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By Hamid Maleki

This paper reviews a study conducted for Australian Coal Research Limited (ACARP) to assist Anglo-American operations with better understanding of coal burst mechanics and control based on U.S. practical experience, investigations, and inspections in three major U.S. coalfields over the past 45 years. The study examined both nonviolent and burst-prone case studies to identify contributing risk factors and addressed failure mechanisms for major U.S. coalfields in Utah, Colorado, and Kentucky, which have diverse characteristics. To investigate the mechanics of coal burst, a multipronged approach is used. First, field measurements in three mines from East Mountain, Utah, are complemented with finite-difference stress analyses to address the importance of horizontal stress in coal pillar mechanics of violent failure. Second, the computational procedures for estimating seismicity resulting from slip along geological discontinuities are reviewed, as these measurements point to seismicity being the trigger mechanism for violent failure of marginally stable structures. This joint-slip seismicity mechanism is in agreement with the more recentimproved re-examination of mining-induced seismicity (MIS) data from the Crandall Canyon Mine, Utah by University of Utah (UOU). Third, a hybrid statistical-analytical methodology is applied for identifying significant factors affecting coal burst. It utilizes data from 30 case studies including those from Utah, Colorado, Kentucky, and other eastern U.S. mines. The statistical approach reinforces field measurements and points to strata rigidity, joint spacings, and horizontal stress field as significant factors affecting damage resulting from coal bursts. This provides practical capabilities for identifying operations of higher risk using a rigidity-cavability variable. Overall, the study provides valuable insights into the mechanics and risk factors associated with coal bursts in major U.S. coalfields. By utilizing a multipronged approach that incorporates both field measurements and statistical-analytical calculations, the study offers practical capabilities for identifying operations of higher risk and improving coal burst control.

Jul 1, 2023

By William E. Bonini

Gravitational field anomalies have been observed over many igneous intrusives of medium (4000 km2) to small (100 km2) size in outcrop area. These studies give good results because the residual anomalies can be separated from larger scale crustal anomalies and density contrasts usually are present. Although unique solutions are not possible, the analysis of the gravity anomalies can put limits upon the geologic interpretation of such bodies. Three examples in Montana, U. S. A. are discussed: (1) the Boulder Batholith, a late Cretaceous quartz monzonite series of intrusives of 4000 km2 outcrop area; (2) the Little Rocky Mountains, an up-domed area, in which an Eocene porphyry (130 km2) has intruded the Precambrian crystallines and lower Cambrian sediments; and (3) the Crazy Mountains, an Eocene diorite (100 km2), which has intruded the Paleozoic and Mesozoic sediments. In both the Boulder Batholith and the Little Rocky Mountains, intrusive rocks are less dense than the surrounding rocks and negative anomalies are found (40 and 28 mgal, resp.). In the Crazy Mountains, the intrusive is more dense than the surrounding sediments and a sharp positive residual anomaly of 42 mgal is observed. The analyses of the gravity anomalies predict that: (1) the thickness of the Boulder Batholith is on the order of 10 to 15 kms and is concave upward; (2) the Little Rocky Mountain syenite is not a simple laccolith, but is T-shaped and extends in depth to about 16 kms; (3) the Crazy Mountain diorite is not a simple small scale series of stocks, but a large connected body extending in depth 5 kms to the basement (although nothing can be said of it within the basement because there is little density contrast). The analyses of the anomalies place important limits on both the areal and depth extent of the intrusive bodies. Of all possible geophysical techniques, gravity studies offer the most promise in the determination of the shape in depth of intrusive bodies.

Jan 1, 1969

By Edward Hall Smith

The E1 Indio Mine is located in the Andes mountains about 180 kilometers East of La Serena, capital of the Fourth Region of Chile. It is reached by an international highway running up the Elqui Valley as far as Juntas from where the last 42 kilometers is on a road constructed by the Company. The plant is located at 3.900 meters above sea level among extremely rugged terrain with nearby mountains rising about 5.500 meters. Climatic conditions at these altitudes are severe with winter temperatures down to -20°C. Snow storms lasting several days and leaving up to two meters of snow have been experienced, while fierce winds are corm=.

