Search Documents

By Neil J. Dahmen, Howard J. Handewith

INTRODUCTION Tunneling machines were introduced into civil con¬struction in the 1800s, but their practical applications were not realized fully until the 1950s. As of 1977, tunneling machines were being used on most tunneling projects of substantial size. As in civil construction, the mining applications of tunneling machines have included long drives such as tunneling for long ore-body develop¬ment drifts, long haulage tunnels, longwall access drifts, and long crosscut developments. Tunneling machines ranging from 1.75-m (5.7-ft) to more than I1.0-m (36-ft) diam are available from several manufacturers; machines for mining applications generally have ranged between 1.75 and 6.0-m (5.7¬and 20.0-ft) diam. Tunneling machines usually operate at or near horizontal grades and are supported by a rail-haulage backup system. However, declines and inclines have been made using alternative backup equip¬ment. Either circular or shaped tunnels may be bored, depending upon the particular equipment used. Using tunneling machines to bore openings through rock offers several advantages over the use of the drilling and blasting technique. These advantages include a rapid advance, continuous operation, uniformity of the opening size, smooth walls, and safe working conditions. Compared to drilling and blasting, boring reduces the disturbance of adjacent rock, thereby reducing the ground-support requirements and the exposure to water inflows. The smooth walls provide natural arching and present minimum resistance to the flow of air. A tunneling machine should be considered a spe¬cialized mining tool that is well-suited to certain mining applications. Properly applied and sustained, a tunnel¬ing machine contributes to realizing substantial econo¬mies in the development of underground mines. All costs herein are expressed in 1977 US dollars, unless otherwise noted. The mention of trade names and manufacturers is not intended to imply an endorse¬ment of any specific equipment. TYPES OF TUNNELING MACHINES As listed in Table 1, five principal types of tunneling machines were being manufactured in 1977. Each type of machine offers a special solution to a specific mining problem. Although each of these types of machines is described herein, most of this chapter is devoted to the full-face rotary rock-tunneling machine that has demon¬strated the greatest production in both civil construction and mining applications. Full-Face Rotary Rock-Tunneling Machines As shown in Fig. 1, a full-face rotary rock-tunneling machine consists of a rotating head that is fitted with rock-cutting tools and is forced into the tunnel face. This head is supported by a bearing on a structural support member that, in turn, is held in place by a hydraulically positioned wall-gripping mechanism. Both torque and thrust are reacted from the cutterhead, through the structural support and gripper mechanism, and to the tunnel wall. The rock cuttings fall to the invert at the tunnel face, and they are removed by means of cutterhead buckets or scoops that transfer the cuttings to a conveyor belt. After advancing the cutter¬head through a preset boring stroke, the tunneling machine is advanced by hydraulically pulling the gripper mechanism in from the tunnel walls, stroking forward, and resetting the gripper to the new forward position on the wall; the machine then is set for the next advance stroke. Full-face machines cut only circular openings. Ma¬chines with diameters as small as 1.8 m (6 ft) and as large as 6.1 m (20 ft) have been used in mining applica¬tions, excavating rock with unconfined compressive strengths in excess of 276 000 kPa (40,000 psi). Although special machines have been designed to turn on a radius of 30 m (100 ft) in both horizontal and vertical directions, the conveyors and backup sup¬port equipment generally limit tunneling machines to turns with a radius of more than 60 m (200 ft). The full-face rotary rock-tunneling machines have provided the fastest and most reliable production of any mining method or machine. These machines can be equipped to place any of a variety of ground-support systems, and they can be provided as "open" machines, as shown in Fig. 1, or as "shielded" machines, as shown in Fig. 2. The open machines have the advantage of allowing the ground to be supported as near to the tunnel face as possible. The shielded machines have been designed principally to allow placing precast con¬crete segments. The shielded machines completely pro¬tect the equipment and personnel at the heading, but they are economically limited to permanent long-life haulageways where full lining is required. Partial-Face Rotary Rock-Tunneling Machines As shown in Fig. 3, the partial-face rotary tunneling machine is equipped with a cutterhead that rotates slowly at about 0.21 rad/s (2.0 rpm). The single-disk cutterhead produces the tunnel section shown in Fig. 4 by means of an oscillating motion. These machines work on the undercutting principle, and they are avail¬able in spring-line dimensional increments of 0.1 m (0.32 ft) from 1.5 to 2.1 m (5.0 to 7.0 ft); the vertical dimensions are 2.4 to 3.2 m (8.0 to 10.5 ft), respec¬tively. Depending upon the tunnel width, the cutterhead disk may be fitted with from 8 to 16 drag-bit cutters. Penetration is achieved by means of hydraulic rams that force the tungsten-carbide bits into the rock mass. The operation is cyclic, with cutting occurring only on the upstroke. On the downstroke, the rotating cutter¬head draws the fallen muck from the invert into the panzer-type conveyor for rearward transfer. This feature allows time to either reposition ore cars or to exit the tunnel with muck trains while the machine is cutting, as shown in Fig. 5. Boom-Type Rotary Excavators The boom-type rotary-excavator tunneling machines commonly are known as boom-type continuous miners

