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By Douglas R. Shaw

The results are discussed herein of laboratory and pilot scale research which has demonstrated some exciting prospects for the exploitation of refractory gold resources by heap leaching. The research examined practical and cost effective methods of chemical; i.e., non-biological, oxidation pretreatment of refrac­ tory old ores to enable successful conventional cyanide heap leachmg. The work has focused on regenerable chemicals, in order to minimize process consumable costs. A nitric acid method has emerged which offers rapid oxidation rates (eg, 0.5 to 6 hours) on ore samples crushed typically to% to ¾-inch. Gold recoveries in simulated heap leaching tests, after nitric acid oxidation of crushed ores, were as high as approximately 80 to over 90%, in contrast, typically, to negligible gold solu­bilities without oxidation. Nitric acid oxidation was effective when applied to several sulfide-bearing refractory gold ores which required either partial or essentially complete sulfide sul­fur conversion for high gold solubilities in cyanide. Ores rich in organic preg-robbing matter also were treated successfully, as were ores which contain significant quantities of acid-consum­ing constituents. Base metals also were recovered with nitric acid oxidation from some of the ores which contain these ele­ments. The work related oxidation and solution diffusion behav­iors and the important physical, textural, and mineralogical characteristics of the different ore types. Conceptual-level feasi­bility studies have defined the principal capital and operating cost components of the nitric acid method, sufficient to allow reliable comparisons with other oxidative technologies.

Jan 1, 1996

By K. F. Hollberg, D. Graehl, L. Despain

OCI Wyoming's recent expansion of its surface Soda Ash production facilities outstripped the mine's ability to supply Trona ore necessitating infrastructure changes to the mine. A computer simulation of the mine's production systems along with the surface facilities was created to determine the most economic investment alternatives to increase mine production. This paper describes the development of the simulation model; the results obtained, and discusses the issues involved in using simulation modeling for mine production system design.

Jan 1, 2002

By Frederick H. Parkinson, Joseph Fernandez, David E. Westfall

The April 13, 1992, flooding in the freight tunnel network under the city of Chicago had a profound effect on the nearby Chicago Transit Authority (CTA) subway service. This paper provides an overview of the evaluation techniques, mitigation measures, and water control efforts used to maintain the integrity of the subway tubes. Specific topics discussed include visual inspections, inflow monitoring, structure and soil testing and sampling techniques, and the development and implementation of chemical and cementitious grouting programs.

Jan 1, 1993

By Jerry Dollinger, Levent Ozdemir

An extensive series of laboratory cutting tests using linear and rotary cutting machines were carried out with the objective of investigating the feasibility of achieving very high rates of penetration with TBMs in rocks of low to medium strength. These tests were performed with large diameter disc cuttrs at cutter path spacings and penetrations of up to 12 and 1.75 inches, respectively. A predictor model was also formulated to characterize rock cutting at large spacings and penetrations.

Jan 1, 1987

By Gary L. Simmons

Many large (refractory) sulfide gold resources exist in Nevada and other parts of the world that are not amenable to conventional flotation concentration using air as the flotation gas medium. Over the past five years Santa Fe Pacific Gold Corporation (SFPG) has investigated flotation process options to economically treat refractory ores and resources of this type at its Lone Tree and Twin Creeks mines. Conventional flotation technology applied to the original high-grade gold resources at Lone Tree and Twin Creeks was initially unsuccessful. Review and analysis of auriferous (gold-bearing) iron sulfide mineralogical characteristics and flotation ..:hemistry provided a fundamental understanding that led to the development of a new flotation process that SFPG refers to as N2 TEC. This paper discusses the development of this technology and compares N TEC results with conventional flotation practice.

Jan 1, 1997

By Frank F. Aplan, Edward C. Jr. Dowling, Richard R. Klimpel

Thirteen kinetic models that mathematically describe the flotation process have been statistically evaluated for the flotation of copper, lead and zinc ores. Comparisons have been made for a variety of circuits involving roughing, cleaning, scavenging and regrind followed by cleaning. Variations in collectors, frothers, depressants and activators have been considered. Based on the statistical criteria used for the evaluation, and the reagent, circuit and ore variations studied, the most reliable flotation models have been identified and subsequently used to characterize the metallurgical results.

Jan 1, 1986

By R. I. Pennington, J. L. Vanderbeek

Investigations have been conducted at Chino Mines Co. into the effect that SAG mill recycle material (critical size) exerts on SAG mill throughput and specific energy requirements. Tests were conducted on laboratory, pilot, and plant scales to evaluate the merits of alternative treatment options. Removing critical size material from the SAG mill circuit has been shown to improve new feed rates by 84% with a reduction in specific energy (kWh./t) of 88%. Test results obtained to date are presented.

