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By D. Bahrami, W. K. Asante, G. L. Danko

It is prudent to interpret atmospheric monitoring signals in real time for checking the safe limits of the air conditions in underground mines. In gassy mines, real-time evaluation increases the safety of operations. In all mines, continuous monitoring and evaluation contributes to maintaining air conditions within healthy and safe limits. Signal interpretation for safety conditions in mines is difficult for many reasons. An increase in hazardous contaminant concentrations can be predicted by signal pattern recognition, root cause analysis of rapid changes toward deterioration, and forward prediction in time using algorithms and numerical models. The paper describes an early warning system for analyzing monitored signal patterns continuously in real time as well as forward predicting the various environmental and working conditions to recognize dangerous trends that may affect safety and health in underground mines. A dynamic, numerical ventilation model with heat and gas contaminant simulation components is used for the analysis of atmospheric data. Methods and test results are discussed with numerical examples for signal propagation prediction. Several mine examples are studied using controlled, synthetic data for malfunction simulations to evaluate time delays between the detection time of suspicious signal trends and the time of dangerous threshold crossing marking an accident scenario. Delay time is found in the order of 20 min in the examples, signifying the useful time period for preventive intervention between EWS warning and the likely breakout of a following accident.

By Stephen H. Partney

Waste clay ponds are a necessary part of phosphate rock beneficiation. They are large, averaging 2.6 km2 (1 sq mile). They are unsightly in that they protrude 6 to 15 m (20 to 50 ft) above natural grade. Stabilization and reclamation is slow and they have had a history of catastrophic failure. Florida has never published a specific rule regarding the configuration or height of these ponds. But it has enforced several policies along these lines. The phosphate industry has been forced to make major monetary decisions that affect mine economics for decades. The Florida Bureau of Mine Reclamation believes that the direction of regulation has been solidified but changes are still anticipated. Phosphate rock has been mined in Florida since 1890 (Fig. 1). Three notable technological changes occurred in the industry that led to major shifts in mining technique and volume. By about 1915, hydraulic mining had been replaced by centralized washers. Hydraulic mines usually started at an outcrop in or adjacent to a stream of the pebble zone. Water was pumped out of the stream through high-pressure monitors and sand and clay were washed away from the pebble. Mobile grizzlies and screens were used in conjunction with animal and human labor to concentrate the pebble and haul it away. Populations were sparse and the clays washed into the stream were considered an acceptable price for the commerce. The clays were not voluminous because the pebble zone typically contained relatively small amounts of them. Machines largely replaced animals by 1910 and provided greater efficiency of production. Centralized washers replaced mobile trommels. They allowed greater ease of access to shipping routes by rail. Some clays were placed in mine cuts from 1915 to 1930. Some were dammed off to increase the capacity of a given site. Some of these also failed, leading to clay plumes that were visible all the way to the Gulf of Mexico. By concentrating the waste clays (slimes) in impoundments, the solids concentration had increased, making plumes persistent for long distances. There were complaints. But there was no litigation against the companies during that time. In 1930, flotation technology allowed the recovery of the phosphate from deeper zones. This was because the "concentrate" size phosphate rock was in the sand-size range and could not be screened out. Centralized beneficiation plants grew into a three-step process - washing and screening, feed preparation and flotation (Fig. 2). Reagent storage, safety and the flotation cell complex made the plants into large capital installations. Larger draglines were required to dig deeper into the matrix. These had dramatically larger production capacities, which were then figured into the overall material balance for a given plant. The number of operators shrank and the production per operator grew. Larger areas were being bermed off for waste clay storage. An economic incentive became apparent for storing as much waste clay as possible in each settling area. At the same time, the population was steadily growing and more eyes were watching the activities of the phosphate mines. Phosphate mining, focused on production and profit, was earning a bad name from its neighbors. When the subject of phosphate mining

