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By Stryker Magnuson

While probe drills are not strictly necessary for all projects, the incorporation and use of probe drills and pre-grouting adds capability and insurance to boring operations. Water ingress and unstable ground can be resolved before becoming a problem and resulting in costly delays through the use of enhanced, 360-degree probe drilling setups. To do this, proper design of the array of drill ports in the shield, matched to the possible ground conditions, is critical. For ground with exceptional water and instabilities expected, additional probing locations are low-cost additions that can lower risk and increase efficiency. In this paper we will look at recent and ongoing projects including the Lower Meramec Tunnel and Jefferson Barracks Phase 2. We will detail the design of those probe drill arrangements, and our overall recommendations for probing/grouting systems that best suit challenging ground conditions and keep projects running smoothly.

Jun 13, 2023

By Qing Wang

Open pit mines require substantial capital investment at the beginning of the operation and replacement investment at later years. The objective of obtaining the highest possible return on investment in a mining project can only be achieved with an efficient long term production plan. This plan consists of optimally determining four principal elements: 1) the amount of ore and waste to be mined each year, 2) the specific blocks to be mined each year, 3) the optimum mine life, and 4) the ultimate pit limits, which delineate the total reserve to be mined. The existing methodologies only provide solutions to one or two elements, by assuming the others known. Furthermore, the cost of mining each block in the deposit is assumed to be known and independent of the production schedule. The four elements of production planning are interrelated and the cost of mining any block is a function of the production schedule. The ultimate goal of this study, ,whose first steps are' discussed in this paper, is to develop a solution methodology that can simultaneously optimize all four elements of the production planning problem in open pit mines without making a priori assumption on any of the four elements.

Jan 1, 1992

By James A. Brierley, Rong Yu Wan

Bacterial pretreatment was evaluated as a process for enhancing gold recovery from a refractory ore from Newmont Cold's Cold Quarry deposit. This ore is refractory due to sulfide locking of the gold and preg-robbing carbon. The microbe Thiobacillus ferrooxidans effectively oxidized the sulfide component of the ore, but the preg-robbing carbon continued to be active. Thiourea was examined as an alternative to cyanide for extraction of the gold from the biooxidized ore. The thiourea, coupled with CIL, was effective for gold extraction resulting in up to 89% gold recovery for the sulfidic-carbonaceous refractory ore. The thiourea gold complex appears not to be bound by the preg- robbing carbon of the ore when in the presence of recovery carbon (CIL)

Jan 1, 1990

By P. Rusin

Many oxide silver and molybdenum deposits remain undeveloped because chemical extraction yields poor recoveries or is environ-mentally unacceptable. Bio-reductive leaching of such ore samples at MBX resulted in high recoveries of silver and molybdenum. When baseline 3-day cyanide bottle roll tests were conducted on manganiferous oxide silver ore, 13.7% of the silver was extracted. In contrast, 86% of the silver was microbially solubilized into the organic growth medium by bio-reduction with 99.8% dissolution of manganese. A follow-up cyanide bottle roll test yielded an additional 8.5% silver recovery for a total recovery of 94.5%. Baseline 3-day acid bottle roll tests of the iron oxide molybdenum ore yielded 1.8% moly. However, bio-reduction solubilized 93.3% of the moly into the growth medium. An additional 0.3% moly was recovered during the follow-up acid bottle roll test. Microbial treatment of refractory oxide ores with bio-reductive bacteria resulted in higher recoveries of silver and molybdenum than conventional chemical leaching. The bioleaching process occurred at a near-neutral pH at ambient temperatures. The bacterial solubilization of silver and moly was achieved without the use of cyanide or sulfuric acid.

Jan 1, 1992

By S. Behl

A major limitation in developing successful selective, flocculation schemes is the difficulty encountered in adsorbing the polymeric flocculant only on the desired substrate. In this paper, a correlation between selectivity of flocculant adsorption and separation efficiency is outlined, and a potential technique to achieve selective adsorption of flocculants is discussed.

