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By Z. Kowalski

In the non-operational ?Górka? quarry, there are situated both a waste disposal site of an area of 6.7 ha, containing approximately 1 million ton wastes from high aluminium content materials (incl. about 400000 t of wastes from aluminum hydroxide production), and a pond of an area of roughly 3 ha, up to 15 m deep, with about 400000 m3 of polluted water and infiltrates from the disposal site mentioned. The basic problem related to the effluents in the Górka pond is both their high alkalinity (pH 12-13.4) and a variable analysis of pollutants whose level increases appreciably with the pond?s depth. The solution offered provides, first of all, remedial pumping and a treatment of effluents retained in the Górka reservoir. Effluents would be treated in a reverse osmosis plant according to a process verified so far on a quarter-commercial scale. The treatment process by-product, a brine solution (containing about 25% NaCl) whose amount may reach up to 100000 m3 might be supplied to the Debiensko Mine, which produces technological salt from salt-bearing mine waters. In parallel, an intake of underflows of infiltrates would be provided (previous geochemical identification) in order to take them away from the high aluminum site (by means of deep wells, and possibly girdling ditches). Such effluents would be subject to treatment. The successive stage is the utilization of approx. 50000 m3 of bottom slurry, left in the emptied reservoir, in the production of self-solidifying mixtures, which would be then used for sealing the bottom and the banks of the Górka reservoir. The empty and sealed reservoir would be filled up with a volume of approx. 600000 t of ashes, coming from coal burning in the thermal-electric power station. For the last stage, instead, is scheduled the rehabilitation of the entire waste disposal site in the Górka quarry. The site will be drained, covered with a leveling, sealing and rehabilitating layer, which will allow to introduce plants on the rehabilitated waste site. Later on, the area could be turned into a town park

Jan 1, 2006

At present the feasibility of developing underground facilities for the storage of a number of products including toxic waste, oil, nuclear waste and low pressure gas is under investigation in e number of countries. A possible method of storage is in large excavations, Preliminary ventilation design work has identified that the climatic conditions encountered within these large excavations are a limiting ventilation pollutant within the ventilation system. This paper examines the design of a variety of sizes of excavation from a ventilation viewpoint. The main phases of an excavations lifetime can be divided into four main phases, these being construction, civil and mechanical fitting, storage, full and sealed. The paper details ventilation design options for the first two phases of e vaults lifetime, giving climatic simulations to assess the likely climatic conditions within the excavations for e number of facility depths. The options for climatic control are given and analyzed by means of climatic simulations techniques. l. INTRODUCTION The feasibility of developing underground facilities for the storage of a number of products is under investigation at present in a number of countries. This paper details a possible design for such a facility where the product is to be stored in large underground excavations. A facility layout has been designed with the aim of allowing concurrent construction and storage operations. Thus from a ventilation perspective the facility consists of two circuits , a construction ventilation circuit and a product ventilation circuit both of which are served by an intake and a return surface connection The construction and storage circuits are considered as independent of each other , any interaction in the form of leakage must be from the construction to the storage circuit. From the facility design a ventilation network was developed to assess the ventilation requirements of the facility. In analyzing the pollutant loads for the construction circuit two pollutants were recognised to be critical to the ventilation design , these being diesel exhaust fumes and heat end humidity. In this paper ventilation design options for the construction and civil and mechanical fitting phases of the excavations are analyzed by means of climatic simulation and options for climatic control within the vaults are outlined . 2. FACILITY DESIGN A schematic diagram of a facility design is illustrated in Figure 1. There would be two distinct ventilation circuits , one to service the construction operations and the second to serve the storage operations which occur concurrently with construction , the circuits are separated by ventilation bulkheads . Access to the facility for intake air is provided by two drifts, one to serve each circuit. Two shafts act as returns to surface. The facility consists of two distinct zones for the storage of two types of product. One type is to be stored in smell linear excavations. The second zone is for the storage of a second product in larger excavations. The maximum cross-sectional area and perimeter for the smell linear excavations are 456.25 m2 and 83.2 m, while for the larger excavations they are 440.1 m2 and 86.4 m. Excavation construction consists of three phases: 1. Initial pilot tunnel development between main intake and return to provide through flow ventilation. 2. Enlargement to produce the required finished cross-section. 3. Civil and mechanical engineering work to fit out the excavation ready for storage. It is proposed to excavate the excavations using drill and blest methods utilising diesel equipment. Spoil is to be transported to surface by a conveyor belt system. At any one time the maximum number of working places requiring ventilation will consist of ; 3 storage sites, 2 excavations under construction, 2 excavations undergoing civil and mechanical fitting. [ ]

