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By Gary L. Mowrey

Visible and sometimes audible indications of excessive underground rock pressure such as pillar fracturing, squeezes on chocks, and "roof talk" are familiar to mining engineers. Such signs often precede rock failure on a larger scale and therefore may be used as a warning. Nevertheless, these subjective observations do not provide an adequate means of evaluating the existing rock pressure conditions in a mine. One method which appears to be extremely promising in determining the stability of geologic structures in general is that of monitoring their associated micro seismic activity. Mining engineers generally agree that during the process of rock deformation and failure small-scale seismic ("microseismic") vibrations are produced in the rock itself. These transient vibrations propagate through the rock structure and may be detected at a considerable distance from the failed rock by employing suitable electronic monitoring equipment. Hardy (1) has presented a detailed review of microseismic research in the mining, petroleum, and geoscience areas, and it is apparent that relatively little application of micro seismic techniques have been made in coal mines. This is especially true in North America since here most coal mines are fairly shallow and consequently are not generally subjected to excessive stresses. Furthermore, strict Federal and State mining laws limit the use of electrical equipment in coal mines complicating the use of the necessary monitoring facilities. In terms of both mine safety and economics, monitoring microseismic activity appears to be invaluable in the detection and location of over-stressed pillars and unstable roof conditions caused by development and production work. In 1970 The Pennsylvania State University Rock Mechanics Laboratory became involved in a research project, sponsored by the U.S. Bureau of Mines, to investigate the feasibility of using microseismic techniques to detect and to locate potential regions of instability around a longwall coal-mine operation [Hardy and t10wrey (2); Mowrey (3)]. In this study geophones (velocity gages) located in an array of shallow boreholes drilled from the surface above the active area of the longwall were employed to detect microseismic activity, and a mobile micro-seismic monitoring facility was used to condition and record this data for later analysis. This project is unique in that measurements were made from near-surface geophones rather than geophones installed on the mine itself. Two advantages are apparent, namely that (1) there are no electrical limitations on the monitoring system and that (2) mining operations can continue normally because there is no monitoring equipment or cables in the mine.

Jan 1, 1978

By Dayu Long, Changhong Li, Yu Wang, Juzhou Li, Yongyue Hu

To address the problem of seepage failure that affects the stability of the fine-grained tailings dam, two kinds of prevention and treatment measures were proposed involving composite flocculants and composite curing agents. The orthogonal test was conducted to determine the optimal ratio flocculant (ORF) and the optimal ratio curing agent (ORCG). Then, numerical models were established to evaluate the effects of the prevention and treatment measures on the seepage and stability of the tailings dam. The results show that the mechanical properties and microstructure of the tailings are significantly improved by adding the ORF and ORCG. Furthermore, numerical studies suggest that the addition of the ORF and the ORCG to the tailings improves the factor of safety of the tailings dam, but the addition of the ORCG also increases the height of the phreatic line. It is also speculated that the addition of the ORF can prevent the formation of through failure zone in the tailings dam. Therefore, the optimal measure to prevent seepage failure in the tailings dam is adding an appropriate amount of the ORF, as it reduces the height of the dam’s phreatic line and lowers the risk of seepage failure. The typical area susceptible to seepage failure can be treated by adding the ORCG. However, it is important to ensure adequate drainage of the area and to maintain the phreatic line at a reasonable buried depth.

Mar 4, 2024

By D. Kang, K. N. Han

The adsorption behavior of silver in ammoniacal solutions on activated carbon was studied. In addition to the concentration of ammonia, the parameters that affect adsorption include temperature, degree of agitation and anion and cation concentrations. In the study, it was found that the adsorption of silver from ammoniacal solutions is dependent on the initial silver concentration in the solution. It was also found that the recovery of silver from ammoniacal solutions is not as effective us gold. The adsorption rate was relatively slow overall, despite a rapid initial adsorption. The apparent activation energy ,for the adsorption was measured at 30.2 kJ/mol. It was believed that the kinetics of the silver adsorption on activated carbon was limited by a mixed control mechanism.

