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By S. Finsterle, R. C. Trautz

Numerical modeling studies were performed to investigate water seepage into underground openings excavated in unsaturated fractured rock. Water seepage is an important factor affecting the performance of a nuclear waste repository, such as the one proposed at Yucca Mountain, NV. The amount of water dripping into an underground opening depends on the connectivity and permeability of the fracture network, as well as on the capillarity of individual fractures intersecting the opening. A high-resolution numerical model of an unsaturated fracture network was developed, and the appropriateness of seepage predictions using a fracture-continuum model was examined. Model calibrations to liquid-release tests performed at Yucca Mountain are also discussed.

Jan 1, 2002

By U B. Pal

Downsizing and decommissioning of nuclear facility operations is increasing the stockpile of various different grades of Radioactive Scrap Iron (RSI). Disposal of this material not only represents significant resource and value lost, but also necessitates long term monitoring for environmental compliance. The latter results in additional recurring expense. It is desirable to be able to decontaminate the RSI to a very low level that can be recycled or used for fabrication of containers for RSI disposal instead of using virgin metal to fabricate the container. Electro-Slag Remelting and Refining (ESR) is often used for decontaminating radioactive contaminated sources of scrap iron such as stainless steel. Non-radioactive oxides of cerium are used to simulate the radioactive oxide contaminants of Uranium and Plutonium. The success of the ESR process is strongly dependent on the capacity of the slag to rapidly incorporate the radioactive contaminant (simulant). In this study we have measured the slag-metal partition coefficient for cerium and investigated the reaction mechanism for the dissolution CeO, in the slag.

Jan 1, 2002

In most surface mining operations, overall project economics is driven to a significant extent by the slope angles that can be achieved within the rock masses present. This is particularly true of precious metal pits in which stripping ratios can be relatively high, although examples from other non-precious metal operations (such as large iron ore and copper pits) can also be found. As a consequence, it is not surprising that in most large (deep) open pit mines, relatively small changes in slope angle (of the order of two or three degrees can translate into changes in project value measured in the tens or even hundreds of millions of dollars. Understanding how this potential value can be realised, and quantifying the associated risks, should be one of the key outcomes of modern slope engineering practice. In striving for optimised slope angles, therefore, mining companies and their specialist consultants are increasingly turning to more sophisticated methods of engineering open pit walls. This paper summarises contemporary slope engineering practice as well as some of the key technical issues that are either currently being researched or will need to be researched in the future. It is written in the context of the slope engineering process; namely, data collection and analysis, failure mode identification and stability assessment, slope design, slope formation, and slope (face) mapping and monitoring (the latter two activities being the primary on-going data collection functions that close the design loop).

Jan 1, 2002

In the mid-1990s, after a long period of antipathy between the company and its detractors, Rio Tinto embarked upon an ambitious cultural change program that sought to transform the fundamental basis of its relationship with global, national and local stakeholders. This has evolved into a broader pursuit of positive cultural change within Rio Tinto as part of the mining industryÆs Sustainable Development initiative. Initially driven from the top down, the communities component of this program comprises an architecture of policies, value statements, social research and verification systems. The commitment to better community relationships is best exemplified in Australia by the scope and scale of the GroupÆs Aboriginal land access agreements, community development programs and the work of the Rio Tinto Aboriginal Foundation. While collectively these form the core elements of an evolving set of internal social competencies, development of second-tier competencies is required to organically embed a culture of sustainable relationships with local and regional communities. Second-tier competencies will include appreciation of social dynamics, social science and diversity at middle management level; rigorous social research that properly informs development options for companies and host communities; career paths and recognition within the mining industry for young professionals both generally and from stakeholder communities; proper community-needs assessments, research into such things as purchasing power and other economics data, and inventories of public goods such as land-carrying capacity and water availability. Without this information it is difficult to gain an appreciation of and to alert people to the consequences of change brought on by a mine. The next decade will see second-tier social competencies promoted within successful mining companies. Measures to achieve this include a range of Human Resource (HR) incentives such as recruitment and career advancement based on broad competencies rather than narrow technical proficiency, humanities training for mining professionals and performance rewards that recognise social competence. A sustainable future for mining in a globally connected social landscape requires selection of people who can listen, relate and act in an open social system. The challenge for the mining industry, its professional organisations and educational institutions is to acknowledge this and develop these new aspects of mining industry professionalism. This cannot be left to individual companies if the industry is to have a sustainable future.