Jan 1, 1982

By S. Peng, Yi Luo

Subsurface strata movements and deformations associated with underground longwall mining activities could cause certain influences to subsurface structures and water bodies. Methods have been developed for the prediction of final and dynamic subsurface movements and deformations induced by underground longwall mining operations in the eastern coal fields. Two new types of strata deformation, vertical and total strains, which could be useful in the field of subsidence research in assessing subsidence influences to the subsurface structures and water bodies, have been introduced. Using the subsurface subsidence prediction model, three types of subsidence influences to surface and subsurface hydrological systems have been identified. Attempts have been made to quantify the two types of subsidence influences that could cause water loss and could lower water levels in aquifers.

Jan 1, 2010

By S. K. Kawatra, K. A. O, DeLa&apos

On-line sensors and process controls are important for efficient operation of coal preparation plants. The objective of this paper is to describe the current practice in on-line measurement of composition, density, moisture, level, flow and weight. This paper also discusses how on-line sensors can be implemented in process control, and how sensors which are currently being developed can be utilized.

Jan 1, 1988

By D. W. Niosi

In this chapter, a review is made of the various stages of an exploration program, mineral rights acquisition methods and the partners involved in an agreement, the after- tax cash flow approach using present value discounting principles, the establishment of computerized financial models for assistance during the negotiating stages for a mineral property, and the various evaluation techniques and their specific applications during different phases of an exploration program. A set of examples is shown encompassing the initial target-seeking stages to the ultimate feasibility study stage.

Jan 1, 1979

By Arun Patel, Diane Hirsch, Pamela Moran

The Metropolitan Washington Airports Authority (Authority) has undertaken a tremendous expansion of Washington Dulles International Airport in Fairfax, Virginia, including upgrading passenger transportation between concourses. The first stage of this expansion envisioned a shallow cut-and-cover pedestrian tunnel between the Main Terminal and Concourse B with associated vertical circulation structures. At the beginning of the design contract, the Authority’s consulting team of Earth Tech, formerly Kaiser Engineers, and the Dr. G. Sauer Corporation compared the cost and disruption of constructing the tunnel as a cut-and-cover structure to mining the tunnel using the New Austrian Tunneling Method (NATM). Upon review, the Authority endorsed the latter method.

Jan 1, 2003

By E. E. Jones

The lignites of Arkansas, Louisiana and Texas are typically described as muitiseam deposits which contain quantities of day and sand in thin lenses or in admixture with the fuel itself. These materials are often included in the run-of-mine fuel and can have very adverse effects in the end use. Since May of 1982 the Dow Chemical Co. has operated a pilot plant for the beneficiation of lignites. This facility has successfully removed sand, clays and petrified wood from the lignite producing a fuel comparable to or better than the selectively harvested run-of-mine materials. The design, operation and results from this plant were presented by J. H. Everitt at the 1984 Coal Technology Conference.

Jan 1, 1986

By A. J. Lynch

For over 30 years the JKMRC has been conducting research aimed at improving the understanding of comminution and classification processes. The result of this research has been the development of a range of comminution and classification models which has been successfully applied in numerous optimization and design studies throughout the Australian Minerals Processing Industry. This paper reviews the current status of our understanding of the mechanisms which govern comminution and classification processes. Outlines of mathematical models of these processes are described together with examples of their application in design and optimization studies.

Jan 1, 1992

By G. D. Criswell, F. Palkovits, J. M. Johnson

A paste technology investigation was completed for non-pozzolanic fly ash from Units 3 & 4 of PPL Montana’s Colstrip Steam Electric Station. The purpose was to assess the feasibility of converting from dilute slurry deposition of ash products to a system using thickened or paste ash to reduce excess water storage in the impoundment, reduce seepage losses, and increase storage efficiency. The investigation included laboratory and field testing to characterize the rheological, geotechnical and dewatering properties of the ash products, an assessment of potential seepage reductions and an evaluation of potential for increased ash storage capacity by modifying impoundment operating procedures. The studies concluded that the conversion project was feasible, cost effective, and permittable. Critical facilities for the conversion project are currently under construction.