Jan 1, 1993

By William L. Jude

INTRODUCTION Although the mining method described in this chapter is locally designated "modified Mitchell," there are so many features which are characteristic of square sets that the designation "modified square set" would describe the method equally well. The method was developed as a result of local operating experience with various mining methods, observing operations in mines in the southwest where Mitchell stoping had been thoroughly developed, and an exhaustive study of min¬ing methods literature. Since 1941, modified Mitchell stopes have con¬tributed over 50% of the total stope production and were largely responsible for supporting production dur¬ing the war years and period of declining manpower and increasing costs. GEOLOGY The community of Gilman is situated on Battle Mountain at an elevation of 2743 m (9000 ft) in the Battle Mountain mining district, about 45 km (28 miles) by highway north of Leadville, CO. The sur¬rounding area, including the Mount of the Holy Cross and Eagle River Canyon, is noted for its beauty and recreational facilities, both summer and winter. Massive sulfide ore bodies of the limestone replace¬ment type occur as chimneys and mantas or as blankets in strata dipping 0.19 rad (11°) northeasterly. A chimney is shaped like an inverted cone with shale, quartzite, and porphyry caprocks forming its base. This relatively impervious capping apparently blocked rising ore constituents which formed the chimneys and mantas. At the apex or lower extremity of the chimneys, the ore follows small fractures and bedding planes in under¬lying quartzite. Dimensions of chimneys vary, ranging up to 61 m (200 ft) vertically and 76 m (250 ft) horizontally near capping. The manta or blanket ore bodies vary in vertical cross section from one hundred to several thousand feet. One such manta was developed from its outcrop to its chimney source approximately 610 m (2000 ft) downdip. Another manta of substantial cross section and length did not follow shale but extended updip with limestone capping from its source at a lower horizon. All chimneys, however, make up to the shale¬quartzite-porphyry capping. Chimney ore minerals are mainly pyrite and chalco¬pyrite with accessory copper and silver minerals, surrounded by, and in places overlain with, marmatite, pyrite, and galena. Manganosiderite extends into the ore. It may or may not be impregnated with sufficient marmatite and galena to be of commercial grade. Ore may be massive, coarsely crystalline, or sandy, some¬times rubbly. Generally speaking, chimney ore masses are incompetent and of variable grade. Caprock is heavy and caves readily. Manta ore minerals are mostly marmatite, pyrite, and galena associated with manganosiderite. Structural characteristics of the ore are similar to those found in chimneys and where the manta contact shale capping the ground is unusually heavy. However, the large manta with limestone capping mentioned previously consisted of a hard strong ore mass in fairly strong host rock. Commercial ore contacts are fairly regular in this manta but in others the ore waste contacts along the walls are irregular with shaly limestone pendants extend¬ing downward into the ore at capping. Dolomite sand is also quite frequently encountered along wall contacts and less frequently overhead. MINING METHODS Practically all stoping in the Gilman ore bodies has been carried on with timber and fill methods and the features which have been briefly described have dictated the choice. Although at the present time modified Mitchell and underhand square-set stopes account for the total production, considerable production has been obtained from alternate horizontal cut-and-fill stopes with Mitchell truss stopes in the pillars. This method was highly satisfactory in the hard manta ore body mentioned earlier and where ore excavations 11 m (35 ft) wide and 23 m (75 ft) long required no auxiliary timber support. It was a pillar recovery application of the method devised by M. W. Mitchell at the Calumet

Jan 1, 1982

By S. K. Kawatra, M. T. Rusesky, T. C. Eisele

An on-line monitoring system for apparent slurry viscosity has been developed at Michigan Technological University. It utilizes a vibrating sphere viscometer in conjunction with a special slurry presentation system to reduce particle settling and turbulence effects. It has proven to give accurate, reproducible results in an on-line hydrocyclone installation. Its performance shows that it can be an effective instrument on an industrial scale, particularly in grinding circuits. Development of the sensor and the importance of rheology in grinding are also discussed.

