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By S. Saeb, C. Francke

Introduction Although mining in one form or another has existed for millennia, the use of numerical methods for mine design is a relatively recent development. The basic physics that control the behavior of rock or soil have been known for centuries, but it wasn’t until the last half of the twentieth century that analytical methods that could accurately predict the behavior of a large, irregular rock mass were developed. Before the advent of modern computers combined with differential and integral analytical methods, numerical methods available to mining engineers were limited to closed form solutions for simple excavation geometries. Today, mine-scale three-dimensional stress analyses can be performed on a relatively inexpensive personal computer. Many of the recent advances in rock mechanics modeling are the result of research funded as part of nuclear waste repositories around the world. The large scale exacting performance requirements of waste repositories are frequently very different from traditional rock mechanics projects. These facilities are designed and built under tighter control and scrutiny because of the potential hazards they present to the public. Therefore, a great deal of research towards advancing rock mechanics and numerical modeling resulted from these projects. Much of the repository research is applicable to commercial mines. The advances in modeling programs have been paralleled by advances in computer equipment. Today, a moderately equipped personal computer can handle most mine geomechanical modeling projects in a reasonable period of time. While the learning curve varies, an engineer with modeling experience can develop a medium sized model in a few days. The relatively low investment cost of geomechanical modeling today makes it accessible to most mining operations. The benefits of a solid geomechanical modeling program include reduced operating costs, improved safety, and reduced design costs.

Jan 1, 2007

By C. R. McKee

In-situ mining of hard rock deposits will only become successful as we understand the engineering parameters involved and the design limitations they impose. As recognized by Wadsworth1 the most critical area is the enhancement of permeability in a hard rock mass. Along with creating permeability, the appropriate flow and fragment size conditions must be generated to insure economic rates of mineral recovery. In this article our interest is confined to true in-situ processes in which boreholes are drilled from the ground surface or a mine drift to deeper strata. We assume that fractures and permeability enhancement will be due to explosives detonated in boreholes. Other techniques such as hydraulic fracturing do not produce the necessary size distribution to promote economic extract ion rates unless the medium is already highly fractured and interconnected. Notable exceptions where hydraulic fracturing is applicable are many oil, gas and salt deposits. For many in-situ processes, an array of explosive charges offers the opportunity of creating a distribution of many fractures not achievable by other techniques. Such a situation would be suitable, for example, to in-situ mine hard rock gold, uranium, copper or oil shale deposits and may enhance oil and gas recovery in certain situations. The purpose of our article is to review and extend the explosive permeability theory of McKee and Hanson 3,4,5 and to apply its results to derive design parameters suitable for in-situ mining.

Jan 1, 1981

By R. P. Benson, D. H. MacDonald, D. R. McCreath

1 - INTRODUCTION The Canadian Shield is well known as being among the older exposed areas of the earth's surface. Except for local zones, its extent from the Arctic to central North America is characterized by strong and durable crystalline rocks. It is generally regarded as highly competent for tunnelling and underground excavation and, as a result, many openings are excavated in it with minimal temporary support. If hydraulic efficiency is not a factor, tunnels do not usually require continuous concrete linings. A high percentage of the crystalline rocks of the Shield are of metamorphic origin and as such one of the dominant characteristics is their foliation. Zones of sheared or faulted rock are common in the Canadian Shield, particularly in association with foliation. These zones may be created during the late stages of the metamorphic process, leaving shear zones as an integral feature of foliated rock. As foliation is a preferred direction of weakness, deformation and rupture during subsequent tectonism may also create parallel shear zones. These "foliation shear zones", as described by Deere (1973), are an adverse feature of the otherwise durable rocks of the Canadian Shield. The zones may range from faults of major proportions to seams only a fraction of an inch thick. If fault gouge or alteration products exist in the zone the strength of the rock mass may be great1y reduced. As foliation is usually continuous, large unstable wedges of rock may be created if the opening is subparallel to the foliation. The effect on the construction of underground openings in terms of excavations, support and scheduling can be significant.

Jan 1, 1974

By G. Chi, M. C. Fuerstenau, R. C. Bradt

Reduction of the total energy expenditure in mining and ore preparation processes was achieved by redistribution of the energy from the crushing and grinding steps to the blasting operation. Reducing the burden/spacing distance by 25% or increasing the charge length by 25% during blasting results in significant energy savings in subsequent comminution processes. The energy cost of mining and comminution is reduced by up to 10%.

Jan 1, 1995

By W. M. Pytel

A simplified two-dimensional model to analyze time-dependent load distribution and surface subsidence associated with longwall mining geometries is described. The model is based on the theory of beams resting on inelastic foundations and includes visco-elastic behavior of immediate floor strata, non-linear behavior of coal pillars, elastic behavior of face supports, and visco-elastic behavior of the overburden strata. The relative importance of the different variables affecting the performance of longwall mining geometries from ground control point of view is also analyzed. The model has been validated for field observations from one Illinois longwall mine.

