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By S. Hartwig, K. Wohiwend, J. Forsberg, G. Bergling

New, larger cutters requiring higher operating loads and thus increased cutterhead thrust, higher cut¬terhead speeds and more pronounced demands of maintaining high penetration rates also in mixed ground, constantly augment the loads on TBM main bearings. At the same time, the demand of a single TBM model covering a wide diameter range limits the available space for the main bearing at the smaller end. Innovative concepts and advanced methods of calculating bearing loads and lifetimes are needed to meet the demands which TBM suppliers and their customers face. This paper reviews different design approaches and covers the influence of lubrication on bearing life and condition monitoring as well.

Jan 1, 1995

By Daniel A. Wasson

A review of the history of boosters is given with examples of the prominent types that have been made commercially. The performance and design features of protected core boosters are discussed in detail. A new gel booster is discussed with its advantages to the mining industry. Booster size, hole configuration, performance and safety aspects are reviewed. Important features of boostering in above ground and underground blasting are related to an economic analysis. This presentation will cover different types of boosters commonly used in mining. However, for the purpose of this paper a few terms need to be defined to clarify the action of different parts of a priming system. Booster* - "Any unit of explosive or blasting agent to be used in a charged hole for the purpose of perpetuating or intensifying the initial detonation". Primer* - "A unit, package or cartridge' of explosives containing a detonator or detonating cord which is used to transmit detonation to other explosives or blasting agents". Detonator - A device for initiating a detonation from a flame or a small electric current, the former being represented by a fuse cap and the latter an electric blasting cap.

Jan 1, 1981

By Richard A. Bideaux

Using computer applications to solve mining problems began in the early 1960s, utilizing the large (for that day) centralized computing facilities at a few universities and major mining company headquarters. Many years passed before technology was adequate to allow any of those applications to be run at the mine sites to provide immediately available solutions. One of the first mining applications attempted was for ore reserve analysis and long- to medium-range mine planning. As these are among the most frequent and familiar minicomputer applications at the mine site, it is interesting to follow the evolution of computing and communications hardware which has finally allowed effective transfer of this technology.

Jan 11, 1981

By M. Karmis

Subsidence planning and control must be an integral part of mine design in order to minimize the economic impact of underground mining on the surface. Pre-calculation of surface deformations which may cause damage to surface structures must be performed and dam-age criteria must be established, if the response of structures to such movements is to be determined and the extent of damages to be assessed. In this paper the Surface Deformation Prediction System (S.D.P.S.), which can be used to predict accurately the vertical and horizontal parameters of surface movements due to underground mining, is discussed. The Subsidence Response Modeling Program (S.R.M.P.). which can be applied to evaluate the response of buildings to subsidence-induced movements, is also reviewed. Finally, an example is presented demonstrating the applicability of these techniques for subsidence design and control.

Jan 1, 1990

By Robert A. Jankowski, Ellsworth R. Spencer, Jay F. Colinet

Longwall mining is the most productive method of under- ground coal mining in the United States (US.), and record levels of production have been reached in recent years. These ever-improving production levels have the potential to generate significantly higher quantities of respirable dust. Consequently, the longwall industry continues to struggle with controlling dust liberation and maintaining compliance with the federally-mandated respirable dust standard. In response, longwall operators have in- creased the application of primary dust controls, airflow and water flow, in an effort to improve respirable dust control and reduce worker exposure. Pittsburgh Research Center (PRC) personnel conducted dust surveys at 13 longwalls operating throughout the U.S. and collected information to: identify current operating practices on these longwalls, identify the types of dust controls in use, document the levels at which these controls are being applied, and measure the respirable dust levels present. This data was analyzed to quantify the dust levels generated by the major sources on the longwall section and to evaluate the relative effectiveness of the control technologies in use.

Jan 1, 1997

By G. R. O?Neil

The justification for a "ligand- selective' approach to fine mineral beneficiation via flocculation is established initially. Special emphasis is placed upon the need to identify non-selective, interfering and complicating adsorption effects. Specific strategies directed towards the design and synthesis of complementary selective flocculants are detailed using a number of different polymers and chelating agents as examples. In this regard, the affinity of polymer-bound ligands for metallic cations, ligand concentration, possible modes of attachment, the application of spaced-out ligands and other considerations in the preparation of selective flocculants are highlighted.

