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By Alan G. Mayton, Jon C. Volkwein

The U.S. Department of the Interior, Bureau of Mines, in cooperation with an American firm, has been contributing toward the creation of a new highwall mining system for extracting coal in active, unreclaimed contour strip mines in the United States. The prototype system features the computer-based, remote control, video operation of a thin-seam continuous miner. Haulage is accomplished remotely also with a 76-m (250-ft) long multiple-unit continuous haulage (MUCH) conveyor system on rubber-tire vehicles. One aspect of this multi-faceted effort has been to design a ventilation system for removing dust generated at the face during the extraction process. The remote mining system eliminates the need for personnel in the mined workings. Ventilation is required to remove visible dust from the area inby two video cameras. These cameras are located approximately 6 m (20 ft) from the face, one on either side of a modified Jeffrey 102HP continuous miner. Removing the dust from this area provides the remote operator with constant visual monitoring of coal extraction at the face and thus, insures the effective operation of the mining system. A ventilation system was designed for use in a mine opening with a maximum cross-sectional area of roughly 4 sq m (44 sq ft) excluding the mining machinery. This paper describes the ventilation system and discusses how it was developed in view of the constraints imposed by the mining equipment, mining conditions, and the extraction process.

Jan 1, 1989

By P. Somasundaran

Flotation of oxide minerals is controlled by a number of factors, such as surface potential and solubility of the mineral, concentration and type of various inorganics, properties of the collector, pH, ionic strength and temperature. The role these factors play depends on the mechanisms of adsorption of the collector inorganics or polymer additives. The major mechanisms include electrostatic interactions, chemical adsorption, chain-chain interaction between adsorbed collector species and modifications of the surface by inorganics. In real systems, flotation is, however, markedly affected by various other processes, including aging of the minerals, surface precipitation of the collector on the mineral and associative interactions between various collector species leading to highly surface active, for example, ionomolecular complexes. These effects are reviewed here with selected examples.

Jan 1, 1999

By Andrzej Luszczkiewicz, Kazimierz S. Sztaba

Flotation tailing of Polish copper sulfide ores represents more than 90% of the mass of run-of-mine ore. The tailing contains mainly quartz, dolomite, clay minerals, traces of sulfides, and some accessory minerals. Almost all minerals of the tailing are well liberated and, therefore, any further beneficiation process applied to the tailing is expected to be inexpensive. In this work, results of investigations on utilization of flotation tailing using classification and gravity concentration are presented. It is shown that due to classification of flotation tailing in hydrocyclones, the coarse fraction becomes suitable material for gravity separation providing backfill material for underground mines as well as heavy minerals, a source of valuable rare elements. It was also found that heavy minerals separated by gravity methods contain a significant amount of rare elements such as zirconium, titanium, silver, rare earth metals, and uranium. The light fraction of the gravity separation contains well deslimed quartz particles and meets strict requirements for hydraulic filling material ked for structural support in underground mines. Evaluation of the cost of the proposed technology indicated that investment to implement the method would provide a return within 2-4 years.

Jan 1, 1995

By J. Hallowell, M. Conley, R. Cook

Inflatable friction rock bolts (IFRBs) are often considered temporary ground support due to their susceptibility to weakening from corrosion. The effective service life of an IFRB can be difficult to estimate due to the multitude of factors that affect the rate of corrosion. Some mine sites have experienced several-year-long service lives of IFRBs without issue, while others experience corrosion-related falls of ground only weeks after installation. The most common industry method of assessing bolt performance is by pull testing the fixture. However, due to the IFRB’s ability to mobilize its full tensile capacity with less than 2 feet of anchored length, corrosion along the bolt at depths greater than 2 feet from the collar cannot be identified using this approach. Alternatively, reinflation testing is a simple and non-destructive method of evaluating the condition of an entire bolt length for breaches in the bolt wall. This can be particularly useful when assessing the extent of corrosive conditions within a particular mining area where instabilities have already occurred and the condition of nearby bolts is unknown, or when re-entering historic mine workings which have not been monitored.

