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By A. E. Prokop, J. P. Rider

Previous research on continuous mining operations has shown that significant interactions exist between dust-control parameter application and the resulting respirable dust levels. However, simply increasing the level of the controls does not guarantee a reduction in respirable dust levels. Full-scale laboratory tests are being conducted to provide information to longwall operators that would assist them in selecting control parameters to reduce dust levels for mine-specific conditions. The interactions between face air velocity, shearer water quantity, drum water spray pressure, external water spray pressure and spray system design were evaluated in a simulated 2.13-m (7 ft) coal seam for two cutting directions. Locations around and downwind of the shearer were monitored to evaluate relative changes in respirable dust levels as a function of each control parameter.

Jan 1, 2003

By Jerry C. Tien

An overcast is a form of air bridge which permits one air current to pass another without mixing. It is an essential and indispensable ventilation device for underground air distribution in horizontal mineral deposits. Overcasts are also a major source of shock pressure loss under- ground. However, a well thought out overcast plan, and a well constructed overcast, will give minimum shock loss, which in turn can save money (Tien, 1986). So far, most research on shock losses has been concentrated on splits and junctions, and bends and turns, or on underground regulators. Practically nothing could be found in the literature regarding losses caused by overcasts (see reference on shock losses). In this investigation, shock losses are quantified for an overcast with different configurations, which will give useful clues toward an aerodynamically designed overcast.

Jan 1, 1987

By K. Morsy, S. S. Peng

A new method of pillar stability evaluation was proposed. The unique feature about the method is that it estimates two types of stability factors for the pillar. The first stability factor is to measure how much the applied stress at that point is smaller than its strength, and the second stability factor is to predict whether or not the pillar will fail violently. The strain-softening behavior of coal pillars was simulated by the Drucker-Prager yield criterion. A new algorithm that simulates the strain-hardening behavior of the gob was used. A numerical technique to estimate the local mine stiffness (LMS) was introduced and verified by both numerical and analytical methods. A case of massive pillar failure in a room-and-pillar mine was used to define the stability limits for the proposed method.

Jan 1, 2003

By T. Cohen

Technological innovation in the minerals industry must be driven by the need to improve performance according to social, as well as environmental, safety, efficiency and production criteria. This paper outlines the possibilities and rationale for incorporating constructive technology assessment into technology research and development within the CSIRO Minerals Down Under National Research Flagship (MDU). The paper develops a process of Social License in Design that attempts to address the future social challenges and opportunities of a technology during development by utilising forecasting techniques and accounting for the perspectives and values of decision makers and likely stakeholders. Interviews with senior technologists and social scientists within MDU reveal the institutional context into which the Social License in Design process is to be situated and highlight key factors that may inhibit or enhance its uptake.

Jan 1, 2011

By D. R. Dolinar, J. Pablic, D. C. Oyler, T. P. Mucho

At a mine in central PA, high horizontal stresses have caused long running roof falls resulting in hazardous conditions for the miners and the premature abandonment of panels. Because of these conditions, the mine requested assistance of the National Institute for Occupational Safety and Health (NIOSH) in utilizing the "advance and relieve" method to mitigate the affects of horizontal stress on the mine roof. "Advance and relieve" mining involves the removal of a pillar or a portion of a pillar during development, thereby creating a cave along one side of the panel. Following cave development, the horizontal stress is relieved over the workings adjacent to the cave in the active panel. The mine has used this system in three panels with a significant reduction in stress damage and no large roof falls.

Jan 1, 2001

By Martin Herenknecht, Michael Knabe, Ulrich Rehm

In Switzerland at present, the longest railway tunnels in the world, the Gotthard(57 km) and the Loetschberg base tunnel (34km) are under construction. For thischallenge six high-tech HERRENKNECHT Hard Rock Tunnel Boring Machines (TBM)are applied, which have to excavate approx. 80 km at the Gotthard and 20 km at the Loetschberg Tunnels. The machines being used are of a single Gripper-TBM type, which are equipped with the latest rock support techniques, in order to optimize the quality of the working conditions for the personnel which have direct impact on the quality of the tunnels. The different requirements of the projects based on different speci?cations within the tender documents led to completely different TBM concepts which will be reviewed in detail in this paper.