Jan 1, 1983

By L. L. Oriard

There are certain site-specific geological and physical features of a rock mass which control its behavior under the dynamic stresses induced by the action of explosives. It is essential that blasting technology be adapted specifically to those features. There does not exist a single, simple "right" way for each type of blasting operation, but rather each operation must be custom-designed for each site. When this is done, it is often possible to produce unusual but highly desirable end resglts, such as undisturbed narrow rock walls, monoliths and square benches. Although the techniques illustrated here were developed specifically for "sculpture blasting", the geomechanics principles would apply to other types of blasting control, both large-scale and small-scale. Because the techniques are designed more for the purpose of modifying the site responses which would ordinarily be expected than they are to developing new "blasting formulae?, the name "Modified Site Response Blasting" will be used.

Jan 1, 1984

By D. Sinha

Mine investment decisions involve both objective and subjective criteria. The subjective criteria are efficiently decided by interaction with company experts. The Expert System approach can incorporate knowledge of experts and interact with conventional computer programs on mine evaluation. Artificial intelligence offers considerable opportunities in comprehensive mine investment decision making process.

Jan 1, 1998

By S. P. Singh

In order to understand the intricate nature of blast damage mechanism and to counter the associated problems, small scale blasting experiments were performed on hydrostone, concrete and granite. This was followed by a 2.4 m x 2.7 m (8'x 9') drifting operation in a quartzite quarry. Interior as well as exterior damage was assessed by different techniques. On the basis of the experimental results, the effect of explosive characteristics on the damage was examined.

Jan 1, 1992

By F. W. Bond

Predictive ground-water modeling is currently being applied to a wide range of engineering applications. In recent years models have been used to evaluate the effect of large ground-water withdrawals on regional water supplies; subsidence associated with overpumping; siting and design studies for chemical dumps; siting and safety aspects of nuclear waste storage; and heavy metal migration from disposal sites. Similar modeling techniques could be used to analyze water-related problems in the minerals industry such as mine dewatering (both open pit and underground), environmental and pollution control, and process water supply and disposal The objective of this discussion is to describe how ground-water models are being used to assist in the solution of water-related problems outside the industry and to extrapolate that use to mining problems.

Jan 1, 1980

By L. Xia, B. Hart, V. Sidorkiewicz

Sodium silicate(s), also known as “water glass”, are one of the oldest and most widely used industrial chemicals. Its first use in North American mining operations can be traced back to around 1925, which coincided with early use of xanthates in mineral flotation. Silicate functions as a sulphide and non-sulphide gangue mineral dispersant, depressant and modifying reagent in grinding and flotation operations. It is believed that soluble sodium silicate promotes selectivity of value added sulphides against gangue minerals, resulting in both grade and recovery improvement. This paper seeks to link improved grade/recovery to the interaction characteristics of minerals and the sodium silicate. A systematic study was performed with individual mineral species, an artificially designed model ore and the feed ore from a copper metallurgical operation. The function of sodium silicate was evaluated in the context of colloidal chemistry and linked to mineral surface chemistry. Measurement of pulp rheology and mineral zeta potential identified that sodium silicate works as a dispersant. The dispersion is accomplished by increasing a mineral’s net surface charge, resulting in a mineral variable change in viscosity. Bench scale laboratory flotation tests suggest that better dispersion leads to a diminished interaction of chalcopyrite with gangue. The improved Cu grade and recovery then are likely in response to an increased accessibility to collector along with a linked increase in particle bubble attachment resulting in better separation efficiency. ToF-SIMS surface chemical analysis of the flotation samples found a higher proportion of sodium silicate on minerals from the flotation tailings relative to the concentrates. Moreover, attachment of sodium silicate appears to be mineral specific; the data indicates that sodium silicate favours the surface of gangue phases over the value sulphides. INTRODUCTION Mineral processing involves enrichment of valuable minerals from an ore, where the separation process utilizes differences between the properties of the value-added and gangue minerals. The properties of minerals, for example composition, specific gravity, particle size, magnetic properties etc., in any flotation feed ore, can vary significantly between the various minerals present. In flotation seperation surface chemistry and wettability is a significant component promoting selective separation of the various mineral phases [1,2] Mineral surface wettability can be changed, advantageously or deleteriously, by many factors including: surface layer alteration through oxidation; galvanic interactions; attachment of secondary precipitates; the adsorption of various reagents [3] In the flotation context the wettability of a minerals surface can be manipulated by various reagents. Collector reagents may selectively attach to specific minerals in the mineral/water slurry enhancing their surface hydrophobicity, increasing bubble-attachment efficiency and improve flotation kinetics and mineral recovery [4]. In contrast, depressant reagents may selectively reduce a minerals surface hydrophobicity resulting in poor particle-bubble attachment and non flotation. In essence, a mineral flotation flow sheet is designed to induce/promote a hydrophobic surface to the value mineral and a hydrophilic surface to all others. Therefore, the versatility of the froth flotation process lies in the selection of different flotation reagents.

