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By Rong Lu, Hao Wu, Bing Dai, Guoyan Zhao, Li Cheng, Weizhang Liang

Affected by the disturbance of blasting activities, deformation instability and rock dynamic disasters are prone to occur in deep hard rock roadways. Thus, it is particularly necessary to understand the failure behavior of rocks and roadways under dynamic loads. In this study, a series of impact loading tests were carried out on sandstone samples with and without a circular cavity by a modified split Hopkinson pressure bar (SHPB) test system. The mechanical properties and energy evolution of the samples were systematically investigated, and the effect of cavity size was analyzed. The results showed that the presence of the cavity in the samples weakens the dynamic compressive strength by more than 10%, and the peak strain and brittleness are also reduced to varying degrees. Under dynamic loading, spalling cracks occur first on the roof and floor of the cavity, and then different numbers of shear cracks are formed on the sample diagonals. The eventual shear failure mode is the result of the connection of the shear cracks and the cavity. As the cavity radius increases, the dissipated energy density and fractal dimension both grow accordingly, leading to smaller and smaller rock fragments. The dynamic failure behavior of the circular cavity can be well explained based on the dynamic stress distribution law. Overall, this study can provide a reference for the study of the mechanism of rock burst in deep roadways.

Feb 18, 2021

By D. F. Malan, L. Scheepers

Seismic risk in the deep gold mines of South Africa has been studied for many decades. A clear understanding of the effect of geotechnical conditions on the seismic hazard nevertheless remains elusive. Certain reef types seem to be associated with a higher risk of rockbursts. The stability and deformation behaviour of excavations on the different reef horizons are affected by the rock types and the varying strength properties. The seismic response to mining is therefore also expected to differ according to the geotechnical conditions. As a case study of this behaviour, the seismicity at Mponeng mine was investigated. On the VCR (Ventersdorp Contact Reef) horizon, two areas can be delineated. On the eastern side of the mine, the footwall is shale, and on the western side it is a strong brittle quartzite. More large-magnitude events occur in the area with the shale footwall than the area with the quartzite footwall. Moment tensor analyses indicated that the majority of the large-magnitude events are not related to geological structures, but are face-related, implying that shear failure of intact rock is occurring ahead of the mining front. Preliminary modelling indicated that the closure volume for the shale footwall may be higher than that for the quartzite footwall, providing a possible explanation for the observed difference in seismic response.

Mar 2, 2022

By E. P. Youngman

The basic mining law of French Morocco is the Edict of 1914, "Danir of Jamary 19, 1914, for the Regulation of Mineral Prospecting and Exploitation in the Zone of the French Protectorate of the Cherifien Empire," which, as the preamble states, was promulgated at the instance of the Director General of Public Works, in consideration of the fact that mines constitute one of the sources of wealth of the Empire. According to a consular report, dated May 18, 1923, by Bradford, men- tioned above, the mining industry of that country, aside from the exploitation of the extensive phosphate deposits, can scarcely be said to exist, but the potential field for mining is promising. However, no large-scale exploitation of the mineral wealth of French Morocco can be hoped for until there is complete pacification of large areas that are still in an unsubdued state or until adequate transportation facilities, scientific prospecting, and large investments of cap- ital are assured. An edict in 1920 (Dahir of January 27, 1920) modified the law mentioned above by declaring the prospecting for and the exploitation of phosphates to be exclusively reserved to the Government. The Dahir o. August 7, 1920, announced the creation of the Cherifien Phosphate Office (Office. Cherifien des Phosphates), a State monopoly charged with the exploration, management, and exploitation of the phosphates of Morocco.

