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By T. Gollaher

The use of paste thickeners for mineral tailings has gained increasing acceptance by the mining industry throughout the world and in the U.S. during the last five years. Advantages of water recovery and environmental sustainability are the driving forces for paste as an alternative to conventional thickening and the slurry pond. This paper presents a summary of the differences between paste and conventional tailings thickeners, along with recent examples of full-scale paste thickener installations.

Jan 1, 2010

By G. France

The Blair Athol Coal Mine (BAC) is a large open cut operation in the Bowen Basin of Queensland, Australia. Current mine capacity is about 11 million tonnes per annum (Mtpa) of export coal. On-line analysis at BAC consists of two Coalscan 9500s installed directly on the output of the crusher plant and immediately before the product stockpiles, while a third Coalscan 9500 is installed on the transfer conveyor feeding the train loading bin. The two product Coals cans have a dual purpose. The first is to provide real time coal quality data directly back to the mining operations. The second is that of modeling the product stockpile with accurate on-line information. This modeling enables both production and coal quality personnel to accurately examine the coal quality of each stockpile with a degree of resolution which previously had never been achieved.

Jan 1, 1999

By Hajime Kitamura, Nobuharu Isago, Yuta Yamanishi, Kosuke Kawata, Hiroshi Yagi, Akira Matsuoka

Mountain tunnels are generally considered to be stable during earthquakes, however, it is known that the portal areas are prone to seismic damages. Characteristics in portals such as the location of the slope, modulus of ground deformation, and the change of overburden are different for each tunnel, and damage degrees are unclear. In this study, we reproduced the seismic behavior to investigate the effect on the tunnel portal by considering some parameters above, using simple static model tests and numerical analysis. As a result, the conditions of the slope condition and minimum distance from slope was confirmed to influence on the mechanical behavior of the tunnel portal during earthquakes.

Dec 1, 2022

By Todd Kilduff, Ryan O’Connell

Pipe canopies continue to gain momentum as a reliable methodology for construction of excavations below critical facilities with minimal surface settlement tolerances, such as railroads or roadways. Two tunnel projects designed by Kilduff Underground Engineering in the Salt Lake City, UT area, each at varying stages of completion, had project design criteria for selection of a tunneling methodology to minimize surface settlement. Both projects consist of a pedestrian tunnel, one crossing beneath a major roadway in downtown Salt Lake City and the second beneath UPRR tracks. Both projects were in difficult, coarse alluvium/fan ground conditions with project criteria that resulted in minimal cover above the tunnel. For each project, a pre-support pipe canopy was designed, requiring the placement of steel, canopy pipes driven the extent of the tunnel length. The pipe canopy is installed using a trenchless technology and then excavated with SEM tunneling and shoring provided by traditional support of excavation methods. The pipe canopy pre-support method offers a low-impact method to install an underpass beneath critical structures by adding significant stiffness to the subgrade to mitigate surface settlement during the main tunnel excavation sequence. These case studies seek to communicate the challenges associated with pipe canopy installation in site-specific ground conditions and explains how these challenges were overcome. This paper aims to define the project risks and describes the pipe canopy methodology as a viable solution to mitigate surface settlement in low cover tunneling scenarios.

Jun 13, 2023

By V. B. Achanti

This paper deals with the effect of various bit geometric parameters on failure characteristics of rock material. Improvement of rock cutting efficiency of continuous mining machines has been an interesting research topic for the last few decades. In the current study, an automated rotary rock cutting simulator, duplicating a continuous miner, was utilized to study these parameters in the laboratory. Improvement of bit performance in terms of its life, cutting efficiency, dust production and energy consumption has drawn wide spread attention over the years. Research shows that optimizing bit parameters can result in efficient fragmentation of rock. Indiana limestone rock material was utilized in this study while bit tip angle, bit tip size, bit spacing, depth of cut and cutting velocity of rotary drum were varied to investigate the failure characteristics. The cutting pressure, penetrating pressure and the depth of cut were monitored on the simulator during the cutting process. Air borne dust and settled dust were measured for each experiment. Then, the specific airborne dust and specific energy were determined for the each type of bit. Triaxial tests were carried out to correlate the failure angle of the rock in static case to dynamic cutting process failure. The physical and mechanical properties of the rock were also determined in order to assess their influence on the wear characteristics of each bit.