Jan 1, 2019

By B. J. Arnold, F. F. Aplan

Prior laboratory work has demonstrated that much of the fine ash forming minerals entering a flotation froth are there as a result of water carryover- from the bulk contents of the flotation cell (Arnold and Aplan, 1986a). Using a bank of four 8.5 m3 (300 cu ft) Wemco flotation cells cleaning a well-liberated Lower Kittanning seam coal, test results show that the sulfur and ash content of the froth is directly related to the water content of the froth (or inversely related to the percent solids in the froth). Reagent changes that result in a watery froth produce a higher ash content in the froth. A direct comparison of laboratory and plant results show that the standard laboratory flotation test produces a product higher in sulfur and ash than that produced in the plant. Caution should be exercised when extrapolating laboratory test results to the plant situation. A method of estimating coal flotation product quality in the plant based on laboratory tests is given.

Jan 1, 1991

By Bo Kyung Sim, Dae Young Kim, Jae Won Lee, Ebrahim Farrokh

"The contract C931 of the downtown line 3 (DTL3) mass rapid transit system of Singapore includes half a kilometer twin tunnels running between Mattar and Macpherson stations. An EPB TBM of 6.6 m diameter was used to excavate both of these tunnels. The tunnels pass predominantly through a very stiff silty/clayey fine to coarse sand from the Old Alluvium Formation. In this paper, TBM selection procedure, TBM performance evaluation, and some of the tunneling operation challenges with the TBM in the Old Alluvium Formation are discussed. In this regard, soil conditioning trial tests were performed to resolve the clogging issue and low TBM performance. Thorough TBM operational data analysis was performed to detect high soil abrasivity, backfill grout leakage, and foam nozzle clogging. The results of some of the applied modifications are also discussed to show their effects on the TBM performance improvement. Finally, some of the challenging TBM design specifications are also discussed. INTRODUCTION Tunneling and underground construction in Singapore has been increased in the last 30 years due to the demand for public transportation systems and the limited space above the ground for the infrastructure development. Downtown Line Stage 3 (DTL3) Mass Rapid Transit (MRT) system has 21 km total route length and consists of 16 stations. DTL3 Contract C931 runs between Mattar station and MacPherson station. The construction works in this contract include twin bored tunnels of 6.6 m diameter and 450 m length and a TBM launch shaft of nearly 30 m depth. The tunnels run in urban area below Kallang Paya Lebar Expressway tunnel (KPE), Kallang River Canal, and Circuit Link. Figure 1 shows the alignment of the tunnels in between two subway stations. The tunnels were excavated by an earth pressure balance (EPB) tunnel boring machine (TBM) through the Old Alluvium (OA) formation, a challenging geological formation in the sense of its abrasivity and stiffness. The Old Alluvium Formation mostly includes stiff to very stiff clayey and silty sand. The soil is un-weathered cemented to semi-cemented dense, mainly with a low permeability coefficient of 10-7 m/s and high SPT values (almost 100). The soil is classified as “very high abrasive” according to NTNU SAT test classification (SAT value of 15 to 42). The construction of the first tunnel drive was slowed down due to a number of factors related to soil conditioning and TBM operation. In this regard, a thorough analysis of the TBM operational parameters from the excavated sections was performed to identify the problems in time to prevent unwanted construction delays in the subsequent sections. In the following sections, a brief overview of the criteria used for TBM selection is presented at first. Then, the results from the analyses and tests performed to assess soil conditioning, grout leakage, and soil abrasion are presented. The last section discusses some of the tunneling design features that challenged the TBM operation in this project."