Jan 1, 1987

By Frederick W. DeVries, J. Brent Hiskey

Cyanide has been recognized for about a century as the most effective reagent for processing gold ores. Cyanide leaching has been adapted to various metallurgical settings and continues to be improved. However, in recent years attention has been directed to alternative lixiviants for treating refractory ores and concentrates, and to the development of less environmentally controversial substitutes for cyanide. This paper reviews some of the reagents considered as alternatives to cyanide and focuses on environmental implications for using these newer reagents.

Jan 1, 1992

Mine managers need useful data to support production and maintenance decisions; for example, to evaluate the performance of replacement components. Today, managers rely solely on past experience, supervisors, opinions, and time studies. Our paper describes the concepts and algorithms we are developing for an automatic, intelligent decision support system (IDSS) that will aid managers by reducing and analyzing large amounts of, monitoring system sensor data and report only key production and maintenance information.. IDSS contains a pattern recognition, subsystem (IDSS/PRS) prototype to report graphical trends in traditional time study elements. We are designing. and prototyping a knowledge representation subsystem, using Knowledge Craft Tools, that will learn and adapt to the dynamic mine environment and reason about the recognized patterns using representations of manager's knowledge, equipment, capabilities, and mine layout and operating procedures. This subsystem will reduce, large quantities of time study type information to key issues that interest different managers.

Jan 1, 1989

By James J. Brady

The basic story at Bear Swamp was how to excavate an underground chamber 79 feet wide by 227 feet long and 150 feet high, along with the related access, tarbrace, leads, power tunnels and shafts, do it under cost and ahead of schedule and still have just about everybody love you. The isometric sketch of the overall project follows. I won't go into any of the details of the physical scope at this point. Instead, we'll bring out the sizes, grades, particular problems of the different areas as we cover them. First of all, let's establish that Bear Swamp was a Target Estimate - Fee with Incentives type of contract. Gates and Fox's contract was with the project's general contractor, J. A. Jones. We were one of three contractors who submitted proposals and estimates to Jones. After much negotiation and many submittals, Gates and Fox was notified we had been selected to do the underground excavation on April 12, 1971. We had our first people back on site in two days, set up a temporary office, made our first steel order for jumbo erection, pacing our jumbo construction to meet the date when J. A. Jones would have the access portal ready for us. The shops, yards, dry house, compressor building were all erected as sites were designated for our use. At last, on Thursday, June 3, we trimmed the face and moved our 9-machine Euclid jumbo up a hastily constructed haul road and started our portal preparation of the access tunnel.

Jan 1, 1974

By David G. Rasmussen

With low commodity prices and continuing high operating costs, the mining industry must revise planning and operating to take advantage of every tool available. Conveyors operated within open pits are such a tool. Dravo engineers have designed conveyor systems into pits as prime movers in unique situations. Three cases are presented with economic comparisons made to conventional truck haulage. Increasing energy and labor costs tend to make conversion of prime haulage from trucks to conveyors. Long term pit planning and scheduling reduce the effects of conveyor inflexibility.

Jan 1, 1983

By Tom B. Corry

INTRODUCTION Located approximately 48 km (30 miles) south of Dallas, Texas, use to be the site of the Superconducting Super Collider. For those of you unfamiliar with the project, this was a multi-billion dollar project taken on by the U.S. Government for the further advancement of technology, medicine, and science. Major components of the project consisted of a Linear Accelerator known as the LINAC; three accelerating rings known as the Low Energy Boosters (LEB), Medium Energy Booster (MEB) and the High Energy Booster (HEB); the East and West Campuses where the Inner Reactor Halls would have been located; and the 87 km (54 mile) main collider tunnel. Unfortunately, this all came to an end on December 6, 1993, with the termination of the project due to the Government's cancellation of funds. This paper will deal with the two of the underground contracts before the termination. These two contracts were the 1122 contract which ran from N25 to N40 and the 1130 contract which ran from N40 to N55. (See figure 1) The 1122 contract was awarded to us in July of 1992 and consisted of the excavation and support of six (6) shaft varying in diameter from 5.5 m (18 feet) to 8 m (26 feet) and ranging from 39.6 m (130 feet) to 61 m (200 feet) deep and the driving of approximately 13,100 m (.43,000 If.) of main collider tunnel. Our second contract, the 1130, was almost identical to our first

Jan 1, 1995

In 1993, the United States' economy grew at a rate of about 3%. The Gross Domestic Product rose to $6.4 trillion. With more than 258 million people - 599,000 in mining including petroleum - the United States has more than 100 million dwelling units and more than 190 million licensed motor vehicles. New private housing starts rose 7% to 1.3 million units, new car production fell 3% to 5.5 million units and truck and bus production rose 21 % to 4.9 million units. The rate of inflation was under 3% and the prime rate of interest 6%. The Producer Price Index (1982 = 100) was unchanged from 1992 for fuels and re¬lated products and power at 80 and met¬als and metal products at 119, while chemicals and allied products rose 2% to 128 and non-metallic mineral prod¬ucts rose 2% to 120. The merchandise trade deficit rose 27% to $116 billion.