May 1, 1930

By F. N. Shi

Ore breakage characterization plays an essential role in the design and optimization of comminution circuits. Recently, the JKMRC comminution research team has developed a Rotary Breakage Tester (JKRBT). The JKRBT uses a rotor-stator impacting system, in which particles gain a con-trolled kinetic energy and are impacted against the stator, causing particle breakage. The first unit of industrialised JKRBT was installed at the Anglo Research in South Africa in March 2007, and five more JKRBTs are currently being fabricated for some of the world?s major mining companies. In addition to the JKRBT, an improved breakage model has been developed at the JKMRC, which more accurately describes the effect of specific energy, particle size and incremental breakage caused by repetitive impacts. The validation outcomes show that the JKRBT, together with the new breakage model, generate statistically similar breakage parameters to the traditional drop weight tester (DWT), but with significant advantages over its predecessor. The limitations of the DWT, specifically its lack of precision of the energy input, the lengthy time required to run individual tests and the challenges en-countered in testing small particles, have all been overcome by the JKRBT. The recent developments in the JKRBT and the new breakage model offer several prospective applications. These developments have the potential to revolutionize the ore breakage characterization in the years to come.

Jan 1, 2014

By Steven Wright, Sharif Jahanshahi, Shouyi Sun

"While there is a large industry based on recovering platinum group metals (PGM) from complex sulphide ores containing Cu and Ni, there is little information on the thermodynamics of the matte phase formed on smelting the ore and in particular the behaviour of Pt in the matte.The equilibrium between metallic platinum and industrial mattes was studied in a series of experiments where a small quantity of matte (5g) and platinum foil of 150 µm thickness (0.5 g) were equilibrated in magnesia crucibles at 1400°C under conditions where the oxygen and sulphur partial pressures were fixed.The chemical composition of the phases was determined from EDS analysis using a scanning electron microscope. Line scans were initially used to confirm that the foils had attained a uniform composition across their thickness. The composition of the matte was determined from analysis of an area of matte including the small metallic droplets and dendrites.The results of the equilibrium study are presented in terms of how the oxygen and the sulphur pressure affect the distribution of Pt, between the matte and the alloy foil (Lmatte/alloy). Other variables investigated were matte chemistry, i.e., the Fe content and the temperature. The activities of platinum in the mattes were calculated using a regular solution model describing the activity-composition relationship in the alloy."

Jan 1, 2003

By Jafar Safarian, Leiv Kolbeinsen, Stian Seim, Hossein Salehi

The present work aims to investigate the link between the oxidation and reduction of a weathered ilmenite concentrate in terms of phase transitions, microstructural changes, and element distribution. An ilmenite concentrate sample was pelletized and fired at 1000 °C in air, and as a result, the pellets were oxidized. The oxidized pellets were reduced by hydrogen gas at 1000 °C, which yielded almost complete metallization of the iron content of the pellets. The ore and the pellets were characterized in each step by XRD and SEM techniques, and distribution of elements and phases were investigated. Ilmenite, pseudorutile, and rutile were the main phases detected in the ilmenite concentrate sample, and depending on the weathering degree of the particles, different fractions of the phases were identified in their microstructure. It was found that irregular rutile grains dispersed in a pseudobrookite matrix is the morphology of the oxidized ilmenite phase. However, increasing microcracks and porosities were the only microstructural changes in the pseudorutile phase after oxidation in air. Studying the specific types of the ore particles and their oxidized and reduced forms indicated that the phase distribution in the ilmenite ore particles dictates the phase distribution in the oxidized and reduced ones. Results show that the morphology of the reduced particles includes a titanium (III) oxide matrix in which reduced iron globules are dispersed.

Feb 8, 2021

By GEORGE O. SUMAN

IN THE operation of oil properties there are various difficulties with pumping wells which can often be overcome or greatly lessened if sufficient attention is, directed towards pump and tubing problems. The difficulties referred to are the wearing out of pumps, sanding up of pumps, and the sanding up of the hole. As the perforations in the oil strings are large and the oil and sand loose and unconsolidated considerable trouble is often encountered in pumping wells due to the ease with which' the sand can come into the holes. DETERMINING FLUID LEVEL In determining the proper depth at which to tube a well it is essential to first find out something about the behavior of the fluid in 'the hole: Facts in regard to this natter can be obtained by finding the fluid level on pulling the tubing, by making a pumping test on the well tubed to various depths, and by bailing tests during cleaning out work. In ordinary oil field operations it is customary to take the fluid level at the time of pulling the tubing. This 'can only be done when the pump is not sanded up. There are two methods used in obtaining the fluid level. One method is to note where the outside of the tubing starts, to be covered with fluid when pulling the