Jan 1, 1984

By Gamal Rashed, Zorica Radakovic-Guzina, Khaled Mohamed

"Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs. Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted this work to understand the loading characteristics of mechanical bolts (stiffness and capacity) installed in coal ribs at five underground coal mines. Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts. Different installation torques were applied to the tested bolts based on the strength of the coal seam. A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests. It was found that the anchorage capacity depends mainly on the coal strength. Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response. The outcome of this research provides essential data for rib support design.INTRODUCTIONThe design of rib bolting in U.S. coal mines is based on a trial-and-error process, which is insufficient to eliminate injuries and fatalities caused by rib falls. In the last 10 years, rib failures have resulted in 17 fatalities, representing 52% of the ground-fall fatalities in underground coal mines in the United States (MSHA, 2018). Recently, NIOSH researchers surveyed 90 sites in 14 underground coal mines in the Eastern United States and found that 11 mines are bolting coal ribs, with 4 of those mines using the conventional mechanical bolts and the others using fully-grouted bolts. NIOSH researchers are developing an engineering design procedure for rib support. Pull-out test programs for mechanical and grouted rib bolts were conducted to understand the rib control mechanisms of rib bolts. Only the test results of mechanical bolts are presented in this paper.Mechanical bolt (or point-anchored bolt) is a tensioned bolt anchored down the borehole with a mechanical expansion shell or a resin-grouted medium (Peng and Tang, 1984). The mechanical anchor bolt consists of a plug, a shell anchor, a headed bar with the top end threaded, a bearing plate, a hardened washer, and occasionally a friction-reducing washer. The shell anchor can be either standard or bail type (Figure 1). The standard type shell is held in place by a nut, while the bail anchor uses a strap to hold the shell in place (Peng, 2008). The diameter of the bar is generally 16 mm (? in) for the #5 bolt or 19 mm (6/8 in) for the #6 bolt. The diameter of the hole that the bolt is inserted into must be carefully controlled, since an oversized hole can result in poor anchorage (Moss, 1971). The anchorage is obtained by applying torque to the bolt head, which in turn pulls the plug down in the shell and expands the serrated leaves against the sides of the hole-wall. In the resin-grouted anchor, the resin replaces the mechanical expansion shell at the end of the hole. The anchorage is achieved by bonding between the resin, bolt, and the hole-wall."

Jan 1, 2019

By K. M. Mohamed, I. B. Tulu

"Failures of coal ribs are major hazards in underground coal mines. For the period of 2010 to 2014, rib falls were the leading cause of groundfall fatalities and accounted for 35% of all groundfall-related fatalities. Currently, the National Institute for Occupational Safety and Health (NIOSH) is conducting a research project to develop an engineering-based design methodology for rib control in coal mines to reduce rib fall accidents and fatalities in underground coal mines. Numerical models can be used as part of the design methodology provided the models are appropriately calibrated and verified. The paper presents a coal rib model to simulate the mechanism of the coal deformation and fracturing that can lead to stress-driven rib falls. The proposed coal rib model was calibrated against published data from an instrumented rib site at the West Cliff mine in Australia. Fracturing of the coal rib was defined by critical values of shear strain of the coal material and rib displacement. A critical plastic shear strain of 2.8% and a sudden increase of rib displacement of 30 to 45 mm were sufficient to develop a fracture plane in the rib model. Accordingly, a discontinuous rib deformation was achieved and it compared favorably against field monitoring data. INTRODUCTION Coal ribs are the vertical walls of coal formed when entries are developed in a coal bed. Failures of coal ribs are a major hazard in underground coal mines. Furthermore, failing ribs can contribute indirectly to roof and floor instability by increasing opening widths across intersections and entryways. Over the last 18 years, there has been a continual occurrence of injuries and fatalities in underground coal mines due to rib falls. For the period of 2010 to 2014, rib falls (excluding longwall face and bursts) were the leading cause of ground fall fatalities and accounted for 35% of all groundfall-related fatalities [1]. Despite the threat of rib falls, the amount of rib falls and rib support research conducted in the U.S. is limited compared with what has been done in pillar and roof support design. Currently, the National Institute for Occupational Safety and Health (NIOSH) is conducting a research project to develop an engineering-based design methodology for rib control in coal mines to minimize the number of rib fall accidents and fatalities in underground coal mines."