Jan 1, 2004

By A. J. Monhemius, S. Raghavan, G. W. Warren, E. Peters, D. W. Furerstenau

A lyometallurgical process for extracting copper from an ore containing chrysocolla by leaching it with a kerosene solution containing LM 63 in the presence of small amounts of aqueous ammonia is described. The experimental results indicate that 70 to 75 percent of the copper can be extracted from the ore using an ammonia content that is about one-fourth the stoichiomeaic quantity required to leach copper in an aqueous leaching system. The rate of copper extraction was found to be a function of particle size, ammonia concentration and temperature. The large quantity of physically adsorbed water together with ammonia in the pores of chrysocolla provides a mechanism for the transport of copper to the external surface of the particles where it is complexed by the LM molecules and transferred into the organic phase. When size reduction accompanies leaching, the extraction process was found to proceed when only "trace" quantities of ammonia are present in the system. The kinetics of the extraction process appear to be controlled by a mixed (reaction and diffusion) mechanism.

Jan 1, 1993

By A. M. Alfantazi, R. R. Moskalyk

Over the years, improvements have been made in the recovery of nonferrous metals, including improvements in the areas of mineral processing, pyrometallurgy and hydrometallurgy to extract cobalt as a byproduct from host minerals containing mainly nickel, copper and associated precious metals. At present, the technological emphasis is on solvent extraction coupled with electrowinning (SX-EW) for lateritic sources of supply within the Southern Hemisphere, such as in Australia and New Caledonia. Although sulfide-bearing ores, such as those found in Canada and Russia, will serve as a viable long-term source for cobalt, a ubiquitous metal, the future trend is anticipated to be in the implementation of compact and efficient SX-EW facilities that apply state-of-the -art innovation with environmental compliance This paper serves to collate the known practices for the recovery of market-grade cobalt by means of electrowinning from either an aqueous sulfate medium or chloride medium after upstream leaching, solvent-extraction and solution-purification procedures. For completeness, other commercial production techniques for the recovery of cobalt as a sulfide or oxide product are included in the summary of current cobalt processing practices.

Jan 1, 2000

By J. Michael Howard

Holes cored through the Prairie Creek lamproite volcanic complex at the Crater of Diamonds State Park by companies interested in the site's commercial diamond potential give an opportunity to redefine the size and shape of the Prairie Creek pipe. Relationships of cored rock sequences and the discovery of a previously unrecognized major rock type allow a reinterpretation of the sequence and type of intrusive activity. Trench sampling of diamondiferous rock units yielded a diamond content far below what was anticipated based on an estimate from historical records. Inadequacies of shallow bulk-testing methods for a diamondiferous pipe are examined.

Jan 1, 1999

By R. I. Yano

Analyses of trace elements in bulk ores and in chalcopyrite and other ore minerals from porphyry copper systems worldwide, including skarns and breccia pipes, reveal some key factors regarding byproduct critical elements. Petrographic and scanning electron microscope analyses combined with a laser ablation inductively coupled plasma mass spectrometry technique developed by the USGS on selected ores from the Mackay-Stanford Ore Deposits Collection suggest that selenium occurs as atomic substitutions in sulfides, particularly pyrrhotite (up to 430 ppm) and chalcopyrite (up to 300 ppm Se); tellurium occurs predominantly as less-than-five-micron-sized inclusions of bismuth-tellurium minerals in other ore minerals, particularly chalcopyrite; cobalt and nickel are locally enriched in pyrite (up to 7800 ppm Co and 9100 ppm Ni); gallium is locally enriched in magnetite (up to 83 ppm Ga); indium and silver are locally enriched in chalcopyrite (up to 890 ppm In and 770 ppm Ag); cadmium substitutes for zinc, particularly in sphalerite (up to 4100 ppm Cd). There is considerable variation, both between and within individual deposits, in both selenium and tellurium content in these copper ores, ranging from 0.6 to 148 ppm Se and 0.09 to 64 ppm Te. Indium tends to be high in copper ores that are also enriched in silver. At current prices, many of these elements are sufficiently enriched to warrant investigation into metallurgical recovery as byproducts of the major elements.

