in the inlet section of hydrocyclones. The governing equations are the two-dimensional, unsteady, incompressible Navier-Stokes equations in cylindrical polar coordinates with primitive variable formulations. In this approach, no assumptions have been made other than independence in the axial direction. The full two-dimensional Navier-Stokes equation in the r-a plane is used. The commonly used simplifying assumption of axisymmetry is not used. A numerical technique based on a newly developed spectral-difference method is used to solve the equations. The spectral-difference method is a multi-domain, and multi-dimensional extension of the Jacobi polynomial collocation technique. The computational grid for the inlet section is composed of 25 sub-domains which result from five partitions in the angular direction and five partitions in the radial direction. Several test cases are used to validate the appropriateness of the numerical model.

Jan 1, 1995

By S. K. Sharma

The Bureau of Mines has investigated the fundamentals of the flocculation process. The objective of this study was to determine the effects of various physico-chemical parameters such as shear rate, polymer dosage, and polymer concentration on floc growth and to determine the applicability of a model in predicting polymer flocculation behavior. A rapid in-line particle size analyzer was used to follow the progress of both the floc growth and the breakage as a function of time. A genetic algorithm (GA) was used to determine the unknown parameters in the model and to fit a curve to the experimental data. Results show that the model, using GA as a tool to determine the unknown parameters, reproduces the experimental data with only reasonable accuracy and was relatively insensitive to the parameters. Results of the flocculation study showed that increases in polymer dosage had greater effect on the time required to reach the maximum floc size than on the floc size itself. It was also determined that, given all the aforementioned parameters, the degree of slurry mixing during the flocculation process had the greatest bearing on the floc growth.

Jan 1, 1993

By John W. Lane

Climax Molybdenum Company, a Division of American Metals Climax, Inc., operated a hydrometallurgical plant* at Climax, Colorado from August 1966 through August 1968 to recover molybdenum from a mixed oxide and sulfide ore. The ore treated for this addition to the existing plant contained sufficient Molybdenite values to be mined for Molybdenite recovery alone, so that the oxidized molybdenum recovery could be regarded as a byproduct operation. Climax is located at an elevation of 11,300 feet. All process equipment, except thickeners, was enclosed in buildings. Annual snowfall is approximately 250 inches per year. Paved highways and rail service to the plant are maintained and kept open all year. Most of the employees live in the town of Leadville, which is approximately twelve miles from the plant site. The sulfide flotation plant handles 40,000 to 45,000 tons per day of ore. The mine is one of the world's largest underground mines.

Jan 1, 1971

By Johan Bosch, Wout Broere, Minh Ngan Vu

"INTRODUCTION Shield tunnelling is often used in constructing underground infrastructure in cities due to the ability to limit settlements and damage to existing buildings. However, in an urban environment with soft overburden and buildings on pile foundations such as the North-South Line project in Amsterdam, there is a tendency to design the tunnel well below the surface and below the pile tip level in order to reduce interaction between tunnelling process and piles. This results in deep tunnels and deep station boxes. When the tunnels are located close to the surface and above the pile tip level, this would reduce the required depth of the station boxes and the construction cost. Moreover, other benefits of shallow tunnels are the low operational cost in the long-term and shorter traveling time from the surface to the platforms. Still, the tunnels should be constructed in such a manner that existing buildings are not structurally damaged, which results in a minimum required distance between tunnelling process and existing buildings. In this paper, the extent of the area that is influenced by tunnelling will be investigated in order to determine the limit distance from tunnelling to existing foundations without inducing too large building deformation. From analysing empirical data of many shield tunnels, Peck (1969) firstly presented the settlement trough on the surface induced by tunnelling in soft soil as a Gaussian distribution. This is also confirmed by other authors (Cording and Hansmire, 1975; Mair et al., 1993; Ahmed and Iskander, 2010). In this study, the Gaussian curve is used to investigate the ground movement when tunnelling in order to find the effects on existing structures. Based on the results from centrifuge test and empirical data, Mair et al. (1993) showed that the subsurface settlement profile distributes as the Gaussian curve also. The width of settlement trough at the depth z depends on the depth of the tunnel z0 and a coefficient K depending on depth. Other studies by Moh et al. (1996), Grant and Taylor (2000) and Jacobsz (2003) based on Mair et al. (1993) proposed a limited change of K in various kinds of soil."