Jan 1, 1998

By D. Bahrami, W. K. Asante, G. L. Danko

It is prudent to interpret atmospheric monitoring signals in real time for checking the safe limits of the air conditions in underground mines. In gassy mines, real-time evaluation increases the safety of operations. In all mines, continuous monitoring and evaluation contributes to maintaining air conditions within healthy and safe limits. Signal interpretation for safety conditions in mines is difficult for many reasons. An increase in hazardous contaminant concentrations can be predicted by signal pattern recognition, root cause analysis of rapid changes toward deterioration, and forward prediction in time using algorithms and numerical models. The paper describes an early warning system for analyzing monitored signal patterns continuously in real time as well as forward predicting the various environmental and working conditions to recognize dangerous trends that may affect safety and health in underground mines. A dynamic, numerical ventilation model with heat and gas contaminant simulation components is used for the analysis of atmospheric data. Methods and test results are discussed with numerical examples for signal propagation prediction. Several mine examples are studied using controlled, synthetic data for malfunction simulations to evaluate time delays between the detection time of suspicious signal trends and the time of dangerous threshold crossing marking an accident scenario. Delay time is found in the order of 20 min in the examples, signifying the useful time period for preventive intervention between EWS warning and the likely breakout of a following accident.

By David H. Carlson

Mechanical sorting of "poor" rock accumulated from past native copper mining operations has been under study at the Michigan Tech's Institute of Mineral Research for several years. Prior to this work, the poor rock dumps totaling approximately 9 million tons containing an estimated 35-70 million pounds of copper (1) have been considered mainly as a local source of road aggregate used from time to time and consequently of minor value. An electro¬mechanical sorting machine developed by International Sorting Systems Corporation of Santa Barbara, California has been tested for preconcentration of the waste rock before conventional milling (2,3). The ISSC machine has possibilities for underground preconcentration of crushed mine-run native copper ores. The objective of the study described here was to provide information about limi¬tations on sortability due to characteristics of the ore and present crushing practices. When the native copper mines were in operation prior to termination in 1969, two types of ore were produced, amygdaloidal and conglomeritic. In the first type copper occurs in vesicles left by gas bubbles entrapped during rapid cooling of the tops of lava flows. The conglomeritic ore beds consist of rounded pebbles and fragments cemented together by calcite, epidote, chlorite, and feldspar; the copper occurs around pebbles, in cracks, and sometimes as partial or total re¬placements of pebbles. The copper in the conglomeritic ore usually is in finer grain sizes than that in the amygdaloidal ore, and large (plus 4 inch) copper masses are virtually absent.

Jan 1, 1970

By Alen Shibu Joseph, Arvind Rajnarayan Singh, Mudila Dhanunjaya Rao, Kamalesh K. Singh

In this article, the cementation of major impurities from zinc sulphate leach solution by the addition of zinc dust was studied by considering different parameters including time, mesh size, and percentage of excess zinc dust. The output obtained from various experiments was utilized for the design of experiments. A multi-level categorical factorial design with a quadratic model was employed during this study. Results were predicted to minimize the concentration of impurity metals in the solution by altering the parameters. Furthermore, these predicted results were validated by performing another experiment. Successfully, it showed that the predicted and experimental data values were close to each other. The predicted optimized values were 40 min, 100% excess zinc dust, and 300 mesh size for copper; 42 min, 100% excess zinc dust, and 300 mesh size for cobalt; 37 min, 100% excess zinc dust, and 300 mesh size for cadmium; and 34 min, 100% excess zinc dust, and 300 mesh size zinc dust for nickel. At these optimized values, the experimental results showed 99.99%, 55.7%, 99.6%, and 76.6% cementation efficiencies for copper, cobalt, cadmium, and nickel respectively. The statistical design of experiments for the effective cementation of impurities corroborates the economic feasibility of optimizing parameters for the proposed process.

