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By A. Wright

Gold Fields Mining Corporation is presently evaluating gold mineralization beneath thick, wet alluvium at the Chimney Creek Project, Nevada. Contamination of reverse circulation samples has been visually apparent since drilling began in the area. Tests have shown that, while contamination can affect assays, reverse circulation holes appear to define mineralized zones almost as well as the diamond drill holes. To improve reverse circulation sample integrity several techniques were tried including a stiff-mud injection system but with limited success. Diamond core drilling continues to be used in conjunction with reverse circulation drilling to further delineate the mineralization.

Jan 1, 1991

By Merline W. Van Dyke

The Surface Mining and Reclamation Act of 1977, PL 95-87 (The Act) granted the Office of Surface Mining (OSM) the duty of collecting fees from the active coal mining activities to be used in abating the hazards associated with abandoned coal mines. Since the passage of the Act, OSM has been instrumental in closing a multiple of mine hazards and in full cooperation with the states involved. Complete mine closures range from simply filling a subsidence hole to exodic designs costing thousands of dollars, such as in the case of the Portal Park swimming pool in Colorado Springs, Colorado. The Portal Park olympic sized swimming pool was built over an abandoned coal mine by a group of local citizens and given to the city of Colorado Springs. This pool receives the largest number of users each year. During the past four years, OSM has abated six mine related hazards in and around the pool. During the summer of 1982, the pool started tipping causing the pool waters to run out the west end. This pool tipping and the associated cave-in problems caused great concern to the city and the local users. This citizens concern generated a request from the city for OSM to assist in checking out the pool problems. Early in 1983, OSM initiated a driling program to investigate the subsurface voids. This drilling effort revealed several large voids within a few feet of the pool deck, with all voids inundated with ground water. Therefore, the void filling method favored the hydraulic backfilling needed to be confined to the area under the pool. This confining problem lead to the development of the gravel bulkhead cutoff walls to confine the backfilling effort to the areas under the swimming pool.

Jan 1, 1985

By Robert A. Pimentel

Dust is still a major problem in increasing production from longwall faces. Over the last decade, significant improvements have been made in the development of techniques for reducing dust exposure on conventional and continuous sections. But virtually no improvements have been made in dust control on longwall sections. It is true, that there are many more continuous mining sections than longwall sections in the United States and that the number of workers overexposed on continuous miner sections is much larger than the number on longwall sections. However, the problem on continuous miner sections appears much easier to solve and, in fact, we believe that the techniques are available to get virtually all continuous miner sections in compliance. The problems on longwall sections are much more elusive. Also, the number of longwall sections in the United States is expected to increase during the 1980's. Thus, dust control on longwall sections remains a formidable and important problem. Companies operating longwall sections with a dust problem are faced with the tasks of having to quantify the various dust sources, of selecting proper techniques to reduce the problem, of implementing the techniques and of evaluating their effectiveness.

Jan 1, 1983

By U. S. Sawant

During the last few years, Process Machinery Division, Rexnord, has conducted extensive research on the effects of cone crusher variables such as speed, throw and cavity design on the productivity of the crushers. Simultaneously, Rexnord's engineers have developed advanced design and testing techniques and criteria that assure efficient and reliable crusher designs. The combination of these two has resulted in a design of the 2390 Omnicone (1000 hp) crusher which fits on an existing 7 ft. Symons foundation and yet is capable of producing twice the tonnage compared to our 7 ft. super heavy duty (500 hp) crusher. Both speed and throw can be varied to give a wide application flexibility from making twice the tonnage to the finest product. The 2390 Omnicone also incorporates innovative features such as full balance, cavity clearing, adjusting under load with automation capability, maintenance-free seals, one head for all cavities, ease of maintenance and servicing, etc.

Jan 1, 1987

By S. C. Sun

Very little information is available concerning the magnetic properties of minerals and only recently has there been any attempt to correlate magnetic susceptibility with varying chemical composition1. The work described here covers a study of the relationship and chemical composition of both the rutile and sphene types of titanium minerals. The relationship between the magnetic susceptibility of three selected mineral specimens and the applied field strength is also presented. Experimental: The equipment and procedures used in this in- vestigation for crushing and cleaning the mineral specimens and for determining the magnetic susceptibilities were the same as that employed by Spokes and Mitchell1. The particle size of-the measured specimens was limited to 270/325 mesh.