Feb 1, 2023

By M. N. Brodie

The paper examines the requirements for electric power used in concentration and dewatering circuits, the effects of plant capacity and process type, the restraints imposed by the primary supply and applicable codes and outlines the procedure by which effective design is carried out.

Jan 1, 1986

By M. S. Riyaz Ulla

The Hutti Greenstone belt, located in the northern side of Dharwar Craton, India, contains several promising gold fields. It is predominantly composed of meta-volcanics with minor intercalations of meta-sedimentaries. Alkali-SiO2 and Zr-P2O5 diagrams, immobile element trends, and an iron-rich trend on the AFM diagram indicate that the volcanic suite is low-potassium tholeiitic basalt. The lower Mg number, MgO-TiO2, MgO-Ni, and Ni-Zr plots reveal that the basalt was derived from a fractionated, highly evolved magma generated by 10-20% melting of the mantle at 1100°C and 5 kb pressure. The chemical variations suggest that the Hutti metabasalt represents volcanic arc rocks generated at a converging plate margin.

Jan 1, 1993

By I. J. Jansen, C. L. Hooks

Successful soil construction involves prepa¬ration of an adequate base, selection of high quality soil ma¬terials, and placement of those materials by means which will establish a continuous macropore network and modest to low soil strength. Where such has been accomplished, experi¬ments reveal row crop productivity on reclaimed land which is very competitive with that on undisturbed land. Inferior productivity and sensitivity to drought stress are experienced where the soils are excessively compacted during construc¬tion. Some deep tillage practices have been quite successful in improving the compacted soils, but it is preferable to avoid compaction as the soil materials are handled.

Jan 1, 1987

By Tom McDonald

Test work and plant operation confirmed that semiautogenous (SAG) milling is a viable option for Inco's milling rationalization project at Sudbury only if pebble crushing is included. Throughput increases more than 50% with pebble crushing incorporated into the comminution process. The finer product of high-speed pebble crushing provides further energy savings. The unconventional approach of pumping the pebble crusher product, while simplifying plant layout, has produced challenging wear problems. Inco Ltd.'s Sudbury operations are located in northeastern Ontario, Canada, about 400 km (250 miles) north of Toronto. Inco has 11 operating mines around the rim of the Sudbury basin. The mines currently produce about 11 Mt/a (12 million stpy) of ore. This ore contains pentlandite, pyrrhotite and chalcopyrite in mafic host rocks. The milling facilities are designed to produce 108.8 kt/a (240 million lbs/ year) of nickel as concentrate. This concentrate is further processed through Inco's smelting and refining facilities to produce nickel, copper and several other metals. Before 1991, -200 mm (-8 in.) ore was shipped to two primary mills. The Clarabelle mill had a design capacity of 29 kt/d (32,000 stpd). Frood-Stobie had a capacity of 16.3 kt/d (18,000 stpd). The flowsheets of these mills were similar. Two stages of open-circuit crushing were followed by rod milling and closed-circuit ball milling. The product from the comminution circuit, at 12% +250 mm (+65 mesh), was first passed through magnetic separators to recover magnetic pyrrhotite. It was then sent through a four-stage flotation process. The first two stages produced a high-grade copper-nickel concentrate. The final two scavenger stages produced a low-grade copper-nickel concentrate containing nonmagnetic pyrrhotite.

