Search Documents

By R. G. Swanton

The Bureau of Mines is investigating the leaching of phosphate values from Florida phosphatic clay wastes using sulfuric acid (H2SO4) as the leaching agent and methanol as the solvent. Acid-alcohol leaching studies were done using pure crystalline apatite to investigate potential causes for low extractions. It was found that a barrier layer formed on the surface of the apatite. Initial discovery of the barrier layer was made by analyzing pure apatite samples before and after leaching using an optical microscope. Subsequent Fourier Transform Infrared (FT-IR) analyses proved the coating was calcium sulfate hemihydrate (CaSO4-1/2H2O) and that unreacted apatite existed beneath the coating. Scanning electron microscope (SEM) photographs depict the CaSO4-1/2H2O morphology as long slender crystals adhering to the apatite surface. It was also shown that grinding the leached tailings and leaching again in the H2SO4-methanol system resulted in additional phosphate extraction.

Jan 1, 1991

By W. L. Van Heerden

In situ complete stress-strain characteristics of large coal specimens by W. L. VAN HEERDEN, B.Sc. Hons. (Pret.) (Visitor) The significance of ;n situ tests on large coal specimens is briefly reviewed. Tests aimed at obtaining complete stress-strain characteristics of large coal specimens with high width-to-height ratios are described. A formula for the relationship between strength and width-to-height ratios of coal pillars is proposed, and the influence of width to- height ratios on the deformation characteristics of pillars is discussed.

By Jeffrey L. Pagnutti

Train derailment can lead to loss of capital, damage to the environment, and loss of life. Machinery condition monitoring techniques can be used to develop a structural health monitoring system for railway track to detect faults at the incipient stage, before catastrophic failure occurs. This study uses vibration measurements from a novel material haulage unit to develop a decision support system for railway track maintenance. A variety of feature sets and classifiers were compared to determine the optimal configuration for fault detection. The results highlight the shortcomings and advantages of certain methods and describe the process in which the optimal result was obtained. The Parzen data descriptor paired with a refined statistical feature set performed the task of fault detection with less than five percent false positive and false negative classification error. Overall, the outcome of these experiments indicated that condition monitoring of railway systems is a promising approach for fault detection and has the potential to avoid catastrophic failure.

May 1, 2013

By Dennis V. D’Andrea, Sidney M. Runke

This paper describes the Bureau of Mines-El Paso Mining and Milling Company cooperative research program at the Emerald Isle mine3 near Kingman, Ariz. This research program was directed toward developing in situ leaching methods for 200,000 tons of ore exposed in the pit bottom and also 1,500,000 tons of ore under 200 feet of overburden adjacent to the pit. A test area in the pit bottom containing 15,000 tons of ore was blasted and leached. The results of this leach test were encouraging, and the entire pit bottom was leached in-place for about 7 months. Two test blasts under 200 feet of overburden and extending to 290 feet were detonated in an area near the open pit. The results of these blasts were evaluated by core drilling and permeability measurements. An in situ leaching system was designed, but not implemented, to recover copper from the 1,500,000-ton area near the pit. The company decided to terminate operations at the Emerald Isle mine in November 1975.

Jan 1, 1976

By Tim O’Neil

The US Bureau of Mines and the Santa Cruz Joint Venture (SCJV) are working on a production-scale, in situ copper recovery project in Arizona. The research is being conducted at the Santa Cruz site, located 11.2 km (7 miles) west of Casa Grande, AZ (Fig. 1). Santa Cruz is a 1.36-Gt (1.5 billion st) porphyry deposit averaging 0.6% Cu, of which 65% is oxidized, concealed beneath post-mineral alluvium at depths of 365-914 m (1500-3000 ft). The Bureau and the SCJV will evaluate in situ mining as a method for extracting copper from this previously unmined deposit. Research objectives of the Santa Cruz project are: - to demonstrate that an in situ research test can be operated in an environmentally acceptable manner ; and * to operate an in situ well pattern long enough to develop information on copper recovery and economic feasibility data. In situ mining of copper from undisturbed deposits has not been attempted commercially. There are several potential advantages with in situ mining: less exposure of miners to hazards, lower pital costs for the mine and plant and lower operating costs. In addition, there are no pits, dumps or tailings, which means less environmental impact.