Jan 1, 2002

By Fred W. Brackebusch

"The use of paste technology for surface tailings disposal may offer economic, technical, safety, and environmental advantages for both underground and surface mining operations. Paste is a non-Newtonian fluid having some shear strength during transport and placement. The strength is augmented after placement by consolidation, water loss, and by addition of chemicals. Economical dewatering systems are necessary to the success of surface paste tailings disposal. In an underground mine, the paste backfill plant can produce paste for surface disposal about 50% of the time because only about 1/2 of the tailings are needed for backfill. The distribution of paste to the surface stack involves expensive pumping equipment and thus a nearby location of the stack is desirable. The viscosity of paste can often be manipulated by modifying pH. Placement of the paste in a designed stack configuration depends on topographic and climatic factors as well as paste properties.INTRODUCTIONThe use of paste technology for mine backfill is becoming accepted for underground mines mainly because of ground control and economic reasons. Paste technology is just starting to be applied for tailings disposal with only a few hardrock metal mines worldwide using the technology; however, it has been used extensively for red mud disposal in the aluminum industry. The disposal of dry tailings is very attractive from environmental and safety points of view because of limited water which might potentially escape and pollute river systems. Dry stacking systems, however, are expensive because of filtration and truck transportation costs. Paste can be produced from most tailings streams by special types of thickeners. Furthermore, it can be transported in pipelines, therefore paste technology may be more economic than dry stacking but still have some of the major advantages. Understanding of paste technology has improved through experience with operating underground backfill systems in recent years and because of testwork and research programs by mining companies, consultants and equipment vendors. Thus we may be on the verge of taking a new look at tailings management using paste technology."

Jan 1, 2002

By A. Boominathan

The behaviour of single piles under lateral dynamic loading is very critical and the study is still a current field of research since 1950's. Though many methods have been developed analytically to estimate the dynamic lateral stiffness, very limited dynamic testing on full scale piles were carried out to study the response of piles under lateral dynamic loading. Hence, field lateral dynamic vibration tests are conducted on driven precast concrete square pile of 400mm size and driven cast in-situ concrete piles of 400mm and 500 mm diameter at a petrochemical complexes site at Haldia (India). The results of steady state and free vibrations tests are discussed herein and compared with the response of the piles estimated from PILAY.

Jan 1, 2002

By James Arthur

In deep coal mining the support of the underground roadway is fundamental and without knowledge of the mechanics of ground control a mine is unlikely to be operating safely and efficiently. It is therefore important for the support system to be designed sat¬isfactorily for the size of the excavation required and to do so an understanding of the behaviour of the surrounding strata is re¬quired. Over the last 15 years there has been a major change in the industry and the support systems adopted. The industry has been privatised, legislation has been updated, a comprehensive research programme has been carried out and guidance docu¬ments produced. The paper will show how privatisation has not allowed support standards to deteriorate, highlight research, the legislation and guidance documents updated and how this has led to a reduction in accidents and falls of ground..

Jan 1, 2002

By Wayne Taylor, Martyn Dawborn

Simulation modeling of portions of two platinum mines using General Purpose Simulation Software (GPSS/H™) is presented in this paper. Both mines, located in the Bushveld Igneous Complex PIC) of South Africa, exploit Merensky and UG2 reef horizons, which are processed separately and therefore handled individually from the stope face to surface, requiring duplication of storage arrangements and batch operation of transport facilities. The first simulation assignment concerns the upgrading of a shaft system operating exclusively on Merensky ore, to hoist UG2 ore and increase production. The second assignment comprises a simulation of rock flow from the stope face to surface by way of tramming, inclined conveying and vertical hoisting. Development ends and stope boxholes were modeled down to individual hoppers (cars) demonstrating the versatility of the GPSS/H™ language.