Jan 1, 1999

By T. S. Golosinski

Use of contractors to excavate, load and haul mined material is widespread in Australia. It is also becoming a common practice in many other countries. The paper reviews current practices in Australian contract mining. Various types of contracts are reviewed, including partnering arrangements and alliancing between the contractor and the mine owner. Applicability of various types of contracts to specific mining situations is discussed, as is their impact on overall mine performance

Jan 1, 1998

By Louis M. Perlman

Quantitative methods are, by now, a standard tool of the mining industry, and are commonly used by Research Departments in their evaluation of production methods and schedules, and their associated costs. Indeed, much sophisticated computer work has been devoted to such evaluation of controllable costs and capital requirements. These data are an important input into the project evaluation formula, which is probably the most important single calculation per formed by a mining company, since the result decides whether a particular project is viable. It is instructive to summarize the broad principles of project evaluation, since they are crucial to the remaining sections of this paper. PROJECT EVALUATION The most widely used method of appraising projects is known as Discounted Cash Flow (DCF) method. Two main variants are used; they are known as the 'not present value' (NPV) approach and the 'internal rate of return' (IRR) approach respectively. The difference between the two is that the former takes the firm's interest rate as given and uses this knowledge to calculate the present value of the project; whereas the latter calculates the highest interest rate the project could tolerate and still just breaks even. The technique is more simply discussed in terms of the first method (NPV).

Jan 1, 1972

By K. C. Ko

The pit slope angle dictates the economics as much as the depth of the pit. Steeper slope provides more ore reserves, at the same time, the steeper slope presents higher probability of instability and associated maintenance problems. While large open pit mines mostly belonged to nonferrous metals in the past, other mines are becoming deeper as the mine economics permits deeper mine operations, Such minerals include coal, uranium, phosphate, and others. There are some basic differences between an open pit slope and slopes that are encountered in usual civil engineering work such as dam embankments and highway cuts (Figure 1). The stability of the civil engineering slope changes continuously with time due to ground-water movements, weathering, etc. But the stability of the open pit slope (Figure 2) changes more drastically day-to-day or even hour-to-hour, These changes occur because not only is the slope geometry being continuously changed by the mining operation, but also different geology and geologic structures are being exposed on the slope. Even when a particular slope area is not presently being mined, excavation in adjacent areas can affect the general condition of that slope area. A pit will experience some slope failures during its life.

Jan 1, 1977

By Jian Deng, Hehua Zhu, Lianyang Zhang

Rockburst is defined as a sudden and violent explosion of rock on the surface of a rock excavation. Rockburst has been regarded as the least understood and most feared hazard problem for underground rock excavations. Traditionally, rockbursts were classified into the strain, pillar, and fault-slip categories. However, rockbursts are also known to occur at stress levels well below the rock yield strength, in mines where the rock is far from brittle, or without the presence of geological discontinuities. A plausible explanation of rockbursts is buckling, which has been identified as one of the main mechanisms for rockbursts. It is observed that rockbursts are often induced by dynamic loadings (pulses) from adjacent blasting. Therefore, the present paper studies the effect of pulse shape and amplitude on pillar rockbursts induced by dynamic loadings from blasting using the method of numerical analysis. The governing equation of a pillar’s motion is set up and the mechanism of pillar rockbursts is investigated through a practical example. The results show that it is not the shape of a pulse but the impact energy to decide the occurrence of pillar rockbursts. If all other parameters remain the same, pillar rockbursts are more likely to occur when the pulse duration is longer. The parametric resonance and the perturbation of dynamic loadings are also found to play an important role in the occurrence of rockbursts. These insights would provide invaluable clues about the mechanism and for better control of pillar rockbursts.