Jan 1, 2016

By D. E. Healy

In 1989 an Autogenous Grinding Task Force was formed to study potential autogenous grinding circuits to replace the existing semi-autogenous grinding at the National Steel Pellet Plant located in Keewatin, Minnesota. Pilot plant test work performed by the Hanna Research Center (HRC) indicated that fully autogenous grinding with pebble extraction and crushing could feasibly be incorporated into the existing circuits. In 1990, one of the existing ten grinding mills was converted for an in-plant test incorporating pebble crushing. The full scale test work conducted in 1990 and 1991 verified the pilot plant projections with primary mill throughputs from the fully autogenous circuit utilizing pebble crushing being greater than throughput of the existing SAG mill circuits.

Jan 1, 1992

By Paul Hewitt, Tim Smirnoff

Design and construction of the Epping to Chatswood Rail Line tunnels in Sydney, Australia required an innovative approach to define hydrogeological properties of the Sydney Hawkesbury Sandstone and provided an insight into the hydraulic behaviour of fractured sedimentary rocks. To meet restrictive water inflow and infiltration criteria both the pre-treatment of zones of fractured or highly jointed rock, and waterproofing using an interior spray on membrane for the finished drained tunnels and stations was required. Methods typically used to address the interaction of groundwater and tunnels in the Sydney Basin are demonstrated by case histories from major design-build tunnel projects.

Jan 1, 2005

By Tevfik Güyagüler

Airborne dust is one of the important environmental problems in mines. Besides conventional dust control methods, recently, extensive studies have been carried out on the elimination of dust before it has actually been formed. Determining to what extend rock characteristics influence the amount of dust produced during different mining activities are considered as a guide for this purpose. The factors analyzed in this study were main mechanical, physical properties and petrographical constituents, namely free and combined silica. In the study regression analysis techniques were applied to investigate the effectiveness of aforementioned factors. INTRODUCTION Nearly every aspect of mining activity contributes to the air pollution caused by dust. Therefore the harmfull effect of airborne dust has been investigated many years and limit dust concentration levels were determined for various types of mine dust. To keep the dust level below limit value different dust control techniques have been applied in mines. So far, the well known techniques regarding dust control focuses on reducing the amount of airborne dust. However, recently various studies have been carried out to avoid the dust before it has actually been formed (Bhaskar and Gong, 1991). In this respect, influence of rock characteristics on dust formation is regarded as a guide for this purpose. The present contribution describes such a study in which the drilling operation is considered as the source of the dust. In this study drilling and dust sampling process were undertaken in a model gallery that simulates an underground working. The mechanical and physical properties of the rock samples were measured in rock mechanics and ore dressing laboratories. Quartz and combined silica contents of the rock samples, on the other hand, were determined in the laboratories of geological engineenring department. Rock samples used in the research were different types of coal measure rocks, namely, sandstone, shale and conglomerate. The rock characteristics studied in this work are brittleness, toughness, rock strength, hardness and hardgrove index as inherent properties; free silica, and total silica contents of rock samples as petrographical constituents. Although there have been various studies to determine the effect of rock characteristics on the dust formation, still the type and extend of effectiveness have not been understood clearly. LITERATURE REVIEW Most of the studies investigating the effect of rock properties on dust formation concluded that they are effective. In such an investigation, it has been found that inherent rock properties influence dust formation (Das, 1973). In the another study, dustiness of the air was considered as a function of the composition, hardness and moisture content (Panov, 1967). It was also accepted that in a drilling operation more fine dust is produced if the rock to be drilled is hard (Skochinsky and Kamarov, 1969). In some other investigations dust production were considered as a function of hardgrove index (Moore and Bise, 1984) or formulated in terms of brittleness, toughness and hardness (Güyagüler, 1991). The effect of the petrographical properties of coal or rock on dust formation characteristics have also been studied (Baafi, 1979) (Panov, 1967). Because of its importance, various researches were conducted the study to find out the effect of free and combined silica content of dust on dust formation. In one of the study, the relationship between quartz in the coal seam and quartz in the airborne coal dust was investigated (Ramani et al, 1988).