Jan 1, 2003

By Ted Budd, Vladimir Goubanov

The East Central Interceptor Sewer, commonly known as the ECIS Project, is the largest public works construction project awarded by the City of Los Angeles. The complexity of this $240 million project, together with the challenge created by the mandated 1,000 calendar days for construction completion, make this project a major interest for the tunneling industry. This paper will describe the ECIS tunnel project, currently under construction by the Joint Venture of Kenny (Sponsor) / Shea / Traylor / Frontier-Kemper. Mining of the18.5 km (about 11 miles) long and 4.7 m (15ft-4in) diameter tunnel is underway with four Tunnel Boring Machines mining at the same time. Details on the mining machines, muck handling systems, innovative construction sequence, together with mining progress will be given.

Jan 1, 2003

By John A. Lombardi

The HW Process Technologies Engineered Membrane Separation (EMS"') technology is a patented system for the removal of multivalent base metal cyanide complexes from cyanide process streams, and EMSni permeate, concentrate and recovery terminology is explained. Specifically, use of the EMS™ system for the removal of Cu(CN)i- and Cu(CN)43- cop­per from cyanide process streams is discussed. The historical "Copper-Gold" processing paradigm of copper related cyanide consumption and complexation and methods to recover copper and copper complexed cyanide from Cu-Au process solutions are summarized. An advanced stage R&D sequential Cu-Au leaching circuit is proposed wherein two PLS streams are generated, i.e., a high copper tenor "first flush" Cu-PLS and low Cu tenor "second flush" Au-PLS. Copper and cyanide recovery from the EMS"' concentrate generated by Cu-PLS EMSTI,f processing by well known acidification processes and lesser developed, but techni­cally feasible, electrowinning processes are projected to be lower cost than similar dilute solution treatments. Gold is described as Merrill-Crowe plant recoverable from the EMS™ permeate stream coming from the Cu-PLS EMS"' process. Gold is also recovered from the EMSTI,f permeate generated by the processing of an Au-PLS bleedstream. The economics of the proposed Cu-Au-EMS"' circuits are estimated as $2/ gpd capital cost for large systems and $1- $3/ l 000 gallons treated operating cost plus royalty.

Jan 1, 1998

By A. J. Hendron, G. Mesri, R. M. Semple

Squeezing ground conditions in hard-rock tunneling are associated with fault zones containing brecciated rock and gouge. Gouge is a stiff clay-like soil that exhibits a propensity to creep. The ground loads applied to tunnel supports in squeezing ground are known to be significantly time dependent. Accordingly, an experimental and analytical study is presented that deals with soil creep and its application to the prediction of tunnel support requirements in squeezing ground conditions. Relatively undisturbed samples of fault gouge obtained from Straight Creek tunnel in Colorado and Pacheco tunnel in California are classified as very stiff to hard clays of low plasticity. Constant-load undrained triaxial compression tests are performed on these materials. A simple, three-parameter creep equation is developed that adequately describes the observed deformation of fault gouge with respect to applied stress and time. The equation is shown to fit existing creep data of various soil types. The creep equation is used to modify an existing continuum-mechanics solution to the time-dependent behavior of unlined and lined cylindrical openings in a creepsensitive medium under a hydrostatic state of stress. Assuming properties for the medium that are representative of the fault gouge materials tested, parameter studies are performed for unsupported and supported tunnels in squeezing ground. The analyses permit estimates to be made of the steel set supports required for tunnels at different depths in various squeezing ground conditions.

Jan 1, 1974

By John Neale, Robert Huberts, Tony Pinches

A major R&D programme for the application of bacterial oxidation to the pretreatment of refractory sulphide gold ores was started at Mintek in the early 1980s. This arose from an established expertise base in the bacterial leaching of base-metal sulphide ores. The refractory gold programme has been supported by a number of South African gold-mining companies, but major support has been provided by the Anglo American Corporation of South Africa (AAC) and the AAC Vaal Reefs Exploration and Mining Company Limited · (Vaal Reefs). The Mintek-AAC collaboration has been formalized as a joint-venture technology agreement for the comme;cialization, as well as continued development and improvement, of the bacterial oxidation process (MINBAC). From a process standpoint, bacterial oxidation involves the contacting of slurries of finely ground sulphide concentrate with suitable strains of iron-sulphur oxidizing bacteria, which act as the catalyst to promote sulphide·· oxidation by oxygen from air. Process engineering is simplified in that this reaction is carried out at low temperatures and ambient pressures. The view was taken that the successful development and implementation of the MINBAC technology should be based on parallel R&D aimed at an understanding of the process fundamentals, the process engineering and scale-up requirements, as well as the ancillary requirements for the gold recovery-processes and environmental management. This has represented a major R&D effort at a total cost to date of around US $10 million.

