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By Larissa Koroznikova, Steve Durkin, Bradley Drake, Michael Tuck

This paper presents the results from the investigation of the application of thermal fragmentation in Australian hard rock underground narrow-vein mining. Two geologically similar samples from an underground narrow-vein hard rock gold mine were collected to obtain a measure of the technology’s ability to recover ore by the creation of large thermal openings to assess the applicability of the thermal method. Particle size distribution showed a higher generation of fine product, − 2 mm, by thermal fragmentation compared with selective blasting by 31%. The Bond work index for thermal ore (12.62 kWh/t) is half to that of the blasted ore value (25.32 kWh/t). The average grindability obtained for the thermal ore sample was greater than the blasted sample by a factor of 2.44, a higher value indicating a decrease in the energy required to grind. The thermal fragmentation method generates product with higher dissolution of gold in cyanide, by 14% for the − 9.5 + 2 mm size fraction samples. Additionally, the thermal fragmentation results in higher production of − 9.5 + 2 mm material by 15 % compared with selective blasting.

By R. B. Khumalo, T. Chauke, T. Mtshali, F. K. Mulenga, B. Makgate, N. M. Chiloane, T. Moyane, V. C. Madanda

While high production rates are important for the profitability of a mine, the influence of geotechnical engineering cannot be ignored. In block caving, a high-stress level is required for cave propagation; this is one of the core elements for ore recovery. Therefore, stress distribution and geological structures play a major role in the planning and layout design of the mine. This paper explores the influence of stress and geological features on the design of the mine from the feasibility study phase. The geology and stress measurement of the mine were determined through logging and overcoring, respectively. This study found that while production rate is the primary operational consideration, the long-term layout design of the undercut face advance, face angle, drawpoint spacing, and undercutting sequence is mainly governed by the stress orientation and major geological structures. Moreover, widely spaced drawpoints result in isolated draw zones, consequently, resulting in ore loss and early dilution whereas closely spaced drawpoints affect the stability of the major apex pillar. This paper also provides insight into how operations can leverage stress distribution to optimise mine layout and safety in massive mining methods.

Nov 24, 2025

By F M. Senda

This paper highlights strategies used at the Barrick operated Kibali Gold Mine (KGM) to improve the drilling accuracy and blasting effectiveness for longhole open stoping. The mine currently uses Solo DL421 for the required stope drilling and has experienced an average deviation of 10 per cent. Strategies are raised to eliminate or at least mitigate the adverse effects of blasthole deviation and the impact of blasting induced effect at the stope faces including the stope crown. The integration of deviation trends in the design would allow the actual blastholes to be established within their required positions to then facilitate a proper energy distribution with the eventual production blasting. The implementation of stope undercutting reduces the hole length from 35 m to 30 m which in return decreases blasthole deviation by 3 per cent. Another strategy adopted to improve the drilling accuracy is to slow down the penetration rate with the use of several operating approaches, including 135 MPa percussion pressure, 65 rev/sec rotation speed and 17 MPa feed pressure. To this penetration rate, a constant k factor is applied to increase the rate when the bedding inclination is less than 45° from the horizontal or when the hole length is under 10 m. This reduces deviation by a further 4 per cent. Where the rock mass is highly jointed it is advised to use the average penetration rate over the entire length of the hole. Furthermore, the paper shows the effect of deviation on the blasting results through a prediction of fragmentation blasting model optimised with reduced deviation and highlights the effect of presplit mining and timing delay on the blasting effectiveness. Although the size pattern increases with deviation, a strategy pertaining to timing delay with blasting would be to align to the work of Grant (1990) where the optimum hole to hole delay is found to be between 7–10 ms/m of spacing, while the optimum delay between adjacent ring varied between 110–160 ms. Stabilisation of crowns and wings will perform with the implementation of presplit blasting.

