Search Documents

By H. W. Rimmer

Automation in the aggregate industry is characterized by the increased use of purpose-built PLC systems put together by independent computer-control houses and/or equipment suppliers. These systems range in complexity from simple startup/shutdown sequencing systems through to complete centralized control/MIS systems that are increasingly concerned with providing timely information on overall plant and/or equipment performance. As such, they should be of considerable interest to the operator seeking low-cost solutions to the many problems associated with the effective operation of small-scale plants.

Jan 1, 1989

By W. M. Tupper

[The two types of sulfide deposits in the Bathhurst Newcastle area are; (a) epignetic fissure deposits, and (b) massive sulfide deposits. Geological evidence has been variously interpreted to suggest a syngenetic origin, a source bed' origin, or a magmatic hydrothermal origin for the massive sulfide deposits. Sulfides disseminated through the black shales and argillites of the host rocks are enriched in S32 (mean value 22.34, S34. = 5.8 per mil) relative to the meteoritic standard of 22.21, and have a broad spread in range of values. S32/S34 ratios of sulfide minerals from the deposits occur in two distinct groups. The massive sulfide deposits exhibit ratios between 21.88 to 22.05, while the fissure deposits exhibit ratios between 22.18 and 22.21. These results suggest two separate sources for the sulfur, each, however, resulting in magmatic hydrthermal deposition because of the narrow spread of ratios in each group. Granite intrusive into the host rocks of the sulfide deposits have a mean K/A age of 386 ± 10 M.Y. Lead minerals in the sulfide deposits have a mean nodel lead age of 370±20 M. Y. Thus the lead minerals and the granite bodies were emplaced during the same major orogenic event. Sulfide minerals from magmatic hydrothermal deposit have a very narrow range of S32/S34 values, as do those of the Bathurst area. It seems reasonable, therefore, that well homogenized magmatic hydrothermal solutions are the most logical source of the sulfide deposits. Furthermore, the homogeneity of the lead isotopic abundance data gives strong independent evidence that the ores are of a magmatic hydrothermal origin.]

Jan 1, 1960

By H. Jung, J. Kim, Y. Lee, Y. Seo

"Shale gas has become an increasingly important source of natural gas supply in North America and around the world. Horizontal drilling and multi-stage hydraulic fracturing are the two key enabling technologies for the economic development of these shale gas reservoirs. It is believed that gas in shale reservoirs is mainly composed of free gas within fractures and pores and adsorbed gas in organic matter (kerogen). It is generally assumed in the literature that the monolayer Langmuir isotherm describes gas adsorption behavior in shale gas reservoirs. In this work, we have analyzed several experimental measurements of methane adsorption from the Horn River Shale core samples that obey the Langmuir isotherm. INTRODUCTION In nature, gas shales are characterized by extremely small grain size, extremely low permeability on the order of nano-Darcy (10-6 md), small porosity, and high total organic carbon (TOC). Shale can serve as both source and reservoir rock. The amount of gas in place in shale is strongly affected by the TOC, clays, and the adsorption ability of methane on the internal surface of solid (Martin et al., 2010). Since a considerable amount of gas in shale reservoirs is adsorbed, investigation of gas adsorption can provide critical insights into evaluation of well performance and reservoir characterization. Generally, natural gas in shale reservoirs is stored as free gas in both larger mineral pores and natural fractures, as well as adsorbed gas within organic matter (Leahy-Dios et al., 2011). EXPERIMENT METHOD & THEORY Adsorption Experiment Several experiments were carried out on 9 shale core samples obtained in a vertical well drilled within Horn River basin (Figure 1). The CH4 adsorption isotherms were measured for the different depth. In order to measure the amount of adsorbed gas, the high pressure Belsorp-HP equipment applying volumetric method was used. The temperature was kept at 298 K and pressure was increased up to 18 MPa. Approximately 5 g of crushed sample was used for each measurement."