Jan 1, 1994

By S. Behl

A major limitation in developing successful selective flocculation schemes is the difficulty encountered in adsorbing the polymeric flocculant only on the desired substrate. In this paper a correlation between selectivity of flocculant adsorption and separation efficiency is outlined and a potential technique to achieve selective adsorption of flocculants is discussed.

Jan 1, 1992

By S. Behl

In the selective flocculation process, polymers with specific functional groups can yield highly selective adsorption and, therefore, high separation efficiency. Selectivity in polymer adsorption may also be attained by specific additives that inhibit the adsorption of the flocculant on some solid surfaces but not on others. Generally, these additives have a different chemical nature than the flocculant. In this study, the lower molecular weight fraction of the flocculant was successfully evaluated as a site blocking agent, leading to higher separation efficiency than obtained otherwise.

Jan 1, 1993

By R. O. Ifill

Alternating current electrocoagulation (AC/EC) may be an alternative to chemical coagulation in the thickening of tailings in the mineral, coal and petroleum industries. In the current study, ground silica (d50 as received, 20 µm) served as the model tailings solid with characteristically poor settling behavior. Its natural initial settling rate was 1.6 x 10-3 cm/min. This paper discusses the indirect application of AC/EC via aluminum electrodes to the enhancement of the settling behavior of the silica. ?Indirect AC/EC? means that the silica was coagulated upon dispersion in water that had been treated by AC/EC. The effect of AC/EC retention time on settling behavior is examined and the water chemistry is analyzed. Test results show that the initial settling rate of silica was enhanced by a factor of 4,000 at its maximum of 6.4 cm/min, under the conditions employed. Settling enhancement was achieved upon contact between the AC/EC-treated water and the silica, and the enhanced initial settling rate was dictated by the floc size. The aluminum dosage increased with AC/EC retention time, reaching a maximum concentration that was equivalent to 13.1% of that predicted by Faraday?s law. Complex aluminum ions are considered to have adsorbed onto the silica surface and an adsorption mass ratio of 0.3 mg Al/g silica was the most effective in enhancing settling behavior. Owing to pH change or slow kinetics, aluminum hydroxide precipitation did not lower the ion product ([Al3+][OH-]3) below the KSP of 6.3 x 10-32.

Jan 1, 2011

By R. Reifsnyder, J. LaRosa Thompson

Slurry or slimes dispersion is a critical factor controlling the efficiency of sulfide mineral comminution and concentration operations. The PQ Corporation has conducted innovative sodium silicate-based studies to determine the effects of enhanced dispersion on whole ore grinding and flotation behaviors and on downstream separation and cleaning steps. The work has advanced the understanding of the role of pulp rheology on the optimization of commercial grinding, agitation leaching, and flotation operations. This paper reviews the role of sodium silicate as a selective wetting agent and surface charge modifier in sulfide mineral systems, and discusses the results of silicate experiments conducted on various ores of copper and molybdenum, gold, platinum-palladium, and copper zinc, all of which contain clay minerals or highly floatable gangue constituents.

Jan 1, 2002

By Yi Luo, Jian Yang

Subsurface strata movements and deformations associated with longwall mining operations in underground coal mines could cause various disturbances to subsurface mine structures, ground water bodies, and coalbed methane reservoirs. In order to assess those disturbances correctly and to design effective and efficient mitigation measures, it is necessary to develop an accurate prediction model for subsurface strata movements and deformations. Decades of research have demonstrated that variations of stratification and lithology in the overburden have significant influence on the subsurface strata movements and deformations during ground subsidence process. The key strata theory states that the thick and hard key strata serve as the backbone of the overburden and control the movements of the thin and soft weak strata located above them. From an engineering standpoint, the overburden strata are subdivided into several individual groups by the key strata with each group consisting of a key layer at the bottom and weak layers overlying it. A new subsurface subsidence prediction model considering the key strata effects on subsurface strata movements and deformations has been proposed. In this method, elastic modulus, specific weight, tensile strength, and uniaxial compressive strength (UCS) of each layer are used to identify the key layers and to determine the needed subsurface subsidence parameters. The influence function method, proven to be accurate and versatile for surface subsidence prediction, was employed to predict the subsidence on each of the overburden layers from mining horizon progressively upward to ground surface with the assumption that the predicted subsidence on a given layer serves as the subsidence source for the layer immediately above. The enhanced subsurface subsidence prediction model has been demonstrated with an actual case to show its applicability and improvement.