Mar 29, 2023

By S. C. Schmelter

The destabilizing effect of water pressure on rock mass stability is examined quantitatively by the finite element method. A coupled code that accounts for the simultaneous effects of rock mass deformation and transient fluid flow is used for this purpose. The traditional soil mechanics assumption of an incompressible fluid is shown to be untenable for the analysis of porous, fractured rock slopes. A Mandel-Cryer effect, a transitory but elevated and potentially destabilizing water pressure following a cut, was not observed.

Jan 1, 1997

By T. O. Hagan

A simulated rockburst experiment was conducted underground at a deep level gold mine. This was done by means of a large explosion detonated in solid rock close to a tunnel sidewall. The resultant shake-out damage is typical of that associated with a small seismic event in close proximity to a tunnel that is subjected to the estimated field stress, as in this case, of 50 MPa. The experiment involved: ?the design of a blast to mimic a seismic source ?seismic monitoring using a dense seismic array ?high speed video filming ?a study of rock mass conditions (fractures, joints, rock strength etc.) before and after the simulation using mapping and ground penetrating radar ?special investigations to evaluate the mechanism and the magnitude of the damage ?a study of support behaviour under excessive dynamic loading.

Jan 1, 2001

By John H. Soulé

This paper describes the location and general features of the ?Red Bed? or sandstone copper deposits in southeastern Colorado and New Mexico. Most of the areas containing this type of deposit were visited, and many deposits were examined. Some deposits were not visited because of lack of information as to their location. In the large area covered a great variety of climatic, geographic, and topographic conditions exists. Some of the deposits are in arid areas, whereas others are in heavily forested regions. Altitudes range from 3,400 to 9,200 feet, and the terrain varies from flat plains to rugged mountains. Transportation is a difficult problem in most of the districts, involving long truck hauls to a railroad and long rail hauls to a smelter.

Jan 1, 1956

By Christopher J. Bise

INTRODUCTION A mine's power system represents the driving force behind all of the extraction and auxiliary operations, because the production and transportation of mined material and the operation of equipment, such as fans and pumps, are all dependent upon a power source. Once, compressed air was the primary power source in mining; today, however, electrical power dominates. This chapter reviews the basic theories of com- pressed-air and electrical power and provides several examples of applications in mine power systems. COMPRESSED-AIR POWER General Compressed air has been, and should continue to be, an important source of power in mining operations. It has been used as a means of blasting coal in conventional mining and is widely used to operate stopers, mucking machines, and other air tools in both coal and hard-rock mines. Such applications demonstrate the suitability of compressed air for applications requiring linear motion, but it is also utilized for its reliability and safety. A compressed-air system is composed of a compressor, a receiver, a distribution network, and the air-operated machines. A compressor takes in air at normal atmospheric pressure (free air) and compresses it to a higher discharge pressure. The discharge pressure must be high enough to overcome the friction in the distribution system of pipes and hoses and deliver the compressed air to the machines at the pressure recommended by the manufacturer. The most common type of compressor used in mines is the reciprocating compressor in which the air is compressed by a piston in a cylinder. An air receiver is a container or storage tank that is located in the distribution system between the compressor and the machines. It stores compressed air, when the full capacity of the compressor is not being used, and gives a more steady flow of air to the machines. The distribution network consists of pipes, Oalves, elbows, tees, and hoses that transmit the compressed air from the receiver to the machines in the mine. It is essential that the distribution system be designed with the proper sizes and lengths of pipe, hose, and other components to keep pressure losses well within allowable limits. The air-operated machines consist primarily of drifters, stopers, pluggers (sinkers), slushers, and several other pieces of equipment. Compressor Operation Every compressor is made up of one or more basic elements; a single element, or a group of elements in parallel, comprises a single-stage compressor. Many compression problems involve conditions beyond the practical capability of a single compression stage. Too great a compression ratio (absolute discharge pressure divided by absolute intake pressure) may cause excessive discharge temperatures or other design problems. It, therefore, may become necessary to combine elements or groups of elements in series to form a multi- stage unit, in which there will be two or more steps of compression. The number of stages commonly used in reciprocating compressors is as follows: Pressure Number of stages 0- 150 pig 1 80- 500 psig 2 500-2500 psig 3 2500-5000 psig 4 When pressure is referred to as pounds per square inch gage (psig), it means the pressure (in pounds per square inch) above barometric pressure as measured by a gage. The sum of barometric pressure and gage pressure is the absolute pressure (in pounds per square inch). The gas is frequently cooled between stages to reduce the temperature and volume entering the subsequent stages, thereby reducing the work required for compression. The basic reciprocating compression element is a single cylinder compressing on only one side of the piston (single-acting). A unit compressing on both sides of the piston (double-acting) consists of two basic single-acting elements operating in parallel in one casing. The reciprocating compressor uses automatic spring-loaded valves that open only when the proper differential pressure exists across the valves. Intake valves open when the pressure in the cylinder is slightly below the intake pressure. Discharge valves open when the pressure in the cylinder is slightly above the discharge pressure. In Fig. 1, Diagram A shows the basic element with the cylinder filled with air at atmospheric pressure. On the corresponding theoretical pressure-volume