Jan 1, 1925

By O. Rielo, A. Pascoal, P. Katsabanis

The dynamic parameters of two different granites have been obtained using Hopkinson bar experiments. One series of experiments were conducted using a Hopkinson pressure bar apparatus with an explosive source to provide the compressional wave. This wave would travel along the granite bar and would be reflected at the free end. Strains were obtained along the bar to examine the process. Using relatively long bars of rock, approximately 300mm long and 18mm in diameter, the separation of the compressive and the reflected tensile pulses was possible. If the net tension exceeds the strength of the material, spalling is witnessed. By properly selecting attenuation materials and explosive sources, single spalls were created, making results easier to interpret. Numerical modelling enabled the calculation of the propagation of the stress wave along the bar and its reflection at the free end. Knowing the location of the spalls, critical stress levels for rock failure under tension were obtained. Dynamic tensile strengths were also obtained, at different strain rates, using a Split Hopkinson Bar Apparatus. The results provide a measure of the increase of the dynamic strength at high strain rates, relevant to blasting applications. They are useful for the calibration of blasting models and the characterization of rocks for blast modelling, but also provide answers to the basic question of what is the rock strength for blasting applications.

Jan 1, 2011

By J. Petersen, H. Naderi, H. Zare, M. H. Nikzad, M. Karimi

In the copper electrorefining process, the dissolution of anodes is significantly reduced or even stopped when the passivation phenomenon occurs. The results of this phenomenon are increasing energy consumption, residual formatting, and voltage levels in the cell. In this study, the electrochemical behaviour of blister copper in the presence of sodium persulfate (PDS) was studied. The electrochemical methods of LPR, Tafel, and Electrochemical Impedance Spectroscopy (EIS) were used. The results showed that the addition of sodium persulfate activates the electrode surface and increases the open circuit potential. In the presence of PDS, the polarisation resistance of the electrode shows an increasing or decreasing tendency, based on the PDS concentration. This tendency is probably due to the formation of surface layers (such as slime layer or copper sulfate) and dissolution of this layer at various concentrations of PDS. The lowest polarisation resistance of 1.8 ohms and the highest corrosion current of 60.6×10-3 and 36.6×10-3 A/cm2 from LPR and Tafel techniques respectively were obtained at the concentration of 40 g/l PDS. Based on the results of potentiodynamic and electrochemical impedance spectroscopy tests, the addition of sodium persulfate to the solution reduces the corrosion resistance, therefore the passivation time of the blister copper anode increases. Keywords: Blister copper, electrorefining, sodium persulfate, anodic passivation

Jan 1, 2020

By D. A. Stanley

The Bureau of Mines is investigating a method of dewatering flocculated fine-particle waste that involves treating the waste with a high molecular-weight polymer such as polyethylene oxide (PED) followed by dewatering on a static screen and/or in a trommel. Dilution of the polymer solution used for dewatering and use of the ion-exchanged form of the montmorillonite clay were found to be major factors determining the amount of polymer required to dewater clay-containing slurries. The amount of polymer, A, required to dewater ion-exchanged montmorillonite can be described by the equation, An = kC + b where n, k, and b are empirical constants and C is the concentration of the polymer solution used for dewatering. Clays that require large amounts of polymer for dewatering also dewater to a lower solids content. The concentration of the polymer solution is important because it affects the radius of the polymer coil in solution and hence its ease of transfer to a bridging configuration by shear. The constant, n, a function of the charge to hydrated radius of the exchange ion, relates to the strength of the bond between the polymer and the surface of the clay through a water bridge. The constant k is related to the hydrated radi-us for sodium or to the unhydrated radius for the other exchange ions.