Jan 1, 1959

By J. H. Fowler

Canada's gypsum industry began over two hundred years ago in the Maritime Provinces when farmers attempted to supplement their incomes by selling "land plaster" to traders bound for the United States. Rising from such humble beginnings, gypsum now contributes significantly to the economies of nine of Canada's ten provinces. Thirteen open-pit and three underground mines produced a total of 8.38 million tonnes of crude gypsum and seventeen processing plants manufactured 2.49 million tonnes of finished products in 1985. Recent economic growth in North America has resulted in steady increases in gypsum production, however, competition from foreign producers and by-product gypsum poses a growing threat to Canada's gypsum mining industry.

Jan 1, 1987

The Kinross DeLamar Mine has been operated for more than 17 years producing precious metals dore' from ores, principally silver bearing with associated gold co-products. In late 1995 a new orebody was commissioned, the Stone Cabin orebody, and the site began a phased shift from silver dominance to gold dominance in terms of precious metals revenue. The Knelson Concentrator was selected to remove gold from a portion of the cyclone underflow stream in the grinding circuit. This paper describes the development of the flow sheet, specific mineralogical impacts on Knelson product and downstream materials, and impacts on mine/mill grade reconciliation.

Jan 1, 1997

By Mogens Henriksen

In the past decade, numerous urge scale drilling projects have made use of reverse circulation air lift methods. Reverse air lift pumping can be established by injecting gas into a column of liquid; the subsequently decreased density of the gas-liquid mixture allows atmospheric pressure outside the lift conduit to establish flow. The rate of flow can be controlled by varying the gas to liquid ratio. A typical reverse circulation air lift system is depicted in Figure 1. Allen1 has described a number of reverse air lift drilling projects. Although cited examples are generally related to large diameter holes, the method has seen use in other applications such as sand dredging, chemical pumping, water well pumping and continuous coring. One particular benefit obtained with enclosed reverse circulation drilling is elimination of lost circulation. The required air/water ratio for pumping at a given submergence and lift has been established experimentally by Gibbs2. His data, however, do not reflect sensitivity of flowrate to air/water ratio. Further, in Gibbs' work, air apparently is injected continuously along the column of water. This configuration differs from that used in reverse air lift drilling where air is injected at discrete points only. Gas lift theory has received considerable attention over the past decades. Orldszewski3 defined flow regimes in two phase flow. Griffith and Wallis4 determined relative velocities of gas to liquid. Two-phase flow has been studied extensively for oil transport in inclined and vertical pipes by Chierici et a15, Beggs and Brill6, and Gould, Tek and Katz.7

Jan 1, 1977

By Baron Miya, Keith Hanks, William Edgerton, Francis Fong

The City of Los Angeles capital improvement program includes the construction of a new 35-km interceptor sewer. This sewer will be built as a deep tunnel with finished diameters ranging from 2- to- 4 meters. The project will be constructed concurrently in two phases; an 18-km East-West and a 17-km North-South segment. The new sewer provides additional conveyance capacity for an existing deteriorating sewer that is scheduled for rehabilitation. Large sewage spills during the El Niño storms of 1998 resulted in a Cease and Desist Order that established an aggressive schedule for the completion of the project.

Jan 1, 1999

By A. Tobey Yu

The smelter is the heart of a copper producing operation. Its principal function is to reduce and convert raw copper concentrates and/or leach plant precipitates into blister copper before it is refined. In addition to concentrates and precipitates, typical feed to a smelter also encompasses matte chips, flue dust, flux and lime. By nature, the characteristics of these materials are extremely variable, ranging from sub-micron to lumps, from slurry to dust, from abrasive to corrosive and free-flowing to adhesive. Furthermore, as a result of geological formation, most of the world's open pit copper mines are located in a semi-arid zone, where precipitation is minimal. This particular climate compounds the problem of handling these materials.