Jan 1, 2016

By Julian W. Feiss

Before undertaking to present to you a current analysis of copper, I would like to preface my remarks with a few observations that in themselves have a bearing upon commodity reviews in general. Having sat through a large number of such reviews since first joining the A. I. M. E. nearly forty years ago, I have no illusions about the hazards of the undertaking. If a speaker presents a statistical summary of commodity economics for the last year, most of his audience, having already read at least four commodity summaries on the identical subject, either get up and walk out or fall asleep. Should the latter happen, and were the listener to tumble from his chair and break his neck, obviously the speaker is liable. The subject matter seldom lends itself to histrionics on the part of the speaker so dangers of heart attack in the audience are not too great. Therefore the speaker, in order to retain listener interest, resorts to prophecy. Such venture was undertaken long ago by weather soothsayers, the "harouspex" of Ancient Rome, who generally cut up a sacrificial sheep and after staring at the entrails made their predictions which I understand had a batting average somewhat better than those undertaken on Wall Street based upon Dow Jones averages. Not being a licensed harouspex I cannot undertake predictions. I shall, however, fall back upon the experts.

Jan 1, 1965

By D. A. Norrgran

The process of magnetic separation is based on the differences among magnetic susceptibilities of various mineral species. Performed either wet or dry, the separation has application in both the recovery and concentration of value minerals and in removing deleterious mineral constituents from a product stream. There are two major catagories to be considered when addressing magnetic separation of minerals. The first catagory refers to particle characterization and relative differences in magnetic susceptibility. The second catagory refers to design parameters and the magnetic field generated by the separator.

Jan 1, 1987

By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay

"The Analysis of Retreat Mining Pillar Stability (ARMPS) program was developed by the National Institute for Occupational Safety and Health (NIOSH) to help the U.S. coal mining industry to design safe retreat room and pillar panels. ARMPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the “abutment angle” concept in calculating the magnitude of the abutment load on pillars adjacent to a gob.In this paper, stress measurements from U.S. and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 650 ft, the ARMPS empirical derivation of a 21° abutment angle was supported by the case histories; however, at depths greater than 650 ft, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases.The new abutment angle equation was tested using both ARMPS2010 and LaModel for the entire case history database of ARMPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the LaModel program was found to give good classification accuracies compared to ARMPS2010 for deep cover cases.INTRODUCTIONIn the early 1990s, the Analysis of Longwall Pillar Stability (ALPS) was introduced by Mark (1990) as a chain pillar design software and was generally accepted and used by the U.S. coal mining industry. Following the success of ALPS, the National Institute for Occupational Safety and Health (NIOSH) developed the Analysis of Retreat Mining Pillar Stability (ARMPS) program for designing retreat mining pillars using a similar approach as ALPS (Mark and Chase, 1997). The Australian mining industry also recognized the success of ALPS, and Colwell, Frith, and Mark (1999) calibrated the program to Australian conditions. The ALPS and ARMPS programs draw their strengths from the large databases that are used to calibrate them (Mark, 2009). However, following the Crandall Canyon Mine collapse in 2007, NIOSH had to reconsider the pillar design criteria used in deep-cover retreat mining (Mark, 2010). The ARMPS overburden load prediction algorithm was improved to more accurately predict the loading of narrow panels with high overburden depths by implementing the pressure arch concept, and this new version is called ARMPS2010."

Jan 1, 2019

By Lixue Wen, Jun Xiao, Dongping Shi, Yan Xue, Jinmiao Wang

Mine ventilation energy consumption is one of the main sources of energy consumption in mining production, accounting for about one-third to one-half of the total energy consumption. Therefore, reducing the energy consumption of the mine ventilation system is crucial for mining production. With the premise of meeting the airflow requirements of the underground work areas and achieving sustainable development of mining production, this paper establishes a nonlinear optimization mathematical model for the mine ventilation network with the objective of minimizing the total power. Regarding the model, optimization of the decision variables was carried out using the method of minimum spanning tree. The constraints for air flow balance, wind pressure balance, and fan operating conditions were optimized using the exterior penalty function method, thereby transforming the model into a nonlinear unconstrained model. Based on this model, a modified sooty tern optimization algorithm (mSTOA) was proposed to achieve optimization. Improved the sooty tern optimization algorithm (STOA) by using the uniform reverse strategy, fitness value-distance balance selection strategy, and mutation strategy. The STOA, mSTOA, and three other classical optimization algorithms were applied to the optimization of a ventilation system of an actual mine. The experimental results show that after using mSTOA to optimize the ventilation network airflow distribution in the mine, the total energy consumption can be reduced by about 35.06% while meeting the constraints and demands of the ventilation network regulation and usage. This is of great value to mine roadway operation environment safety and clean production.