Jan 1, 1992

By Hisakazu Matsushita

1. Introduction This is a report on applications of the earth pressure type balanced shield tunneling projects executed under narrow streets on soft alluvial layers in Japan. Japan is a long island country surrounded by the sea. Steep mountain ranges run along the archipelago and numerous rivers originate from the mountains, leaving only limited areas of flat land along the upper and middle reaches of the streams. The majority of cities in Japan are on soft alluvial layers. Alluvium represents an extremely complex soil formation, sections bordering diluvium being characterized by sharp undulations. Various difficulties are therefore encountered in shield tunneling work undertaken in such ground conditions. Particularly, at work sites lying in an unstable, waterbearing layer with high permeability, shield excavation becomes utterly impossible, hampered by large amounts of underground water as well as land collapsing caused by the water. Even when work can somehow be accomplished by using chemical grouting or by lowering ground water level, which require extra expenses and time, undesirable effects such as ground surface settlement are unavoidable in projects undertaken in the past. The newly developed method allows safe and accurate tunnel excavation at normal speed and without giving any adverse effects on buildings above, even under such unstable ground conditions. An outline of this new method was announced at the "International Tunnel Symposium '78" held in Tokyo, and the method has since been employed in a number of tunneling projects in this country. This report provides further data on the new method with reference to some of those projects, explaining how it allows tunnel excavation with

Jan 1, 1979

By M. H. Foroughi

In this paper, the compressive strengths, failure modes and acoustic emission behaviors of cubic coal specimens containing bedding planes at various inclinations are considered. Test results showed that the compressive strengths and the modes of failure of coal specimens depend on the inclination of the bedding planes. From the acoustic emission (AE) measurements, the count rate detected through a low-pass window (AE (L)) was compared with that through a high-pass window (AE (H)) in each test. The results of accumulated AE history were compared with AE signatures of others. It is shown that the AE signature of coal depends on the inclination of the bedding planes, and the AE signatures can be classified into three groups. Each group corresponds to a particular mode of failure, namely, slip on the bedding planes, fracture across the bedding planes and fracture extension through the bedding planes. The parameter r, defined as the ratio of AE (L)/ [AE (L) + AE (H)], is plotted against the stress for each test. Test results showed that r also depends upon the inclination of the bedding planes.

Jan 1, 1999

By S. A. Shuey, E. E. Vidal, P. R. Taylor

The complex chemical make-up of electronic waste as well as the variability of feed material from post-consumer sources requires resilient processing systems that are able to handle a range of material without adversely effecting production. Several of the successful processes that are being operated by a number of large-scale metal producers are reviewed in this paper. This review outlines the processing path and final disposition of many of the important individual elemental components. Determining the chemical characteristics of processes is required to understand both metal recovery possibilities and controlling the fate of minor elements. The behavior of both the organic and metallic fractions of electronic waste during processing is evaluated thermodynamically and general conclusions are given. I

Jan 1, 2006

By Yuchen Wu, Purushotham Thkkaraja, Marek Borowski, Jie Liu, Jianwei Cheng, WANCHENG ZHENG, Yu Wang, Weidong Lu, Gang Zhao, Zhanyou Sa, Huan Yang, Yuhang Wu, Hui Wang

The abstract discusses the importance of gas drainage in coal mines for safety, environmental protection, and resource utilization. It highlights the significance of borehole sealing technology for efficient gas drainage. The study introduces a new inorganic retarding sealing material and investigates its properties, including stability, thermal stability, fluidity, and thixotropy. The material's diffusion performance in cracks is tested using a self-designed system. Field tests in a coal mine demonstrate the material's effectiveness in improving borehole sealing compared to traditional materials.