Jan 1, 1992

By L. G. Austin, R. S. C. Rogers

INTRODUCTION Coal is geologically a sedimentary rock with distinct bedding planes containing a mixture of petrographic constituents. Yet. because of its chemical nature, it also has some of the characteristics of a polymeric material. In addition, it is extensively precracked to give a macropore structure and also has a substantial internal volume of microporosity. Add to this the mineral constituents dispersed in the coal in a variety of forms and sizes. and it can be readily appreciated that coal is a complex and heterogeneous material. It has to date not been possible to predict the particle size distributions produced by breakage of coals from a priori application of the principles of fracture mechanics. However, there is a substantial body of data resulting from empirical observation of size distributions produced under various conditions, primarily from grinding mills. It is the function of this review to outline how this empirical information can be used to predict product size distributions for those systems which have been studied systematically, and to suggest future avenues of research using similar methodology. FRACTURE THEORY APPLIED TO COAL It is, of course, possible to devise experiments for slow crack propagation in a coal. However, the evidence is that coal breaks by brittle fracture in the mills and mining machines of industrial importance and therefore the theory of brittle fracture is sufficient to illustrate the important features of the fracture of coal. In order to produce size reduction a solid must be stressed by the application of force. The force can be a tensile (stretching), compressive, or shear force, and the three dimensional stress pattern in the solid represents the tensile, compressive, and shear forces per unit area acting in any direction through any point in the solid. As an illustration consider the case of a simple one-dimensional tensile stress: then stress is defined as a=F/A where F is the force. A is the cross-sectional area of the solid normal to F and strain. E, is defined as the fractional change in the length of the solid. so that E= x/L where x is the extension of an original length of L. Coal behaves as an elastic material over short times (although viscoelastic creep can occur if the stress is maintained over long times) and if it is not stretched too far the coal returns to its original shape when the stress is removed; otherwise catastrophic failure occurs and the coal fractures at a stress termed the tensile strength. The failure under stress of an elastic material is termed brittle fracture. Elastic material fails at small stain and the stress-stain relation to where brittle fracture occurs is the empirical Hooke's law. a= YE, where Y is Young's modulus. The work done on the solid to take the solid from zero external stress to a stressed state by slowly increasing F up to a final stress u is the integral of the stress times the strain. This reversible strain energy is stored in the solid and. using Hooke's law. is u /2Y per unit volume of solid. If the solid is immediately loaded to u the work done is [EAuL] which Is a2 /Y per unit volume, that is, twice the reversible work.

Jan 1, 1988

By Robert F. Conley

This paper describes attrition milling as exemplified in rotary and vibratory mills for ultrafine grin¬ding application Without attempting to narrate the differences between various devices, generalized differences between the broad categories of rotary and vibratory milling are presented and compared with the ball mill Applications of these mills for coal, limestone, kaolin, mica, talc and iron oxides are described giving specific differences of the mineral properties that affect their behavior in the grinding mills Where applicable, specific recommendations are provided for ultrafine grinding of various industrial minerals

Jan 1, 1983

By J. A. Delgadillo, C. A. Pérez-Alonso

"Tumbling mills using balls as grinding media are used extensively in the mining and cement industries to produce fine powders; however, it is well known that the process of size reduction is highly energy-intensive. For this reason, much of today’s comminution research is aimed at understanding grinding mechanisms, by estimating power draft and modeling milling circuits using the discrete element method (DEM). DEM predicts individual particle trajectories, the distribution of energy and contact forces at each collision, lifter wear and power draw. This paper presents a prediction of the discharge particle size distribution using three components, mass balance model (sometimes referred to as a population balance model, PBM), impact energy distribution of the mill obtained from the simulation of the charge motion using DEM and breakage characteristics of particles determined from drop-ball tests. DEM simulation of the charge of a tumbling mill was done using the code MinProSim 1.0 to obtain impact spectra at different operative conditions. Then, the population balance model (PBM), based on impact energy distribution, was used to predict the final particle size distribution in a batch mill and compared with experimental data. It is demonstrated that the DEM-PBM approach allows a reliable solution to predict particle size distribution for tumbling mills. Ideally, the model has to predict size distribution for any operational condition and feed characteristic; however, it has been shown that predictions include some degree of error.IntroductionThe discrete element method (DEM) has recently become a powerful numerical tool that can be used to investigate internal mill charge in ball mills. The early work of Cundall and Strack (1979) used DEM to analyze soil as a discrete medium. Later, the method was improved to simulate the operation of tumbling mills and optimize the design in order to increase the efficiency of energy utilization. Also, it is of great interest to relate ore breakage based on impact energy spectra obtained by DEM simulations and the breakage distribution function used in the PBM to predict particle size distribution in tumbling mills.King and Borgeous (1993) broke single particles in an ultra fast impact load cell to compute the phenomenological parameters in a microscopically more detailed population balance model. Kapur et al. (1997) simulated the size spectra of progeny particles produced by impact grinding as a function of the impact energy. Narayanan (1987), Narayanan and Whiten (1988) and Lira and Kavetsky (1990) estimated the energy-dependent breakage distribution function for scaleup and modeling of industrial ball mills."