Jan 1, 1986

By Peter Fajfa, Heinz Palkowski, Jakob Kraner, Matjaž Godec

The study of asymmetric rolling on the AA 5454 aluminium alloy plates was carried out. The plates were taken directly from the industrial hot rolled sheet. They were cold rolled on the laboratory mill with different rotation speed of the upper and the lower work roller with the strains around 33 % and 44 %. To get closer to the industrial conditions the maximal dimensions of the rolled plates for laboratory rolling mill and the special industrial lubricant were used. After deformation the plates were annealed to the soft condition. This research was focused on all possible effects of asymmetric rolling: The reduction of rolling force, the increase of strain at same set roll gap, bending of workpiece, finer microstructure, more heterogeneous textures and as a consequence of that better mechanical properties. The asymmetric rolling with favourable mechanisms in the deformation zone has created the material with the homogeneous hardness in the cross section and with lower anisotropy, which is crucial for improvement of formability properties of aluminium work hardened alloys and to get closer to properties of steels. In the presented paper the general impact and different effects of speed difference of rollers was investigated on cold rolled aluminium alloy. Obtained and analysed results explain the function of asymmetry in rolling process and the options to implement the asymmetric rolling in industrial plant.

Oct 1, 2019

By G. Rong, W. Du

Stability of some potential unstable blocks in the left bank slope of Baihetan hydropower station is evaluated in this paper using the three-dimensional (3D) limit equilibrium method. The Baihetan hydropower station is in the downstream of Jinshajiang River, China. The geological condition in the river valley is complex, and many large discontinuities are detected in the slope of the two banks. As a result, much attention should be paid to the stability of the slope in the feasibility study stage. Because the left bank slope is an oblique consequent one, we mainly focus on the slope stability analysis in the left bank. Comprehensive geological exploration is conducted in the studied area and the detected discontinuities are well researched. By building a 3D geological model of the left bank slope, three potential unstable blocks which are close to the dam site are detected. An irregular wedge analysis method is then used to calculate safety factors of the three blocks under three conditions, which are natural condition, rainfall condition, and seismic condition, respectively. It is found that the safety factors of the block 1# and the block 2# are quite low when compared to the suggested values. Extra care must be exercised when excavating the slope near the block 1# and the block 2#. A preliminary reinforcement is also suggested.

Jan 1, 2015

By R. J. R. Schaller

NO. 3 winze, the sixth shaft to be sunk on the San Antonio property, is practically a duplicate of No. 3 shaft, which was the main shaft prior to the installation of the larger hoisting equipment in 1939. It is collared on the tenth, or 1,500-ft., level, and goes down vertically to the sixteenth, or 2,500-ft., level, with a loading pocket, spill pocket, and sump below this. It is 1,000 feet east of No. 3 shaft. All ore, men, and materials are handled through the latter. The winze location with reference to the rock formation is shown in Figure 1. (In plan, this section strikes N.30°E. and cuts most of the main orebodies of the mine normal to their strike.) It is collared eighty feet inside the footwall contact of the basalt and cuts through it before reaching the eleventh level. In this location there will be no ore tied up in shaft pillars, as the closest ore to the shaft is on the tenth level, and here it is eighty feet northeast of the collar. The winze headframe and hoist-room straddle the main haulage to the No. 3 shaft, on the tenth level (see Figure 2). At no time during the excavation for the headframe and hoist-room was the general routine work of this haulage held up.

Jan 1, 1941

By A. J. Duncan, S. Viswanathan, Q. Han

"Measurements of liquid permeability in the mushy zones of Al-15.42% Cu and Al-8.68% Cu alloy samples have been performed isothermally just above the eutectic temperature, using eutectic liquid as the fluid. A modified method has been developed to determine the specific permeability, Ks, as a function of time during the test from the data collected on these alloys. Factors affecting permeability measurements are discussed. Permeabilties are observed to vary throughout the experiment. This is attributed to rnicrostructural coarsening and channeling that occurs in the sample during the experiment. The permeability is related to the rnicrostructure of the sample using the Kozeny-Carman equation. The correlation between the measured Ks, liquid fraction, gL and the specific solid surface area, Sv, improves markedly when compared to previous studies in which rnicrostructural coarsening was ignored.IntroductionThe permeability of interdendritic liquids flowing through dendritic structures ·is an important parameter needed to predict the level of porosity in castings. The permeability is a component of Darcy's Law, used to estimate the pressure drop due to the resistance to the flow of interdendritic fluid to feed shrinkage. Therefore, much research has focused on measuring the permeability of alloys in the mushy zone (1-10). The Kozeny-Carman equation for liquid permeability in the mushy zones of alloys may be written as"