Jan 1, 1976

By D. L. Misterek, E. J. Slebir, G. W. Ring, M. A. Laird

INTRODUCTION In 1973, the Federal Highway Administration (FHWA) initiated a 10-year program of research on tunneling technology for future highways as a part of a larger Department of Transportation effort on tunnels. The objectives of the FHWA program are to: improve tunnel design technology, reduce costs, minimize adverse environmental impact due to construction, increase the rate of construction, and assure the maintenance of a safe and attractive tunnel environment. The program is divided into four research tasks designed to solve tunneling problems identified by the engineering and field offices of the FHWA. These tasks are as follows: 1. Cut-and-Cover Tunneling 2. Site Investigations 3. Ground Movements - Prediction and Control 4. Highway Environmental Criteria for Tunnels In order to provide input into Tasks 2 and 3, the FHWA is sponsoring an investigation and testing program by the U.S. Bureau of Reclamation to instrument and monitor two sites in the second bore of the Eisenhower Memorial Tunnel located on Interstate Highway 70 at Loveland Pass approximately 97 km (60 miles) west of Denver, Colorado. The tunnel will be approximately 14.0 m (46 ft) in diameter when excavated. The study is designed to generate data on: (1) changes in the state of stress, and movements during and after tunneling, (2) tunnel lining design requirements, (3) developing a

Jan 1, 1976

By Peter Hall

The need for large volume covered storage has increased drastically in the last ten years. Increased world demand for such products as thermal coal, potash, metallic concentrates, etc., availability of land for large open storage and environmental issues have brought about this need. This paper discusses briefly demand, environment, types of covered storage and the Alternative Storage System "Eurosilo", a proven system for storage of dry bulk mateials in units up to 100,000 m3.

Jan 1, 1982

By A. J. Neale

Much has been published lately about the application of advanced control strategies in the automatic control of autogenous and semi-autogenous grinding circuits. The application of adaptive control algorithms, self-tuning controllers, state estimation, and expert systems has been well documented. While these approaches can be very effective; experience has shown that quite often simply "fixing the fundamentals" can have a significant positive impact on overall grinding circuit performance. This paper will highlight the results of process optimization and process control work by the authors at a variety of autogenous and semi-autogenous installations. A review of one approach for quantifying the mill load/bearing pressure/power relationship is provided. Accurate monitoring of key mill process variables is a necessary prerequisite for both effective process analysis and process control. This paper discusses some of the concerns related to defining steady state operating conditions and the issues related to signal conditioning. The paper concludes with a discussion of an effective application of algorithmic constraint control which incorporates many of these considerations.

Jan 1, 1994

By Keros Cartwright

Distribution of temperature within the lithosphere can be significantly affected by the movement of ground water. Stallman (1960) presented the basic equation for the simultaneous transfer of heat and fluid in a porous medium and first used earth temperatures to determine aquifer permeability. Subsequently, studies of rock and soil temperatures were used to determine the flow of water through clay layers separating aquifers (Bredehoeft and Papadopulos, 1965; and Sorey, 1971), and to locate shallow aquifers (Cartwright, 1968; Birman, 1969). Cartwright (1968) showed that shallow aquifers maintain a nearly constant temperature throughout the year and that heat is exchanged between the aquifer and land surface. These temperature data also suggest that shallow aquifers hydrologically connected to surface-water systems have significantly greater effect on temperature distribution than aquifers in the deep artesian basins. Water wells developed in the shallow glacial and dolomite aquifers to depths of over 122 meters (400 feet) in northern and central Illinois produce water at temperatures very close to the mean annual air temperature. An analysis of the character of the rocks and soils suggests that the tem¬perature gradient should, and does, vary according to changes in thermal conductivity due to changes in lithology. This is because, under conditions of steady and uniform flow of heat from the earth's interior to the surface, a greater temperature gradient is required in poorly conductive rocks than in highly conductive rocks to transmit the same quantity of heat. Based on estimated values of thermal conduc-

Jan 1, 1972

By S. K. Kawatra

Under normal conditions, a significant amount of pyrite is recovered in the froth during flotation of high-sulfur coal. In order to reduce this pyrite recovery, it is first necessary to determine the primary recovery mechanism, as different measures are required for reducing entrainment, locked-particle flotation, or true hydrophobic flotation. In this paper, evidence is presented which suggests that hydrophobic flotation is not the major mechanism for recovery of liberated pyrite, and that the bulk of the recovered pyrite is there either as a result of simple entrainment or by being physically locked with floatable coal particles.