Jan 1, 2015

By Gerald Pinter, David Nitsche, Márton Bredács, Markus Haager, Andreas Frank

"The reliable prediction of service lifetime of tunnel constructions is of essential technical and economic interest. Polymers used for tunnel liners have to fulfill the requirement of 100 years lifetime. However, today no reliably proven test method is available which confirms such long lifetimes. The current paper introduces a recently started research project which focuses on lifetime prediction of highly flexible, very low density polyethylene (VLDPE) for tunnel geomembranes. Different PE grades in combination with different antioxidant packages are conditioned at elevated temperatures and immersed in different media. Initial results confirmed significant material aging of unstabilized resins already after exposure of up to 34 weeks, at least at the highest exposure temperature of 80 °C. To consider application relevant material properties the material characterization was done by means of tensile tests and dynamic oxidation induction temperature tests. High pressure liquid chromatography was used for further investigation of antioxidant consumption kinetics. 1. INTRODUCTION For a reliable service of modern tunnel constructions a sustainable proofing against water infiltration is essential for the lifetime of the structure. Geomembranes made of polymeric materials have been used successfully for tunnel lining since several decades. Whereas previous geomembranes usually were made of plasticized polyvinylchloride (PVC-P), due to several technical advantages today very low density polyethylene (VLDPE) has become a more and more popular material for such applications. For modern geomembranes, current guidelines expect minimum lifetimes of at least 100 years (ÖBV-Richtlinie 2012). In contrast to this requirement it must be considered that today no test methodology is available which reliably confirms such long lifetimes of polymeric materials."

Jan 1, 2016

By J. Gallagher

Henderson Mine has been transporting molybdenum ore using a rail haulage system for the past 21 years. Due to the age of this system, limited performance, and obsolescence, a capital investment decision was imminent. Henderson used this opportunity to evaluate other transportation methods and continuously improve their mining practices. These efforts resulted in a new mine plan for Henderson, which ensures that Henderson will continue to supply high quality molybdenum into the 21st century. This paper will discuss the dramatic changes taking place at the Henderson Mine as a new production level is mined. These changes include the installation of an underground crushing, conveying, and truck haulage system, as well as increasing the scale of the panel caving process. Each of these topics will be discussed, as will their rock mechanics and material flow implications.

Jan 1, 1998

By Nikhil Dhawan, Veeranjaneyulu Rayapudi, Singh Rahulkumar Sunil

The ever-increasing demand for steel and the subsequent depletion of high-grade ores requires the massive utilization of low-grade iron ores. In the present study, an iron ore slime sample containing 56.1% Fe was investigated using physical beneficiation, carbothermal reduction, and a microwave-assisted process; however, physical beneficiation and microwave exposure were found to be inefficient as they yielded lower iron recovery. Using coconut shell as an alternative reductant was found to be promising and does not lead to the formation of higher iron oxides, such as fayalite and wustite phases. The microwave-assisted carbothermal reduction was found at par with conventional reduction, saving time and heating. The optimum magnetic concentrate obtained in both carbothermal reduction routes (microwave and muffle furnace: Fe grade, Fe recovery, and yield of 64.3, 97, and 84%, and 67, 99, and 83%, respectively) are suitable for alternative iron-making or blast furnace units.

By R. J. Lutton

The suitability of large-stone materials continues to present occasional problems in US construction. Distinctive modes of rock deterioration cracking, spalling, delaminating. disaggregating, disintegrating, and dissolving help to distinguish causes of deterioration. Design requirements, costs, and environmental factors remain critical to performance. The rating of material quality from superior hypes such as granite to marginal types such as conglomerate is too simplistic but may be useful in a preliminary way. Regardless, the market is dominated by limestone/dolomite material types because of their widespread availability. Certain tests that have been standardized are widely accepted and used for evaluating stone as riprap and armor. These tests are adapted from those used extensively for concrete aggregate; they explore the resistance of the rock to destructive processes such as abrasion, freeze-thaw, and wet-dry environmental attack. The field evaluation of the rock source is often as important as testing. Important limitations imposed by natural jointing and variations of bedding are documented in this manner. The field examination also supports the testing by estimating how much of the quarry is rep¬resented by each of the samples to be tested. Finally, quarrying and processing methods and transportation are carefully considered in regard to stone quality, average size, size gradation, and cost.