Jan 1, 2016

By L. Sandbak

The TRJV Mine is located approximately 43 miles northeast of Winnemucca, along the east flank of the Osgood Mountains in the Potosi Mining District, Humboldt County, Northwest Nevada (see Figure 1). The Turquoise Ridge Mine is an underground mine, and is a 25% joint venture partner with Newmont Mining. The TRJV mine utilizes the underhand cut-and-fill mining method due to the relatively low rock quality in the ore zones and the relatively shallow dipping 25-45 degree ore body geometries. This paper defines a rehabilitation risk rating system (RRRS) for prioritizing rehabilitation of drifts damaged in the mining processes including long term development drifts providing access to the mining areas. The ultimate use is as a mine planning tool for the organized scheduling of rehab in a timely manner. A few case studies of the most needy rehab areas identified by the RRRS mapping system is presented, and the type of rehab completed design for these areas. Suggestions on improving the rehab risk mapping system include the use of support history and rock mass strength rating factors.

Feb 23, 2014

By Wolfgang Gütter

India is targeting to boost its electrical capacity from 100 GW to 200 GW within the next 10 years. The National Hydroelectric Power Corporation (NHPC) has decided in2001 to take execution of the 800 MW Stage-II of the prestigious 2,051 MW Parbatihydrol electric project in Kulu district of the northern province Himachal Pradesh. Two parallel 30° inclined underground pressure shafts of 1.542m in length each will be excavated in different geological formations and lined with hexagonal concrete segments by a hard rock double shield TBM. That kind of heading will be a novelty to India and an innovative method for inclined pressure shafts. The 4.88m Mitsubishi DSTBM will be assembled underground on a swivelling steel platform especially designed for the launching as well as for the acceptance of the TBM in the upper cavern of each shaft. The hexagonal segmental lining system causes a significant higher job safety than an open TBM with conventional support. Each ring consists of four honeycomb segments with 20 cm thickness. After finalisation of the excavation a steel liner will be installed and concreted. The Joint Venture Jäger-Seli will perform the two pressure shafts as a sub-contractor for the Indian company Gammon India Ltd.

Jan 1, 2005

By S. P. Singh

Drifts are the nerve centre of underground mining. They provide essential communications between primary openings and production areas. In view of their strategic importance in the overall safety, economy and productivity of mines, an empirical approach for blast design during drifting has been proposed in this paper. The approach was developed with the objective of minimum blast damage and provides computerized blasthole patterns for drifting operations. The drift blasting practices and problems in Canadian mines have also been reviewed in this paper.

Jan 1, 1991

Commercialisation of outcomes from research projects is a process often poorly understood and managed, but has the potential to achieve significant benefits for the industry and community as a whole. JKTech Pty Ltd was established in 1986 to transfer viable research outcomes from the Julius Kruttschnitt Mineral Research Centre (JKMRC) at The University of Queensland, Australia. This paper describes successful and unsuccessful examples of commercialisation by JKTech over the years, and draws some conclusions as to the factors that contribute to success and failure in technology transfer.

Jan 1, 2012

By A. D. S. Gillies

Inertisation is used to enhance the safety of underground mine areas either to avoid the potential for a combustion event or to stabilize a situation after an ignition, fire or heating. The primary objective of a recently completed Australian Coal Association Research Program (ACARP) study was to review coal mine inertisation and in particular to focus on use of the Polish mine fire simulation software Ventgraph to gain better understanding of how various inertisation units interact with the complex ventilation behavior underground during a substantial fire. Critical aspects targeted for examination under the project grant included location of the unit for high priority fire positions, size of borehole or pipe range required, time required for inertisation output to interact with and extinguish a fire, effects of seam gases on fire behavior with inertisation present and main fan management. A major accomplishment of the project has been to take findings from the simulation exercises to develop inertisation related modifications to the Ventgraph fire simulation program in conjunction with the Polish program authors. Selected mines were ?evaluated or audited?as to the ability to deliver inert gases generated from GAG units to high priority underground fire locations .A coding system has been developed and many potential underground mine fire sources cannot be successfully inertized with the GAG docked at the current specified point; this is particularly so for fires in extended areas of workings or in panels. There is a limit to the ability of the GAG jet engine to deliver exhaust down smaller dimension borehole. There is a need to examine the use of the GAG for production or proactive uses in a wider application in Australian mines responding to recovering from mine fires, spontaneous combustion heating?s, elimination of the potential explosibility of newly sealed gobs or inert mines or mine sections on closure. Some of the current uses of low flow inertisation facilities could be more effectively undertaken with the GAG unit.