Jan 1, 1993

By M. Fan, Z. Long

"This paper presents some studies on recovering valuable elements from Chinese coal by-products, including coal combustion fly ash, stone coal ash, and coal flotation tailings. Both commercialized technologies and economic potential recovery methods are described in this study. Magnetically stabilized air-dense medium fluidized bed separation, tribo-electrostatic separation, froth flotation, and hydrometallurgical methods are discussed in recovering various valuable elements in Chinese coal by-products from different coalfields. These valuable elements include iron, carbon, aluminum, rare earth elements, lithium, gallium, germanium, uranium, titanium, scandium, silicon, vanadium and phosphorus, etc. The ultimate goal is to fully utilize all valuable elements in coal by-product. Each component within coal by-product should be efficiently segregated to its highest value. INTRODUCTION Coal is mainly composed of energy-producing elements carbon and hydrogen. In addition to these elements, coal usually contains many other valuable elements, including iron, aluminum, silicon, rare earth elements, lithium, gallium, germanium, vanadium, uranium, titanium, scandium, and phosphorus, etc. These coal-associated elements are significantly enriched in coal combustion by-product fly ash because of majority of main components, carbon and hydrogen elements, being removed. Table 1 provides the chemical composition range of the main elements oxides in 12 Chinese fly ash samples collected from coal power plants located in Northeast China, Northwest China, Southwest China, and Southeast China. It can be seen from Table 1 that the major mineral components of different ashes are similar, but the bulk chemistry of different fly ashes may vary widely due to the changes of ratios of the mineral components in different coals. The major mineral components in various Chinese coal combustion fly ash are silicates, iron oxides, and unburned carbon."

Jan 1, 2017

By A. R. Wagner, E. Berkman

The use of high-resolution seismic surveys in coal exploration and mine development is becoming established as a standard technique in the industry. Their most significant contribution is in the effectiveness of reducing the number of core holes needed to understand the complex geological nature of coal by identifying geologic faults and mapping coal seam continuity and relative coal thickness. With these goals in mind, a high-resolution seismic survey was conducted in 1980 in the Wasatch Plateau coalfield of Utah. As a result of the success of this initial survey, numerous additional surveys have been performed over the past six years.. The interpretations of these subsequent surveys have led to the location of faults, fluvial channel sandstones, and coal thickness trends. This paper presents a review of high-resolution seismic technology as applied to coal exploration followed by three case histories, two of which illustrate the utility of the technique related to coal thickness determination and faulting and one that serves as an example of pitfalls in interpretation.

Jan 1, 1987

By Mark E. White, John H. McCowan, Michael C. Costello

Minproc Engineers has carried out the design construction and commissioning of thirty two process plants in the period 1978-87. Twenty eight are gold silver recovery plants, and of these twenty two were gold alone and six were gold and silver. In most plants carbon was used for gold adsorption. Desorption has been carried out using the USBM Homestake method, the Anglo American Research Laboratories method, and the Micron Methanol method. Electrowinning has utilised steel wool, stainless steel wool, and aluminium cathodes. Electrorefining using polished stainless steel cathodes is practised. This paper summarises the experience gained in these operations

Jan 1, 1987

By C. D. Hebert, T. Gregor, M. Ghazi, G. J. E. Kramer

This paper describes the recent application of gasketed, precast concrete segmental lining design that has improved tunneling productivity and quality. The speci?c segment arrangement includes: six-piece ring with equal 60 degree gasketed segments, juxtaposed key and counter-key segments, trapezoidal and parallelogram shaped segments, inclined and skewed radial joints and plastic circumferential joint connectors. This allows rapid, but accurate ring erection, reducing mine cycle times. The design avoids cruciform joints, minimizes potential gasket damage and eliminates the need for separate left and right ring molds. The implementation on the Los Angeles ECIS and NEIS sewer projects is described.

Jan 1, 2003