Dec 20, 2023

By D. Morgan Warren, David Hanson, Alice Alex, Tom Meuzelaar, Heather Lawson, Sam J. S. Wright

Dynamic coal failure events remain a safety concern in underground coal mining due to their sudden nature and high fatality rate. Previous research utilized Principal Component Analysis on field samples revealing strong empirical correlations between positive failure history and low sulfur content (S) and high volatile matter (VM). Further studies indicated that bumping coals tend to be less mature and less well-cleated than non-failure coals. However, these in situ studies faced the challenge of distinguishing intrinsic coal properties from external geological and stress-related influences. This study augments previous findings through laboratory experimental testing of coal samples that included unconfined compressive strength, chemical composition analysis, and qualitative observations on cleating, combined with compositional data analysis and machine learning techniques, to isolate and understand coal’s inherent bursting capacity. These results further confirmed the relationship between coal chemistry and failure classification.

Feb 22, 2026

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

By D. Malhotra

The effect of some of the reagents, namely hydrocarbon oil, Syntex (sulfated coconut oil surfactant), pine oil, sodium silicate, and lime, used at the Climax mill on the recovery and grade of molybdenite and gangue minerals has been investigated experimentally using factorially designed test approach in the laboratory. The results of the investigation are presented in two dimensional plots. The lower additions of lime (equivalent to a pH of 8 to 8.5) were desirable for maximizing recovery subject to constraints on grade. Higher additions of pine oil improved recovery, but only at the expense of grade. A mathematical model of the objectives of an operating plant was formulated and optimum reagent conditions obtained.

Jan 1, 1977

By Douglas R. Shaw

Normal dodecyl mercaptan was evaluated as a collector for flotation of sulfide minerals and precious metals. The reagent is from the class of normal mercaptoalkanes (n-alkyl thiols), and is commercially available in the form of a mixture of n-dodecyl mercaptan and a dispersant, under the trade name Pennfloat(TM)3. Reported are results of bench-scale flotation experiments on many commercially treated base metal and precious metal sulfide ores. Dosages, points of addition, and flotation pH were among the uariables studied. Most notable results were increased copper, molybdenum, and precious metals recoveries. Dosages of dodecyl mercaptan on some ores were considerably lower than required for conventional collectors.

Jan 1, 1979

By S. J. Stokowski

Abstract An extensive drilling and laboratory testing program indicates that a construction aggregate resource is present within the Oligocene Sombrerito Formation limestone, southwestern Dominican Republic. The first part of the testing program included the collection, photographing and geologic logging of diamond drill cores to allow lithologic subdivision of the strata into potential quarry layers. The primary lithostratigraphic units are: I- (youngest) approximately 10 m of white, dense marine limestone II-approximately 5 m of white, interbedded dense and chalky marine limestone III-more than 2 m of tan, chalky, calcitic dolomite. Unit I is often altered by lateritic weathering and/or dolomitization. Unit II is often altered by dolomitization. The cores were individually crushed by quarry layer into coarse and fine aggregate sizes for chemical and physical analyses: specific gravity and absorption, MgSO4 soundness, sand equivalent, Atterberg limits of the minus #40 mesh fraction, and LA degradation. The unaltered portion of Unit I is suitable for all construction aggregate uses. Unit II is best suited for crushed stone base. Each of the non-weathered units decreases in coarse-aggregate yield and quality with depth and diagenetic dolomitization. Dolomitization typically causes about 5% lower yield of coarse aggregate, a sand equivalent of about 20 units below the original value an increase in absorption of about 3%, an increase in the LA of up to 13%, and a decrease in the average five-cycle MgSO4 soundness of about 17%.

Jan 1, 1991

By Micah Nehring, MEHMET KIZIL, Farzad Sotoudeh, Amin Mousavi, PETER KNIGHTS

Production scheduling in underground mines is one of the most important and complex processes in maximising the economic value of an operation over the life of the mine. Due to increasing energy, transportation, processing and smelting costs and reducing water availability, the extraction of ore deposits through underground operations has become more expensive and challenging. A potential productive and efficient solution to mitigate these issues is to integrate pre-concentration systems into the existing mining system to increase ore grades through a preliminary process of rejecting some waste before sending the ore to the energy intensive mineral processing plant. Further benefit of such systems includes the utilisation of the waste and low-grade material in backfilling of open stopes to reduce the transportation costs and surface environmental impact such as reduction of CO2 emissions and waste transportation. The objective of this paper is to present a new mathematical model to optimise the production schedule of underground metalliferous mining operations in the presence of a pre-concentration system. The proposed model optimises the production schedule and sequencing of stopes within a sublevel stoping operation. The results of this study illustrate the potential economic benefits of using a pre-concentration system prior to a mineral processing operation as a result of increased net present value.