Jan 1, 1999

By R. S. Douglas

Introduction The mine at Copper Mountain of the Granby Consolidated Mining, Smelting and Power Company was one of the pioneers in the use of blast-hole diamond drilling for ore breakage. This method of mining has now been brought to a high degree of perfection. The system in use has?been described in a previously published paper which has become an important part of the literature o the blast-hole drilling method. At the time of the establishment of the system at Copper Mountain, standardized loading and drilling procedures were set up. These procedures were based partly on the results of experiment and partly upon the judgment of men experienced in breaking rock in the mine. The success of the method has been proof of their adequacy. With the progress of scoping in the mine, the diamond drill method of breaking was applied to other ore blocks where different conditions obtained. It was found necessary to make adjustments in the standard procedures to get the best results under the new conditions. The following paper attempts to express, in terms of mathematics, the relations of the variable factors. Until recently, estimations of drilling required were based upon the tonnage to be broken and the proposed rate of explosive loading. A revised method of estimating is outlined below which is direct and which involves no unrelated variable factors.

Jan 1, 1947

By M. R. Geer, H. F. Yancey

"INTRODUCTION Throughout the history of coal washing, the jig has been one of the most important coal-cleaning appliances. In 1935 34.7 percent of the 45,361,021 tons of clean coal produced was the product of jigging. 4/ Previous to 1928, most of the jigs used in the United States were of the piston type, with which sufficient mobility to allow stratification in bed is imparted by the reciprocating up-and-down movement of a piston in the water compartment adjacent to the screen compartment. In 1928, the Baum type of jig was introduces in this country and has since come into wide spread use. In this type, water pulsations are imparted by application and release of compressed air to the water compartment. All prior studies of the mechanism of seperating cleared coal from impurity by piston-type jigs. 5/ The same laws of settling, of course, apply to both types, piston or Baum, but the character of the separation with the Baum type may be modified more easily because of the flexibility with which air may be handled, as distinguished from the fixed action of eccentrics commonly used in piston jigs. Since no detailed studies are available to show the performance, that is, the character of the separation between coal and impurity, of the Baum type the Bureau of Mines undertook the investigation recorded in this report."

Jan 1, 1938

By G. M. Lee

SEVERAL improvements have been made in Granby smelting practice since the company abandoned the direct smelting of raw ore in the blast furnaces in June, 1927, in favor of sintered concentrate. These improvements have been made in several fields, but the most novel and outstanding change was the development of a process of concentrating most of the gold, and a somewhat smaller fraction of the silver present, in a small portion of the blister copper produced. The practice of making "copper bottoms" is usually associated with the reverberatory smelting of copper ores containing high percentages of impurities, or of copper matte high in precious metals. It has for its object, in the one case, the production of a major part of the copper relatively free from impurities and, in the other case, the production of a small per¬centage of the copper carrying the major part of the precious metals. Although the blister copper produced at the Anyox plant of the Granby company is remarkably free from deleterious impurities and normally contains no great amount of precious metals, certain economic considerations made it advisable to concentrate the existing precious metals into a relatively small percentage of the blister copper produced. The process devised took advantage of principles and reactions of the usual bottoms processes, but was carried out in the converters instead of in a reverberatory furnace.

