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By S. K. Kawatra

Under normal conditions, a significant amount of pyrite is recovered in the froth during flotation of high-sulfur coal. In order to reduce this pyrite recovery, it is first necessary to determine the primary recovery mechanism, as different measures are required for reducing entrainment, locked-particle flotation, or true hydrophobic flotation. In this paper, evidence is presented which suggests that hydrophobic flotation is not the major mechanism for recovery of liberated pyrite, and that the bulk of the recovered pyrite is there either as a result of simple entrainment or by being physically locked with floatable coal particles.

Jan 1, 1991

In the screening process, used to prepare particles for many applications, shape is known to have a significant effect. The degree of flakiness of construction aggregates has been considered particularly important. The objective of this research was to find values of operating parameters that optimize the separation of flaky from non-flaky particles by slotted screens. Thus an investigation was conducted to experimentally determine the influence of the particle size and thickness on the screening process. The Response surface method was employed for modelling and analysis of the data. Experiments employing a central composite design were performed on a pilot-scale, rectangular-aperture, vibrating screen to examine the effects of the screening variables the mass recovery of flaky and non-flaky particles to the oversize product. The SAS statistics package was used to fit a second-order model to each response and to analyze the fitted surface to determine the optimum levels. The optimization associated with a dual response system was then considered. The results of this study should provide a basis for optimizing screening conditions to obtain maximum recovery of non-flaky particles to the screen oversize while minimizing the recovery of flaky particles, which should be of interest to the aggregate industries.

Jan 1, 1999

By E Mutaz, M Bahaaddini, D J. Williams, M Serati

The contribution of the mining industry to the global economy has reached (and gone beyond) $1,800 billion in recent years that necessitates (more than before) the need to ensure workability, viability, health, and safety of mine sites and workers to meet the ever-increasing global demand for mineral resources. Amongst the many challenges facing the excavation industries, rockburst and spalling failures in deep mines in hard and brittle rock formations are yet happening that are still deemed as unsolved problems. During unconfined compressive testing of brittle rocks, microcracks initiate at approximately 0.3–0.5 of the peak strength (which is commonly known as the Crack Initiation stress level) mainly in the direction of the major principal stress, then grow unstably and coalesce to form macro fractures at approximately 0.7–0.8 of the peak load at a so-called Crack Damage stress threshold. From a stress-strain perspective, the crack damage stress threshold () is associated with the reversal point of the volumetric strain, which is also proved to be strongly affected by the intermediate principal stress. This paper extends the previous studies on the impact of true triaxial loading conditions on the CD stress level in high porosity rocks, and introduce a new Crack Mode-Changing Stress (CMCS) defined as the minimum principal stress required to change rock fracturing from splitting to a sliding failure mode. A large number of experiments on sandstone specimens were carried out at different true triaxial loading conditions and the effect of principal stresses on the CI and CD as well as CMCS were studied. The results show that not only the intermediate principal stress, but also the minor principal stress can significantly affect the CD and CMCS thresholds.

Apr 26, 2022

By J. Fuller, J. Beale, Q. Justice, Z. Agioutantis, S. Hicks, Z. Khademian

Seismic events can be induced by mining due to unstable rock failures or slips along geologic structures leading to the sudden release of strain energy stored within the rock near underground openings. Depending on their intensity and proximity to the working area, seismic events may raise safety concerns, and thus the forecasting of the seismic potential in advance of mining can mitigate safety hazards. The integration of seismic data into geomechanical modeling can provide a tool for identifying areas with elevated potential for seismic activity. In previous works, a methodology was developed to forecast seismic potentials in a pseudo-2D geomechanical model. In this paper, seismic events, ranging in magnitude from about -1.0 ML to 3.7 ML, recorded in a deep longwall mine (> 450 m) in Virginia during mining of six adjacent panels, were evaluated to identify areas where larger magnitude events (> 1 ML) had occurred. A three-dimensional geomechanical model of the same area was constructed in the 3DEC software to calculate the state of energy in the system with the progress of mining along the entire length of each panel. The variation in the energy content of the model was monitored, and zones with potentially damaging slip-type events along bedding planes followed by compressive-type events in the sandstone roof are the mechanism for large seismic events in the studied mine. The locations of anomalous events corresponded to the regions where both compression-type SPI (C-SPI) and slip-type SPI (S-SPI) were elevated. The modeling results were compared with the recorded seismic events to evaluate the model performance in forecasting the seismic potentials. The model was able to forecast 100% of regions with elevated and moderate seismic potential and 89% of regions with low seismic potential. This shows the applicability of energy balance calculations for forecasting the approximate location and timing of destructive seismic events in advance of mining.

