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By N. C. Miller

In situ stope leaching is an innovative mining system that reduces the surface impacts of conventional underground mining. As in any leaching operation, stope leaching requires hydrologic site characterization and control of leaching solutions. Several tracer tests, using sodium chloride (NaCl) in various concentrations, were conducted by the U. S. Bureau of Mines (USBM) in an underground experimental stope to simulate a leaching environment. The tests were conducted in fractured crystalline rock that was partially saturated. As tests progressed, the surrounding fractures became more saturated. A predominant flow direction away from the stope was found during testing. Testing procedures, preliminary results, and remediation ideas based on field observations are presented in this paper.

Jan 1, 1995

By M. D. Chatham

Revolutionary electronic monitoring and control systems provide a gold mine of diagnostic and prognostic information. Lower cost per ton results from timely operator action, increased visibility of information to production and maintenance personnel, and better fleet management. When information is effectively integrated into fleet management systems lower costs result from higher availability, longer component life and reduced repair cost. This paper will present the objectives of the Caterpillar Vital Information Management System (VIMS) and provide actual examples of successful use.

Jan 1, 1995

By M. J. Klishis

This paper presents the findings of a study on roof bolters' hazard exposure. A "micro-analysis" of accident data was combined with ergonomic observations of roof bolter operators to categorize bolting-related injuries and a checklist was constructed. Bolting-related problems were identified as situations that could expose bolter operators to hazards. Approaches to avoid these situations were applied at six mining operations to evaluate specific problems in roof bolting operations. The re-search emphasized the importance of analyzing worker behaviors in the context of mining situations and equipment design problems that lead to human error accidents.

Jan 1, 1995

Integrated mining information and process control systems can reduce information delays, enhance decision making and improve the responsiveness of mining operations to, for example, variations in market conditions, mineral grades and ground conditions. This paper examines developments in the areas of: monitoring, data analysis and diagnosis,' communications systems; integrated mining support system;, and process and machine control. It concludes that the development of a comprehensive information technology plan is fundamental to the phased implementation of these technologies. In addition, hardware and software standards and concurrent digital design and simulation practices in selected manufacturing industries are examined and concluded to have relevance to the mining industry. Integrated information and process control systems will lead to emergence of the "digital mine". Such advances in mining information infrastructure as well as mining equipment will enable mining operations to shift from mass production methods to leaner production techniques. "Lean mining" aims to enhance and accelerate cash flow over the life of a mine by focusing on reduction of' throughput times; stockpiles for volume and quality control; and wastage and rework.

Jan 1, 1995

By M. R. Grant, G. S. Kruger, H. D. van der Merwe, T. N. Huffman

Sixteenth to seventeenth century Kalanga miners dug a series of sub-vertical shafts into a 10 to 30 m wide zone of copper ore at the Thakadu Mine near Matsitama, Botswana. They went down at least 6 m in search of thick malachite veins. The host rock was hand 'cobbed' to remove the veins, which were then smelted nearby in small bowl furnaces. Evidently, the furnaces lacked clay superstructures, since a simple pit was sufficient to smelt the almost pure malachite. The copper bloom was probably refined in villages further away.

Jan 1, 1995

By Yoshiharu Tanaka, Toshiyuki Ichijo, Masaaki Yamamoto

We utilized electronic detonators (EDs) to investigate the effect of high detonator delay accuracy on overbreak, remaining rock damage, and surface smoothness, in comparison with that of long-period delay detonators (0.25 sec interval) PDs. The experiments were conducted in a deep mine, in a test site region composed of very hard granodiorite with a seismic wave velocity of about 6.0 km/see and a uniaxial compressive strength, uniaxial tensile strength, and Young's modulus of 300 MPa, 12 MPa, and 73 GPa, respectively. The blasting design was for a test tunnel excavation 8 m in cross section, with an advance per round of 2.5 m. Five rounds were performed, each with a large-hole cut and perimeter holes in a 0.4-m spacing charged with 20-mm-diameter water gel explosive to obtain low charge concentration. EDs were used in the holes on the perimeter of the right half, and PDs were used in all other holes.

Jan 1, 1995

By Reynold N. Hoover, Davis S. Shatzer

The Bureau of Alcohol, Tobacco and Firearms (ATF) is responsible for the regulation and enforcement of the explosives laws codified in the Organized Crime Control Act of 1970, Title XI. To meet its responsibilities ATF has special agents, inspectors and specialists who regularly interact with the explosives industry. However, with just over 2,000 special agents and 800 inspectors and specialists, it is difficult to visit the almost 10,000 explosives licensees and permittees in the United States.