Jan 1, 1991

By R. Singh, A. K. Dhawan, M. Dixit, H. Dev

ABSTRACT: The modulus of deformation of rock mass is an important engineering parameter required for the design of foundation of hydraulic structure and to study the interaction of rock mass and the structure at the foundation support. Different equipment and techniques are used to arrive at the design modulus value. Since any error in the estimation of modulus values results in multiplication of its effects in the analysis, it is necessary to know about the reliability of testing equipment and procedures. In the present study modulus values obtained by different in-situ equipment at different project sites have been compared. KURZFASSUNG: Der Verformungsmodul von der Felsenmasse ist technisch ein wichtiger Parameter, den man zur Konstuktion des Grunds fuer die Hydro – Tektonik, benoetigt um auch die gegenseitige Beeinflussung der Felsenmasse und der Tektonik am Traggrund zu betrachten. Verschiedene Geraete und Methoden werden angewandt, um den Ausfuehrungsmodul -Wert zu erreichen. Es ist erforderlich, die Zuverlaessigkeit der Pruefeinrichtung sowie des Verfahrens zu kennen, da irgend ein Fehler in der Abschaetzung von Modulwerten in der Analyse zu einer Vervielfachung ihrer Einwirkung fuehrt. In der vorligenden Arbeit werden die Modulwerte gewonnen aus unterschiedlichen Einrichtungen an Ort und Stelle and verschiedenen Projekt -Stellen mit einander verglichen. SOMMAIRE: Le module de deformation d’une roche est un parametre important pour la conception et realisation des ouvrages hydrauliques ainsi que pour etudier l’interaction de la roche et de la structure d’appuis de base. De divers equipments et techniques sont employes pour determiner la valeur de ce module de conception. Puisque l’effet d’une erreur d’evaluation du module devient multiplie dans l’analyse, il est necessaire de savoir la fiabilite des equipments et des methods qu’on ulilise. Dans cette etude, on a compare les valeurs des modules obtenues en employant les equipments in-situ aux sites differents de projets.

Jan 1, 2003

Detemine the elastic properties and structural integrity of a rock mass in situ. Approach An acoustic device that transmits and receives high-frequency seismic waves between boreholes was designed, built, and field tested. How It Works The acoustic cross-borehole apparatus operates by sending a seismic wave from a transmitter in one borehole to a receiver in a second bore? hole which may be located as far as fifty feet away, depending on the wave transmission quality of the rock. By measuring the wave's travel time and the distance between boreholes, the acoustic velocity of the rock mass can be determined. Characteristics of the seismic wave arriving at the receiver (such as the wave velocity, amplitude, and frequency content) are related to the physical properties of the geologic media, as calcu-

Jan 1, 1982

By V. J. Hucka

Coal, which was discovered in Utah in 1849, covers about 18% of the total area. Production in 1981 vas more than 14 million tons. However, some Utah coal mines are quite gassy. If longwall face technology is applied, then a release of a high volume of methane may be expected during the mining process. Investigations on methane content have been made by use of an isothermic bubble desorbometer. The desorbable methane content of 5 m3 to 16 m3 of methane per ton of coal mined has been determined.

Jan 1, 1983

By U. W. Lisner, V. J. Hucka

Coal, which was discovered in Utah in 1849, covers about 18% of the total area. Production in 1981 was more than 13 Mt (14 million st). However, some Utah coal mines are quite gassy. If longwall face technology is applied, then release of a large volume of methane may be expected during the mining process. Investigations on methane content have been made by use of an isothermic bubble desorbometer. A desorbable methane content of 0.5 to 16 m3/t (20 to 632 cu ft per st) of coal has been determined.

Jan 1, 1985

By William F. Brace, Howard R. Pratt, Wayne S. Brown

In many engineering structures, the mechanical properties of large volumes of rock must be considered. Typically, such properties are assumed to be the same as those of small laboratory samples, although it is clear that the laboratory samples do not contain the joints, faults, and other natural planes of weakness of the rock mass. A cheap, convenient testing procedure is needed with which the engineer can more accurately assess the strength and elastic properties of natural jointed rock. As a first step in this direction, a test has been developed capable of determining mechanical properties of large samples in their natural undisturbed state. In the present paper, some preliminary experiments on relatively unjointed material are described. Numerous attempts have been made to measure the deformation modulus of rock masses with varying degrees of success. Rocha (1), Grimm (2), and Alexander (3) have placed flat jacks in a slot in the rock and measured the pressure required to deform the slot. Bonnechere (4) has grouted large flat jacks in granite masses and performed similar experiments using a variety of strain measuring techniques. The U. S. Bureau of Mines has conducted radial jacking tests in which a uniform radial stress is applied to the inside of a tunnel of circular cross section and radial deformation is measured by extensometers located at various depths in the tunnel fall. Plate jack tests (Rocha (5), Shannon and Wilson (6)), pressure chamber tests, and cable jacking tests (Zienkiewicz and Stagg (7)) have all been used to determine in-situ deformation modulus. Several bore hole techniques have also been used to measure rock deformation. These include bore hole jacks (Goodman (8)), bore hole dilatometers using expandable membranes (Menard (9)) and bore hole penetrometers. Most of the above tests except the radial jacking test have an unknown stress distribution and require considerable approximation to calculate a deformation modulus. These approximations include the use of elastic theory for solutions of rigid plates, thick-walled cylinders, etc., and determination of values for Poissons