Jan 1, 1994

By T. S. Golosinski, J. Wolski

Procedures are presented for determining the hourly production rate, mechanical and physical availability, utilization, use of availability, and global performance factors for the bucket wheel excavator (BWE) itself, as well as for the system composed for the BWE, conveyors, and stacker. An example demonstrates the flow of calculations. Using available data from mines that use BWE technology, the ranges of values of the BWE performance factors are presented in tabular form. They can be used as a guide during mine planning as well as to evaluate existing systems.

Jan 1, 1987

By Zhengbin Cheng, Wenguang Lu, Baoqi Sun, Jiaying Tang

This paper studied the flotation separation of feldspar, zircon and kyanite from quartz with a mixture of cationic and anionic collectors. Tests show that collector mixture has specially good effect, using it, the separation of these three silicate minerals from quartz can be successfully achieved at the natural pH value of tap water in the absence of any acid, fluoride and other inorganic reagents. The properties and characteristics of collector mixture were analysed. By means of IR-spectra, ESCA and AES, the action mechanism between collector mixture and minerals was throughoutly studied.

Jan 1, 1995

By Johanna I. Wong, R. John Caulfield, Victor S. Romero

The existing Hetch Hetchy water system, owned and operated by the San Francisco Public Utilities Commission (SFPUC), serves 2.4 million people within the San Francisco Bay Area. The system has existing 1920s-era pipelines crossing under the Bay that are vulnerable to seismic damage from the nearby San Andreas and Hayward fault zones. The SFPUC plans to replace the pipelines with the first TBM-driven tunnel underneath the San Francisco Bay. The tunnel will be constructed using an Earth Pressure Balance machine. The new tunnel will pass under environmentally sensitive habitats and will be approximately eight kilometers (five miles) long with no intermediate shafts. The project challenges will include tunneling through a prominent buried bedrock ridge that transects the alignment and through soft soils under the Bay. Seismic performance criteria include maintaining service flows after a large earthquake on one of the active faults in close proximity to the project site.

Jan 1, 2007

By D. Triantis

This paper presents the results of laboratory experiments for the detection of electric signals from Fiber Reinforced Polymer (FRP) sheet samples which have undergone a temporally increasing loading of bending type up to fracture. Electric signals that were recorded while the sample was subjected to bending are referred from now on as Bending Stimulated Currents (BSC), in order to differentiate them from the relevant signals emitted by materials that suffer uniaxial compressional stress. The latter signals are referenced as Pressure Stimulated Currents (PSC). BSC emitted from FRP sheet samples presented here, were recorded after applying three successive load steps to samples. The increase rate of applied stress was about 0.15kN/s. Initially starting from low load values to higher load values until the FRP sheet reaches at a state just before its failure. The BSC records from FRP samples are compared to equivalent recordings from cement mortar beam and distinguishable differences are discussed.

Jan 1, 2006

By Terry M. Hertel

Zortman Mining has spent approximately three years evaluating the metallurgy of the sulfide ores from the mining area of the possible expansion project. As the test program proceeded, an interesting series of events took place which changed the scope of the work. During the agglomeration work, one of the control columns was inadvertently set up without the addition of lime to the material prior to loading and subsequent leaching. The gold recovery from this column was comparable to those columns that had a lime addition of 10 pounds per ton of ore. In fact, the gold recovery curve had a much steeper slope than those of the other columns. Furthermore, the pH of the pregnant liquor from the "no lime" column recovered to typical levels as fast as the solutions from the "lime" columns. These observations led to the concept that rinsing the ore with water prior to cyanide leaching could be advantageous to the heap-leach process.

Jan 1, 1992

By Egons R. Podnieks, Wallace W. Roepke

Mining technology to utilize vital lunar resources will be required for any commitment to permanent lunar basing. Lunar mining must be viewed both as a major supporting element for space resource commercialization and for creation of human settlements on lunar and planetary surfaces to support long-range space exploration. The Apollo missions to the lunar surface and results from fundamental research on analogue lunar rocks by the Bureau of Mines, and others, have provided the initial data for developing lunar mining technology. The multi-disciplinary research projected in this paper outlines the scientific and engineering needs to realize the lunar mining goals.

Jan 1, 1990

By Jean-Luc Cornet

Downhill, or regenerative conveyors have always been a challenge to the design engineer due to their natural instability under load. The last decade has seen the appearance of high tonnage, high negative lift conveyors with several hundred meters of drop. These conveyors have made necessary the development of new braking systems and intelligent drive controls to address their starting and stopping requirements under various load conditions. This paper describes the critical design criteria of large regenerative conveyors and some of the advances in mechanical braking systems and drive control technology developed by Conveyor Dynamics, Inc. (CDI) to address their specific requirements.

Jan 1, 1993