Jan 1, 1993

By Victor F. Hollister

The great increase in post-World War I1 use of molybdenum was made possible by discoveries of that metal in porphyry molybdenum and porphyry copper deposits. This section documents significant porphyry molybdenum discoveries of the post-war period. The most important discovery was Henderson in Colorado. It is not only one of the world's largest and richest, but it was found by a team of geologists who defined the hood model and tested it successfully at Henderson. Under the leadership of Stewart Wallace, these scientists established a set of criteria for exploration for Henderson-type de- posits that was copied by the industry. The discovery bf vertical cylinder type porphyry molybdenum deposits was less renowned. Boss Mountain in British Columbia and then Mt. Pleasant in New Brunswick were given relatively scant notice, compared with the Henderson discovery. However, these deposits have geometrics distinct from that found in the typical hood, which directly affects their exploration characteristics. Mt. Pleasant, included in this section, is a well defined, near vertical breccia pipe. Both the Henderson and Mt. Pleasant discoveries were made by relatively small groups operating independently of the bureaucracy that characterizes large corporations. The management role in each case was one of encouragement. In addition, Wallace had the beneficial experience of working for Climax, whose objective was the discovery of porphyry molybdenum deposits. Henderson was the natural outgrowth of the exploration effort by those who studied and understood the Climax deposit.

Jan 1, 1991

By W. de Moura, R. Fueyo, M. M. Botz, J. C. Scola

The Cerro Vanguardia mine is an AngloGold Limited operation in southern Argentina that includes multiple open pits and a hybrid Merrill-Crowe and CIL circuit to recover gold and silver from oxide ore. Operations were commissioned at the site in 1998, which included a plant in the metallurgical circuit to recover cyanide from mill tailings. The cyanide recovery plant was initially configured to process tailings slurry and achieved greater than 90% cyanide recovery from tailings containing about 600 to 800 mg/L WAD cyanide (as CN). The cyanide recovery circuit was operated in this manner for approximately eight months, during which time the consumption of sulphuric acid and sodium hydroxide was relatively high, leading to high rates of scale formation in the acidification tank and stripping towers. In July 1999, several piping changes were made in the cyanide recovery system to permit its operation with clear solution, which reduced the sulphuric acid consumption and eliminated scale formation in process equipment. The cyanide recovery system currently operates with a two-stage counter-current decantation (CCD) circuit which provides clear solution for processing in the cyanide recovery plant. The cyanide recovery efficiency now averages about 90% to 92% from solution containing about 350 mg/L WAD cyanide (as CN). Recovered sodium cyanide now accounts for about two-thirds of the total cyanide added to the leaching circuit. This paper presents a description of the cyanide recovery plant and details regarding its current operating efficiency.

Jan 1, 2004

By J. F. Dresser

Managing environmental compliance at a complex facility has the potential to bring a high degree of personal and professional satisfaction to both the corporation and the individuals responsible for day-to-day operations. The decade of the 1990's, however, has seen the emergence of a nationwide trend of aggressive federal and state civil and criminal enforcement for environmental violations. This trend, spearheaded by the U.S. Department of Justice (DOJ) and the U.S. Environmental Protection Agency's (EPA) Office of Enforcement, has the potential to place the corporation, its corporate officers, and compliance personnel at collective professional risk, as well as a growing tendency to place accountability on individuals. Management of environmental compliance has been anecdotally compared to a shooting gallery at a carnival, with the following exception: At the shooting gallery, successfully hitting nine out of ten targets usually brings a reward and recognition of shooting skill; hitting nine out of ten environmental compliance expectations not only brings agency consternation and negative publicity, but the "gallery" will likely shoot back with stiff fines and possible criminal allegations. Faced with the challenges of the new environmental compliance shooting gallery, corporations and professionals are often left asking themselves, "How do we (or more appropriately, can we) win at this game?" This paper examines recent federal enforcement statistics and offers several suggestions for coping with the responsibility of managing environmental compliance in the 1990's.