Feb 27, 2013

By Andrew Burton, Damian Schofield, Jeremy Noond

This paper will introduce and discuss a range of techniques that utilise new developments in Computer Graphics (CG) and Virtual Reality (VR) for the investigation of incidents and accidents in mining environments. The future of mining safety may not be totally led by the demands of the mine operators, but sometimes by the academics, commercial software developers and legal pioneers who generate new ideas and products and set admissibility precedents which may change the way certain traditional investigative operations are performed. In any accident investigation the outcome from the investigating team is often a complex affair and the results of the investigation are often reported in large, convoluted documents. Computer-generated forensic reconstructions allow investigators to present accident scenarios in an accessible and easily understood, visual manner. Surveys in the US have also shown that people have increased recall of computer-generated images over many other forms of evidence. The AIMS Research Unit in the UK have been pioneering the use of Computer Graphics (CG) and Virtual Reality (VR) technology for both industrial and road traffic accident reconstruction. This paper and accompanying presentation will contain examples of forensic reconstructions developed by the authors that explain some of the methodologies used to ensure admissibility of this type of digital evidence. The paper will contain a number of case studies based on UK and International industrial accidents. The paper will focus on how AIMS Research is extending the capabilities of the accident reconstructions created to take advantage of the latest developments in VR technology. As digital technology makes its impact within professional and commercial fields, computer generated forensic reconstructions will form important admissible evidence in the courtrooms of the future. The technology will also make a great impact in the way we train our workforces, with highly visual three-dimensional (3D) interactive training tools becoming the norm. Acceptance by the public, courts and workforce is an important issue, and implementation strategies must be considered carefully.

Jan 1, 2002

By Michael Li

Unsaturated flow and solute transport were studied in three large columns measuring 1.5 m diameter x 2 m height, loaded with up to 3.7 t of oxidised waste rock, which was excavated from the Stratmat pile at Heath Steele Division, Noranda Inc. and contained elevated concentrations of zinc in the pore water. The bottom of each column was partitioned into 37 squares, each of which was drained independently. Following rain simulations at the top of the rock bed, the drainage in each drain port was monitored for volume and physicochemical parameters at pre-determined intervals. This paper describes some of the observations resulting from the experiments. The main conclusion of the study is that unsaturated flows in waste rock are heterogeneous, and flow channelling is ubiquitous. The results imply that the transport of solutes from oxidised waste rock to its toe drainage is subject to various controlling mechanisms, including geochemical equilibrium control and successive pore water dilution control.

Jan 1, 2000

By R. E. Johnson, J. E. Dutrizac, B. R. Palmer

Silver sulphide (acanthite) and lead sulphide (galena) dissolve relatively rapidly in FeCl3 media with the formation of elemental sulphur and soluble silver and lead chlorides. Parabolic kinetics are observed, and the leaching rates are controlled by the outward diffusion of the AgCl and PbCl2 reaction products through the constantly thickening elemental sulphur layer formed on the sulphide. Hence, both leaching rates are strongly dependent on those variables which affect the solubility of AgCl or PbCl2 at the reaction interface. The rates therefore increase with increasing temperature and total chloride ion concentration, but decrease in the presence of elevated concentrations of AgCl or PbCl2. By contrast, neither sulphide is significantly attacked by ferric sulphate media, even at high Eh values. Although the reasons for the refractory behaviour of Ag2S in sulphate media remain unknown, the low rate of PbS attack is attributable to the passivating layer of PbSO4 and elemental sulphur formed on the surface of the galena.

Jan 1, 1993

By J. W. White, J. P. Olson

Computer-based dispatching in open-pit truck haulage operations yields many benefits of current interest to mine management. The key tangible benefit is a substantial productivity increase with a given fleet of equipment or, alternately, a significant reduction in equipment required to meet production quotas. Other tangible benefits in mines with concurrent operating objectives include minimizing rehandle, meeting several blending constraints simultaneously, and ensuring a target plant feed rate. Intangible benefits include production forecasting, performance comparisons of trucks or shovels of different manufacture, and extensive on-line report generation. Recent advances in mini- and micro-computer hardware and software and solid state electronics permit design and implementation of system features not feasible a few years ago. This paper discusses system aspects with emphasis on dispatching algorithms needed to meet concurrent objectives.