Apr 26, 2022

By R. D. Begley, A. W. Khair

This paper presents an assessment of modeling techniques in predicting subsidence over longwall areas. Extensive instrumentation has been made, both at the surface and subsurface, at three longwall mines in northern West Virginia. Ground movements were monitored during a three- year period until subsidence ceased in these areas. A comparative analysis of empirical subsidence prediction techniques including graphical (NCB), profile function, influence functions (USBM, Bals', Knothe's, and zone area) will he presented. A brief geologic and topographic description of each site, along with the instrumentation and monitoring program, will also he presented.

Jan 1, 1990

By R. S. Olsen

Intensely altered rock has had a large effect on slope stability as slopes increase in height at Island Copper mine. Traditionally used, fracture-controlled rock slope stability design techniques have been supplemented with analyses of failure modes which include failure along curved surfaces typical of soil materials. A rock mass rating (Pa) system has been developed that addresses the lower end of rock mass strengths. Rock masses are rated in terms of fabric integrity, alteration, fracturing intensity and gouge strength. Rock mass classes have been defined using statistical frequency distributions of rock mass rating values. Strength values have been assigned to the various classes from shear testing, back analyses of failures and engineering judgment.

Jan 1, 1987

By Kanaan Hanna, Mir Heydari, Dipack Sengupta, Gordon B. French

This article, first in two, discusses the safety, technology, and economic impact of eliminating safety fuse from metal and nonmetal mines. It is based on operation and manufacturer experience over the past five to 10 years. If safety fuse is eliminated, blasting accidents will decrease. There should be only limited technical impact. The economic impact will be minor for large operations, but will be significant enough for small operations that some will likely close rather than change. Most mines would probably change over, with the market absorbing the extra cost. Elimination of safety fuse would obviously have an impact on the two safety fuse manufacturers. One manufacturer produces an alternative system and would be unaffected. The other, however, will be affected if it does not change its production strategy. From the standpoint of employment and production, abolishing safety fuse will have a very minor effect on the mining industry as a whole. This article discusses the current use of initiation systems, incidence of accidents, and fuse consumption. Next month, part two describes the economic impact of eliminating safety fuse on the mining industry and manufacturers, and presents an economic analysis of the initiation systems. Introduction The objective of this study was to determine the safety, technology, and economics of eliminating safety fuse from metal and non-metal mines. There were five major tasks: • Studying initiation-related accidents from the Health and Safety Accident Center (HSAC) data file; • Visiting mines, collecting relevant data, and interviewing mine operators; • Establishing the trend in safety fuse consumption and type of users; • Corresponding with fuse manufacturers, domestic and foreign; and • Developing an idealized blasting cycle to evaluate the possible economic impact of safety fuse elimination on large and small operations. More than 450 explosives-related accident reports have been screened and analyzed by investigating HSAC files. These reports have been studied and classified according to the four initiation systems, size and type of mines, and time and frequency of accidents from 1973 through 1978. Twenty-four mining operations were visited to obtain supporting data for this study. Mine personnel were interviewed to determine attitudes about safety fuse and alternative detonating systems. This article decribes available data. It also attempts to provide information that can be used to answer such questions as: • Is the use of safety fuse (an antiquated detonation system) a major cause of mining accidents? • Are alternative systems available that could result in fewer in-juries to miners?

Jan 1, 1984

By J. A. Herbst, Z. Rogovin

In order to develop more accurate procedures for scale-up and design of semi-autogenous grinding mills through detailed mathematical models, a better understanding of the charge motion and rocklball segregation is needed. To achieve this a 0.61 m (2.0 ft) diam by 0.305m (1 .0ft) length plexiglas mill was constructed as a scale model of a commercial SAG mill. Rock motion in the rotating mill was simulated using various sizes of ceramic balls. Quantitative measurements of dynamic angle of repose, water and slurry motion, holdup and size segregation of the charge were taken. In addition, a video presentation (available to the public) was prepared to elucidate charge and water motion at various mill speeds, charge volumes, rocksize distribution, and flow rates.