Jan 1, 2002

By Kadri Dagdelen, Thys B. Johnson, Salih Ramazan

Long-term production scheduling design is a very important part of mining because it determines the economic outcome of a project There have been many attempts to solve the optimum pit scheduling problem, but there has been no success in developing a scheduling method to give optimum results in maximizing net present value of a mining project. Open pit production scheduling problem can be formulated as a mathematical programming problem and solved using Mixed Integer Programming technique. However, it is not possible to solve the formulation within a reasonable time since the number of integer variables required for the mathematical model is too great to do that by today's available computer technology. There- fore, a methodology is required to combine, or aggregate, the mining blocks and to decrease the number of integer variables in scheduling without losing the optimality. Therefore, the fundamental tree concept was developed in this paper to combine the blocks. A fundamental tree is defined as any combination of blocks such that: 1. the blocks can be profitably mined, 2. the blocks obey the slope constraints and, 3. there is no subset of the chosen blocks that meets 1 and 2. A Linear Programming (LP) formulation is developed as a mathematical model to find a set of fundamental trees that exist for a deposit. Since the blocks are combined to form the fundamental trees, the number of variables required for the scheduling model is decreased significantly. This decrease in the number of variables makes it possible to mathematically formulate the multi-time period scheduling problem as a Mixed Integer Programming (MIP) model. A case study is performed on a multi-mineral copper deposit in Peru, South America. NPVs of annual after-tax cash flows generated based on the schedule provided by the "Fundamental Tree Algorithm" is compared with NPVs resulted from the schedules coming from three of the computer packages presently available to the mining industry. These are Mintec's M821V, Earth- work's NPV Scheduler, and Whittle's Milava open pit mine schedulers.

Jan 1, 2002

By H. Ogasawara

To study the preparation process of an earthquake, we should get closer to the hypocentre. In co-operation with ISS International, we had an experimental field (~200 m x~200 m) without dykes and faults in a South African deep gold mine. We have monitored more than 20,000 seismic events (M<2) with borehole tri-axial accelerometers. We used a data acquisition system with 15 kHz sampling and 120-dB dynamic range. In a remnant area at a distance of 100?200 m, an earthquake sequence associated with an M~2 event occurred. Significant changes in seismic parameters such as stress drop, b-value, energy index were observed associated with the sequence. We installed Ishii?s borehole strain meters and could monitor as large a strain change as 10-4associated with mining. However, sampling was only 4 times per hour and 12 bit A/D. A distance from the M2 sequence was ~100 m, being not close enough. Therefore, we found another field with several crosscut tunnels excavated across a fault where an M=2-3 event is expected. We installed the strain meter within several metres of the fault to monitor both shear and normal strains on the fault. The strains are continuously digitized with a 24-bit 25-Hz A/D conversion. The Earth Tide (10-8)is clearly detected. Seismicity induced by longwall mining can be compared to earthquake swarm induced by fluid intrusion to vertical dykes. We also found a decrease in energy index in the source area of M>5events a few days before the major events. Keywords: seismic monitoring, strain monitoring, seismic parameters, preparation process of an earthquake, South African gold mine.

Jan 1, 2002

By D. Veigel, J. D. McKay

Model enhanced Expert control has been implemented at the Newmont Lone Tree mill grinding plant as well as rule based Expert control for flotation and thickening circuits. The project has been successful in producing benefits but more importantly has contributed to an ongoing effort for continuous process improvement. This paper discusses how the control at Lone Tree has evolved and the part that Expert control has played in the overall improvements made. Specific examples of how the advanced control has integrated with instrumentation and stabilizing control are given and illustrations of how it has been effective in defining limitations and bottlenecks in the process or process control areas are provided.