Nov 16, 2023

By G. W. Cutting

It is well known in both the research field and in commercial flotation processes that the grades and recoveries obtained from flotation plants are heavily influenced by the structure and height of the froths produced in the flotation cells. The development of steady-state mathematical models of flotation processes based upon practical and readily obtained parameters have demanded detailed information about the structure of flotation froths. The important parameters are the distribution of floating values, gangue and water in the froth with respect to froth height, cell pulp density, cell air flow rates and flotation inducing additives. Little work has been conducted in this field although considerable attention has been paid to bubble loading and other factors close to the cell froth/pulp interface. Laboratory batch tests are prefaced for the derivation of the above mentioned parameters for both practical and economic reasons. The standard laboratory flotation tests using a batch cell produces a froth of low height (1 to 3 cms generally) together with a varying cell pulp density as the test progresses due to the addition of top up water and the removal of froth from the cell. This form of test can be considered only as giving information about froth conditions close to the cell froth/pulp interface under conditions of widely varying cell pulp densities. In commercial processes the froth heights are much larger (frequently greater than 10 cms); therefore the laboratory batch test, although useful in many ways, does not directly yield parameters relating the state of the froth flowing over the cell lip to process operating conditions. To investigate flotation conditions, where more realistic froth heights are developed, an equilibrium type of batch cell has been developed at Warren Spring 1 Laboratory . In this a tank with high walls is used to contain the pulp and whole froth and, after a short period of operation, an equilibrium between froth

Jan 1, 1975

By Robert Charles Alfred

Evolution is continuing in the field of rock drilling, Campbell Limestone Company is experimenting in the higher air pressure phase of drilling, It has been determined that there is a definite relationship between Air Pressure, Penetration Rate, Bit & Tool Wear and Life, In our drilling we have determined that &e higher air pressure gives a better penetration rate with less bit wear per foot. Drilling with 180 to 200 PSI air pressure, instead of 100 PSI for air and/or churn drills, has decreased our primary costs by approximately one half.

Jan 1, 1963

By R. W. Utley

Over one half billion tons of coal per year is scalped, classified, deslimed, drained and rinsed, dewatered and final sized on rotary, vibrating, shaking or stationary screens. The vibrating screen is the industry work horse and performs the bulk of the screening functions in the coal preparation plant. There are two major types of brute force mechanical vibrating screens used in coal preparation plants: (1) the two-bearing one-shaft inclined screen and (2) the four-bearing two-shaft horizontal screen. Both of these types are familiar to coal producers.

Jan 1, 1966

By Wayne D. Gould

Planning for a project does not start with the announcement of the approval for a project. Planning actually begins when the project is only a prospect and it involves the years of experience of many people because their expertise influences the final decisions. In partial anticipation of the Pinto Valley project, as well as a search for improvement in the Copper Cities operation, two projects were undertaken. The first project was to substitute one 26" cyclone for three 20? cyclones in the single stage grinding circuit. The second project was to replace the Hunt air flotation cells with 300 cubic foot mechanical cells. The 300 cubic foot cells were just being introduced, consequently two types of cells were selected for testing. The results from both projects influenced the decisions on equipment for the Pinto Valley project.

Jan 1, 1975

By A. S. Henderson

Eastern Mesabi taconite is one of the hardest rocks known, but fortunately it shows little tendency to pack in the crushers, when the minus 5/16 inch material is removed. The crushing circuit is essentially as shown in the Engineering and Mining Journal article, "Reserve's New Taconite Project", dated December, 1956 except that the grizzly screen between the two stages of gyratory crushing has been eliminated. The Reserve operating staffs aim is to utilize the crushing equipment in such a manner that the maximum tonnage of taconite can be crushed to the required size at a minimum cost. As is readily apparent, the primary consideration is to produce a desired size product, with the other operating factors to be balanced, thus achieving the best setting for each crusher. Much effort has been expended toward the development of a satisfactory sized material for feeding the rod mills. The characteristics of this feed must allow the following situations to be handled by the existing equipment: 1. The material being fed to the rod mill must be such that it can be fed into the unit with the proper quantity of water to maintain the correct density within the mill. 2. The rod mill must produce a product from this feed which can be handled without difficulty by the magnetic cobbing and ball mill circuit. 3. The incidental tramp must not exceed that quantity which can be handled easily after the rod mill and after the ball mills.

Jan 1, 1959