Jun 25, 2024

By L. Zhou, D. Bahrami, Y. Xue

Underground mine fires are a threat to the safety and health of mine workers. The timely determination of the location and size of an underground fire is of great importance in developing firefighting strategies and reducing the risk of any injuries. Machine learning was used in this paper to develop a predictive model for fire location and fire size in an underground mine. The ventilation data were obtained by simulating different mine fire scenarios with MFire. The ventilation data of all airways were used as features to predict the fire location. Based on the feature importance, five airways were selected to monitor, and the airflow data of the selected airways were used to predict the fire location and fire size. An accuracy score of 0.920 was obtained for the prediction of fire location. In addition, in-depth analyses were conducted to characterize the wrong predictions with the purpose of improving the performance of the random forest model. The results show that the occurrence of fire at closely connected airways at some locations can generate misleading ventilation data for each other and the model performance can be further improved by grouping them. Fire size is another factor affecting the model performance and the model accuracy increases with increasing fire size. The result from this study can help mine safety personnel make informed decisions during a mine fire emergency.

Mar 2, 2022

By P. F. Mataich

"Why bother with computer control?" This question and others like it have been heard over and over again by those who have tried to convince operating men that there are sound merits to installing a process control computer. At IMC we have done a great deal of thinking and talking about computer control. In the course of these discussions the operating people have asked a number of questions about computer control. These questions and our answers to them make up the main part of this article. Obviously, the answer as to whether or not to go into computer control will be an individual problem conditioned by your company's circumstances. What I hope to do here is raise some questions, give you an idea of our thinking on the subject, and lay out some general guidelines for you to consider.

Jan 1, 1965

By R. E. Cook

"Mineral deposits require substantial amounts of energy to transport and be processed into useable form, and as such present a real processing challenge in that the deposits are never homogeneous and ore body compositional characteristics are all over the map! Extracting the desired mineral(s) from the deposit at sufficient profit margin, despite severe fluctuations in market price, requires process automation architecture capable of supporting an integrated enterprise solution. Such an architecture will encompasses the activities of individuals, process units, process areas, plant level activities, mine management and business planning and accounting systems. Key to the automation process is the aspect of value generation. This paper brings together the various requirements for the automation of a mining enterprise and presents the different aspects of how to obtain value across the entire mining operation.INTRODUCTIONMinerals’ processing sites are historically long lived, 20 year life of mine is not uncommon and 75 years is not unheard of. Considering that hardware technology advancements are introduced every six months, or less, it is prudent to select process automation systems that adhere to “open” industrial standards versus proprietary based systems. In the minerals processing industry, the key to survival is driving the cost of production per unit volume to the lowest possible level and provide enough profit to sustain operations. Control system architecture and Business information technology are rapidly becoming important tools in the quest for productivity. Getting key dynamic business performance information at the right time to the right person or process unit is crucial to successfully achieving corporate goals. The process automation architecture selected must therefore be able to integrate to the various networking enterprises and business systems.The mining industry is generally known as an “extractive” industry that is very physically-oriented with respect to operations and the activities in which workers engage. Large numbers of people performing manual tasks in difficult surroundings, produce very variable outputs. But, times are changing – and so are industry best practices. While the nature of work still consists of activities such as ore extraction, ore movement, ore concentration, refinement and logistics, automation innovations are starting to change the nature of many of the production steps. The industry has transitioned from requiring more physical activities by workers, to more information management, automated control and collaboration within the operation. Humans are good at situational intervention and non-linear reasoning and do best when empowered with an overall production perspective. Machines and automation are good at repetitive functions, steady state operation, and managing transitions. Thus, a combination of advanced technology solutions, reliable and useful information and full human contribution are necessary to mining operations for value generation."