Jan 1, 1998

By Jake Coibion, Elmira Riahi, Dominic Reda, Walter Klary, Vojtech Gall

Progressive Design-Build is becoming a more common delivery method in the tunneling industry. This approach allows the Owner to select a design-builder primarily based on qualification instead of lowest price. The delivery method promotes flexibility and collaboration at all levels from the initial design stage through construction. Using the example of the Atlanta Airport Plane Train Tunnel West Extension, value-added risk management was added during the initial design phase with an independent reviewer. This paper presents the independent reviewer transitioning from constructability review in the very early stages of design to independent design verification to on-site supervision during construction.

Jun 13, 2023

By T. Wisdom, D. Romo, G. Seale, R. Jansen

Thickening remains relatively misunderstood since it is typically near the end of the process and not directly involved in metal recovery. When operating well, thickeners are ignored and left to run independently, the ‘out of sight, out of mind’ phenomena. However, when operating poorly, there is a lack of basic understanding and remedial actions to solve issues are reactionary rather than proactively addressing shortcomings. This series of papers breaks down in sequential order the stepped phases required to gain an appreciation and thorough understanding of the science behind thickeners, and key thickener components, and basic troubleshooting skills. This second paper starts with identifying the different approaches to thickener test work including static and dynamic settling tests followed by high-rate versus paste thickening. Complimentary to test work, the mechanisms surrounding coagulation and flocculation are presented and explained. The basic mechanisms for coagulation and flocculation are discussed to support the different test work approaches and provide the reader with the basic background.

Mar 2, 2022

By E. Yan, M. Mankosa, G. Luttrell

"During the past decade, column flotation cells have become widely accepted for upgrading ultrafine sulfide ores. However, the use of columns has been widely relegated to cleaner circuits due to their comparatively high selectivity derived from the use of wash water dispersed over a deep froth. High tonnage rates and low feed grades make using column technology in roughing and scavenger stages challenging due to the resulting size of the needed equipment. To specifically address this challenge, a new high-intensity flotation system known as the StackCell™ was developed. This technology makes use of a novel pre-aeration method coupled with froth washing to simultaneously provide improved flotation kinetics and selectivity. The novel aeration system provides efficient bubble-particle contacting thereby shortening the residence time required for particle collection. This article reviews the technical design features of this new flotation technology and presents recent data from in-plant pilot testing in a copper-sulfide application. INTRODUCTION Column flotation cells have become very popular in the minerals processing industry for cleaner circuits due to their ability to produce a high-grade froth concentrate via the use of froth washing (Luttrell et al., 1999; Kohmuench et al., 2004). The use of wash water minimizes the nonselective recovery of ultrafine impurities that are normally entrained into the froth product from conventional flotation machines. On the other hand, the unique design of a column cell typically requires a large tank volume. Column cells must be tall to ensure that the pulp residence time is long enough to offset their inherently slow flotation kinetics and to minimize internal mixing that is detrimental to overall cell performance. The tall design minimizes the total floor space required for the column installation, but substantially increases the foundation load. The large size of the column tank can also create issues during fabrication, transportation and installation. To address these concerns, the engineering team at Eriez Manufacturing developed a next-generation flotation technology called the StackCell?. This high-intensity flotation machine was designed to provide column-like separation performance within a very compact volumetric footprint. This article describes the key working features of this new technology and provides data from recent pilot-scale tests conducted in gold and copper-sulfide applications"