Jan 1, 1971

By Leonard Obert

The structural stability of any mine or under- ground opening in rock is dependent on the stress field, that is, the state of stress in rock before mining, the stress distribution in the rock created by the opening, and the in situ strength of the rock. In the past mine design problems have been considered by assuming that the stress field is due only to the weight of the overlying rock, the stress around the opening can be calculated from elastic theory using laboratory-determined elastic constants, and the in situ strength of the rock can be determined from laboratory tests on small specimens. Solutions to hypothetical problems using this procedure are given in a report by Obert, Duvall, and Merrill.' Because of the uncertainties of these assumptions, this method can give only a rough approximation to the solution of actual structural problems. Obviously, this approach to determining the stability of underground openings would be greatly improved if the rock stress could be measured in situ, and it is undoubtedly for this reason that in recent years many investigators have spent considerable effort on the development of procedures for measuring rock stress. In this report a method is described for determining in situ the absolute stress in rock. The method requires the measurement of the deformation of a borehole before and after the rock is stress-relieved. The magnitude and direction of the applied stresses are calculated from the borehole deformation and modulus of elasticity of the rock. Also, the results of absolute stress determination made in the walls and pillars of underground openings in five rock types are presented. From these results a number of conclusions are drawn regarding the accuracy and limitations of this method and the problem of stress measurements in general.

Jan 8, 1962

By N A. S Webster

The reaction sequences involved in the formation of iron ore sinter phases were determined using in situ synchrotron-based X-ray diffraction. Experiments were carried out using a synthetic sinter mixture containing 77.36 per cent Fe2O314.08 per cent CaO, 3.56 per cent Si.O2 and 5.00 per cent Al2O3 corresponding to a basicity of ~4. The alumina content represents the upper level of alumina concentrations measured in phases formed in industrially produced plant sinter. Data were collected during heating of the sample to 1350°C under an atmosphere of 0.5 per cent O2 in N2, equivalent to an oxygen partial pressure of 5 × 10-3 atm. This temperature was sufficientto ensure melting. Data were also collected on cooling of the sample back to room temperature to examine recrystallisation of phases from the melt.Results showed the sequence of reactions initially involved the formation of calcium ferrite phases C2F and CF. These subsequently reacted with the silica and haematite leading to the solid state formation of SFCA and SFCA-1. SFCA and SFCA-1 were the last phases to form in the system and were both stable up to ~1260°C. Above ~1260°C, melting of the SFCA phases and reduction of the remaining haematite occurred producing the assemblage magnetite + melt.During cooling, both SFCA phase types recrystallised from the melt initially coexisting with magnetite until secondary haematite formed. This is the fi rst study to demonstrate that both SFCA and SFCA-1 are precipitated from the melt during cooling of iron ore sinter. Future work will extend the range of compositions studied to examine the effect of basicity and alumina concentration on the phase assemblages as a function of temperature and oxygen partial pressure.

Jul 11, 2011

By P Mikula, B Darlington, J Graham, P Young

In underground mines experiencing dynamic events, there is an ever-present challenge to design and maintain a capable ground support system. One key component of ground support systems is surface support, which serves the essential roles of retaining failed rock and transferring forces generated by surface displacement to rock bolts or other support elements. Observations underground show that in many instances, standard mesh panels alone do not provide sufficient dynamic support to retain substantial bulking failures imposing displacement onto mesh, and in such cases Mesh straps and W-straps may be employed. Determining the performance of surface support elements proves to be difficult, with a multitude of variables at play in the underground environment. Quite comprehensive work has been completed on laboratory testing of surface support systems; however, very little work has been conducted on in situ dynamic testing of Mesh straps and W-straps. In 2019 in Western Area’s Flying Fox Mine, in situ dynamic testing was conducted on a series of Mesh straps and W-straps using Sandvik’s in situ Dynamic Test Rig (DTR). The testing regime applied impact energies from 5.1 to 15.3 kJ to Mesh straps and W-straps. The performance of the straps that did not fail was a maximum absorbed energy of 9.3 kJ and 14.2 kJ for the Mesh straps and W-straps respectively. The testing successfully demonstrated the ability of Sandvik’s DTR to test not only rock bolts, but also surface support elements, creating new testing and research possibilities. The testing also provided important design guidance data that is not practicable to obtain using laboratory dynamic testing facilities.