Jul 18, 2022

By John C. Stankus, Xiaoting Li

"Underground structures such as square/arch steel sets, king beam structure, etc. are widely used for the roof support in underground mines. In designing and calculating the required carrying capacities of these underground structures, how to identify the potential rock loads on the structures over long term is a challenging question for ground control engineers. Based on design practices of both surface and underground structures, the authors have designed and applied appropriate load factors in underground structural design projects to accommodate different rock types, entry/intersection dimensions, roof geologic conditions, availability of roof bolts and water, etc. Classification of load (reduction) factors for large-span underground intersections are presented for reference. Success of designed underground structures in effectively controlling roof stability over years indicates the applicability of the load factor concept for underground structural design, and its same significance as of the load factor specifications in ASCE/SEI 7-10, ANSI/AWC NDS (2015), and AASHTO LRFD Bridge Design Specifications (2012). The load factor concept will facilitate ground control engineers to appropriately utilize popular structural design software, such as RISA-3D or -2D to efficiently design and analyze underground structures.LOAD FACTORS IN STRUCTURE DESIGN APPLICATIONSIn structures, loads cause stresses, deformations, and displacements. Assessment of their effects is carried out by the methods of structural analysis with the help of load factors. Loads can be increased or decreased by load factors to meet the requirement that design strength be higher than maximum loads. For example, in designing a staircase, a dead load factor may be 1.2 times the weight of the structure, and a live load factor may be 1.6 times the maximum expected live load based on the Load and Resistance Factor Design (LRFD) method. These two “factored loads” are combined (added) to determine the “required strength” of the staircase. Some typical load (adjustment) factors used for structural design are as follows:"

Jan 1, 2019

By Godfred Amponsah, Mehrdad Razavi

Slope failures very commonly occur during a long period of heavy rainfall and groundwater rise. The failures pose a substantial risk to people, infrastructure, and equipment downslope. In the recent past, the mining industry has faced an increase in tailings dam failure due to several reasons including pore pressure increases in the dams. Many failures have been observed to occur during times of water level fluctuations but the critical factors that influence the initiation of slope failures still need to be adequately clarified. To investigate these factors, laboratory experiments were conducted on model sandy slopes to determine pore pressure-induced slope failure initiation. This study also presents a method to examine water seepage through soil slopes using an ultraviolet (UV) dye and a UV flashlight. The small-scale model test simulation demonstrated failures induced by either water percolation from the upslope tank at a constant level or by raising the water level at intervals. A bottom chamber fully filled with water to replicate groundwater rise was also simulated. The soil slope was monitored at every stage to study the deformations and behavior until failure occurred. Results gathered from the controlled laboratory conditions were useful for the verification of the numerical modeling method created in the computer program Slide. The analysis showed that slope failure always occurred when the toe was fully saturated. High pore pressures and seepage forces reduce the shear force at the toe to almost zero causing it to slide. A comparison of slope height to water level also indicated an average of 96% water level to cause a failure. At this point, the soil slope is fully saturated and has no matric suction. The findings in this study show that, by monitoring the moisture content of slopes, failures can be predicted.

Feb 1, 2024

By J. Kemeny, J. Lyons-Baral

"Point cloud technology is now an indispensable tool in geological and geotechnical data collection, interpretation and analysis. Open-pit and underground mines of all sizes are regularly collecting point cloud data as laser scanning (LiDAR) and photogrammetry surveying devices have become affordable and the workflows fast and efficient. Past challenges of large data processing and manipulation are gone with recent technological advancements in computer hardware and software. These innovations reduce file sizes, ease rendering requirements and allow for the implementation of real-time 3D viewers and surface meshing tools. With its ability to remotely and safely, rapidly and accurately extract large quantities of georeferenced and 3D-oriented data, point cloud technology provides numerous applications to the geomechanical field. The list of uses is continuously growing. This article specifically focuses on digital outcrop modeling and digital terrain engineering. Point clouds. The high-resolution and increasing availability of point cloud technology is rapidly improving open-pit and underground mines’ investigation, interpretation and characterization of site geology and rock mass properties (Kemeny et al., 2015; Lyons-Baral, 2012). LiDAR and photogrammetry are common remote sensing methods employed to measure the coordinates of surfaces in three dimensions (3D), providing the X, Y and Z locations and typically the reflective intensity and/or the visible three-band color of each point (Fig. 1).LiDAR uses either a time-of-flight or phase-shift measurement of a laser beam reflected off targeted surfaces and received back into the device.Photogrammetry generates point clouds by merging multiple overlapping photographs and uses stereographic plotting to define the locations of object points in 3D space. These methods can be deployed from airplanes, unpiloted aerial systems (UAS or drones), tripods, land vehicles and even in a mobile backpack shown in Fig. 2. RADAR, Total Station-Prism and other remote sensing systems also offer very precise “point clouds,” but this article does not address these due to their higher cost and lower versatility and mobility."