Jan 1, 2016

By Rodolfo V. de la Cruz

The broad front concept is based on the principle that gasification can be achieved more efficiently and completely from a plane broad combustion front in contrast to other geometries obtainable with current methods of gasification. By restricting combustion to a plane broad front, the ideal condition for gasification is achieved. A plane broad combustion front can be developed in coal by initiating and propagating combustion from the walls of an oriented channel and collecting product gases from another similarly oriented channel. Flow will then be directed along the highest permeability of the coal bed, the available cross-sectional area for fluid flow is substantially increased and, more importantly, the increased flow will be uniformly distributed throughout the whole mass of coal. The success of the method is greatly dependent on how well an initial and rigorous permeability survey and associated corrective measures yield a well-characterized coal bed. To maintain uniform reaction rates, the advance of the combustion front is located with pressure- or mass flow-transducers. These sensors are then connected to servo-controlled mufflers for controlling segments of the fire front which are advancing ahead of others. Finally, the development of the concept to overcome problems of roof collapse, reactant and product gas leakages, and water invasion are briefly summarized.

Jan 1, 1976

By Neal I. Rosenberg

There is an old education maxim that a good teacher "first tells 'em what he's gonna tell 'em, then he tells 'em, and finally he tells 'em what he told 'em. I'm sure this says something about me as a teacher, and therefore as a student as well, but I'm going to begin by violating that maxim. The first thing I'm going to do is tell you what I'm not going to tell you. I'm not going to tell you that my company has found the solution to frozen coal problems. I'm not going to tell you that there is a miraculous new formula, and your frozen coal worries are over. Actually, it is really questionable whether there is a single step or process which will provide the answer. On the other hand, I do believe that at Union Electric we have made significant improvements in our ability to deal with frozen coal over the last couple of years, and I propose to describe some of the things we have done, what conclusions we have drawn so far, and the direction in which we are now headed. It would be well here to give a brief picture of the Union Electric system and the frozen coal problems we face. Union Electric is an investor owned electric utility with headquarters in St. Louis, Mo. Total generating capability is on the order of 6800 megawatts, which snakes us 24th or 25th largest in the United States. Power generation is by steam (both coal and oil fired), hydro, pumped hydro, and combustion turbine units. Although that is a diverse power supply, by far the largest source is our four coal fired steam plants. One receives coal exclusively by barge, the other three by rail. It is at these last three plants that the frozen coal difficulties arise.

Jan 1, 1980

By Ron M. Canon, John M. Begovich

Chromatography, ion exchange, and other techniques based on the interaction of solutes with solid phases offer versatility, high resolution capabilities, and near-universal potential applicability for the separation of valuable constituents in liquid solutions. The expense associated with obtaining reasonable throughput for these separations has been the only, albeit overwhelming, obstacle preventing widescale use of these methods. Attempts to devise continuous (cheaper) systems have previously resulted in moving, or simulated moving, beds of resin with complicated valving and timing sequences. These disadvantages, plus technical problems associated with the disturbing effects of non-plug flow and reduced resolution of moving versus packed beds, severely limit applicability of these systems. Over the past decade a new device has been developed that overcomes many of these problems. It utilizes a slowly (less than one revolution per hour) rotating annular bed of sorbent material with fixed-feed inlet and product withdrawal points. Numerous units of various diameters and lengths have been fabricated and operated, and a parallel effort has developed a satisfactory theoretical treatment of the device. Several simple control systems have been incorporated to thoroughly demonstrate the simplicity of operation, even for multiple products and multiplecarrier flows. This device has been developed using several metal solutions and has demonstrated its power with some of the most difficult, including the zirconium-hafnium, separations. Design equations are available for sizing units based on simple laboratory data and have been tested for units as large as 18 in. in diameter.