Jan 1, 2009

By LINDSAY BOTTOMER, Tassos Grammatikopoulos, Massoud Aghamirian, MARK FEDIKOW

A master composite (Master Comp) sample was prepared from three pegmatite zones from the Zoro Dyke D1 for mineralogical analysis and heavy liquid separation (HLS). The mineralogical examination was conducted on a subsample that was crushed to approximately P80 = 600 μm. The sample consists of spodumene (10.5 percent), quartz (29.3 percent), plagioclase (29.0 percent), K-feldspars (21.3 percent), micas (5.1 percent), tourmaline (2.9 percent) and Fe-Mn-phosphates (0.1 percent). Liberation of spodumene (88 percent) and gangue minerals, including quartz (89 percent), feldspars (94 percent) and micas (83 percent), is very good at this P80 . The average lithium (Li) concentration is 3.7 percent in spodumene, 2,196 ppm in micas, 1,001 ppm in tourmaline and 115 ppm in K-feldspars. Spodumene accounts for 96 percent of the total Li in the sample. The mineralogical data indicate the potential to recover spodumene by flotation with minimal Li losses due to other Li carriers. The HLS was conducted on a subsample that was crushed to smaller than 6.4 mm, with the smaller than 600 µm fraction removed from this test. The HLS results indicate it is possible to produce a high-grade lithium concentrate, with close to 6 percent Li2O, after the rejection of iron silicates with magnetic separation.

By Faruk Oksuz, Cary Hirner, William A. Rochford

Grouting is a frequently utilized remedy in the planning and implementation of ground improvement and tunnel rehabilitation practice. The state-of-art grouting application used for Chicago’s McCook Reservoir project offers a unique alternative to the tunneling industry for pre-excavation grouting as well as tunnel rehabilitation, rescue and post-excavation ground improvements. The McCook Reservoir project included a computerized grouting control and data collection system for a precise and highly effective groundwater cutoff in fractured dolomites. By using balanced and stabilized grout mixes, the effective permeability of the rock mass was reduced over two orders of magnitude to less than 0.1 Lugeon by installing a double line grout curtain. The stable grout mix designs allowed high pressure and effective grouting at depths up to 125 m (410 ft).