Jan 1, 2016

By C. Maltesh

Anionic conditioning of phosphate ores prior to fatty acid flotation is a very critical step that determines the eventual selectivity, recovery and hence the economics of the process. However the chemical mechanisms operating during this conditioning step are not established. Several studies have been conducted in the past to determine the mode of interaction of collectors with the phosphate fractions however these have been done on a laboratory scale using pure phosphate minerals. In order to test the relevance of the observed effects to plant practice in this work a comprehensive survey of plant practice was first conducted and then adsorption on flotation feed and francolite were studied under simulated plant conditions. Effects of conditioning energy and water chemistry as well as solids loading and fuel oil were determined. Most importantly, different adsorption mechanisms were found to be dominant under laboratory and plant conditions. In plant water, there was some physisorption of oleic acid on phosphate flotation feed and francolite in addition to chemisorption. However, in distilled water under laboratory conditions only chemisorption was detected. Fuel oil reduced the residual oleic acid in solution after adsorption, which explains the beneficial role of extender in phosphate flotation. The dissolved species in solution arising from the flotation feed or plant processing water are shown to clearly play a major role in determining the adsorption of oleic acid on the substrates. The study also specifically demonstrates the importance of conducting research tests under plant mixing conditions and plant water chemistry for the results to be useful commercially.

Jan 1, 1996

By G. Ferrara

Hydrocyclones and other dynamic separators are normally fed with pulps of water and solid particles. The particles have different sizes, shapes and densities and, except in the special case of mono-characteristic particles, are segregated into size, shape and density. Segregation is magnified by the high values of centrifugal acceleration in the hydrocyclones. This paper develops the theory of the segregation, indicates the major variables involved and reports experimental data of segregation under different operating conditions for mixtures of magnetite and/or ferrosilicon and non-magnetic minerals.

Jan 1, 1995

By Morgan M. Sears

The stability of gateroad pillars is crucial in deep-cover longwall mining, especially during transitions to wider panel layouts. This study evaluates the transition from a 700-foot to a 1,000-foot panel layout with an inter-panel barrier in a deep-cover longwall mine in Southwestern Virginia to identify a configuration that enhances stability and reduces operational risks. Using the LaModel program, three pillar configurations were simulated to assess their performance based on stress distributions and pillar safety factors. These included the previously used 4-Entry Yield-Abutment-Yield layout, the current 3-Entry Yield-Abutment layout with a 220-ft inter-panel barrier, and the proposed 3-Entry Yield-Yield layout with a 320-ft inter-panel barrier. The findings of this study suggest that the proposed 3-Entry Yield-Yield pillar layout is more effective in managing stresses in deep-cover mining environments. By optimizing pillar placement and improving load management, this layout could positively impact mineworker safety and health. The study underscores the importance of advanced simulation tools in developing innovative solutions to address the challenges of modern longwall mining operations.

Feb 1, 2025

By S. C. Sun

Very little information is available concerning the magnetic properties of minerals and only recently has there been any attempt to correlate magnetic susceptibility with varying chemical composition1. The work described here covers a study of the relationship and chemical composition of both the rutile and sphene types of titanium minerals. The relationship between the magnetic susceptibility of three selected mineral specimens and the applied field strength is also presented. Experimental: The equipment and procedures used in this in- vestigation for crushing and cleaning the mineral specimens and for determining the magnetic susceptibilities were the same as that employed by Spokes and Mitchell1. The particle size of-the measured specimens was limited to 270/325 mesh.

Jan 1, 1959

By C. R. Fahnestock

One of the major problems for us in the earthmoving industry is the analysis of materials under the ground surface. Countless engineering and construction jobs would be simplified if there were an inexpensive and fast way to obtain information on problems such as: Depth and solidith of bedrock? Nature of the materials between bedrock and the surface? Adequate foundation for bridges and drainage structures? Location of supplies of materials to be used in construction? Investigation of tunnel sites? Characteristics of swampy areas and investigation of existing and potential slide areas? These questions are of paramount interest to highway contractors as they bid jobs and plan, equipment spreads to handle them at optimum efficiency. Such information also is invaluable to engineers in the design and construction of bridges, buildings, railroads, canals, and tunnels.

Jan 1, 1961

By S. E. Knalafalla

The availability of a fluid whose gross behavior sharply changes in a magnetic field without affecting its rheologic characteristics has been recently demonstrated. A colloidal solution of a ferrimagnetic material, such as magnetite, in a liquid that is immiscible with and lighter than water is projected for use in selective separation of particles according to their density spectrum in a continuous fashion. Magnetic levitation forces were created as an antigravity field when the fluid was properly placed in an inhomogeneous magnetic field. Five spherical non¬magnetic objects with densities ranging from 2.70 to 11.35 gram cm ' were made to float or submerge at will in a 0.96-gram cm-3 density fluid placed at vertical magnetic field gradients ranging from 0.2 to I kilooersted cm-1. The magnetic levitation farce in dyne cm-3 was found to vary linearly as a function of the object-fluid density mismatch with a slope equal to one g, the acceleration due to gravity.

Jan 1, 1972