Jan 1, 1985

By K. J. Shoop

An analysis of an iron ore processing plant showed that its performance was affected by seasonal temperature variations, resulting in reduced grinding efficiency in the winter months. Laboratory and pilot plant studies were conducted to determine the cause of the observed loss of efficiency at lower temperatures. Experiments were divided into two groups: 1) Drop testing, which was performed to determine the effect of brittleness and frozen pore water on the breakage characteristics of the ore. 2) Wet grinding, which was further divided into laboratory tumble tests and pilot plant scale tests. Laboratory tumble tests were performed to determine the effect of temperature on the grinding of iron ore. This was done by varying the percentage of fines and percentage of metamorphic clay material added to the iron ore grinding charge. The pilot plant scale tests were conducted as a scale-up of the laboratory tumble tests and to determine the effect of temperature on slurry rheology, and how this changing rheology affected the grinding of iron ore. The combined results of drop testing and wet grinding were used to make some predictions of the performance of plant scale autogenous grinding. In drop tests the breakage characteristics of the iron ore had no noticeable change in size stabilities for dry and water saturated samples over the temperature range studied (-25°C to 25°C). The effect of frozen pore water was not observed due to the low apparent porosity of the iron ore. The addition of fines to the test charge caused a decrease in the amount of new fines produced for both the laboratory tumble tests and pilot plant scale tests. The production of fines further decreased when tests were performed at the colder temperature. The increased energy consumption at lower temperatures was dominated by rheology phenomena. The addition of metamorphic clay material to the iron ore test charge resulted in more fines being produced in the laboratory tumble tests. This was due to the metamorphic clay material grinding easier than the iron ore. This caused an increase in the amount of fines in the mill, which in turn, would prematurely slow down the grinding of iron ore because of an increase in the viscosity of the slurry.

Jan 1, 1995

By Dean Treweek, Anthony Harding

"Creating stable, safe, constructible and cost effective support to openings in segmental linings is often an important component of successful delivery of a tunnel project. The many constraints on successful implementation include operational, spatial, geotechnical, structural, and constructability. Failure to address these adequately can lead to significant impacts on cost, schedule, and safety. With reference to past project experiences, this paper provides a guide to the most commonly deployed solutions and their pros and cons to help designers quickly identify the most appropriate solutions for a particular project, or act as a starting point for developing new and/or project specific solutions. It highlights the challenges that designers and contractors must address together for successful support of tunnel openings, and the constraints that arise. It then describes the common structural forms of support, and how each form can mitigate the constraints, allowing an effective opening support system to be implemented. INTRODUCTION While only a small portion of the total excavated volume of a typical tunnel, cross passages are often one of the most complex elements of a bored tunnel to construct. Cross passages in soft ground typically involve ground improvement, groundwater control, and multiple temporary support measures to ensure safe construction in ground that has been overstressed due to the construction of the running tunnels. Permanent lining construction requires careful detailing of waterproofing and reinforcement to support both long term ground and water loads and support the broken out rings of the main lining. While there is not a great deal of literature specific to cross passage construction, the main issues are discussed in some detail by Lawrence and Taylor (2011). However, the temporary support of the running tunnel segmental linings during cross passage construction is not always given the attention it deserves. The authors have been unable to find much literature on the design of such systems, much less the considerations that have led to a particular solution. Lawrence and Taylor only mention two potential methods of support. It may be easy to dismiss the opening support as an inconsequential item, but selection of the wrong support type can have significant impacts on both cost and schedule."