Jan 1, 1990

By V. Roze, R. N. Parkinson, R. Shepherd

The alphaDOSIMETER is a complete, integrated system designed to monitor the immediate worksite of underground miners where the disintegration for radon daughters is a risk to the health of mining personnel. The dosimeter weighing little more than one pound is worn by each miner throughout the entire shift and is powered by the miner's cap lamp battery. After this integration period, the unit is connected to a reading network whereupon the day's data is dumped, calculated and stored. Beginning in July 1980, prototype units were subjected to vigorous underground testing in uranium mines in Canada and the United States and in tin mines in Cornwall, U.K. The testing results are summarized and proposals advanced for a typical mine monitoring system utilizing the alphaDOSIMETER.

Jan 1, 1981

By R. S. Ondrey

MSHA has prepared two pamphlets that provide guidelines for selecting dust control parameters for underground coal mining sections. These guidelines are based on research conducted by the Bureau of Mines and underground studies conducted by MSHA. One set of guidelines is specific for longwall mining operations. Another set of guidelines covers room-and-pillar operations. The guidelines contain a general discussion on the appropriate use of ventilation and water to optimize the control of dust.

Jan 1, 1995

By M. D. Martin

Low metal prices and increasingly stringent environmental regulations, coupled with the threat of higher governmental royalties are adversely affecting both existing and new operations. Existing operations must therefore be run at maximum operating efficiencies to enable mining companies to survive and grow. Well planned and executed "outsider" reviews can help achieve this goal. Many mine managers and those who direct them resist the idea of "outsider" reviews for a variety of reasons, some valid and some not. Those managers who do bring in the "outsiders" are nearly unanimous in reporting that the exercise in self-discipline was well worth the pain and effort and repaid the cost many times over. This paper makes a strong case for "outsider" reviews and gives recommendations on the kinds of reviews to undertake. The authors draw upon their nearly 70 years combined experience, much of which has been in operations.

Jan 1, 1994

By E. DeLilia

For the past 30 years, surface mines have moved toward more highly mechanized, automatic systems that continuously mine overburden and ore to in-crease productivity, lower operating costs and minimize manpower needs. To achieve these goals, mine operators must be involved in every step of the machine procurement process. Several factors are involved in making the machines operate economically and efficiently: ? Prudent engineering. ? Proper planning. ? Realistic feasibility studies. ? Effective specification. ? Thorough training of the mine personnel.

Jan 1, 1995

By S. K. Mukherjee, A. W. Laurito, M. M. Singh, N. I. Jayaraman

This paper describes the application of foam to control respirable dust in a double-drum longwall mining section. The feasibility of injecting an adequate quantity of foam through the shearer drum was initially established in the laboratory. Thereafter, underground testing of the foam system to determine its effectiveness on an active operating longwall was conducted in a mine in West Virginia. The foam system proved superior to the water spray system. The details of the laboratory and field investigations, the results obtained, and the degree of acceptance of this system by the mining company are discussed in this paper.

Jan 1, 1987

By S. Chander

The use of various electrochemical techniques to study mechanisms of sulfide mineral- flotation reagent interactions is briefly reviewed in this paper. Prior to such studies it is desirable to thermodynamically determine solution conditions favorable for formation of hydrophobic species deemed to be responsible for flotation. The thermodynamic equilibrium involving both the stable and metastable species can be conveniently represented by an Eh-pH diagram. Thermodynamics can also be used to predict conditions where a mineral might not float if depressants are present. Under favorable conditions of flotation there is competition between reactions leading to formation of hydrophobic species with reactions that lead to formation of hydrophilic species. Due to the sluggish nature of the reactions involving sulfide minerals, a knowledge of the kinetic behavior of the system is necessary. Electrochemical methods of investigation are wed in laboratory studies to (1) control the state of oxidation, (2) determine the type and amount of electroactive species present at the mineral surface, and (3) study kinetics of electrode processes. By combining electrochemical techniques and wetting measurements the identification of hydrophobic species that might be present at the mineral surface could be achieved. Both contact angle measurements at mineral electrodes or flotation in a cell equipped with a particulate bed electrode can be used for the wetting measurements.