Jan 25, 2021

By Yi Luo

Subsurface strata movements and deformations caused by longwall mining operations in underground coal mines could affect many important coal mining activities, such as gob well degasification, ground water protection and multiple seam mining. The stratifications in the overburden have significant influence on the subsurface and surface movements and deformations in the ground subsidence process. An enhanced subsurface subsidence prediction model considering overburden stratifications has been introduced in this paper. In this method, the entire overburden strata are equally divided into a finite number of layers and the percent of the hard rocks in each layer is an additional input. The proven influence function method is applied to predict the subsidence on each of the predefined layers progressively upward using the predicted subsidence on the previous layer as the subsidence cause for the current layer. A computer program is developed to facilitate the calculations. A case demonstration is used to show the applicability of the proposed subsurface subsidence prediction model.

Jan 1, 2012

By Donald E. Scheck, Syed F. Abbas

Public domain ventilation simulation programs have been well accepted by the mining engineers, but preparing the input and interpreting the results are labor intensive tasks. High performance personal computers and versatile CAD packages provide the means to quickly create the network and display the results. The enhanced simulators work from computerized as-mined map, the projected mine layout and timing maps. Using on screen displays of these maps and the snap-on feature of AutoCAD, the planner designates nodes in the ventilation network, connects them into branches and selects the branch characteristics from a side bar menu. The color coded ventilation network appears with the parameters shown along each branch. The software then calculates the length of airways and computes the branch resistances where needed and converts the input into the required format and passes the data to the Pennsylvania State University or U.S. Bureau of Mines ventilation programs. Output is available in graphical as well as report format. The color coded graphs include pressures at the nodes and flow quantities on the branches. Since the networks come from the mine maps, the ventilation displays are to scale and can be plotted separately or superimposed on the mine maps.

Jan 1, 1991

By A. Noble, R. Q. Honaker, J. Werner

Recovery of rare earth elements (REE) from coal-related resources has recently received significant interest due to supply concerns and their key roles in critical industries and defense-related technologies. An integrated flowsheet consisting of sorting, crushing/grinding, physical separation, acid leaching, solvent extraction, and selective precipitation was designed to achieve continuous production of rare earth products from various coal-related resources such as coarse refuse and acid mine drainage. A pilot plant was constructed that enabled continuous testing of the circuitry on a range of different coal-based feedstocks. Despite achieving significant success in producing high-grade rare earth oxide products, low REE recovery values and high operational costs necessitated a re-evaluation of the process flowsheet. This article describes the circuitry improvements that were based on both laboratory and pilot plant test results. Roasting as a pre-leach treatment was found to significantly improve the leaching rate and overall REE recovery values. After roasting West Kentucky No. 13 and Fire Clay coal refuse materials at 600 °C, REE recovery increased by 60 and 40 absolute percentage points, respectively. Rare earth concentration in the pregnant leachate solution (PLS) was increased to around 700 ppm prior to solvent extraction using a staged precipitation method. REEs in the precipitate were re-dissolved, purified, and extracted from the PLS using solvent extraction and selective precipitation to values of around 80%. As a result of the improvements, chemical consumption in the acid leaching and solvent extraction processes was significantly reduced. A techno-economical assessment of the improved flowsheet indicated significant commercialization potential.