May 1, 2022

By Jean E. Kiel, Rob Dorey, Dirk J. A. van Zyl

1.1 INTRODUCTION This chapter seeks to provide an overview of important factors involved in the implementation of heap leach technology as a vehicle for gold extraction from its ores. Toward this end, brief discussions of the various elements important to this process are presented here. Topics covered in this chapter include a brief history of the process; basic chemical reactions responsible for the process ; characteristics of ores amenable to heap leaching; location of the greatest concentration of heap leach projects in the U.S.; heap leach components, methods, regulatory/permitting considerations; and economic considerations. Most of these subjects are treated at much greater length in subsequent chapters. Thus, this chapter serves as a summary for those which follow, in addition to providing the reader with a feeling for those topics which may be of most immediate interest. 1.1.1 History of the Process Modern Day Precious metal heap leaching technology has developed over the past decade, although the principles of heap leaching per se, as well as those of gold extraction through cyanidation have a long history (see discussion below). However, it is in the past 10 years that heap leaching has developed into an efficient method of treating oxidized gold and silver ores. It has proven to be both an efficient way to extract precious metals from small, shallow deposits, as well as an attractive way to treat large, low- grade, disseminated deposits. Heap leaching has several advantages compared to conventional milling (i .e., crushing, grinding, and agitation leaching). In general, these advantages include simplicity, lower capital and operating costs, shorter start-up times, and less intensive environmental regulatory concerns. A possible disadvantage of currently existing heap leach technology is a potentially lower percentage of metal extraction being obtained from the ore than would be the case with conventional milling (Potter, 1981; Hiskey, 1985; and Thorstad, 1987) The actual principle of heap leaching has a long history as inferred previously. For example, mines in Hungary recycled copper-bearing solutions through waste heaps in the mid-sixteenth century (Hiskey, 1985), and Spanish miners percolated acid solutions through large heaps of oxide copper ore on the banks of the Rio Tinto around 1752. By 1900, leaching operations were employing such techniques as leach/rest cycles to maximize copper recovery (Taylor and Whelan, 1942; Thorstad, 1987). Copper dump leaching is currently

Jan 1, 1988

By J. C. Yingling, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Much of the land reclaimed since enactment of the 1977 Surface Mining Control and Reclamation Act is overcompacted. Research has shown that excessive compaction in replaced growing media is detrimental to the establishment of trees. If trees are to be grown on reclaimed surface mined sites, something must be done to alleviate this excessive compaction. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed growing media. The University of Kentucky developed test cells on reclaimed areas at a surface mine in eastern Kentucky to determine the impact of tillage (ripping) on soil compaction and tree survival rate. The ripping methods being evaluated include shallow tillage using conventional farm equipment and deep tillage using a dozer with a ripping arm. Each test cell was planted with various species of trees, and for the first two years of tree growth, data were collected at these test cells for soil dry bulk density, penetration depth and resistance, and survival rate of trees. These data were statistically correlated to determine how ripping affects the relationship between soil compaction and tree survival rate.

Jan 1, 2003

By Thomas M. Hanna, John W. Anthony, Lee C. Atkinson

Ground water can pose major engineering and environmental problems to the new generation of large, deep gold mines currently being developed throughout the world. It is important that the potential magnitude of these problems be assessed early in the planning of such projects and that any necessary dewatering and environmental remediation programs be designed at least preliminarily in the feasibility stage. The assessment should begin with acquisition of hydrogeologic data during exploration drilling and be followed by carefully designed and analyzed aquifer tests. Once a sufficiently detailed conceptual hydrogeologic model has been defined, state-of-the-art numerical models should be used to estimate ground-water inflows to proposed pits and underground openings, to design and evaluate the potential effects of various dewatering schemes, to define specific environmental impacts, and to predict pore pressures in highwalls relative to slope stability. The modeling results will indicate which method(s) of dewatering will be most effective both technically and economically. If wells are used, it is imperative that they be as hydraulically efficient as possible. There are new methods of drilling and completing dewatering wells that can help assure maximum efficiency.

Jan 1, 1989

By T. Freeman

In the past ten years, the Geotechnical Baseline Report (GBR) has arguably become the key document for tunnel construction. This report not only allocates much of the risk involved with the work, it serves as the basis for bid preparation and is used extensively in resolving disputes during construction. This paper discusses some important issues related to the GBR and presents suggestions for improving these vital reports.

By D. F. McCarthy

INTRODUCTION Mined underground chambers specifically designed for the purpose of storing liquefied petroleum gas (LPG) at ambient temperatures have been in use for over thirty years. The first caverns were developed by Warren Petroleum of Tulsa, Oklahoma, in 1948, for its plants in Texas. The basic concept of an LPG-storage cavern is to create a space in an impervious formation at a depth sufficiently below the water table so that if any movement of fluid occurs the ground water will enter rather than the gas escape from the cavern. In the past, the primary reason for LPG storage underground has been its attractive cost advantages over steel storage on the surface. At current prices the cost of storing 7.949 ML (50,000 barrels) would be equivalent, whether stored on the surface or underground; whereas 79.494 ML (500,000 barrels) of storage underground costs only one-fifth of surface storage. It is usually uneconomical to excavate less than 79.494 cu m (50,000 barrels) of storage space. The fixed costs - engineering, mainshaft and ventilation shaft - are a substantial part of the total cost, whereas the incremental costs for excavating additional storage are relatively low. Recent concern over the hazards posed by the handling and storage of LPG and liquefied natural gas (LNG) has led to a new interest in the underground storage of these gases. Underground storage offers the following advantages: safety, security, low initial cost, low maintenance cost, operating, cost, minimum land require-