Nov 29, 2022

By P. Ret, E. Üstiindag, R. Dieckmann, R. Subramanian, S. L. Sass

"Partial reduction reactions in the Ni-AI-O system, starting with the spinel compound NiAI20 4, are used to form metal-ceramic microstructures. By suitable choice of processing parameters, such as reduction temperature, oxygen partial pressure and time, two different morphologies of nearly pure Ni particles, equiaxed and rod-like, form within a ceramic matrix, which is either a-A12O3 or a metastable ""defect spinel"". Electron microscopy studies were performed for microstructural characterization, phase identification and chemical analysis. The fracture toughness of the Ni-AI2O 3 mixture was significantly improved with respect to that of the original spinel phase. The important issues that must be addressed to form useful metal-ceramic microstructures by partial reduction reactions rue discussed. It is shown that cracking at the original spinel grain boundaries, likely due to the large volume changes associated with the reduction reaction, can be avoided by the addition of small amounts of ZrO2• Initial results illustrating effect of ZrO2 on the microsuuctures are presented.IntroductionEngineering materials used in load bearing circumstances, particularly under extreme conditions (e.g. high temperatures or stresses), generally are formulated with complex microsuuctures. Such composite-like materials can possess properties unobtainable by either of the individual constituents. With metal-ceramic composites, for example, a material can be obtained with an optimum combination of the low density and high strength of the ceramic, and the toughness of the metal. For high temperature service, where demanding conditions are often present, for example, inside jet turbine engines, a successful new material must have low density, high Young's modulus as well as good oxidation resistance, strength, fracture toughness, creep and fatigue resistance. The candidates include intermetallic compounds, and metal-ceramic, intermetallic-ceramic and ceramic-ceramic composites."

Jan 1, 1994

By Anna M. Ferrero

Stability condition of underground excavations have to be assessed to guarantee safe operations within the quarrying working areas. This objective requires a reliable assessment of the rock mass natural state of stress and of the stress redistribution induced by the excavations. This goal is often complicated by difficult geological conditions induced by tectonic stresses, complex topographies and large and irregular excavation geometries. Consequently, the acting state of stress needs to be measured by specific in situ measurement devices. This work refers on an in situ measurements campaign carried out by CSIRO tests in an underground quarry located in the Carrara marble basin. The difficult path carried out for interpretation of the measurements is described in this paper. In particular, the numerical modeling performed using the Boundary Element Method (BEM) first, to study the influence of both surface topography and excavation geometry and then the Distinct Element Method (DEM) to evaluate the influence of rock discontinuities in the measurement zone are illustrated in this work. Parametrical analysis of the rock mass mechanical features is also described in order to calibrate the numerical models and analyze the experimental results. The work has been carried out trough several phases, which are: characterization of the rock mass through geostructural surveys: this allowed us to classify the rock mass and determine the mechanical and physical parameters necessary for modeling; on-site measurement of stress levels through the application of over coring techniques; numerical analyses for the simulation of excavation phases, using the Examine3D (BEM) engineering analysis code. comparison between the measured stress levels and those numerically calculated and subsequent calibration of the BEM model; Numerical model of the forecasted excavation based on the calibrated (BEM) model.

May 1, 2009

By B. Das, V. Hucka

In light of the present energy crisis, coal appears now as the only reliable source of energy. The production of coal is expected to regain a rising trend after the latest slump. Aside from the competitive price with natural gas and oil, the other retarder of coal production is its environmental pollution effect. Gasification of coal has been advanced as the partial solution to the energy-ecology crisis. All the Advantages In situ gasification of coal may be considered a further step in this direction. It carries all the advantages of normal coal gasification as a stable source of energy; it is clean to handle and nonpolluting of the environment. It partially and sometimes fully does away with mining, makes uneconomical low grade coal and lignites economical and places some formerly unworkable seams within the scope of modern technology. The seams posing problems for mining due to tectonic disturbances may be converted into gas in situ. Low grade coals, such as lignites, which otherwise would be left in nature as uneconomic wealth, may be exploited by underground or in situ gasification. Thus, in situ gasification is likely to increase the exploitable reserves of coal and may reduce the cost of production. An additional merit of this method is that coal substance never reaches the surface and there is no problem of cinder disposal.