By A. Noble, R. Q. Honaker, J. Werner

Recovery of rare earth elements (REE) from coal-related resources has recently received significant interest due to supply concerns and their key roles in critical industries and defense-related technologies. An integrated flowsheet consisting of sorting, crushing/grinding, physical separation, acid leaching, solvent extraction, and selective precipitation was designed to achieve continuous production of rare earth products from various coal-related resources such as coarse refuse and acid mine drainage. A pilot plant was constructed that enabled continuous testing of the circuitry on a range of different coal-based feedstocks. Despite achieving significant success in producing high-grade rare earth oxide products, low REE recovery values and high operational costs necessitated a re-evaluation of the process flowsheet. This article describes the circuitry improvements that were based on both laboratory and pilot plant test results. Roasting as a pre-leach treatment was found to significantly improve the leaching rate and overall REE recovery values. After roasting West Kentucky No. 13 and Fire Clay coal refuse materials at 600 °C, REE recovery increased by 60 and 40 absolute percentage points, respectively. Rare earth concentration in the pregnant leachate solution (PLS) was increased to around 700 ppm prior to solvent extraction using a staged precipitation method. REEs in the precipitate were re-dissolved, purified, and extracted from the PLS using solvent extraction and selective precipitation to values of around 80%. As a result of the improvements, chemical consumption in the acid leaching and solvent extraction processes was significantly reduced. A techno-economical assessment of the improved flowsheet indicated significant commercialization potential.

By A. A. Bilgin

The prevention of acid mine drainage (AMD) in situ is more attractive than down-gradient treatment alternatives that do not involve source control. AMD source control can be achieved by shifting the microbial activity in the sulfidic rock from pyrite oxidation to anaerobic heterotrophic activity. This is achieved by adding biodegradable organic carbon amendments to the sulfidic rock. This technique was applied to an abandoned coal mine pool in Pennsylvania. The pool had a pH of 3.0 to 3.5. Following treatment, near-neutral pH and decreased effluent heavy metal concentrations were achieved. In situ bioremediation by the enhancement of bacterial iron and sulfate reduction is a promising technology for AMD prevention.

Jan 1, 2007

By James M. Harrington, A. Azra Bilgin, JoAnn Silverstein

The prevention of AMD in situ is more attractive compared to subsequent downgradient treatment alternatives that do not involve source control. AMD source control can be achieved by shifting the microbial activity in the sulfidic rock from pyrite oxidation to anaerobic heterotrophic activity. This is achieved by adding biodegradable organic carbon amendments to the sulfidic rock. This technique was applied in an abandoned mine pool with a pH of 3-3.5. Following treatment, near-neutral pH and decreased effluent heavy metal concentrations were achieved. In situ bioremediation by enhancement of bacterial iron and sulfate reduction is a promising technology for AMD prevention.

Jan 1, 2005

By P. Rusin

A new bacterium, Thiobacillus cuprinus, can extract copper from chalcopyrite as rapidly as T. ferrooxidans. On solution with and without nutrient amendments and bacterial growth media were supplemented with T. ferrooxidans or T. cuprinus in shake flask studies. Both species extracted -42% of the copper using growth media. In one case, T. cuprinus solubilized approximately twice as much copper as T. ferrooxidans utilizing a seeded On solution. Thiobacillus prosperus also oxidizes chalcopyrite and tolerates high chloride concentrations. These sulfide-oxidizing bacteria are representatives of the mixed microbial community found in sulfide dumps. Rates of biological copper extraction from sulfide ores, using the native microbes, have been significantly enhanced by amending On solution with PGM.

Jan 1, 1994

By Noel C. Joughin, Orrie Fenn, Brian E. Protheroe

Work has shown that the use of high-pressure water jets enhances the performance of mechanical cutting in very hard rock. To assess the potential of this approach for use in conjunction with free rolling cutters, a series of tests has been conducted using both disc and button type cutters, to determine the relative effects, on cutter performance, of variations in relevant jet and cutting parameters. In these tests it was found that water jet assistance can result in reductions in the forces on a free rolling cutter typically of the order of 40%.