Jan 1, 1986

By J. Peterson

A review of blast designs and improved blasting practices at the Ekati??Diamond Mine is presented along with the results of three blast-monitoring experiments. Blast monitoring was undertaken to investigate blast damage mechanisms in the mine's well jointed rock mass. Rock mass damage caused by production, pre-shear and wall control blasts was measured. Ekati??uses 270mm holes for production blasting, and 165mm holes loaded with a decoupled charge for pre-shearing. The production blasts are loaded with bulk emulsion / ANFO blends. The mine plan involves using 30m double benches. A 30m high pre-shear is drilled and blasted prior to the production blasting that is done with sequential 15m benches. This paper summarizes the monitoring equipment and data gathered to date.

May 1, 2001

By Isabella Faria da Cunha Peixoto

O emprego das ligas NiTi proporcionou a fabricação de instrumentos endodônticos com diferentes desenhos de lâminas cortantes. Este estudo investigou a relação entre as características geométricas destes instrumentos e a força apical necessária para inseri-los em canais artificiais em blocos de acrílico. A força apical foi registrada através de um dispositivo de bancada de testes. Dez instrumentos de cada tipo ES, Mtwo, ProFile GT, ProFile GTX, K3, RaCe e PTU F1 foram testados a uma velocidade de 300 rpm e um torque de 5 Ncm com um movimento vertical de 17 mm de comprimento. Os dados foram comparados por análise de variância (a = 0,05). Avaliação geométrica e dimensional mostrou que o instrumento K3 tem a maior área de seção transversal, seguido por PTU F1 e GT. Os ângulos helicoidais menores de RaCe, ES e GTX podem ter contribuído para os baixos valores de força apical encontrados. Maiores valores de força apical foram determinados nos instrumentos GT, K3 e PTU F1 em relação à RaCe, ES e GTX. Foi observado que a força apical exercida durante o preparo do canal está diretamente relacionada à área de seção transversal e aos valores dos ângulos helicoidais dos instrumentos.