Jan 1, 1987

By Chester A. Rowland, David M. Kjos

INTRODUCTION Mineral ore comminution is generally a feed preparation step for subsequent processing stages. Grinding, the fine product phase of comminution, requires a large capital investment and frequently is the area of maximum usage of power and wear resistant materials. Grinding is most frequently done in rotating drums utilizing loose grinding media, lifted by the rotation of the drum, to break the ores in various combinations of impact, attrition and abrasion to produce the specified product. Grinding media can be the ore itself (autogenous grinding - primary and secondary), natural or manufactured nonmetallic media (pebble milling) or manufactured metallic media - steel rods, steel or iron balls, or a combination of autogenous media and steel balls (SAG milling). This chapter covers rod and ball mills utilizing manufactured metallic grinding media. MILL DESIGN The interior surface of rod and ball mills exposed to pulp and/or grinding media are protected from wear and corrosion by rubber, metallic or a combination of rubber and metallic wear resistant materials. Rod and ball mills essentially draw constant power, thus are well suited for use of synchronous motors with power factor correction capabilities as drive motors. A net of approximately 120 to 130 percent of running torque is required to cascade the charge in these mills. The pull-in torque is about 130 to 140 percent with the pullout torque to keep the motor in-step (in-phase) generally in excess of 150 percent. When rod and ball mill are started across-the-line the starting and pull-in torques result in inrush currents exceeding 600 percent which possibly result in high voltage drops. To deliver 130 percent starting torque to the mill the motor design must take into account the maximum anticipated voltage drop. Motor torque decreases as the decimal fraction of the voltage available squared. E.g., a motor rated 160% starting torque with a 10% system voltage drop will deliver 160% x or 129.6% torque to its output shaft When it is not possible or practical to start a fully loaded synchronous motor across-the-line it is possible to utilize the motor's pull- out torque to start the mill. By using a clutch, normally an air clutch. between the motor and the mill, the motor is brought up to synchronous speed before the clutch is energized. If the motor has an adequate amount (175 or greater) of pull-out torque the pull-out torque starts the mill without major disruptions on the electrical system. Since the energy release at initial cascade of the mill charge is an inverse function of acceleration time, a minimum acceleration time of 6 to 10 seconds or more is recommended to prevent damage to the mill or the mill foundation. Economics at the time of plant design and mill purchase determine the drive to be used. The simpliest drive is the low speed synchronous motor with speeds in the range of 150 to 250 RPM connected to the mill pinionshaft by either an air clutch or flexible coupling. Using a speed reducer between the motor and pinionshaft permits using motors having speeds in the range of 600 to 1000 RPM. In this speed range, if power factor correction is not required induction motors can be used; squirrel cage where there is no restriction on inrush current; slip ring where a slow start and low inrush current is required. Air clutches can also be used to ease starting problems with squirrel cage motors. In some areas of the world induction motors and starters are less expensive than synchronous motors at a sacrifice of motor efficiency and power factor correction. Dual drives, that is two pinions driving one gear mounted on the mill, become economical for ball mills drawing more than 3500 to 4000 horsepower (2600 to 3000 kilowatts). Further developments of the low frequency, low speed synchronous motors with the rotor mounted on the mill shell or an extension of one of the mill trunnions could improve the cost picture for these "gearless drives", making them practical for large ball mills. The percent of critical speed, which is the speed at which the centrifugal force is sufficiently large to cause a small particle to ad- here to the shell liners for the full revolution of the mill is given in mill specifications. Critical speed is determined from the following: Where D is mill diameter inside liners (specified in meters). Cs is critical speed in RPM. When D is specified in feet

Jan 1, 1998

By P. Sander, M. Spiegl, J. Reilly, A. Van Droogenbroeck

Although the outdated idea of calculating risk as the deterministic product of its likelihood and impact is not entirely a thing of the past, a multitude of organizations have adopted the usage of probabilistic methods for risk analysis, as they better reflect the inherent uncertainty of cost and risk estimates with ranges. But are these advancements sufficient in a complex environment such as tunnelling projects, where inadequate modelling of cost and risk can result in estimate discrepancies that run into millions of dollars? This paper explores two advanced probabilistic modelling techniques for tunnelling projects. The first one demonstrates how the cost and schedule uncertainty related to changes in excavation and support classes can be modelled with correlated variables. The second example models the risk related to explosive ordnance clearance on construction sites using a probabilistic event tree.

Dec 1, 2022

By L. Bloom

"Man-Made Parameters" refers to the importance of selecting appropriate analytical procedures to acquire useful chemical data. The correct procedures are particularly critical at the sample preparation stage where decisions concerning pulverizing equipment, sample size, contamination and dissolution will impact on the final results independent of the instrumental method of analysis. Several experiments were designed to quantify the impact of these approaches.

Jan 1, 1993