Jan 1, 1992

By Thomas R. Kuesel

In traditional construction contracting practice, the owner allocated almost all risks to the contractor, saying in effect, "you deal with all construction problems and all third parties, and don't bother me." In this same tradition, the architect or engineer designed a structure in its finished condition, and if he thought about the construction problems that might be involved in building it, he was careful not to express any opinions on these matters in the contract documents. This feudal attitude fostered two results: 1. Contractors added high contingencies to their bids to cover the costs of risks. 2. Litigation of construction contract claims blossomed. Broadly, the owners lost--the courts reallocated many risks the owners thought they had laid on the contractor. Thoughtful owners and engineers recognized that owners were paying for risks twice --once in bid contingencies and a second time in court. Meanwhile, contractors were not getting rich; they were losing money on delays and disputes, and just about getting even (if they were lucky) in court. And construction law was becoming an increasingly lucrative field--for lawyers. Furthermore, with the growing influx of lawyers onto the construction scene, the owner-contractor-engineer relationship became increasingly an adversary one. The emphasis came to be on culpability rather than capability--who could be held responsible for breaching some contract clause, not who might find a solution to some common problem. This game was played with equal vigor by owners and contractors.

Jan 1, 1979

By B. L. Gibbs

Computers have been used in the minerals industry for about 30 years and, in a few cases, longer. With the explosion of microcomputing during the past 10 years, computers have changed how many minerals producers go about their work. What computer usage trends are active in the minerals industry today, and what can we expect in the future? In general, computer usage is accelerating. Engineers and geologists are becoming increasingly "application literate." Soft¬ware is increasingly oriented to how people work. User interfaces have improved, so most users need to know only a mini¬mum of system commands and structure to work with a computer. Most industry professionals know how to use word processing and spreadsheet pro¬grams. AutoCAD appears to be the drawing program of choice. One reason is availability of training and add-on programs for earthwork, mapping, contouring, etc. Another frequently cited reason for using CAD is the ability to quickly make changes to a map or design, as compared to hand methods. Management is moving toward greater acceptance of computer usage. Computers do not need workman's compensation ... even though they may get sick and take a few days off! Computer hardware used in most minerals-producing companies is strongly personal-computer based and likely to remain so. The 486 personal computers are inexpensive as compared to workstations and provide the power and speed to run most applications in minerals industry engineering offices.

Jan 1, 1994

By John J. Peregoy, James E. Downes

INTRODUCTION The U.S. Department of Energy's Waste Isolation Pilot Plant (WIPP) is being constructed to provide permanent storage of radioactive TRU waste materials emanating from military weapons production. These wastes are contaminated with radioactive elements heavier than uranium, thus the name trans-(or beyond) uranic (Uranium wastes). The WIPP site, which is located 26 miles east of Carlsbad, New Mexico, was chosen thru a selection process after the National Academy of Sciences recommended salt deposits as a promising host strata for the storage of radioactive wastes. Throughout the United States numerous DOE facilities have produced and stored defense-generated TRU wastes. Once WIPP becomes operational in the fall of 1989, all sites may ship directly to this repository. A companion project has developed special shipping containers (TRUPACT) for safe transport of materials to WIPP. The WIPP facility is currently composed of surface buildings, three shafts, and underground storage and experimental rooms and tunnels. Frontier-Kemper Constructors, Inc. (FKCI) has nearly completed the construction of the fourth shaft, an intake shaft, to provide additional ventilation to the underground workings. PLANNED SHAFT EXCAVATION METHOD Full-face raise boring ( upreaming ) was the allowable method selected by Frontier-Kemper Constructors for the excavation of the shaft. After arrival of an oil-field type rotary drill rig in December 1987, a 9 inch diameter pilot hole was drilled from the surface to the mine level, a depth of approximately 2145 feet.

Jan 1, 1989

By Harold D. Stevenson, Gerald G. Carlson

The Flow-Through Shares Program was set up by the Canadian Federal Government in 1978. While initial annual expenditures in flow-through shares was small, recognition of flow-through as a significant tax advantage combined with exploration successes, particularly in the gold sector, soon resulted in the majority of exploration dollars raised in Canada utilizing the flow-through share mechanism. What Are Flow-Through Shares As many exploration companies are non-taxable, they are not in a position to benefit from the tax deductions arising out of their exploration activities. Flow-through financing provides a mechanism for the exploration company to transfer these deductions to an investor. In addition to the deductions which an investor can apply against his personal income, the investor receives common shares in the exploration company (flow-through shares). To add to the attraction, the Federal government provides a 33 1/3 percent mark-up on qualifying expenses incurred by the exploration company, giving the investor a deduction of up to $1.33 for every $1.00 invested. By providing the investor with tax deductions in addition to the flow-through shares, flow through shares can often be sold at a premium to market which makes-the mechanism attractive to the exploration company as well. These shares are often sold through private placements and therefore have to be held for one year. The tax cost of the share is deemed to be ril, so the entire proceeds on disposal are