Jan 1, 2005

By Wolfgang R. Wawersik, Charles M. Stone

INTRODUCTION Hydraulic fracturing was applied in horizontal drill- holes in the Salado salt formation near Carlsbad, New Mexico. Tests were performed approximately 650 m be- low surface to validate the design of a Waste Isolation Pilot Plant (WIPP) for the disposal of radioactive waste from defense activities of the United States. Hydraulic fracturing was performed primarily to determine whether the virgin in situ stress state at the WIPP site is isotropic and whether the magnitude of the virgin in situ stresses corresponds to the weight of the overburden. Beyond these limited objectives, however, measurements are now being reviewed to evaluate the usefulness of hydraulic fracturing in salt formations in general. Such measurements are desirable to determine stresses induced by mining and to monitor time-dependent stress changes around underground excavations in salt masses. Hydraulic fracturing was chosen because it is the only technique that can be readily applied in virgin ground far from existing mine openings. The method also appeared to yield directly the magnitude of the least compressive principal stress, regardless of the mechanical properties of the rock mass. A knowledge of the least principal compression was deemed sufficient to establish the isotropic character of the virgin in situ stress field under two conditions: (1) the Salado formation was mechanically isotropic, i.e., the fracture toughness did not vary normal and parallel to bedding so as to permit preferred fracture paths, and (2) pressure measurements were combined with determinations of the orientations of hydraulic fractures and, more generally, with observations of the characteristic hydraulic fracture patterns. The latter was possible by locating the drillholes for hydraulic fracturing along the axes of drifts that were mined several months later. The success of general stress measurements by hy- draulic fracturing of salt subjected to anisotropic stress conditions was and remains less certain. While the smallest in situ compressive stresses should still be equal to instantaneous shut-in pressures, there may not exist any unique relationships between the greatest and intermediate in situ principal stresses on one hand and the primary breakdown and fracture reopening pressures on the other. This problem would be a consequence of stress relaxation due to salt creep around any drillhole in which hydraulic fracturing tests are conducted. Moreover, lab- oratory measurements suggest that creep and stress relaxation could be so rapid that it might not be possible to interpret the measurements for anisotropic stress conditions even if hydraulic fracturing were performed as soon after drilling as possible. The primary objectives of the stress measurements in the WIPP were met by combining hydraulic fracturing tests with finite element analyses of the effects of salt creep, observations of hydraulically induced fracture pat- terns, and laboratory hydraulic fracturing tests on oriented core. In situ hydraulic fracturing tests in long drillholes were preceded by several trial tests to establish the best test methods and to demonstrate that salt could be fractured. The resolution of anisotropic stresses and special problems, e.g., in the identification of instantaneous shut-in pressures, are currently being addressed in hydraulic fracturing tests in a mine pillar, in tests following different delays between drilling and fracturing, and in tests with different frac fluids. This paper will review the main results of the analyses above and of one group of hydraulic fracturing tests at different distances from existing excavations. The paper will conclude with a brief description of the geometry of the hydraulically induced fracture patterns. Because of space limitations, it will be assumed that the reader is familiar with hydraulic fracturing or will first consult other sources (e.g., Cleary, 1980; Gronseth and Detournay, 1979; Zoback and Haimson, 1983; Nemat-Nasser et al., 1983; Kim et al., 1984)

Jan 1, 1986

By Jieliang Wang, Shiwen Yi, Zhao Cao, Peng Zu

Bayan Obo ore contains mainly bastnaesite, monazite and associated iron, fluorite, calcite, dolomite, barite, and trace amount of columbite. Due to its complex mineral compositions and similar mineral properties, it is difficult to separate and obtain rare earth and fluorite concentrates with high purity by conventional magnetic separation and flotation. In this paper, a stepwise magnetic separation process comprised of wet permanent magnetic separation (PMS), wet electromagnetic separation (EMS), and superconducting magnetic separation (SCMS) was proposed to pre-concentrate iron, rare earth, and fluorite minerals from Bayan Obo ore. The results showed that iron, rare earth, and fluorite preconcentrates with high purity and low impurity content could be achieved, which might be helpful to shorten the technological process and improve the separation efficiency for the subsequent flotation of iron, rare earth, and fluorite minerals.

Sep 15, 2020

By D. Tao

Coal is a major source of energy in the U.S. and more than 51% of the electricity used in the country is generated from coal. Coal cleaning prior to combustion is necessary and often accomplished using wet physical processes at coal preparation plants to remove impurities such as ash, sulfur, mercury. However, the resultant clean coal product still contains a significant amount of impurity due to the fact that impurities are not well liberated from coal particles ranging from several millimeters to inches in size at which wet cleaning processes take place. A cleaner coal product can be obtained if a cost-effective dry process is developed to further clean pulverized and thus better liberated fine coal at the power plants prior to its combustion. The benefit of such a process is a significant reduction in the cost of expensive post-combustion chemical cleaning processes such as flue gas scrubbing employed to meet the stringent environmental air quality regulations. In this study, a novel rotary triboelectrostatic separator (RTS) was investigated for its application to dry cleaning of fine coal samples acquired from the power plants in the state of Illinois. The pulverized fine coal contains well liberated ash and pyrite minerals and is an ideal feed to the triboelectrostatic separator for further cleaning without the use of water or any chemical reagents. The proprietary rotary triboelectrostatic separator (RTS) is characterized by an innovative high efficiency rotary charger, charger electrification, laminar air flow, and specially designed electrodes. Compared to existing triboelectrostatic separators, the rotary triboelectrostatic separator offers significant advantages in particle charging efficiency, solids throughput, separation efficiency, applicable particle size range, etc. Testing with several fine coal samples has demonstrated that this technology can significantly reduce ash content with a process efficiency similar to or better than froth flotation. Important process parameters such as charger rotation speed, injection and co-flow rate, feed rate were investigated for their effects on separation performance.