Jan 1, 1981

By Jon T. Langstaff

The microseismic method of detecting instability and high-stress zones in underground mines was first developed in this country by the US Bureau of Mines in the early 1940's (Obert and Duvall, 1957). Early laboratory experiments showed that when competent rocks are stressed in a testing machine, the rock noise rate (number of rock noises per unit time) increases with increasing applied stress. This increase is more pronounced as the ultimate strength of the rock is approached. Subsequent testing of rock noises in underground mines confirmed this laboratory experience and much effort has been directed in recent years to make use of this property to develop a practical method of predicting rock failure. Investigations conducted in the Coeur d'Alene district mines have pointed out a definite relationship between the stress buildup in a rock mass caused by mining activity and the emission of audible and subaudible seismic activity (microseisms). In 1968, a concentrated joint effort by USBM Denver Mining Research Center and American Smelting and Refining Co. at Asarco's Galena mine was undertaken to verify several theories regarding the generation of microseisms (Blake, 1971; Blake, Leighton, and Duvall, 1974; and Kovacs, 1973). Findings indicate that (1) rocks under stress emit detectable seismic energy; (2) the energy source can be located using a triangulation method involving travel time differences to various receiving stations; (3) the rate of release of seismic energy increases with increasing stress; and (4) this increase in noise generally precedes a major rock failure (rock burst).

Jan 1, 1979

By Muhammet Mustafa Kahraman

Despite technological advancements and organizational adjustments, lost time accidents are major issues in occupational safety. However, there is very limited work that focuses on variables influencing days lost as a result of occupational accidents. In this study, decision tree and artificial neural network methods were used as machine learning techniques to investigate the impact of factors on accident lost day duration. Degree of injury, worker age, and worker activity were found to be the top three variables impacting loss of time from work. It was also identified that the mining method, location, and nature of injury had a moderate influence on duration lost due to occupational accidents. However, worker experience and ore type did not have any significant impact on the duration, which is an unexpected result. These results confirmed that some accident factors that might have a large influence on the number of mine accidents can be less critical when it comes to accident lost day duration.

Feb 3, 2021

By M. S. Safarzadeh

Over the last fifty years, the treatment of enargite concentrates has not received much attention primarily because of the availability of other clean concentrates suitable for processing with existing smelting and/or leaching technologies. As traditional copper ores have become scarcer, copper-arsenic ore deposits have garnered more interest. Arsenic release is a significant concern during the treatment of enargite by pyro or hydrometallurgical methods. Enargite is also very refractive in standard leaching procedures. Thus, economical treatment options for enargite concentrates are needed. Preliminary experiments have shown that the acid-bake leach process could be adapted and used for the treatment of enargite concentrates. In this study, low-temperature (100-400 ºC) sulfuric acid baking of an enargite concentrate followed by water-leaching has been evaluated. The results indicate the thermal transformation of enargite to copper sulfate during sulfuric acid baking, with most of the arsenic being released from the concentrate into the gas phase for baking at 400 ºC. The condition for maximum copper extraction (~100%) from the concentrate was found to be 400 ºC, sulfuric acid amount of 0.5 mL/g of concentrate, and 2 h baking time. Part of the arsenic was captured in the form of arsenopyrite (FeAsS). XRD analysis proved the presence of some arsenic in the form of claudetite (As2O3) in the baked concentrate. Acid baking of pure enargite behaved in similar fashion.

Jan 1, 2012