Jan 1, 2016

By Pengfei Wang, Guorui Feng, Shufeng Zhang, Yuxia Guo, Tingye Qi, Dian Li

"Based on the geological conditions of the No. 10203 mining face of the Xinyang coal mine, a numerical model of the longwall backfilling face is built using the FLAC3D software to calculate the limit broken length of the key strata. Based on the deformation laws of the immediate roof, the backfilling parameters are determined. Furthermore, the movement laws of the overburden strata with different volume filling rates (0, 40, 60, 100, and 100%) and with different layout forms of the filling strip (under a volume filling rate of 60%) are analyzed. The results of the numerical modeling show that the stress of the two sides of the working face and the deformation of the overlying rock are gradually reduced with the increment of the volume filling ratio. In view of the deformation of the roof strata within the allowable range, a volume filling rate of 60% is selected to simulate and analyze the filling effect under different layout forms of the filling strip. The filling width, stress concentration area, and layout form of the filling strip are the key factors to control the movement of the overlying strata. In addition, the probability integral formula is used to calculate and predict the ground subsidence on the filling area, which confirmed that the backfilling mining method is fully applicable in the Xinyang coal mine. The results of this study provide a certain theoretical basis for the determination of the filling process in the field.INTRODUCTIONIn China and other coal producing countries, gob is managed using the caving, filling, supporting, and slowly sinking methods (Zhang, Zhou, and Zhang, 2009). With the continuing development of the concept of green coal mining (Guo, Deng, and Zou, 2004), the filling method, which is safe and environmentally friendly, has been widely used in the field. On one hand, this method could reduce waste rock and other waste discharge. On the other hand, it could effectively slow the surface subsidence. Recently, strip-filling mining mostly adapted the arrangement of the strip backfill with equal intervals and widths (Xie et al., 2004), but the reasonability of this arrangement should be discussed. To arrange the intervals and width of the strip-filling body reasonably, Feng et al. (2019) put forward the “constructional backfill mining (CBM)” concept. The CBM is a type of backfill mining with low backfill rate, strong structural stability, and good backfill effect. The targets of the CBM include the efficient usage of solid waste resources in mining areas to reduce the backfill cost, the improvement of backfill materials and backfill technologies to increase the backfill efficiency, and rational planning of backfill and mining scheme to reuse the underground mining space. The determination of proper width and intervals for the strip-filling body is the main content of the CBM. Strip-filling mining using cemented coal gangue backfilling is the main method to undertake overburden of the overlying strata and to slow down the surface deformation. It also plays an effective role in cost reduction (Xu et al., 2007). This study focuses on proper determination of the strip-filling body parameters according to actual geological conditions by a simulation. It provides an appropriate reference for backfill mining in the Xinyang coal mine."

Jan 1, 2019

By A. L. Coello Velázquez

The subject of this paper is particle population balance models (PBM) that describe mineral impact crushing behavior; it is mainly concerned with the selection and fragmentation distribution function due to their importance in this context. The data obtained by Datta (1999) by applying impact pendulum testing to single limestone particles, used by Austin (2002, 2004a and 2004b) to obtain the principal parity of fragmentation functions, were processed in order to compare them with the results of other authors, such as Nikolov (2002 and 2004) and Vogel and Peukert (2003 and 2005) so as to increase knowledge of impact crushing. From this data it has been possible to obtain the performance models of the principal parameters of fragmentation function, thereby reducing the number of experiments necessary to model the impact crushing process. The authors also propose a simplification of the selection function model posited by Austin (2002).

Jan 1, 2011

By Louis M. Schlesinger, Joel F. Hutwelker

A pilot plant was constructed to attrition scrub and deslime North Carolina phosphate ore. A 15.2 cm (6 in.) diameter pilot-scale Linatex Hydrosizer was used for desliming. Four tests were run at a throughput of 2.9 t/hr/m2 (0.30 ton/hr/f t2) and a teeter bed density of 1.12-1.13 g/cm3. The teeter water flow rate was varied to create an upflow velocity ranging from 0.25-0.47 cm/s. (This latter value is equal to the terminal settling velocity of a 200 mesh (74 micron) particle having a density of 2.7 g/cm3.) The recovery of +200 mesh oversize to the sizer underflow was 95%-96%, regardless of the teeter flow rate. The recovery of -200 mesh undersize to the sizer overflow increased from about 90% at 0.25 cm/sec to 100% at 0.47 cm/sec. A metallurgical balance that was conducted for one of the tests showed that less than 2% of the phosphatic value was lost to the overflow. A fifth test was run using an upflow velocity of 0.47 cm/sec; however, the teeter bed density was maintained at 1.05 cm/sec. This change had the effect of reducing the cut point (d50), while maintaining complete slime removal.