Jan 1, 1935

By Edward J. Felten

THE oxidation resistance of chromium and Fe-Cr alloys is increased by small additions of yttrium or other rare earth metals.1,2 In addition, the presence of the additives increases the resistance of these alloys to spalling of the external oxide above 1000°C. This ability to prevent spalling appears to be related to the formation of an internal oxide in alloys containing yttrium or the other rare earth metals. The internal oxide is found in the form of a filamentary growth concentrated in the grain boundaries of the unoxidized metal. In alloys containing yttrium this internal oxide was found to be either Y2O3 Or YCrO3.' In an earlier report,' the growth of the external oxide was found to be controlled by diffusion through the oxide layer. Thermal balance studies were used to establish the kinetics of external oxide formation. In this related study the rate of growth of the internal filamentary oxide has also been studied. The results obtained indicate that the growth of the internal oxide is also diffusion controlled. Internal oxidation appears to occur in at least two ways. Using copper alloys containing small amounts of silicon, Rhines 3 found that between 600" and 1000oC a subscale was formed which consisted of particles of silica dispersed in the metallic matrix. The conditions requisite to internal oxidation as suggested by Rhines are: 1) a solubility of oxygen in the alloy, 2) the ability of oxygen to diffuse at an appreciable rate into the alloy, 3) the possibility of the formation by the alloying element of an oxide more stable than the oxide of the host metal, and 4) a relatively low solubility of this oxide in the metal. These conditions are fulfilled for a number of other copper alloys.3-5 Furthermore, the relationship between the depth to which the internal oxide is formed and the oxidation time follows the simple parabolic law.6 The activation energy for copper containing small amounts of silicon, germanium, iron, or manganese as calculated from Rhines data6 is about 48 kcal per mole. In some cases the internal oxide is found segregated at the grain boundaries, especially near the the surface. Observations of this type of oxide formation have been reported by stead,7 Rhines,* and Lustman. Evans" cites these cases as examples of the simultaneous movement of anions and cations during oxidation. Furthermore, Evans states that the presence of a minor constituent with a high

Jan 1, 1962

By AIME AIME

THE Coal Division holds its fall meeting in the Pocahontas coal field, at the West Virginian Hotel, Bluefield, W. Va., Oct. 9 and 10. The first day will be a busy one-two sessions for the presentation of papers and a dinner in the evening. Hon. E. Fudge, Assistant Undersecretary, Mines Department, and R. V. Wheeler, head of the Mines Research Board of Great Britain, will be the guests of the Division. Mr. Wheeler will discuss the British Mining Act as relates to the coal industry. George S. Rice, Chief Mining Engineer, U. S. Bureau of Mines, will present an account of the recent meeting at Buxton in England, of representatives of England, Germany, France, Belgium and the United States to formulate a plan and to correlate research work now in progress in the various countries. The second day the members will be the guests of the operators on a trip through the Pocahontas field. The work of preparation for the meeting is being actively pushed by committees headed by T. H. Clagett, R. M. Lambie and H. D. Smith, and a good attendance, both local and from the general membership of the Division, is anticipated. Because many will make the trip by car the principal automobile as well as rail-road connections to Bluefield are given here. The program for Friday, Oct. 9, follows:

Jan 1, 1931

H. W. Turner, San Francisco, Cal. (communication to the Secretary*): This excellent paper apparently represents the results of extensive observation and experience among the mines of the Mother-Lode, but I strongly question its relegation of the dioritic intrusions to the period of fissuring and ore-deposition. The dioritic rocks referred to are evidently those areas represented by Ransome in the Mother-Lode folio1 as meta-diorites, and, as he says, are merely basic facies of the great granodiorite batholite of the Sierra Nevada. If followed downward I venture to predict that these meta-diorite areas would be found to connect with the great batholite, and to be in fact mere apophyses of it. I see no reason for supposing that these apophyses were intruded into the Mother-Lode slates at a period later than the intrusion of the granodiorite in general. The period of fissuring was subsequent to this intrusion; the basic granodiorite or quartz-diorite areas of the foot-hill region are themselves fissured extensively; and the fissures were filled with quartz, apparently during the same general period of the formation of the Mother-Lode veins. Prichard and Ransome2 both refer to the deposition of quartz in the same lode at different periods resulting from a reopening of the fissures. Some time since, I saw in the stopes of the

Jan 1, 1904