Jan 1, 2015

By D. A. Bird

Geochemical models using published thermo-dynamic data and laboratory derived kinetic rate laws allow prediction of post-closure pit lake geochemistry at open pit mining sites. A combination of "forward" and "inverse" modeling techniques can predict the pit lake geochemical evolution from initial infilling to eventual steady state attained decades or centuries after closure. Computer codes have been developed to model chemical reactions such as pyrite dissolution, describe the ground-water flow regime, and provide rock-water ratios. The incorporation of site specific information, such as ultimate pit dimensions, geologic and hydrologic data, acid generating potential (AGP) vs. acid neutralizing potential (ANP), and laboratory derived kinetic rates, allows application of the model to open pit mines at any stage of development.

Jan 1, 1994

By Ken Bright

This paper is an overview of approaches to assessment of ore grade for gold and the platinum group at the exploration stage of a project. Proper sampling techhniques must be complemented by good assaying. In turn, correct assaying has its roots in thoughtful, systematic sampling and sample preparation procedures. While intricacies of the subject matter could occupy a book, we will comment on acceptable sampling approaches, outline a lab hand- ling scheme, and discuss preferred analytical methods. Pitfalls previously encountered by the mining and exploration industry will be highlighted with emphasis on a perceptive under- standing of the nature of ore occurrence. Lastly, focus will be centered on reliable assay approaches.

Jan 1, 1988

By R. Hogg, T. F. Dumm

With increasing interest in the physical cleaning of fine coal, there is a need for extension of the sink-float analysis procedure to finer sizes. Problems arise, however, in ensuring complete dispersion of the particles in the heavy liquids. A procedure has been developed in which surfactants are wed as dispersing agents, and solids concentration is minimized (using a simple formula to estimate the minimum weight needed for statistical reliability). Using centrifuges to increase separation rates and subsieve particle size analysis of the specific gravity fractions, a complete size-specific gravity distribution can be obtained. Analyses have been performed on coal samples as fine as - 10 µm.

Jan 1, 1987

By Art Hamid, Manfred Wong, Carlos Jaramillo, Greg Raines, John Caulfield

"The Central Bayside System Improvement Project (CBSIP) is a critical element of the Sewer System Im-provement Program (SSIP), a 20-year, $6.9-billion investment by the San Francisco Public Utilities Commis-sion (SFPUC) to upgrade San Francisco’s 100+ years old seismically vulnerable combined sewer system. The CBSIP’s centerpiece, a proposed 10,000-foot-long (3,048-meter-long) Channel Tunnel, will provide reliable and redundant gravity conveyance and storage of combined wastewater flows from the northern and central parts of San Francisco to the Southeast Water Pollution Control Plant (SEP) while ensuring compliance with regulatory requirements for combined sewer discharges to the Bay. A tunnel with a diameter of 23 to 30 feet (7 to 9 meter) is being planned using pressurized-face tunnel boring machine technology. Project challenges include tunneling through Franciscan Bedrock, mixed ground conditions in close proximity to the Bay, connector tunnels and shafts, construction in congested urban environment, and challenging real estate issues for shaft access. BACKGROUND AND NEED FOR TUNNEL The City of San Francisco is one of the most beautiful cities in the world. About 850,000 people live in the city and many more come to work, for tourism, and for attending conferences. The SFPUC is a department of the City and County of San Francisco that provides energy, drinking water and wastewater services to San Francisco, wholesale water to three Bay Area counties, and green hydro-electrical and solar power to San Francisco municipal departments. The SFPUC wastewater system includes tunnels, large storage/transport boxes, 1000 miles of collection sewers, 28 pump stations, and three wastewater treatment plants. San Francisco’s combined sewer system collects both wastewater and stormwater in the same sewers, which is then pumped, treated to stringent state standards and discharged into the San Francisco Bay and Pacific Ocean. After decades of service, much of the sewer system is nearing end of its working life. During the 1989 Loma Prieta earthquake, damage to SFPUC water and wastewater infrastructure was extensive. The 11,200-foot-long (3,400-meter-long), 66-inch-diameter (1,676-mm-diameter) Channel Force Main, built in 1976, and a critical component of the SF wastewater system was also damaged. This force main carries 70 percent of the bayside dry weather sewage flow from the northern and central part of the city to the SEP. The force main is at the end of its life and was not constructed to the current seismic code; in addition it has no redundancy. Figure 1 shows the project background and the force main that will be provided redundancy by the new gravity tunnel."