May 1, 2016

By Joseph P. Sobanski, Michael P. Bruen

The North Branch tunnel segment of the Tunnel and Reservoir Plan Mainstream System consists of 14,075 m (45,885 ft) of 9.2 m (30.2 ft) finished diameter and985 m (3,232 ft) of 2.5 m (8.25 ft) finished diameter concrete lined rock tunnels. The TBM mining and concrete lining methods used in completing this $166million project differed from “typical” TARP construction methods in that a two-stage concrete lining was placed and the lining was initially placed concurrently with TBM mining as a two pass system in the same tunnel segment. For the main tunnel (9.85 m diameter), TBM mining averaged 24 m/day (79 ft/day), excluding downtime associated with two main bearing changes, and the concrete lining placement, averaged 117 m/day (380 ft/day) and 53 m/day (174 ft/day) for the invert and arch segments, respectively.

Jan 1, 1999

By L. K. Eigenbrod

Throughout the mining industry, pneumoconiosis is one of the most severe occupational health problems being faced. The goal of completely eliminating pneumoconiosis as an occupational health hazard was underscored by the Federal Government with its enactment of Public Law 91-173 (Federal Coal Mine Health and Safety Act of 1969). Under this law, permissible dust level standards will be placed at 2 mg/m3 in mine atmospheres by December 30, 1972. The mining industry is thus faced with the tremendous technical challenge of achieving this level. Two basic questions can be raised with regard to this legislation. First, does a maximum dust concentration of 2 mg/m3 prevent the occurrence of pneumoconiosis? Secondly, can this dust standard be achieved using presently available methods and equipment? A precise answer to the first question has not yet been developed by the medical profession. Studies are continuing on the origin, prevention, and therapy of pneumoconiosis, and permissible dust levels could become even lower as medical evidence accumulates. The mining industry has addressed itself to the problems of dust con-tro1 for many years as related to personnel health, explosive mixtures, visibility, and machinery damage. Dust control methods being employed involve

Jan 1, 1971

By Jie Long, Zijie Liu, Pu Liu, Bo Li, Menghua Li, Qiang Wu

During coal mine operations, roadways may be located close to faults. When designing these roadways, it is important to determine the width of the rock mass between a roadway and a fault area to prevent water inrush. In this paper, the Xintian Coal Mine in the northern Guizhou Province of China is selected as a typical case. Through numerical simulation based on orthogonal tests, range analysis, and multiple linear regression (MLR) analysis, the process of water inrush from faults in excavation roadways is studied. The results show that the influencing factors of the safe width of a rock mass preventing water inrush (RMPWI) can be ranked according to the degree of influence from large to small as follows: the hydraulic pressure of the fault, the surrounding rock grade, the overburden depth of the roadway, the cross-section height, and the dip angle of the fault. Among them, the dip angle of the fault, the cross-section height, and the surrounding rock grade are negatively correlated with the safe width, while hydraulic pressure of fault and overburden depth of roadway are positively correlated with safety width. The predicted value for the safe width based on MLR is greater than the measured value of the width of the RMPWI when water inrush occurs, but less than the calculated value based on the empirical formula in the standard, which proves the accuracy and practicability of the prediction method. This research provides a certain basis and reference for the prevention and control of water inrushes in mines.