Jan 1, 1986

By I. Iwasaki

Differential flotation of bulk sulfide concentrates from Duluth gabbro into copper and nickel concentrates could be implemented by first destroying the hydrophobic coating with ozone and then by recovering the copper concentrate with a copper-selective collector. A number of parameters involved in the use of ozone; such as the sequence and the conditioning time of ozone treatment, the pulp pH, and the level of xanthate addition, were investigated.

Jan 1, 1985

By P. Schiavi

A trend towards the independent verification of sustainable development reporting and assessment using third party certification can be discerned in the global minerals industry. Various codes that provide for the third party assessment and certification of performance against a range of externally developed sustainability indicators are being adopted by minerals companies, and there is also considerable activity in the broader area of third party assurance. Using a sociological approach, this paper examines the reasons why third party certification schemes are appearing in the minerals industry to address sustainable development imperatives in preference to other forms of regulation, and considers the broader implications of this trend. Data are drawn from a series of qualitative, in-depth interviews conducted with some of the key players in the development and adoption of certification schemes in the minerals industry, with executive managers of a range of large mining corporations, with representatives of global non-governmental organizations that are active in mining issues, and with government officers responsible for the regulation of mining corporations in Australia. Factors responsible for the emergence of the new certification schemes include: increasing demands from stakeholders for greater credibility in reporting against sustainable development indicators; broader contextual factors including globalization and neoliberal policies; and issues relating to trust and risk. Using insights from our research, and the work of others in this field, we identify some of the critical features of a credible third party certification scheme, and note some of the challenges for the design and implementation of such schemes. We conclude by discussing some of the broader implications of third party certification as an emerging form of regulation in the minerals industry.

Jan 1, 2007

By R. V. Ramani, R. A. Jankowski, R. Bhaskar

The spatial distribution of airborne dusts, deposition of dust in the airway, as well as the effect of airflow velocity and particle density on dust behavior in mine airways were studied in a set of experiments performed in a mine airway under controlled conditions. Considerable deposition of dust near the source was indicated. Pronounced effects due to velocity were observed in ambient dust concentration and deposition along the mine airway, both in the respirable and the total size ranges. Cross-sectional concentration measurements indicate an increase in concentration from the roof to the floor. The average cross-sectional concentration is about 75% of the concentration in the center of the airway.

Jan 1, 1987

By Albert W. Evans

Introduction Engineering Health and Safety is concerned with the understanding of the complex interplay between the risk of injury with technological ,environmental, individual, organisational and legal factors. With this understanding, the design and decision making processes can be balanced with the other objectives of industry and employment to arrive at solutions which place appropriate controls on technology and other aspects of human activities to prevent disease and injury to personnel in the coal mining industry and the design of safe production machinery and ancillary equipment. Advances in the detection and diagnosis of causes of diseases and the need for engineering health and safety in the coal mining industry has increased the need for appropriate education and training. Hazards arise in many forms; exposure to toxic chemicals, escape of radio - active materials, explosion of pressure vessels, contact with moving machinery, exposure to dust, environmental dangers such as excessive noise, high temperatures and manual handling etc. As technology advances, these dangers become more complex and less clearly defined and less easily perceived. Consequently, the ways of controlling the dangers also become more complex and wide ranging. The need to educate and train people in coal mining applications of engineering health and safety has been enhanced over the last five years and courses should be established to fulfil the need for competent people to deal with the problems which modern coal mining technology creates together with the legislation that governs engineering health and safety and to carry out research and development work in the coal mining industry. Industrial Involvement The engineering health and safety experts must be prepared to take a more active part in monitoring conditions that exist in the mining industry, and not design from information obtained from the mechanical, electrical and hydraulic expertise and off-the-shelf components from other industries. Surveying and control of the operating environment must be essentially the concern of the engineering health and safety experts and, whilst it is not possible to create a perfect environment for each machine, every effort must be made to minimise failures and hence plan for designs which will maximise

Jan 1, 1986

By Robert E. Moore

Investigators have attempted to develop lime refractories on a scale for broad applications in the metal and ceramic industries for several decades. There was a flurry of activity in the early to mid-fifties but no commercial developments were forthcoming. The literature of that period yields little information on plant trials. A major factor suppressing past interest in lime has to have been the high success with the application of magnesic and dolomitic materials. These materials, usually tar-bonded or impregnated, have become the refractories success story of the past two decades, especially in BOF applications. It is safe to say that their development and application has essentially plateaued, and that work today is focussed on finding cheaper paths to produce MgO-based refractories. For example there are efforts underway to extract MgO from mineral magnesite and to combine natural dolomite with MgO1. Beginning in the late sixties, rather intensive research began on the development of CaO brick, especially in East and West Germany, in Poland, and other communist bloc satellites, 'and also in Italy and Spain. One speculates that the motivation was a regional shortage of good magnesia and dolomitic material. Of course, There has always existed the prospect of cost savings should it be possible to use raw limestone as the starting material. Quite a large literature has appeared treating of these developments which in the early seventies had already reached full plant scale trials and uses. Some of the directions followed in the research have led to novel methods of brick manufacture.