Jan 1, 1993

By T. D. Rourke, E. J. Cording, O&apos

INTRODUCTION Detailed investigation of a 60-ft-deep excavation in a mixed profile of sands and stiff clay was performed by the University of Illinois for the Washington Metropolitan Area Transit Authority (METRO). The work was coordinated through DeLeuw, Cather and Co., the General Engineering Consultant of METRO. Instrumentation was concentrated in a portion of braced excavation for the Gallery Place Station near the intersection of 7th and G Street. The early construction date, the 60 ft depth of cut, and the proximity of large buildings formed the basis for selection of this site as the focal point of observation and measurement. A history of lateral and vertical displacement is provided wherein movements which occurred during excavation to the full depth of cut and, subsequently, during station construction and the removal of braces are described in detail. Observations of preloading and the consequent brace loads and wall displacements are described. The effect of temperature change on brace loads is discussed and the measured apparent earth pressure for the 60-ft cut is provided. The paper discusses the relationship of lateral displacements of the cut wall to the construction procedure, and compares the lateral wall displacement with both lateral and vertical movement in the surrounding soil mass. Based on observed movement, the method by which displacement was predicted for a nearby 82-ft-deep excavation is described. The performance of the 82-ft-deep excavation has been summarized elsewhere (2).

Jan 1, 1974

By G. Mbuyi Kamba

Literature is rather abundant on the topic of steady-state network analysis programs. Many versions exist, some of them have real extended facilities such as full graphical manipulation, fire simulation in motion, etc. These programs are certainly of great help to any ventilation planning and often assist the ventilation engineer in his operational decision making. However, what ever the efficiency of the calculation algorithms might be, their weak point still is the overall validity of the model. This numerical model, apart from maybe the questionable application of some physical laws, depends directly on the quality of the data used to identify its most influencing parameters such as the passive (resistance) or active (fan) characteristic of each of the branches in the network. Considering the non-linear character of the problem and the great number of variables involved, finding the closest numerical model of a real mine ventilation network is without any doubt a very difficult problem. This problem, often referred to as the parameter adjustment problem, is in almost every practical case solved on an experimental and "feeling" basis. Only a few papers put forward a mathematical solution based on a least square approach as the best fit criterion. The aim of this paper is to examine the possibility to apply the well-known simplex method to this problem. The performance of this method and its capability to reach the global optimum which corresponds to the best fit is discussed and compared to that of other methods.

Jan 1, 1995

By C. Caceres

Fibre reinforced shotcrete in combination with other types of support systems is becoming the leading support method for underground excavations, especially those present in low quality rock masses. Sudden or rapid ground support failure can expose workers to safety hazards, damage to equipment and others resulting in production interruptions that will impact the cost of operation. Knowing the peak and post-peak strength characteristics of the support system over time are of major importance. Round Determinate Panel Testing of fiber reinforce shotcrete is the primary test used by the mining industry to determine strength characteristics; however, the tests are costly and significant manpower is required in a mine environment to build, store, handle and test the panels. For these reasons numerical modeling can result in an effective method to produce realistic results. This paper examines the strength characteristics Round Determinate Panel tests and its ultimate application in underground excavations, using Itasca?s three dimensional particle flow code (PFC3D).

Jan 1, 2010

By F. F. Peng

For a given flotation system, the rate-controlling step in fine coal flotation can be the attachment of bubble to the fine coal particles. The probability of attachment depends upon the surface characteristics and the collector adsorption on the coal particle surfaces. Thus, to further improve the flotation rate and selectivity is to alter the distribution of hydrophobicity on coal particles efficiently by applying the effective means of collector dispersion. In order to enhance the combustible recovery and selectivity of fine coal flotation, and lower the amount of collector used in the fine coal flotation processes, four modes collector dispersion/addition techniques are tested. They are direct liquid addition in pulp (mechanical agitation), ultrasonic energy dispersed collector into pulp, atomized collector into pulp and gasified collector transported by air and formation of collector-air bubbles in pulp. The effect of four collector dispersion/addition methods on the floatability of -600 µ m (-30 mesh US sieve) coal samples from four ranks of coals were studied. The ultrasonic energy dispersed collector and atomized collector flotation processes enhance flotation yield and most significantly improve the kinetics of fine coal flotation. The gasified flotation process can increase the selectivity of separation and decrease the collector consumption due to starvation flotation is achieved in this process. The flotation efficiency of gasified collector process is as high as that of conventional flotation. It is because that the effect of the decrease in the combustible recovery is offset by the increase of selectivity. In addition to flotation experiments, induction times of bubble attachment to the bed of fine coal particles for four ranks of coals are measured.

Jan 1, 1992