Jul 5, 2023

By Alexander E. McHugh

A study of some variables affecting the recovery of molybdenum from oxidized molybdenum minerals was made. The effects of variations in contact time, temperature, pulp density, particle size, and solvent concentration on the recovery of molybdenum using acid and alkaline solvents were investigated. Chemical analyses, screen analyses and microscopic examinations were made and the presence of important elements determined. A hydrometallurgical method was developed to recover the molybdenum from the oxidized molybdenum ore by simultaneous dissolution of the molybdenum with sulfuric acid, adsorption on activated charcoal and flotation of the charcoal. The molybdenum was extracted from the activated charcoal with sodium hydroxide, precipitated with calcium hydroxide as calcium molybdate and this regenerated sodium hydroxide for additional stripping. A solvent extraction method, using mines, was also studied to recover molybdenum from both alkaline and acid molybdenum solutions. Satisfactory results were obtained.

Jan 1, 1967

By W. Rocher

The Minera Ojos Del Salado (?MINOSAL?) concentrator is located 20 kilometers southeast of Copiapo, Chile and processes copper ore provided by its Santos and Resguardo mines at a capacity of 4,200 tip (4,620 stpd). Phelps Dodge acquired the majority interest in MINOSAL in 1982. The principal incentive for this purchase was the exploration potential of the property. At that time, the concentrator plant was a small, antiquated installation with a capacity of 674 t/d (740 stpd). In 1982, the majority of the ore was produced from the Santos and Resguardo mines, but custom ores of copper, silver, and gold were also treated. The acquisition occurred at a crucial time in the copper business, since the price had fallen to nearly $0.50 per pound. In 1985, Phelps Dodge purchased the outstanding interest in MINOSAL and acquired 100% of the property. Today, after numerous improvements and two expansion projects, the concentrator is an interesting combination of old and new equipment. The regrind mills, for example, have been in service for about 50 years, while the ceramic concentrate filter represents the latest technology.

Jan 1, 1993

By Gabriele Eccher, Michele Caponero, Paolo Cucino, Roberto D’Angelis

"This paper describes the optic fiber structural monitoring system implemented for Pavoncelli Bis tunnel. The paper highlights the optic fiber sensors customization capabilities, how they smoothly fit precast concrete lining processes and TBM operations, and how a lifelong service monitoring can be achieved. An overview of readings’ evolution during excavation concludes the paper.INTRODUCTIONPavoncelli Bis is a 10 km hydraulic tunnel designed to by-pass the existing Pavoncelli tunnel which experienced severe damages during the 1980 Irpino-Lucano earthquake, in south of Italy (Barla 2009). Pavoncelli Bis excavation work commenced in 1988-90, however, when excavation approached pk. 0+583 in 1992, water percolations became more and more consistent and resulted in work suspension. The tunnel was eventually sealed at pk. 0+383, leaving a flooded section between pk. 0.383 and pk. 0+583. Work resumed in 2012 where EPB-TBM excavation was adopted to cross the flooded section and to overcome complex hydro-geological conditions in various lito-types and, in particular, in the Varicolori Clay-shales area (Figure 1).Consequently, stress evolution monitoring is extremely important during construction and during the service life of tunnel lining in clay-shales and in faults areas. In particular, the paper focuses on the monitoring system proposed for the newly EPB-TBM excavated portion from pk 0+583 onwards where optic fiber sensing technology was chosen for its reading stability and reliability in presence of water and its ability to be connected in series and remotely interrogated at kilometers of distance. FBGS OPTICAL FIBER SENSOR TECHNOLOGYFiber Bragg Grating Sensors (FBGS) are gaining increasing attention in the field of experimental stress analysis. Basically, Fiber Optic Bragg Sensors are strain-measuring devices and therefore provide many of the advantages of the well-known metal foil strain gages (Kreuzer 2007).Bragg gratings are written into so called single-mode fibers. These fibers consist of a very small inner core of 4 to 9 µm diameter and an outer part (cladding) of pure glass (SiO2) of 125 µm diameter. The difference of refraction indexes between inner core and cladding causes the light to propagate only inside the small core."