Jan 1, 1990

By J. Miller, B. Slaker, M. M. Sears, G. Rashed

Ground falls represent a significant hazard at underground mines in the stone, sand, and gravel (SSG) sector in the USA. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are currently conducting detailed investigations into the complex loading conditions at underground stone mines operating in challenging conditions. This paper presents the application of numerical modeling to analyze pillar and roof stability at a dipping underground limestone mine. A validated numerical model was used to explore the potential behavior of the pillars and roof as loading conditions change. The validated model was used to compare changes in mining sequence, overburden depth, and the in situ stress field. This will allow mine operators and engineers to have a better idea of the conditions that could be encountered as mining progresses. Results from the numerical modeling indicate that roof displacement more than doubles as the vertical stress increases from 10 MPa (1450 psi) to 19 MPa (2750 psi) when the maximum and minimum horizontal stresses were 41 MPa (5950 psi) and 22 MPa (3190 psi), respectively. Consequently, as the pillar load increases, the safety factor of the pillars is projected to decrease by about 25%. The impact of the practical application of numerical models can result in a reduction of ground-fall accidents and injuries as well as generally safer working conditions.

Feb 2, 2021

By Amy McBrayer, Andrea Brickey

Limited research has been conducted related to the development of mathematical optimization models for production scheduling at large surface coal mines using the area, i.e., strip, mining method. Increased economic and technical challenges have led to a new interest in production schedule optimization models for these type of mining operations like those currently applied to model underground and open pit mines. While area mines share similar characteristics to both open pit and underground metal operations, neither an open pit nor underground production scheduling model adequately depicts an area mine mathematically. We present an integer programming model with blending constraints and discuss the challenges and opportunities related to the implementation for area mines as well as future research in area mine production scheduling.

Jun 25, 2023

By H. Nemutolluhi

Discussion by G.E. Agar In the April issue of Mining Engineering there is a technical note "New size laboratory ball mill for Bond Work Index determination" written by M. Nematollahi which is very confusing. My recollection is that a description of an experimental procedure should be such that someone skilled in the art should be able to reproduce the results. Applying this test to this particular article would according to me cause a failure to be registered. There are apparently three batch laboratory test procedures referred to in the article. One of these is the traditional Bond test with all its limitations such as dry grinding followed by exclusively dry screening, two attributes which fail to simulate conventional industrial grinding. There is a second procedure (NSBM) which the author is advocating as an improvement of the Bond procedure but from the description I doubt that anyone would be able to repeat the procedure. For instance, is the grinding to be done wet or dry, if wet at what pulp density, and how is the screening to he done, wet or dry or a combination? On top of that uncertainty the author refers to a simplified "Anaconda" test. No reference is provided for this procedure and in the text the results of the technique are referred to "Denver wet ball mill" results and say nothing of Anaconda results. Reply by H. Nematollahi I think that the method proposed to determine the Bond Work Index in this paper is clearly described in the paper as follows: •The method of grinding is dry (Ref. paragraph I, subject Method description); •The size of ball mill, the quantity and size of balls are noted (Ref. paragraph 1, subject Test equipment); and The test procedure is described in detail (Ref. paragraphs 1, 2 and 3, subject Test procedure). As it is noted in the paper, the test has been worked out under the same condition as Standard Bond Test with ball mill, so dry (screening should be dry also), but using a smaller ball mill and a smaller quantity of sample. Considering the above mentioned points, I believe that the method has been fully and clearly described and it ought to be repeatable as well. The Anaconda test is a method for determination of Work Index and could be done by any types of laboratory wet ball mill (Yan, R.F., et al., cf. References). I applied this method using a laboratory Denver ball mill (Ref. paragraph I subject Determining the Bond Work Index). So the results referred to Denver wet ball mill can be equated the same as Anaconda method.

Jan 1, 1996

By W. L. O?Connell

[Patent Issue No. Date Issued To Subject 386,504 July 24, G. Sweanor The separation of quartz from a 1588 metal with a liquid such as CS2 or CHC13 under water by introducing mixture into water layer. Quartz will stay in water layer while metal sinks through organic.]