Jan 1, 1991

By C. L. Pillar

In many cases, substantial time may elapse between the exploration stage and a serious detailed planning stage which has the objective of putting a mineral property into production. This is always true where properties change ownership and new partners are brought in for joint venture situations. Such conditions make it imperative that the recording of complete and accurate geological data for the property is done during the active part of the exploration phase and accomplished by competent geologists and engineers. This work should not be left to helpers and technicians. Furthermore, it should not have to be redone years after the actual drilling was accomplished, when either those involved have parted company or those present have lost the touch and feel of their part of the exploration program and must rely on a memory sketchy in detail, at the best. All of this emphasizes the importance of thorough geological evaluation and reporting during the exploration program. To evaluate and comment on the application of geological data by a mine planning department, we must assume (1) that sufficient diamond drill holes have outlined the existence of a potentially economic ore deposit, and (2) that the next step is to obtain the required information to allow a detailed feasibility study. This paper will comment on: 1. what types of geological information are required, 2. how it can be obtained, and 3. comments on the application of this information by the mine planners.

Jan 1, 1973

By H. EI-shall

The conventional beneficiation scheme for Florida phosphates involves reverse flotation with an intermediatory acid scrubbing step. A single reagent flotation process, using fatty acids or amine as the collector, would eliminate the scrubbing step along with the other flotation step. This can not only simplify the process flowsheet, but also result in reduced reagent costs. The potential of single reagent flotation of Florida phosphates using fatty acids as the collector was examined in this study.

Jan 1, 1993

By Y. C. Lo

This paper presents the development of ultrasonic grinding technology for material and mineral processing. The principles underlying this new technology, as well as their implementation in two laboratory scale devices are described in detail. Ultrasonic grinding experiment results are discussed with respect to operating variables and the achieved product sizes. Special attention has been given to the electrical energy consumption of the grinder, and an attempt to compare its efficiency with tumbling mills has been made. A mechanical system capable of measuring the specific grinding energy is also described.

Jan 1, 1991

By R. Flores V.

The Refugio Project is located in the Andes mountains of northern Chile, in the Maricunga Hineral Belt. The Verde, Pancho and Guanaco Au ore bodies have been recognized and are Early Miocene in age. Mineralization consists of fine-grained disseminated gold hosted by dacitic to dioritic subvolcanic porphyries. Alteration comprises massive to veinlet-controlled silicification overprinted on earlier potassic and propylitic alteration and surrounded by later argillic alteration. Geologic relationships suggest that the Refugio ore bodies occur within an Early Tertiary volcano overlying Paleozoic and Mesozoic basement rocks. Geologic reserves at Refugio are approximately 300 million grams (9.7 million ounces) of gold. The Verde deposit contains 185 million tonnes of mineable and leachable ore with an average grade of 0.90 glt Au and is currently in the pre-construction stage after a positive feasibility study. Proven and probable mining reserves at Verde deposit are 101 million tonnes at an average grade of 1.02 glt gold. Additional potential exists at to other deposits within the Refugio property (Pancho and Guanaco) but no reserves have yet been defined due to the limited drilling to date.

Jan 1, 1994

By James D. Bennett

Relationships among mine and injured miner characteristics and HSAC's degrees of injury are examined for 91,404 injuries in under- ground bituminous coal mines in the United States from 1975 through 1982. Injury severity varies by the mining system, geographical region, circumstances surrounding the injury, the injured miner's age, whether the miner was using powered equipment, the year which the injury occurred, and the location in the mine where the injury happened. Injury severity is not related to the injured miner's total mining experience, job experience, and experience in the mine in which the injury occurred.

Jan 1, 1984