Jan 1, 2016

By Wei Victor Liu, Omer Faruk Ugurlu, Chengkai Fan, Bei Jiang

Accurate prediction of truck productivity plays a pivotal role in improving the efficiency and profitability of openpit mining operations. This paper proposes a deep neural network (DNN) model to overcome the challenge of predicting truck productivity in openpit mines. The prediction model was built using eight variables and was optimized by considering different train-test split ratios, numbers of hidden layers and neurons, and activation functions. The proposed model’s performance was evaluated using various metrics and compared with other commonly used machine learning algorithms. The results showed that the proposed model outperformed traditional machine learning models by achieving higher prediction accuracy. Moreover, a single-variable sensitivity analysis showed that haul distance is the most influential variable for predicting truck productivity. This study marks a pioneering effort in employing DNN to predict truck productivity in openpit mining, signifying a notable advancement in the field.

Jul 1, 2024

By M. Downing

This paper gives a brief overview of impacts of coal blending on coal-fired power plants performance and discuses the preliminary results of an on-going study aimed at evaluating the effect of coal properties on the effectiveness, compatibility and thermal reactivity of coal blends. Plant survey studies reported no significant impacts on an existing plant designed for a high rank coal when switched to a blend of low-and high-rank coal. However, slight modification of some aspects (handling, fuel storage/stockpile, transportation, preparation, and general housekeeping) of plant design and operation may be necessary. The preliminary results of an on-going study at the Mineral Industry Research Laboratory shows that more compatible and better blends could be made from coals where ranks are closer than from those where ranks are far apart.

Jan 1, 1997

By W. A. Haley

As far back as 1939 state laws have required reclamation of mined lands. Reclamation has been the topic of many discussions and presentations, especially since the late 1960's. In the past ten years many states have added legislation concerning the reclamation of coal-mined lands. In the near future, it seems certain that some federal regulations will be passed that will set minimum guidelines for the states to regulate. Besides the requirement of returning the land to the approximate original contour, future regulations will more than likely demand replacing topsoil from one to five feet thick. As regulations become more stringent, costs will rise accordingly. Since no one has developed a machine that can do all reclamation work by itself, it is necessary to review in detail the tools available and to select the most economical means.

Jan 1, 1976

By L. B. Bramlett

The Archean (2.65 b.y.) aged Canning Stock at Copper Mountain, Wyoming contains an average of 20 ppm U. The North Canning and Fuller deposits occur within the enriched interior of the stock. Post-Laramide development of super gene enrichment blankets occurred in wide (25- 100 m) crushed zones. Hematite and chlorite accompany pyrite and sooty pitchblende in the mineralized zones. Reduction mechanisms proposed for deposition of pitchblende are: 1) sulfides, 2) hydrocarbons, 3) bacteria, 4) the water table, or 5) some combination of these. Abundant tar- type organics appear to have preserved the enrichment blankets from degradation. Trace element and radiometric data define target zones, but exploration models focus on favorable structure.

Jan 1, 1980

By Verya Nasri, Jaeseoung Lee, Ashish Bhargava, Shashank Gupta

This paper presents the unique design and construction challenges for the Technoparc Station, located in downtown Montreal as a part of Réseau Express Métropolitain (REM), a light rail rapid transit system. The station is located 15 m below the street with rock-bearing secant pile wall as the primary structural system working as both the retaining and gravity structure. The paper highlights the challenges related to the support of excavation structure, invert slab resisting high hydrostatic forces, waterproofing tightness etc. It also focuses on the importance of Building Information Modeling (BIM) in underground tunneling projects for effective coordination, clash-free, optimized design and costs.

Jun 13, 2021

By Guillermo V. Borquez

The economics of open pit mine design are dictated by three basic elements: cut-off grade, stripping ratio and slope angle. Although these elements are functions of a number of independent parameters, they are interrelated through their influence on the overall economics. The optimum slope angle is the most uncertain element to determine, because rock mass properties are difficult to obtain. However, for preliminary estimation, the slope angle can be determined from the relationship between the probability of failure and the safety factor. The economics of the slope selected will depend on a profit versus risk judgment. In this paper, the author will present an actual case of application of this postulate.

Jan 1, 1977