Aug 16, 2017

By A. G. Metcalfe, A. Siede

The hardening of annealed copper during fatigue testing appears to be independent of the applied stress and to occur largely within the first 4000 cycles. Copper hardened by fatigue is more resistant to annealing than copper hardened by static means, and softens by a multistage process. Creep studies at 300°C show that copper hardened by fatigue also has greater resistance to creep than statically hardened copper. Some theoretical explanations are discussed. RECENT interest in the behavior of metals subjected to fatigue stems from observations of phenomena which could not be explained by current theories of the structure of metals. In 1953 Bullen et al.l showed that the hardening caused by fatigue at low stresses did not cause severe bending of the lattice as did hardening by static methods. This was later confirmed by Wood, 'and Broom and Ham.3 Clarebrough et al4 showed that as the stress level used in fatigue hardening was increased, bending of the lattice was introduced, eventually approaching that of metals deformed by conventional cold-working methods. The type of hardening introduced by fatigue has other interesting characteristics. Kemsley5 showed that copper fractured by fatigue at low stresses resisted annealing as compared to copper hardened an equal amount by static means. The work of Clarebrough etal, shows that the manner of energy release during annealing differs for fatigue-hardened and statically hardened metal in both magnitude and temperature range of release. In addition to hardening of the lattice, fatigue has been shown to cause softening in materials previously hardened by static methods,5 and also in age-hardened alloys.7 The superposition of a small fatigue stress on the static loading of high-temperature alloys has been shown to increase their resistance to creep.' The present work was an attempt to determine the relationship between fatigue hardening, resistance to annealing, and the creep properties of pure copper. EXPERIMENTAL PROGRAM The program described here was designed to answer three questions: 1) Can stress-cycle combinations well below the failure values give significant increases in hardness? 2) Does hardening, under different stress-cycle combinations, give increase resistance to annealing? And if so— 3) Does superior resistance to annealing confer superior creep properties over statically hardened material? Three-quarter hard OFHC copper was annealed in vacuo at 550°C for 1 hr to produce a strain-free material having a fine grain size and uniform hardness. (The standard deviation of the mean hardness of the annealed samples was less than + 1.9 Dpn). Annealing was performed after machining the fatigue specimens so as to avoid work-hardened surfaces. Jigs were used to avoid distortion. The fatigue properties of the annealed copper were determined using an accurately aligned Baldwin-Sonntag SF1-U machine operating at 1800 cycles per min. This limited the minimum number of cycles which could be examined to about 4000 stress reversals. Since failure resulted in specimen damage, hardness increase with number of cycles was measured by testing specimens fatigued to different fractions of the failure values. The results are shown in Fig. 1, and are superimposed on the S-N curve of the copper in Fig. 2. The resistance to annealing of fatigue-hardened material was compared to that of material hardened by uniaxial tensile straining. Specimens hardened to equal values by both methods were progressively annealed for 1 hr at temperature in vacuo. After each annealing treatment the hardness was measured using a Leitz Durimet hardness tester with a 500-g load. At least five tests were made for each hardness determination. The standard deviation for individual specimens varied from 0.26 to 1.48 hardness points. The results are shown in Figs. 3 to 5. The discontinuous nature of the annealing process has been brought out by drawing idealized curves through the data points. This can be justified by the consistency of the results as well as by general agreement with results of Kemsley.5 The creep resistance of fatigue-hardened and

Jan 1, 1960

By Siavoljub D. Maksimovic

The Bureau of Mines, through a cooperative agreement with Duquesne Light Co. of Pennsylvania, field tested a method of using pneumatic stowing of crushed limestone to construct seals in long-abandoned mine openings that were part of an active mine closed shortly before sealing. A total of 13 openings at 11 sites were backfilled. In pneumatic stowing, material is conveyed through a pipeline and into the mine opening under low air pressure. The stowing equipment consists of a power sup-ply, a blower, a feeder to inject material into the pipeline, and a nozzle for directing the placement. Material is ejected from the nozzle at high velocity, creating a high-compaction fill upon impact. The fill material used was well-graded limestone aggregate up to 1-1/2 inches in diameter, with sufficient fines. This fill was modified at five locations by the addition of portland cement, expansive cement, and/or bentonite. The pneumatic stowing method is safer and faster than conventional methods, is cost competitive, and eliminates or reduces the exposure of workers to possible hazards since the nozzle can be kept outside the mine opening. The equipment is mobile, but some modifications in the technique would improve performance. The technique was used at remote locations where other methods could not be used without disturbing the environment.