Jan 1, 1995

By J. M. Dean

With the continued downward pressure on coal selling prices, mine management must make its operations as efficient as possible. The problem is the same one throughout the mineral industries, streamlining operations to maintain competitive mining costs (Born, 1991). There has been a great deal of research into better using production manpower. But the story is different for operations support personnel. Traditionally, planning man-power requirements are done annually, with modifications to the operating plan occurring generally quarterly. On the other hand, the demands on manpower are often dynamic, being responsive to changing productivity levels ,mine conditions (including water influx, bad roof, poor floor)and unanticipated project requirements (responses to machine breakdowns or a new section setup requirement because of a drop in coal quality in another area). Such changes may impact the manpower structure significantly. At times they may cause serious labor relations problems concurrently. Realignments and the generation of instability in the workforce because of active job switching (bidding) are a result. Most responses by coal operators are reactive rather than proactive, a situation that could be mollified by more accurate and detailed planning of predictable manpower requirements. A manpower planning tool is needed that takes into consideration such things as changing productivity levels and conditions as manhour requirements for different work areas are planned, rather than blindly allocated through traditional staffing modes.

Jan 1, 1995

By Yves Lizotte, Malcom Scoble, Sanu Hanspal

"This paper reviews the physical, chemical and mechanical components of what is considered to be the anatomy of a blast muckpile. These relate principally to geometry, floor, fragment size and shapedistribution, density, hydrology, weathering, and diggabiity characteristics."

Jan 1, 1995

By Lawrence Devon Smith

"The concept of risk is well established in the mining industry. It is acknowledged when estimates of reserves are expressed as proven or probable, when mining and metallurgical recoveries are applied to the ore, and when contingencies are added to costs. However, it is difficult to provide a quantitative assessment of risk. The significant sources of risk in a mineral project and how these are addressed in project evaluations are discussed.The discount rate is examined as a fundamental means of reflecting risk in discounted cash flow evaluations. Current industry practice is discussed, and a methodology for the analysis of risk levels is proposed that assesses the constituent components of the discount rate: real interest, mineral project risks, and country risk.IntroductionThis paper examines the components of the discounted cash flow discount rate and proposes a method of estimating project-specific discount rates. The motivation for this work comes from experience of project evaluations in which owners and purchasers had agreed on virtually every aspect of the evaluation except how much the project was worth. Agreement was reached on reserves, grade, recovery, capital costs, operating costs, taxes, and, by combining these components, even on the final cash flow values. The only difference in opinion concerned the discount rate to be used in the calculation of the net present value. Depending on the life of the project, such differences of opinion can cause a variation of more than 50% in the value placed on a project! This is illustrated in Figure I."

Jan 1, 1995

By B. Weaver

Every year Pit & Quarry Magazine surveys the industry to produce their annual review. Here's a sampling of some of the statistics the survey produced from the end of the year 1994 survey.

Jan 1, 1995

By W. Gutmannsbauer

Thin films of TiO2 nanoparticles have been prepared by different reactive deposition methods, such as electron evaporation, ion plating and ion beam sputtering. Many properties especially the optical properties, are strongly related to the film morphology and surface roughness. Scanning force microscopy was employed to obtain information on the surface structure of as-deposited Ti(h thin films. The influence of the deposition conditions and the film thickness on the optical and structural properties has been investigated. The as-deposited films were found to be amorphous or polycrystalline with anatase structure.

Jan 1, 1995

By F. Chavan

1. Introduction The new Cleuson-Dixence development project in the Valais region of the Swiss Alps, involves the construction of a new link between the Grande-Dixence dam (still world recordholder with a height of 300 m) and a power house on the banks of the Rhone consisting of approximately 20 km tunnels and shafts, and involving a fall of about 1900 m. This 1200 MW project will replace an existing 900 MW structure built in the 1960s, no longer considered efficient. The new project comprises a head race drift about 15.8 km long, a surge tank, an inclined cascade shaft 4,2 km long, and an underground power station. The work for lots C and D (head race drift from Tortin to Tracouet, surge tank, six adits ans the complete inclined shaft) was awarded to our group (Prader, Locher, SELL, Losinger, Evéquoz, Dénériaz, Imboden and Bouygues). The geological conditions are: Lower part of the shaft (300 m) : sedimentary - sandstone and soft tertiary sandstone. Middle and upper part (2600 m) : metamorphic - upper and lower carboniferous, interrupted by triasic chipping. The horizontal section (7 km) consists of mica

Jan 1, 1995

By Charles V. Jude

This U.S. Bureau of Mines report presents a review and evaluation of existing and new backfilling materials and methods for their applicability to the problem of gate road stress reduction in deep retreat longwall coal mines. Candidate backfill materials include pulverized coal combustion fly ash, flue gas desulfurization, and fluidized bed combustion by-products from coal-fired electric power generation plants. Properties of both backfill and its component materials are presented, with particular emphasis on the unconfined compressive strength and elastic modulus of backfill mixtures. Hydraulic mix designs discussed in this report include high-water content slurry and low-water content paste fills. Three gate road stress-transfer-modification concepts are proposed to reduce abutment stresses in gate road systems. The first concept, packwalling, involves packwall construction behind the headgate shield inby the face and adjacent to the headgate pillars. The second concept, gob-filling, involves infilling a strip of gob inset from and parallel to the headgate using paste injection methods patterned after a technology recently developed in Europe. In the third concept, entry-filling, slurry fill methods are used to fill abandoned gate roads and crosscut entries inby the face.