Jan 1, 2016

By A. B. Cecala

The US Bureau of Mines has designed and evaluated total mill ventilation systems (TMVS) at two mineral-processing operations. Both systems have proven proficient at cost-effectively reducing respirable dust levels throughout the mills. An 11.8-m3/sec (25,000-cfm) system installed at a clay-processing mill provided about 10 air changes per hour(acph). This system reduced respirable dust concentrations by about 40% throughout the mill building. The second evaluation was performed at a silica sand operation. Tests were performed with 23.6 and 47.2 m3/sec(50,000 and 100,000 cfm) of ventilation to the mill building, corresponding to 17 and 34 acph. Average mill-wide respirable dust reductions were 36% and 64%, respectively. This work was done to determine general guidelines and design criteria for operations that may be interested in implementing TMVS. TMVS should be designed to draw clean make-up air in near the base of the mill. This air provides general purging and may clear some dust-laden areas throughout the mill structure. It is discharged at or near the top of the structure. Without the TMVS, dust can exit the building through open doors, windows, etc. and contaminate outside plant workers. This dust can also be recirculated back into the mill building causing additional contamination problems. TMVS is not a stand-alone system. It is a supplemental technique to assist other localized dust control systems (Mody et al.,1987).

Jan 1, 1995

By H. J. Ilgner

Previous applications for using waste rock for backfilling in South African gold mines were reviewed and it was found that in many cases the mechanical equipment selected and the design philosophy applied did not meet the requirements. A more simplified system configuration is proposed, which allows the equipment to be relocated as mining progresses. Innovative high-intensity grinding and dense-phase pumping technology are proposed to provide a low-porosity backfill with a particle top size of 5 mm to 8 mm. According to recent rock mechanics modeling work, this comminuted waste backfill material can provide a good compromise between underground support characteristics and reliable hydraulic transportation behavior.

Jan 1, 2001

By Jerrold J. Marcus

United states reserves of oil and gas have been steadily declining while consumption of petroleum products has continued to increase. The nut result has been an ever increasing shortfall between supply and demand. This imbalance has been made up by imports of both oil and gas causing a strain on the United States Balance of Payments. To complicate the situation further, exporting nations have recently formed a cartel and dramatically increased the selling price of petroleum products. To meet U.S. energy demand, increased attention has been drawn to the production of synthetic oil and gas from coal. To date, considerable research has been conducted and is continuing on various processes for liquefaction and gasification of coal. Some of these processes are now in the pilot plant stage and at least one demonstration plant has been proposed. The coal conversion complexes envisioned will be very large, requiring substantial capital investments and abundant reserves of coal. Coal production to feed these proposed complexes has been estimated on the order of 75,000 tons per day. With the viability of these projects becoming economically attractive, the Office of Coal Research initiated a contract with Fluor Utah to determine and define the problems of surface mining coal at very high mining rates, under varied physical, geographic, and climatic conditions. The flow of recent events in the Middle East has created a greater sense of urgency for this study.

Jan 1, 1975

By Roberto Pimentel de Souza

Since 1976 CVRD is carrying out tests to develop a type of pellet made with organic binder. One binder that showed good possibility to be used in industrial plants is Peridur. An extensive framework of tests was run in CVRD's pilot plant. The results are presented in this paper. Finally, the decision was taken to carry out an industrial production of 50.000 t of pellets. It was scheduled for March '81. The results are shown in this pager. It was not observed any detrimental effect of the peridur neither in the process nor in the product quality.