Jan 1, 1987

By John D. Gardner

This paper describes a process which finds the maximum worth of a mineral deposit. The procedure requires two phases. The first uses a microcomputer evaluation model to find the optimum design input, with minimum attention giving to actual mining constraints that might exist. The second phase runs the first-phase design parameters through a direct simulation model on a mainframe computer. In phase one, financial, economic, and geotechnical data are entered; and an idealized list of design parameters is output. The list includes optimum values for cutoff grade, mine life, mine size, paytons, paygrade, and payvalue. In addition, the model generates pro forma operating and cash flow statements and it indicates the maximum net present value (NPV) possible for the deposit along with the probability of that oc¬curring. The initial results imply perfect mining conditions. In phase two, when actual mining selectivity, sequence, and other practical design considerations are related in a direct simulation model to the optimum criteria found above, the maximum NPV invariably decreases. However, if it is still satisfactory (NPV greater than or equal to zero) then the maximum worth/ optimum design have probably been found in the first iteration. If, on the other hand, NPV is now unsatisfactory, then design compromises must be made and simulated, and the results rerun through the evaluation model. If several iterations fail to yield a positive NPV then the deposit is most likely unfeasible t for the forecast economic conditions used in phase one.

Jan 1, 1986

By Henry J. Jacoby

This report concerns Contract No. 3B of the Port Richmond Project, for the Department of Water Resources of the City of New York. It involves the construction of 7, 000 ft. of 7 ft. finish I. D. interceptor sewer by tunneling in soft ground, as well as associated manholes, regulator chambers, siphons and miscellaneous sewers and structures, beneath a heavily travelled perimeter road in Staten Island. The Contractor is Richmond Constructors, a joint venture of Grow Tunneling Corp., sponsor, MacLean Grove & Company, Incorporated, Morrison-Knudsen Company, Inc., and Andrew Catapano Co., Inc. Project manager is Paul DeMarco, Vice-President of Grow Tunneling Corp. The cortract, as designed and bid, requires the use of liner plates 101 -0" O. D., and both cast iron and steel designs of several widths were included in the bid documents by the owner. The specifications also required the contractor to install and put into operating condition, prior to commencement of mining, a complete low pressure compressed air plant and all accessories for mining in compressed air, even though the contractor was given the option of using other methods of ground water control. A third requirement of the specifications was that a shield be used, either manual or mechanical, and with full provision for "breasting". BACKGROUND The first soft ground shield driven tunnel in the United States was in New York City and was built under Broadway in lower Manhattan in 1869

Jan 1, 1974

By Z. D. Yu, J. E. Gebhardt, D. I. Phillips, S. X. Jiang, R. Z. Zhang

The potential application of flotation for the treatment and processing of a fine-particle coal stream was investigated for the Chaili Coal Washery of the Zaozhuang Coal Mine Administration, Shandong Province, China. A goal of the test work was to evaluate the application of the Microcel™ flotation column and compare its performance to conventional flotation. Small-scale flotation tests were performed in the laboratory and on-site with fine coal slurry samples from the plant thickener underflow, i.e., the washing plant's undersized reject material. Flotation tests were conducted on-site with a 7.6-cm diameter Microcel™ column and with small-scale conventional cells. Column flotation tests were performed to determine a recovery-grade relationship for the fine coal feed, which contained about 24% ash, and to obtain sufficient data to enable scale-up to a large diameter unit. A primary objective as to establish the maximum throughput capacity of a Microcel™ flotation column while operating to produce a clean coal product with ash content of 7.5-7.8%. Results of the test work indicate that this product quality could be achieved at feed rates of 15-19 tph to a 3-m diameter Microcel™ flotation column. Lower ash products, i.e., 5-7% ash, were obtained but at lower column throughput capacities. Comparative flotation tests, conducted with conventional flotation cells, indicated that a product ash of only 8% or greater was achieved in a single-stage test.

Jan 1, 1995