Jan 1, 1985

By Rudolf E. Pfister

One of the Swiss transalpine highways includes two remarkable tunnels: the 16.3 km long Gotthard Road Tunnel and the 9.3 km long twin tube Seelisberg Tunnel, both presently under construction. Large diameter shafts up to 900 m long are required for ventilation. Excavation techniques for rock formations ranging from loose sedimentary rock to granite and very hard siliceous limestone were carefully evaluated. The methods finally applied include excavation of shafts in hard rock, conventional drilling and blasting, excavation by ripper-tooth excavator ("Big John") in marlstone, shield protected heading in loose material and soft rock, and tunnel and shaft lining, both by poured concrete and by prefabricated elements. A critical review of the success of these methods can now be made after a five year construction period.

Jan 1, 1976

By J. D. Miller, Jon J. Kellar

Researchers in flotation chemistry have long sought to describe collector adsorption phenomena in greater detail including kinetics, orientation and interactions between adsorbed species. Now a quantitative description can be made in-situ using FTIR internal reflection spectroscopy. Details of the adsorption process at the surface of mineral crystals, machined into internal reflection elements, can be described from first principles, provided the refractive indices, incident angle, and wavelength of light are known. Collector orientation can be established based on spectral characteristics of plane polarized and perpendicular polarized light. Examples of the use of in-situ FTIR internal reflection spectroscopy are given for the sapphire-sodium dodecyl sulfate system and for the fluorite-sodium oleate system. It is expected that quantitative in-situ analysis of collector adsorption reactions by FTIR internal reflection spectro-scopy will continue to grow in importance and will provide an important new dimension in our understanding of flotation chemistry.

Jan 1, 1989

By Robert R. McDougal, Anne E. McCafferty, Bruce D. Smith

Magnetic, electromagnetic, and radiometric airborne survey data have been used in regional and local (drainage basin) scales. In a regional geoenvironmental assessment of the state of Montana, magnetic and radiometric data compiled from airborne surveys were used along with other digital geologic and geochemical data to prioritize mining districts for potential acid water generation. Probability ratio mapping was done in order to integrate the interpretation of many different digital data sets. On a more local scale, the Animas (CO) and Boulder Basin (MT) watersheds have been studied using helicopter geophysical surveys. The airborne geophysical surveys show many more structural features than the geologic maps. Combined interpretation of the geophysical data sets using the probability ratio method has resulted in identification of areas of alteration. Airborne radiometric data in the Boulder Basin area suggests that rocks with high potassium and thorium also have a high acid water buffering capacity.

Jan 1, 2000

By Z. T. Bieniawski, D. A. Newman

The Geomechanics Classijication (RMR System) (Bieniawski, 1979) was modified for entry and roof support design in underground coal mines. Adjustment multipliers were introduced to incorporate the influence of high horizontal stresses and the roof support reinforcement into the existing classification system. Sixty- two case histories of standing and fallen mine roof were collected from two mines in the northern Appalachian coalfield. Twenty-seven engineering and geologic parameters were recorded for each case. A partial correlation analysis was carried out on the cases to establish which parameters have a significant im- pact on the stand-up time of supported coal mine roof. Survival analysis, a statistical technique used in medical research to assess the effect of a drug or treatment on a patient's life expectancy, was conducted together with stepwise multiple regression to derive values for the adjustment multipliers. A practical example is included to illustrate the application of the modified Geomechanics Classification to underground coal mine design.

Jan 1, 1987

By N. C. Saxena, S. K. Puri, A. K. Pal

The condition-based monitoring system is an important innovation for reducing the downtime of costly, heavy earth- moving machinery (HEMM). Vibration severity measurements were made on the HEMM located at the Gevra Project, the largest coal opencast project in India. Whenever the vibration severity levels exceeded the permissible limits, necessary actions were taken to replace the defective parts of the ma- chine. The systematic vibration monitoring of 120-t (132-st) dumpers, followed by corrective measures led to a substantial increase in component life (8.18% for an 445E Dressor and 28.44% for an MK-30 Unit Rig). The associated costs (including spareparts) were reduced by 21.55% and 25.74%, respectively. Because of the reduced downtime, savings for these two dumpers over the period from March 26 to June 25,1998, were of the order of Rs.26.47 (US$0.649) million.