Jan 1, 1963

By Z. D. Hora, W. N. Hamilton

Evaporite units of the Western Canadian Sedimentary Basin are known to host native sulfur. In British Columbia, a large number of oil and gas exploration drilling holes reported intersections with native sulfur. The most important ones include 6 meters (20 feet) and 27 meters (90 feet) of native sulfur among 23 occurrences in Devonian Muskeg evaporite or adjacent Slave Point reef facies carbonates. A small Frasch sulfur deposit is known from Devonian Wabamun Group sediments near Camrose in South Central Alberta. Occurrences of native sulfur are common also in association with presently mined gypsum of Devonian Burnais Formation in southeastern British Columbia. Triassic sediments with evaporite members in British Columbia are also known to contain native sulfur showings. A widespread presence of anhydrite in many sedimentary units of Alberta and British Columbia together with oil and gas fields in the same areas and associated native sulfur occurrences point to a possibility for Frasch sulfur deposits in this part of western Canada.

Jan 1, 1992

By George F. Swindle

This paper discusses a composite of two coal reserve studies, each of which made use of a computer-based modeling system to assist in an evaluation of multi-seam deposits. The model permitted simultaneous consideration of seam thickness, seam structure, overburden thickness, over-burden ratio, and quality parameters for sulphur content, ash content, BTU values and the EPA Compliance index. The model is designed for use by a non-programmer, geologist or mining engineer. It enables the user, from a computer terminal in his office, to specify constraints (for example maximum um sulphur and maximum- ash content, minimum seam thickness and minimum BTU rating), and produces a report showing the volume, quality and location of that part of the total in place deposit satisfying all the constraints.

Jan 1, 1983

By A. Ramage

Since late 2010, CH2M HILL has been working with a confidential client who holds a long-term commitment to sustainable development (SD). The commitment is aligned with all three elements of the triple bottom line: people and society, ecosystems and environment, and financial and economic systems. These commitments are carried forward by the firm?s executives, managers, and operational sites, and are evident in materials posted on the company?s public website. These materials include a formal sustainability report prepared in accordance with the Global Reporting Initiative (GRI) guidelines (GRI, 2006), a report that outlines key SD challenges and progress toward the GRI targets, and a delineation of risks and opportunities outlined in the firm?s Form 10-K and Annual Report. In keeping with its commitments to SD targets, our client wished to consider SD issues in its decision processes for facility expansion or new projects. The company engaged CH2M HILL to meet this goal, based on working relationships established through existing contracts and CH2M HILL?s leading capabilities in sustainable solutions.

Jan 1, 2012

By Liming Yuan, Wei Tang, RICHARD THOMAS, JOHN SOLES

Lithium-ion battery pack fires pose great hazards to the safety and health of miners. A detailed experimental study has been conducted at the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) to investigate the effectiveness of different fire suppression systems on Li-ion battery pack fire extinguishment. Tests were conducted in a well-ventilated container. Two sizes of battery packs (12 V, 24 V) were heated by heater strips to trigger thermal runaway and fire. Water mist with different flow rates, ABC powder, type D dry chemical, and water mist with F500 additives were used as the fire suppression agents. Multiple thermocouples were installed on the battery packs to measure the temperature evolution during the tests. The results indicated that the water mist with F500 additives is the most effective suppressant among the agents tested. Dry chemicals, however, do quench the fire for a moment, but cannot prevent re-ignition of the battery since they do not provide enough cooling. The findings of this paper can be used to develop safer battery fire suppression techniques in mining environments.

May 4, 2023

By Van Price

Some technical developments of the National Uranium Resource Evaluation Program which are of general application in geochemical exploration are being studied. Results of stream water and suspended and bottom sediment analyses are compared for an area near Williamsport, Pennsylvania. Variations of uranium content of water samples with time in the North Carolina Piedmont are seen to correlate with rainfall. Ground water samples from coastal and piedmont areas were analyzed for helium. All media sampled provide useful information when properly analyzed and interpreted as part of a total geological analysis of an area.

Jan 1, 1979