Jan 1, 1982

By Bert Sandell

MUCH has been said and written about the various uses of die-castings, their applications in the various industries and their advantages and disadvantages. Examination of this literature, however, fails to disclose any data concerning the effect of temperature upon any of the physical properties of die-casting alloys. The uses and applications of die castings are so numerous, and of such a varied nature, that far too lengthy a manuscript would be required to list all of them. Brief mention of some specific cases will suffice to illustrate the temperature ranges in which certain die castings function. Automobile hardware, such as hub caps, door handles, radiator caps, etc., can be used as one example. Castings of this type are constantly exposed to varying climatic conditions, temperatures ranging from below zero to upwards of 100° F. Refrigerator parts, such as ice-cube trays, etc., form another example. Approaching the other temperature extreme, we encounter conditions such as are found in kitchens in which oven-heat indicator parts, cooking utensils, waffle grids, etc., embody use of die castings, where temperatures as high as 500° F. are often met with. Because of this variation in service temperatures, it was felt necessary to ascertain the effect of these temperatures upon the physical properties of die-casting alloys. The Charpy impact test was chosen first because of its simplicity, and because of the fact that brittleness is more likely to be objectionable in die castings than hardness or other physical properties.

Jan 1, 1932

By C. A. Garzonio, A. M. G. Affuso

The paper describes the analyses and the tests carried out on representative slabs of white Carrara marble which have highlighted the correlation between the micro fabrics and physical and mechanical parameters. The aim is to determine the conditions which indicate the triggering and evolution of the deformation phenomena. La note écrit l’analyse et les epreuves effectuée sur un echantillon représentatif de nombreuses dalles en marbrede Carrara. Les études montrent la correlation entre la minéralogie et les paramètres physiques et mecaniques. Le but est déterminer les conditions qui indiquent l’amorçage et l’evolutions des phénomènes de déformation. Diese Arbeit gibt eine Beschreibung der experimentalen Untersuchungen und der Analysen über die Marmorplatten von Carrara. Daraus resultiert, dass die Charakterisierung der Mineralogie und die Porosität der Gesteinsmaterialien die physikalische mechanische Degradation beurteilen und die Krümmungen bestimmen.

Jan 1, 2003

By Roy H. Borde

The design of foundations to support overhead signs is primarily based on providing adequate resistance against horizontal wind loads. The typically used subgrade reaction model for the load-deflection analysis of laterally loaded piles and shafts has been found to underpredict the capacity of shafts with length to diameter ratios less than five. The general applicability of an improved model incorporating the influence of shear and moment resistance at the shaft base is demonstrated. The detrimental effect of ground surface slope angle on the ultimate capacity is discussed, and a design chart for estimating the magnitude of the reduction in capacity is presented. A comparison between the predicted and measured responses of nine full-scale load tests performed within this study and sixteen external tests is presented. The models described are implemented in the computer program "LTBASE".

Jan 1, 1988

By R. L. Crosby

Microscopical and X-ray diffraction techniques were used to identify two intermediate phases in that part of the solid region of the magnesium-cerium system between and Mg3Ce. Previous literature had reported only one intermediate phase for this region, 1)12t chemical analysis determined the approximate composition of the two compounds to be Mg23Ce2 and Mg17Ce2. The range in composition of the two intermediate phases was found to be limited to less than 0.3 atomic percent cerium. The study did not determine the crystal structure of Mg17Ce2, but that of Mg23Ce2 is tetragonal with a = 10.33 A and c = 19.51 A.

Jan 1, 1966

By Alan A. Campoli

The US Bureau of Mines (USBM) conducted research to develop improved guidelines for selecting the type and pattern of roof support in different geologic environments. The goal is to minimize the over and under design of mine roof support, resulting in more productive and safer mines. To obtain the necessary data on roof behavior and support performance, USBM conducted several field studies. Each study covers roof geology, stress regime, ground reaction, support interaction and mining environment. A consistent experimental design is being used. This includes measurements of roof bolt loads and roof movements. So far, 10 studies have been conducted in several geologic settings.