Jan 1, 2000

By Dipak D. Shah, Sajjan K. Jain

An interceptor sewer, 2103 linear meters (6900 Ft), 1.52 meter (5 ft) in nominal diameter, is installed by a direct pipe jacking system utilizing a remotely controlled fully automatic slurry shield machine called "Unclemole". The system involves placement of custom designed fiberglass pipe with Unclemole. The sewer alignment is along a heavily travelled thoroughfare in Staten Island, New York with invert varying from 20 meters (65 ft) to 28 meters (92 ft) beneath the road surface, and passes through soils of Glacial and Cretaceous origin. Dewatering was carried out at the jacking and receiving pits. Details of ground conditions, the pipe jacking system and method, and tunneling experiences are herein described.

Jan 1, 1991

By David J. Kruse

The proper modeling of granular flow using discontinuum mechanics has the potential to be one of the most significant scientific advancements in the mining industry today. This paper will examine the status of discrete element technology, specifically focusing on current and future applications. The fundamentals of the Discrete Element Method (DEM) will be briefly introduced, as well as relevant design parameters. Various types of granular flow problems currently being solved using the DEM methodology will be presented. The results and potential benefits of these cases will also be discussed. All simulation results and figures used throughout this paper are from studies and designs preformed by the DEM group at Conveyor Dynamics, Inc. (CDI).

Jan 1, 2000

By Meliton M. Garcia, Satya Harpalani

This paper discusses the results of an investigation carried out in an underground mine to characterize the volatile by-products adsorbed on airborne particulates following the detonation of four common explosives including ANFO. The primary objective of this study was to determine if any organic amine compounds, particularly nitrosamines, and any polycyclic aromatic hydrocarbons were produced and trapped in the dust that a miner might inhale during the workday. The production of these substances is of great concern because of their suspected carcinogenic nature. The results of the study indicated that a large variety of the by-products are adsorbed on the particulates generated, and thus remain airborne following the detonation of explosives. The major by-products retained by the dust were bis(2-ethylhexyl) phthalate, and aliphatic hydrocarbons with carbon chains ranging from C12 to C28. One explosive, a water gel, produced the polycyclic aromatic compound, trimethylnaphthalene. No nitrosamine compounds were detected.

Jan 1, 1989

By R. Schuerch, G. Anagnostou, R. Poggiati

"The paper presents dimensionless design diagrams for estimating the stand-up time of a tunnel face in saturated ground of medium-low permeability. The diagrams cover a wide range of ground parameters and apply to shallow tunnels (overburden less than two diameters). As the time-dependency of the face stability in water-bearing ground is associated with the consolidation process in the soil ahead of the tunnel face, the stand-up time is determined by means of hydraulic-mechanical coupled spatial stress analyses. The results presented are important for tunnel engineering practice, e.g. when estimating the feasibility of atmospheric interventions in the working chamber of a closed shield. INTRODUCTION The response of water-bearing medium-low permeability ground to tunnel excavation is time dependent. The time-dependency is due to a transient seepage flow process that is triggered by the excavation and develops slowly over the course of time. Experience shows that the short-term behavior the ground is more favorable than the long-term one: the deformations increase with time; the tunnel face may be stable initially and fail only after some time. The time over which the tunnel face remains stable is called the stand-up time. This paper investigates the time dependency of the tunnel face stability assuming that all time effects are due to consolidation rather than creep. This assumption is reasonable for shallow tunnels crossing water-bearing soils. In the problem under analysis, the unsupported tunnel face remains stable under the undrained conditions prevailing after excavation, but collapses before reaching the drained conditions prevailing at a steady state. The assessment of the stand-up time is important from an economical point of view for both mechanized and conventional tunneling through weak water-bearing ground, as a long stand-up time removes the need for face support or ground improvement works during standstills, thus saving time and money, while short stand-up times require hyperbaric interventions or the implementation of costly and time-consuming auxiliary measures."

Jan 1, 2016

By V. K. Paruchuri, J. D. Miller, J. Nalaskowski

An understanding of forces responsible for the stability of dispersions of colloidal particles when interacting with each other in aqueous solutions is of great interest academically and industrially. When water-soluble polymers are adsorbed onto colloidal particles, various effects on the stability of their suspensions can be expected ranging from steric stabilization to bridging flocculation. The possibility of detailed characterization of such systems using direct measurements of interaction forces between particles can help in further improvement of existing technologies of solid-liquid separation. An atomic force microscope (AFM) colloidal probe was used to measure the interaction forces between a silica sphere and a silica substrate in the presence of water-soluble polymers. Poly(ethlene oxide) (PEO) with three different molecular weights (7,000, 43,000, and 63,000), each with a very narrow molecular weight distribution, were used in this study. The interaction forces measured with the AFM over an extended time scale are discussed in terms of the adsorption kinetics measured through in-situ FTIR/IRS measurements.

Jan 1, 2003