Jan 1, 1981

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

The integrated grouting method, as developed in the USSR, can be applied to multi-purpose operations that in¬clude the construction of shafts, drifts, and tunnels. In the USSR it has been used extensively for primary and final grouting of underground excavations in mining engineering and civil engineering projects. It has been applied in projects where the primary objective was waste contain¬ment. It has also been used to control subsidence beneath buildings located over mined out openings and to eliminate the flow of ground water beneath and around dams. This chapter considers several industrial applications in the form of case histories. The word integrated means that grouting activities were integrated with other activities. 9.1 CASE HISTORIES OF GROUTING FRACTURED ROCK WHEN SINKING VERTICAL SHAFTS The integrated grouting method has been applied most widely in the sinking of vertical shafts in fractured, satu¬rated rock. As explained previously herein, grouting oper¬ations preferably are carried out from the ground surface where they are integrated into the schedule of the setting up of the shaft excavation and construction equipment. Such integration reduces significantly the length of time required for preparation of shaft construction and the time required to sink the shaft. The increased efficiency is achieved by the elimination of cementing operations from the working face upon the penetration of each aquifer. Concomitantly, labor and energy consumption during shaft sinking are minimized because the more complicated and labor-intensive work is carried out at the surface section. Table 9.1 presents the essential parameters for the pri¬mary grouting of saturated fractured rock carried out by the integrated method when sinking vertical shafts. 9.1.1 NAGOL'CHANSK MINE NO. 1-2, VENTILATION SHAFT NO. 1 The integrated method of grouting saturated fractured rock through holes drilled from the surface was employed for the first time during the sinking of vertical shaft No. 1 at the Nagol'chansk mine No. 1-2 in the Don Basin. The shaft had an inside diameter of 6 m. The grouting operations commenced by using cement grout with a density of 1.7 to 1.8 g/cm3. Clay-based grout with cement and other addi¬tives was used only for grouting the aquifers where cement grout proved to be ineffective. By the time of the grouting of ventilation shaft No. 1, hydrodynamic analytical methods were well in hand and a preliminary method for designing isolation curtains had been developed. A method for designing and drilling ori¬ented directional drillholes whose natural curvature re¬flected the characteristics of the fracturing had been devel¬oped. The majority of the necessary equipment had been developed. Clay-based grouts were considered ready for the first industrial application. The hydrogeologic environment at the Nagol'chansk mine No. 1-2 contained many prolific aquifers. According to monitored drillhole data, the total expected inflow into ventilation shaft No. 1 without grouting was 425 m3/hr. This large ground water inflow rate was supported by in¬formation obtained during the sinking of the main shaft and from the auxiliary shaft of the "Nagol'chansk" mine No. 1-2. The construction contractor at the site began sinking ventilation shaft No. 1 to a depth of 217 m by cement grouting from the working face of the shaft. As a result of the cement grouting operations, the inflow of water was reduced from 105.4 to 40 m3/hr over this 217 m interval. However the residual inflow rate caused the shaft to become functional at the depth of 217 m. At this point all grouting operations were transferred to SPETSTAMPONAZHGEOLOGIA (STG) in an effort to improve the operation. In order to carry out preliminary grouting from the sur¬face, seven drillholes were installed and designed for re¬ceiving grout. Drilling was implemented by the ZIF-1200A rig to the design depth of the shaft. The geometry of the principal fracture system that would be encountered by the shaft was estimated while breaking ground using informa¬tion from other shafts. The drillholes were arranged so that they cut through the aquifers uniformly around the shaft. Some preference was given to intercepting the aquifers that were located along the rock dip above the shaft bottom because it was established that the ground water in the aqui¬fers flowed downward along the dip into the cone of de¬pression of the shaft. Investigations in the drillholes using the DAU-3M flowmeter described in Chapter 3 showed that all of the nine aquifers were penetrated by the time a depth of 690 m had been reached. The flowmetric information showed that aquifer numbers [1 and 2], [4, 5, and 6], and [7 and 8] had practically identical hydrogeologic characteristics; so it was decided to connect them into combined stopes and inject the grout using five stopes instead of nine. Table 9.2 shows the results of the grout injection into the aquifers. The volume of grout pumped into the separate intervals through single holes varied from 204 to 15 m3. The trend of grout consumption showed a reduction of grout consump