Jan 1, 1996

By Y. Q. Li, X. H. Long

In this work, structural and electronic properties of smithsonite (ZnCO3) and cerussite (PbCO3) as the typical lead-zinc oxide minerals is simulated by means of DFT. The calculated results could be concluded as: (1) The density of states (DOS) of Zn atom in ZnCO3 is nearer to the Fermi level than that of Pb atom in PbCO3, suggesting that the Zn atom of ZnCO3 is more active and easier to interact with water molecules and hydroxyl ions. Smithsonite, therefore, could be more readily depressed in the flotation process. (2) The bond population value of Zn-O (0.23) and C-O (0.92) in ZnCO3 is obviously larger than that of Pb-O (-0.01) and C-O (0.85) in PbCO3, indicating that the covalent characteristic of ZnCO3 is stronger than that of PbCO3. (3) It is shown that the charge of Pb (+1.32e) in PbCO3 is more positive than that of Zn (+1.22e) in ZnCO3, suggesting that cerussite is easier to interacting with HS- compared with smithsonite in the flotation process. In summary, the structural and electronic property of smithsonite is completely different with cerussite, leading to the difference of their flotation behaviour.

Jan 1, 2015

By R. Cao

Geostatistics was initially developed in the mining sector, but has been extended to other geoscience applications, including forestry, environmental science, soil science, and petroleum science and engineering. This paper presents methods, workflows, and pitfalls in using geostatistics for hydrocarbon resource modelling and evaluation. Examples are presented of indicator variogram analysis of categorical variables, lithofacies modelling by sequential indicator simulation and hierarchical workflow, porosity modelling by kriging and stochastic simulation, collocated cokriging for integrating seismic data, and collocated cosimulation for modelling porosity and permeability relationships. These methods together form a systematic approach that can be effectively used for modelling natural resources.

Jan 1, 2014

By Xiaoyan Luo, Congcong Dai, Gaipin Cai, Xin Liu, Lu Zong

To overcome the difficulty of accurately judging the load state of a wet ball mill during the grinding process, a method of mill load identification based on the singular value entropy of the modified ensemble empirical mode decomposition (MEEMD) and a probabilistic neural network (PNN) classifier is proposed. First, the MEEMD algorithm is used to decompose the vibration signals recorded under different load states to obtain the intrinsic mode components, and a correlation coefficient threshold is used to select the sensitive mode components that characterize the state of the original signal. Second, singular value decomposition is used to obtain the singular value entropy. Finally, the load state of the wet ball mill is judged based on the magnitude of the singular value entropy. A characteristic mill load vector is constructed from the singular value entropies of the cylinder vibration signals recorded under different load conditions and is used as the input to a PNN, which then outputs the predicted ball mill load state; in this way, a load state identification model is established. Grinding experiments are presented to verify the effectiveness of the proposed method, showing that the method can accurately identify the load state of a wet ball mill. ()

By Paul Hatmaker

Lime was a highly useful commodity thousands of years before the simple chemistry of its manufacturing process was known. The employment of lime for agriculture, building, and even certain essentially chemical purposes is so old that its origin is among the unrecorded details of man's first ventures into the manufacture and use of prepared substances. Lime is a most versatile material and consequently has come to be widely utilized in modern civilization. Immediately before the depression of the early 1930's the annual production of lime in the United States was more than 4 million tons, valued at 33 to 42 million dollars. This output was sold to many industries, so many that mere enumeration becomes tedious. In addition to agricultural and building lime the sales statistics compiled annually by the Bureau of Mines include lime sold to the steel and other metallurgical industries as refractory and fluxing material, as well as that used by paper mills, glass works, tanneries, and water-treatment plants. These major uses normally consume about 86 percent of the domestic sales. The remaining 14 percent includes lime sold for use in the manufacture of alcohol, alkalies, bleaches, calcium acetate, calcium carbide, coke gas and byproducts, glue, insecticides, oils and fats, paints, and rubber, in the refining of salt, in the manufacture of sand-lime and slag brick, in the disposal of sewage and garbage, in the manufacture of silica brick, in the refining of sugar, in the textile industries, and in wood distillation. Many other uses are also known for which complete sales data are not available.

Jan 1, 1934