Jan 1, 2010

By D. Wenstrup, K. Perry, J. Hatfield, P. Sainato, B. Lusk

Concrete-infused cloth is used in several civil and mining surface applications whose circumstances are similar to some of those in underground mining. A feature of this material is that it cannot be overhydrated. In underground conditions, however, the excess supply of water to the cloth for hydration could lead to muddy and potentially unsafe working conditions, as well as resource wastage by supplying more water to the construction site than is needed. The objective of this study is to verify the water-to-cloth ratio and study the effect of hydration level on the strength of the Concrete Cloth product. We found that the strength increases with increased hydration up to a 1:2 water-to-cloth ratio by weight, after which the strength holds steady regardless of additional hydration. This confirms the 1:2 water-tocloth ratio by weight for hydration and confirms that strength is retained even if the cloth is excessively hydrated.

Jan 1, 2014

By Vernon K. Garrett, Gerhard Sauer

INTRODUCTION Generations of tunneling engineers had to fight not only against bursting rock and squeezing ground but also against the destroying power of water. Intrusion of groundwater into the tunnel opening affects the stability of the tunnel support system, reduces the safety of the traffic inside the tunnel, induces corrosion of installed equipment, and provides for creeping currents at electric facilities. Aware of these problems, engineers of the Washington Metropolitan Area Transit Authority and their consultants opened the way for a new approach in sealing a tunnel. It was made possible by accepting a new method of tunnel construction scarcely applied in the U.S. before. This new technique, the New Austrian Tunneling Method (NATM), provided the basis for the successful installation of a PVC-membrane between two separated shells of tunnel lining, and the carefully directed drainage of groundwater. Beside of the economic benefits already attained by applying the NATM for tunnel construction, the Authority now saves millions of dollars otherwise necessary to maintain the tunnel during its lifetime (Garrett, 1986; Setzer, 1986). But there is a large number of leaking tunnels built according to conventional methods, some of them facing severe problems jeopardizing the safe utilization of these structures. Recently developed methods indicate that even those tunnels can be rehabilitated without extensive costs by draining and sealing them afterwards. A road tunnel in the Austrian Alps provides the scene for a major attempt to convert one of those leaking tunnels into a dry structure.

Jan 1, 1987

By A. Kevin Beaton, Robert W. Laakso

The desire for dry passageways promotes the NATM as it provides a final support system most suitable for the installation of a waterproofing membrane. Waterproofing during construction is a cost effective way to enhance safety and function as well as increasing the life of an underground structure. The NATM approach utilizes the surrounding mass as an integral element of the "ringlike" support system. At the Pennsylvania Turnpike Commission Lehigh Tunnel No. 2 various rock classifications were determined to require support measures ranging from 2 to 12 inches of shotcrete along with spiling, wire mesh, deformed bar, lattice girders and rock bolts as needed. Field instrumentation and monitoring programmes are a key factor for the success of the NATM. When the support "shell" stabilizes smoothing shotcrete, waterproofing and a final liner can be placed.