Jan 1, 1993

By E. Bonates

Truck/shovel systems are a major form of materials handling in open-pit mines in spite of the high associated capital and operating costs. Mine management is usually faced with a decision to purchase new equipment in order to support the steadily increasing on production. These decisions involve a high degree of uncertainty with respect to future demands and technical developments. This paper describes a computer simulation model for evaluating the optimum equipment fleet in an open-pit mining operation. The system is based on a stochastic simulation program which accounts for the various mining and economic parameters. It calculates the type of equipment and the optimal number of trucks needed to meet the production targets. Two types of selection criteria: maximum rate of production or minimum cost can be applied.

Jan 1, 1989

By J. Van Kleunen

In the Spring of 1959 the Riverside Cement Company, a Division of American Cement Corporation, placed into operation at their Oro Grande California plant a new crushing-blending-reclaiming facility. This new facility, in conjunction with other modernization in the plant, has established a degree of automation and reliability on a-plant-wide basis which heretofore had not been attained in the industry. The blending and reclaiming facilities for raw stone and cement clinker at this plant represent not only the first computer programmed materials handling system of its type in the industry, but also the first installation of specialized equipment which was designed for high capacity, fully automated operations.

Jan 1, 1963

By Giorgio Höfer-Öllinger, Peter Pointner, Manfred Stadlober

"SUMMARY Investigations from tunnel face are part of risk mitigation measures during the excavation works. With the tunnel equipment, percussion drillings of up to 30-40m can be achieved. Core drillings are state of art method for investigation exceeding 50m. At Koralm base tunnel, up to 270m deep percussion drillings were performed with drilling rigs and accompanied by an intensive investigation program. These investigations consisted of monitoring during the drilling, field tests (with packer, using the preventer, borehole imaging) and in laboratory. Percussion drillings are cheaper and save time of interruption of the excavation progress. INTRODUCTION As part of a proper risk management, horizontal advance drillings during excavation of underground works can be seen as state of art and meet wide acceptance. Core drillings, deep and shallow percussion drillings can be differed. The selection of the type of drilling, meanwhile, causes intensive discussions. On the one hand, only a core drilling allows a direct investigation of the rock mass expected during later excavation works. On the other hand core drillings are expensive in both cost and time – if there is no excavation progress during the investigation measures – in construction time. Percussion drillings can be performed as rapid investigation measure with the excavation equipment (“Jumbo”) allowing two dimensional image of the ground around the cross section. There is some limitation concerning a reasonable depth of approximately 30m and a borehole diameter of 76mm. The applications of preventer, packer or borehole imaging are hardly applicable. By use of a drilling rig depths of percussion drillings of several hundred meters can be achieved relative easily and there is less limitation of the borehole diameter. Installation of a preventer is possible, as well as packer tests and borehole measurements (imaging, gyroscope, borehole geophysics). The gap of information between core and percussion drilling cannot be closed completely, but it can be reduced substantially and sufficiently by combination of an intensive program of measurements and analysis accompanying the investigation works."

Jan 1, 2016

By D. Wenstrup, K. Perry, J. Hatfield, P. Sainato, B. Lusk

Concrete-infused cloth is used in several civil and mining surface applications whose circumstances are similar to some of those in underground mining. A feature of this material is that it cannot be overhydrated. In underground conditions, however, the excess supply of water to the cloth for hydration could lead to muddy and potentially unsafe working conditions, as well as resource wastage by supplying more water to the construction site than is needed. The objective of this study is to verify the water-to-cloth ratio and study the effect of hydration level on the strength of the Concrete Cloth product. We found that the strength increases with increased hydration up to a 1:2 water-to-cloth ratio by weight, after which the strength holds steady regardless of additional hydration. This confirms the 1:2 water-tocloth ratio by weight for hydration and confirms that strength is retained even if the cloth is excessively hydrated.

Jan 1, 2014