Jan 1, 1985

By Erik S. Bernard

"INTRODUCTION Reinforced Concrete (RC) members such as beams and columns are usually required to include stirrups to maintain post-crack shear capacity, and some may include stirrups that act as confining steel to maintain structural integrity during a seismic event (eg. NZS3101, ACI 318). To achieve seismic resistance, the spacing between stirrups is usually required to be much closer than is ordinarily prescribed for non-seismically resistant structures. Each stirrup must also fully enclose the longitudinal reinforcement with long end-hooks to ensure that the contained concrete is sufficiently restrained during reverse-cycle loading and the reinforcing bars are confined to prevent buckling. The close spacing between stirrups can lead to congestion of reinforcement within members, and can also be expensive to construct due to the labor-intensive nature of steel fixing. A possible alternative to closely-spaced stirrups is the use of fibers to provide restraint and confinement during a seismic event, although this is not yet recognized in codes. Previous experimental research (Jiuru et al, 1992; Filiatrault et al, 1995; Bayasi and Gebman, 2002; Billington and Yoon, 2004) has demonstrated that steel fibers are relatively effective in this application, but suffer the problem that their stiffness can make them difficult to consolidate within an already tight reinforcement cage, especially if they are relatively long (>40 mm). Moreover, steel fiber reinforced concrete (SFRC) is subject to embrittlement with the passage of time, leading to a steady loss of ductility beyond crack widths of 1-2 mm (Banthia and Trottier, 1994; Bernard and Hanke, 2002; Bernard, 2014; Bjontegaard et al, 2014; Bernard, 2015). Since cracks during seismic events are generally much larger than this, embrittlement may present a challenge to the long-term efficacy of SFRC during seismic events. An alternative to steel fibers for enhancement of seismic resistance is the use of macro-synthetic fibers. This type of fiber usually offers the advantage of being flexible so that consolidation is easier between reinforcing bars. They also offer superior durability compared to steel fibers and can reduce flexural crack widths (Bernard, 2016). Several recent small-scale investigations (Ma et al, 2012; Carnovale, 2012; Osorio et al, 2014) have indicated that macro-synthetic fibers can produce meaningful improvements in seismic resistance if used in combination with conventional steel reinforcing bars. The present investigation has extended research in this field by examining whether embossed macro-synthetic fibers can be used to increase the spacing between stirrups while maintaining seismic resistance."

Jan 1, 2016

By Rahul Singh, Sunil Kumar, Erich Dohm, Maoming Fan

The rapid increase of P2O5 use for food, biofuels, and LiFePO4 batteries etc. accelerates the depletion rate of phosphate reserves. In the phosphate industry, a significant amount of ultrafine phosphate has been discarded as slime tailing due to processing difficulties. The major problems associated with ultrafine particle flotation are low probability of bubble-particle collision and adhesion, and high probability of unwanted gangue particles entrainment. This paper investigates the enhanced ultrafine phosphate particle flotation probability by Eriez’ CavTube generated fine/ ultrafine bubbles and the improved flotation selectivity by wash water etc. Ultrafine phosphates with various gangue minerals of quartz/muscovite, calcite/dolomite, and iron/ silica were studied. Microscopic observations show that the entrained ultrafine gangue minerals can be minimized by using wash water in column flotation. A three-factor threelevel central composite experimental design was conducted for ultrafine phosphate flotation. For comparison, both benchtop mechanical cell and laboratory column flotation tests were performed at their optimal respective flotation conditions. Using Eriez CavTube column flotation technology for Industries Chimiques du Senegal (ICS) ultrafine slime tailings, a concentrate grade of 36.0% P2O5, was achieved at 89.4% P2O5 recovery. Improved flotation performance was achieved using column flotation as compared to benchtop mechanical cell flotation. The benefits of Eriez’ column flotation technology realized from this study include the high P2O5 grade and recovery.

Feb 1, 2024