Jan 1, 1991

By Gilbert A. Bonforte, Hugh P. Caspe, Tracy K. Lundin

The Narragansett Bay Commission (NBC) Combined Sewer Overflow Abatement Program is a major effort to address and mitigate discharges from combined sewer overflows in the Providence, Rhode Island area. The proposed system consists of three deep rock tunnel segments totaling 17.8 km (11.1 miles) in length that will provide 860,000 cu m (227 million gal) of storage at depths up to 99m (325 ft). This paper discusses 13.5 km (8.4 miles) of 6.64m (21.8 ft) finished diameter tunnel, four construction shafts, 19 dropshafts and one large diameter pump station shaft tapered from 1 5.2m (50 ft) at the surface to 27.4m (90 ft) at depth. All facilities are in preliminary design.

Jan 1, 1995

By T. R. Ellis

Considerable movement is afoot internationally to rationalize standards and regulations relating to valuations and the qualifications for valuation professionals. In July 2000 the International Valuation Standards Committee released expanded standards, and additional important improvements are planned by 2003. Possible updates to the International Accounting Standards (IAS) and potential adoption of IAS by the United States could significantly impact minerals appraisers. Standards designed specifically for mineral asset valuation are under development in Canada and the United States, with Australia's internationally respected VALMIN Code providing the benchmark. In the United States, the all-encompassing Uniform Standards of Professional Appraisal Practice (USPAP) is annually modified and continues to gain deeper acceptance, while the SEC holds fast to its 1981 rule prohibiting reporting of a quantitative estimate and value for non-reserve mineralization. Some important international trade agreements are driving actions to free the trade in professional services. In July 2000, an international workshop was held to initiate discussion on minimum qualifications for appraisers to work internationally. Pressure for uniform minimum qualifications and rules for professionals internationally will continue to build. The United States is historically among the slowest countries to implement such initiatives, with its state level licensure barriers having the potential to cause some of its professionals to be stranded in an international backwater. Structural change is needed in Australia's VALMIN Code to remove conflict with the latest International Valuation Standards. The mineral valuation standards developers of Australia, Canada and the United States should work jointly on updating VALMIN for global use.

Jan 1, 2003

By R. B. Berg

Montana sapphires were first discovered in alluvial deposits in the Helena area in 1865 and subsequently were discovered in other alluvial deposits in southwestern Montana and also in a lamprophyre dike at Yogo in central Montana. From about 1900 until the late 1930?s, when synthetic sapphire began to come into widespread industrial use, Montana sapphire mines produced large quantities mainly for watch bearings with lesser production for the gemstone market. The Yogo deposit is now mined for the gemstone market and two of the alluvial deposits are mined to produce sapphires for the fee-sieving of sapphire-bearing gravel and for the direct sale of gemstones. The generally pale-colored sapphires from the alluvial deposits in southwestern Montana are heated to enhance their colors whereas the generally blue sapphires from the Yogo deposit require no treatment. Markets for sapphires from both the alluvial deposits and the Yogo deposit are strong. In spite of reported historic production in excess of 70 tonnes, mineable resources appear to remain at most major deposits. Also abundant untested lamprophyre dikes in central Montana may host sapphires similar to those at the Yogo deposit.

Jan 1, 2009

By W. Baguley

There are many carbon-in-pulp and resin-in-pulp screening devices which are at present in use in the South African mining industry. Each one of these screens has been an improvement, from the very basic air cleaned and 'EPAC' types which were either circumferential or · diametrical launder screens, which were developed for C I P in the early 1980's, through to the more sophisticated LAP and Kambalda Screens. Each one of these screens not only increased the performance or throughput per square metre than its predecessor, but also addressed maintenance problems, wear, reliability and the ability to handle surge conditions, thereby preventing tank overflow. However, very little theory has been presented concerning, the flow of pulp through internal screens, carbon loss and screen wear rates. Almost all this information is based on empirical data. The NKM screen continued this trend and was able to offer flow rates in excess of 180 cubic metres per square metre of screen per hour and an average screen life of approximately six months. However, with increasing sophistication of the screen and the use of wedge wire as opposed to the normal woven wire, the mass was significantly increased and costs began to mount. Therefore, Mixtec undertook to develop a radically different screen, which incorporated many of the advantages of .the existing equipment and combined a few of its own.

Jan 1, 1992