Jan 1, 1987

By J. J. Daniels

Advances in borehole geophysical research for mineral assaying and remote detection of mineralization away from the borehole are cited. Nuclear activation measurement research has provided accurate in situ assays of economic metals with neutron-gamma activation, using a high resolution intrinsic-germanium detector. Although nuclear activation analysis is the present "best hope" for obtaining in situ assays for some elements, gamma-gamma and magnetic susceptibility measurements can provide accurate assays for lead-zinc and magnetite, respectively. Borehole optical spectroscopy and X-ray fluorescence are being investigated as possible in situ assaying techniques for some minerals. More laboratory and field calibration research is needed before non-linear complex resistivity (NLCR) can be routinely used as a quantitative assaying tool. Field tests have shown that variations in the local geologic environment can affect the quantitative accuracy of assay values from downhole NLCR measurements. Deeply penetrating borehole geophysical methods are increasingly being used for mineral exploration as drilling costs and exploration have increased. Borehole electrical measurements have been shown to be useful for detecting conductive ore bodies that are not intersected by a drill hole. Hole-to-surface resistivity and surface-to-hole time-domain electromagnetics are demonstrated to be particularly effective for defining mineralized zones in a massive sulfide environment. Borehole gravity meters and three-component magnetometers have been developed and should prove useful for defining geologic anomalies away from the drill hole.

Jan 1, 1987

By H. Maleki, G. Tetreault

This study was initiated by the US Bureau of Land Management (BLM) to develop guidelines for determining the maximum economic recovery of resources in coal mines. The work was in response to a requirement in the Mineral Leasing Act of 1920 and Federal regulations. The intent was to address the economic rainability of small, irregular reserves in existing longwall mines. In particular, there was a need to determine if room- and-pillar mining using a continuous miner (CM) was economically sound or whether unconventional (short or odd-shaped) longwalls could be used to recover small coal reserves economically. Small reserves, called "widgets " are left in longwall mines on one side of the mains near outcrops and adverse geological conditions or near any other location where reserve geometry does not lend itself to mining with a rectangular longwall panel. The work included the analysis of the geologic, geotechnical and economic factors that influence the recovery of small coal reserves; the analysis of historic changes in supply, demand and coal prices; the development of typical cost models for room-and-pillar and longwall mines; and the development of a practical methodology for determining maximum economic recovery. The methodology included an evaluation of the ratio of coal mined during longwall mining to that mined for development (LDR), as well as costs of maintaining coal quality depending on market conditions. The LDR is a good indicator of mine efficiency and overall coal recovery in modern longwall mines and, thus, is used to evaluate the increased costs associated with adding new development sections for extraction of small reserves. The study examines the economic feasibility of using unconventional longwalls for the recovery of medium-sized reserves, depending on site-specific geologic and geometric conditions.

Jan 1, 2002

The use of controlled recirculation can be dated back to the early 1930s. Although this method has been applied in many mines since then, a generalized comprehensive network analysis is still lacking. This paper presents a unique approach in which the ventilation network with a controlled district recirculation is divided into two subsystems: a main subsystem and a recirculation subsystem. The subsystems are analyzed individually and the results and their relationships are then integrated into discussions of the total ventilation system. The analysis of the recirculation subsystem is facilitated by introducing a non-dimensional parameter A, which represents the ratio of the air quantity for the working face to that for the subsystem. As a result, fan and regulator pressures and air power for various recirculation arrangements can be effectively expressed as a function of A and the subsystem air quantity. Numerical examples are included.

Jan 1, 1995

By Charles H. Jacoby

In 1960 the management of International Salt Company made the decision that all waste material from the Watkins Glen plant would be stored in underground salt cavities. The cavities which they contemplated using had been depleted of salt to a point where continued operation would have impaired their structural stability. Originally, the waste to be disposed of included vacuum pan bleeds, cinders, contaminated salt and sewage. It was proposed that this material, in a slurry form, was to be injected into the salt cavity through one of the abandoned wells. Brine, displaced from the cavity, was to be recovered from an adjacent well and subsequently injected into the Cherry Valley limestone, This Cherry Valley limestone which underlies a large portion of north central New York contains a connate water with high concentrations of ammonia, hydrogen sulphide and the chlorides of calcium, magnesium and sodium. A number of questions were immediately raised on various aspects of the technical feasibility of the project. Of major concern was the buildup of insolubles adjacent to the bore of the injection well. Another pertinent question was the carryover in the displaced liquor of finely-divided, mechanically-suspended particles. Criticism was leveled at the inclusion of sewage. Engineering studies were started by the company's Mineral & Mines Development Department and on April 3, 1961 a preliminary feasibility report was issued.

Jan 1, 1973