Jan 8, 1973

By R. Z. Pyrih

Uranium tailings at Cotter Corporation's Canon City, Colorado Mill were moved to a double-lined impoundment, but uranium and molybdenum salts remaining in the fractured bedrock underlying the old tailings ponds seeped into groundwater. Fluor Daniel GTI recommended an in situ geochemical fixation remedy, flushing Best Sulfur Products' calcium polysulfide reductant into the subsurface with clean water. Residual metals became immobile, trapped in the bedrock. Fluor Daniel GTI designed and implemented the process on ten acres with high metal concentrations. Cotter is operating and monitoring the system, which can be expanded to "hot spots." The original remediation time was estimated at less than five years.

Jan 1, 1998

By P. Soupios

Seismic geophysical methods have long been used by geologists and geophysicists to delineate subsurface features. These techniques work because different types and strengths of soil and rock transmit energy at different velocities. The Crosshole-Downhole tests (CH-DH) and seismic refraction survey (RS) are among the most used methods in engineering applications to obtain the elastic properties of subsurface layers. As a result, seismic methods have evolved into a cost-effective tool for rapidly determining depth to bedrock in engineering and construction projects. The seismic methods are best suited to sediment thickness analysis, bedrock quality determination and detection of the presence of weaknesses in the bedrock before the erection of any civil engineering structures such as bridges, tunnels, dams and portals. Seismic methods are also useful in estimating the rippability of bedrock ahead of construction. These methods are particularly useful for large-scale projects that require a significant number of drill holes, resulting in a substantial investment of time and costs for drilling. The CH-DH and RS methods are typically comparable in total cost to drilling, but provide significantly more information in 2-D and 3-D and therefore reduce the likelihood of conceptually oversimplifying the subsurface conditions. The above mentioned methodologies were considered to be the most appropriate geophysical methods for investigating the shallow structure and the dynamic soil properties of the area where the Ilarionas Dam is scheduled to be constructed. The main target of this work was to prove the potential of geophysical methods in providing accurate information to the civil engineer and to obtain information on the dynamic soil and rock properties for earthquake design analyses for the dam construction. Specifically, nine refraction seismic profiles and three cross-hole-downhole seismic tests were implemented to determine the subsurface conditions of the study area. The tests determined the shear and compression wave velocity profiles versus depth and other crucial parameters such as Young and Rigidity modules. Furthermore, they allowed the detailed 2-D mapping (along several profiles of the study area) of the subsurface variation of the soil and rock dynamic moduli.

Jan 1, 2006

By E. Fregeau-Wu

The mineralogy and grain size distribution of phases in a steelmaking slag and experimental products from the heating of the slag under various conditions were determined to explore the possibility of recycling of the iron and manganese to the blast furnace. The steelmaking slags consisted of three major phases: dicalcium silicate, dicalcium ferrite, and Mg-Mn-wustite. Most of the phosphorus was contained in the dicalcium silicate and to lesser extent in the dicalcium ferrite. Due to the fine grain size of the dicalcium silicate, grinding and magnetic separation required pretreatment to increase the grain size and hence the liberation. Experiments on a steelmaking slag were conducted by heating the slag to 1633-1748°K( and slow-cooling in an inert atmosphere at various rates with or without the addition of fluorspar (CaF2) as a flux. Grain size distribution analyses of the starting material and the slow-cooled products were performed using the SEM-IPP area scan method and the QEM*SEM linear scan method. Comparable and reproducible results were obtained on the same sample using both methods. A size versus volume percent plot showed the increased grain growth most effectively. Examples of the grain size distributions obtained were used to show that a higher soaking temperature prior to slow-cooling, a slower cooling rate, and the addition of fluorspar to the slag promoted grain growth.

Jan 1, 1989

By S. Pignolet-Brandom, E. Fregeau-Wu, I. Iwasaki

To recycle steelmaking slags for their iron, manganese and lime contents, removal of the phosphorus-bearing dicalcium silicate and calcium phosphate is essential. Slow-cooling of slags was necessary to promote sufficient grain growth to achieve liberation. In situ grain size distribution determination showed that a high soaking temperature, a long soaking time, a very slow cooling rate and the addition of fluorspar promoted grain growth. High gradient magnetic separation on slow-cooled slags removed much of the dicalcium silicate. Liberation modeling was used to discuss the breakage and beneficiation characteristics of the slow-cooled slags.

Jan 1, 1993