Jan 1, 2002

The typical reactions which the reductants undergo during ferroalloy production are reviewed, and identified as reaction with CO2 and with SiO, and dissolution in metal. Available reactivity tests for these three reactions are reviewed. It is proposed that it is worthwhile considering dissolution kinetics as a reactivity parameter. Greater crystallinity of the reductant decreases CO2 and SiO reactivity, but increases dissolution rates.

Jan 1, 2002

By Timothy J. Orr, Jami M. Girard

A NIOSH study on occupational deaths between 1980 and 1989 indicated that in the United States, mining had the highest average annual fatality rate (3 1.9 per 100,000 workers) of any other major industry. Since "lack of training" was often cited as the primary cause of accidents, NIOSH has been investigating new methods for effective training. One such method is the use of low- cost, desktop computers to simulate a virtual mining environment. Computer-based training offers several advantages over conventional training because the computer programs provide a three- dimensional environment that allows the trainee to practice using evacuation routes, encounter mining hazards, and view mining operations without being exposed to any real danger. One major focus of the project is mine escapeway multiuser training using desktop virtual reality programs. Researchers have imported mine maps into the software for the purpose of practicing actual evacuation routes and procedures. Various scenarios for evacuation can be practiced in a three-dimensional computer simulation of the mine in a disaster situation, complete with smoke, fire, and other dangers. Depending on the trainee&apos;s job description (i.e., foreman, shift boss, beltman, etc.), certain tasks need to be performed in addition to navigating primary and/or secondary escape routes. Each scenario allows for individual or team-based training and provides a means to educate mine workers in hazard recognition and hazard avoidance. Using this program, mine workers can practice evacuating various mine layouts without the danger and expense associated with escapeway training in an actual underground mine. Each scenario can be changed to test the trainee&apos;s reaction in a variety of circumstances and run many times so the trainee can practice concepts. This training experience will help reinforce the knowledge acquired during more conventional classroom instruction, and the inherent flexibility of the program allows training materials to be tailored to meet the specific requirements of individual mines.

Jan 1, 2002

Seven legendary figures of American mining will be enshrined in the National Mining Hall of Fame in ceremonies on Saturday, Sept. 7 at the Little America Hotel in Salt Lake City, UT. The 15th annual induction banquet will begin with a reception at 6 pm, followed at 7 pm by the dinner and the program. Of the seven inductees, one is living. He is Alexander Murray (Bud) Wilson, 80, of Los Altos, CA. Wilson led Utah Construction (later Utah International) to become one of the world’s most diversified and successful mining companies in the 1960s and 1970s. It was acquired by General Electric in 1976.

Jan 1, 2002

By Ian R. Firth

For the majority of open pit precious metal mines in the western United States, grade control practices have evolved as a direct result of the variable geology of the ore body and the lack of a clear visual or geologic distinction between ore and waste material. These practices often include the extensive use of buffer or choke blasting, in an attempt to minimize lateral movement of the muckpile. The Mackay School of Mines is conducting ongoing research, which aims to develop a practical method of measuring the movement of discrete “targets” placed within the body of the blast. The movement experienced by these targets can then be used to interpolate the movement of the blast as a whole. Typically, the boundaries between different material types are known as digging limits or polygons and are marked using colored flagging on the muckpile. If material movement can be measured using targets placed in the blast, these digging limits can be altered to reflect the blast-induced rock movement, reducing dilution and improving value recovery.

Jan 1, 2002

By Osama El-Fiky

There are many types of deep foundations currently being used in the San Francisco Bay Area, one of the most common being driven precast, prestressed concrete (PC/PS) piles. PC/PS piles are frequently selected for use due to of ease of installation, availability, and relatively low cost. Disadvantages of using PC/PS piles are noise, vibrations, pollution, front-end delays due to indicator pile programs, and reduced flexibility. An acceptable alternative to driven PC/PS piles was selected for construction of foundations for the heavy housing and administrative buildings at the San Francisco County Jail #3 replacement project in San Bruno, California. The pile type selected, the Auger Pressure Grouted Displacement (APGD) pile, was chosen to reduce noise, vibrations, installation time, and cost, and to allow for greater flexibility of installed pile lengths. This paper presents a case history of the use of APGD piles that were substituted for driven PC/PS concrete piles for the subject project. Standard and quick loading pile load tests were performed to confirm adherence with the design criteria originally used for the driven PC/PS concrete piles. The APGD piles were found to increase shear strength around the piles similarly to driven displacement piles. In addition, this paper presents the methodology used in monitoring APGD pile installation.