Jan 1, 1995

By Torres F, Cerda I, Gimenez P, Gonzalez G, Castelli L

Slurry density measurement, specially in cyclone feed streams, is fundamental to grinding circuit control. With the purpose of increasing the availability of such a measurement, the design of a soft-sensor in an actual grinding plant is addressed in this paper. The system is designed to substitute the momentary unavailability of the real density sensor, either because it has failed or because it has been removed for any other reason. The ARMAX model structure is determined using the stepwise regression method. Starting with a list of the candidate variables, the method selects, one by one, and in a systematic manner the variables which best model the measurement to be replaced, choosing them from the set of presumably correlated candidate variables. In this paper not only the single measurements are included in the list of candidates, but also combinations of such measurements having physical significance. A phenomenological model has been built with the purpose of determining these combinations. It turned out that in most of the cases the components of combined measurements having physical significance were selected by the stepwise regression method, instead of the single measurements. Actual grinding plant data is used to determine the model structure, to estimate the model parameters and to test the predictive capability of the developed soft-sensors. Good results are shown to be obtained during periods of up to 30 hours of the density soft-sensor operation.

Jan 1, 1995

By Gaballah Djona M.

Spent hydrorefining catalysts contain about 5 % of CoO and/or NiO, 12 % of MoO3 and up to 10 % of V205. They are generally supported by alumina and contain up to 25 percent of C, S and hydrocarbons. Such materials are potentially hazardous to the soil and to water resources. Selective chlorination of raw unroasted samples with Cl2 + air gas mixture had been investigated. At temperatures lower than 600 °C, it was possible to recover more than 90 % of nickel and cobalt chlorides, about 99 % of the molybdenum and up to 75 % of vanadium chlorinated compounds. CoCl2 and Ni/Cl2 were extracted from the chlorination residues by their dissolution with acidified water. Molybdenum and vanadium chlorinated compounds were recovered by selective condensation from the vapor phase. The chlorination of Al2O3 could be limited to less than 6 %. The scale up of this treatment was successful and a flow-sheet is proposed.

Jan 1, 1995

By Thomas W. Healy, David V. Boger, Yee-Kwong Leong, Lee R. White, Peter J. Scales

The concentration of mineral slurries by conventional thickening devices is discussed. The role of additives on the compression of mineral slurries is also examined. Results for a range of flocculation conditions are presented. The compression of flocculated mineral slurries is found to be highly dependent on the fundamental particle-particle interaction forces and hence, the rheology of the particulate fluid. It is demonstrated that a detailed knowledge of the properties of both the mode of operation of the thickening device and of the solid/liquid interface is required for improvement in the rate and in particular, the extent of dewatering.

Jan 1, 1995

By H. A. D. Kirsten

The paper reports on loading tests conducted on shotcrete reinforced with mesh and various types of steel fibre, and compares the results with the energy absorbing capabilities of 16 mm rebar shepherd's crooks. It is concluded that mesh-reit1forced shotcrete has sufficient energy-absorbing capabilities to contain rockbursts of significant magnitude, having greater energy absorbing capabilities, even at a thickness of 50 mm, than 16 mm rebar shepherd's crooks. Fibre-reinforced shotcrete has energy absorbing capabilities of the same order as, or better than, those of 16 mm rebar shepherd's crooks, but its performance is erratic.

Jan 1, 1995

By Levent Ozdemir, Roy H. Spitzer, Don W. Deere, John B. Blyler

This paper documents the construction of the Stanley Canyon Tunnel, the geologic conditions encountered, boreability of the rock, and the impacts of the conditions encountered on the construction. The 5.05 kilometer long (3.1 miles), 3.47 meter (11.4 feet) diameter, tunnel was driven through granites with a refurbished tunnel boring machine (TBM). Difficult ground conditions encountered included shear zones, high groundwater flows, and hard, tough, and strong rock. Detailed geotechnical studies during construction revealed that microscopic changes in the rock grain boundaries due to contact metamorphism, resulted in the hard boreability. Originally scheduled for five months, the tunnel construction required nearly three years, including periods of project shutdown.

Jan 1, 1995

By L. A. Panek

A new pillar strength formula is presented. It incorporates a function [IF] of size and shape that takes into account the size-shape interaction effect as well as the enhanced strength exhibited by wide pillars. Existing pillar formulas, lacking these capabilities, are not suitable for extrapolating small-specimen test results to mine-pillar sizes and shapes. Interpreting compressive strength test results as function of [Y] reveals wide-pillar behavior in much old test data. Model relationships are discussed, along with their scaling implications.

Jan 1, 1995