Jan 1, 2002

By B. McCosker

The choice of the appropriate delivery process for a project is often not adequately thought about. The industry needs to be prepared to break its preconceived mind-sets on delivery procedures. Industry should also be prepared, on a project by project basis, to commit to a critical review as to how the assessment and then selection of the best procurement method can best optimize the project outcome for both client and contractor. Conventional standards and biased reliances and experienced based preferences should be challenged. To achieve this requires a paradigm shift in attitude to both the process of tendering and the evaluation of tenders. Tender and contracting practices are dynamic and have moved away from solely cost based assessments. Tendering contracts arise imposing changed duties upon owners. Traditional contract delivery models have shifted, reflected in part by the trend towards relationship contracting. The categories of contract options are not closed. Many are but hybrids of other time-tested models. This paper considers options available for any brownfield or greenfield project. The principles outlined are translatable to supply, upgrade, operation and maintenance arrangements.

Jan 1, 2002

By Douglas Kathol

Coal in the 1990?s Exit of the integrated oil company [Shell Arco Mobil Exxon Mapco Kerr McGee Hansen Nerco Sun] Continued decline in coal prices Significant mergers & acquisitions (M&A) activity ?Most properties traded, some twice ?Significant consolidation ?Massive recapitalization ?New industry leaders ?Frustrated expectations

Jan 1, 2002

The aim of this research was to study the absorption characteristics of thermally dried fine coal from South African collieries. After milling to ?150 µm and pressure filtration, the samples were subjected to either air drying or thermal drying at 150°C. The samples were then put into a climate box at 28°C and at three different relative humidity levels, namely 30, 60 and 94 per cent. It was found that the equilibrium moisture content of thermally dried coal at a specific relative humidity was lower than that of air dried coal. The relationship between the equilibrium moisture content and relative humidity is described by 1 ? RH = exp (-KTMen). There was no relationship between the volatile matter content and equilibrium moisture content, but there was an increase in the equilibrium moisture content of the coal with an increase in mineral content. The moisture uptake rate increased with an increase in temperature and a decrease in particle size. A model is discussed that fitted the experimental data and gave a good prediction for changes in the conditions. There was no evidence of greater moisture absorption by thermally dried coal. Keywords: Fine coal, thermal drying, drainage, South Africa, drying

Jan 1, 2002

By K Guilfoyle, A Robertson

In the mid-1970s, trucking ore from 400 m depth to the surface was perceived to be the practical and economic limit for metalliferous underground mines. Improvements in truck design and decline development resulted in the economic depth of haul exceeding 600 m by the mid-1990s. Today, mine operators and contractors are planning to use trucks for ore haulage from depths in excess of 1000 m. The authors of this paper estimate that there are in excess of 300 diesel-powered trucks operating in mines in Australia, and that by the year 2005 more than five per cent of these trucks will be æroad trainsÆ (ie trucks towing powered trailers or truck-trailer combinations). This paper examines the road train concept, presents cost and performance data and describes the advantages and disadvantages of the road train system as well as proposing the types of applications for use of road trains in Australian metalliferous underground mines. Truck performance is based on payload and average speed (expressed as tonnes x kilometres per engine hour (t km/h)). A road train with a powered trailer has a large payload capacity and two engines to provide a high ratio of power to gross weight. Thus it is possible to exceed 300 t km/h per cycle for an average haulage gradient of 1:9 compared to 250 t km/h for conventional articulated dump trucks (ADTs). It is likely that road trains in excess of 100 t capacity will have application for level ore haulage at large mines in Australia.

Jan 1, 2002