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By Gregory E. Korbin

The effectiveness of pre-reinforcement as an immediate stabilization measure as well as its contribution to the permanent stabilization of a tunnel were studied through the use of physical (Figure 1) and numerical models (1). Physical models were designed for the investigation of two pre-reinforcement systems: first, reinforcing far ahead of the main excavation (Figure 2); second, spiling reinforcement ahead of the face (Figure 3). In both cases, the use of reinforcement was responsible for permanently stabilizing an otherwise unstable opening. Data from the physical models were used to calibrate a numerical model from which additional information on long term behavior, methods to account for the capacity of a pre-reinforcement system, and the mechanisms involved were ascertained. These studies indicated that pre-reinforcement can stabilize a rock mass effectively as it reduces deformations and thereby deterioration due to strain softening, provides rock mass confinement leading to increased available strength, and maintains rock arch continuity allowing for increased tangential stress in the immediate vicinity of the opening. Field studies verified the capacity of spiling reinforcement to restrain initial deformations.

Jan 1, 1976

By Roberto Zaragoza

Historically, the control of flotation operations has been viewed by many as an art. Only recently has process measurement and control come to be viewed not as an ?art? but as a very complex and productive science. In recent years, process control applications to flotation plants have been established and already some gains have been reported for several industrial operations using individual stabilizing control loops including level, pulp flow, pulp density, reagent addition rate and pH (Paakinen, 1979; Hales, 1985). The use of process control computers combined with on-line x-ray florescence (XRF) in industrial flotation circuits has made the application of more sophisticated control techniques feasible in the mineral recovery process. In spite of the availability of reliable instrumentation in modern flotation plants, satisfactory control strategies are difficult to develop and implement. Extremely important factors such as changes in ore type, liberation characteristics, flotability, degree of oxidation on particle surfaces, and specific gravity constitute unmeasured disturbances to the process. Most current control systems cannot adapt specifically to such disturbances.

Jan 1, 1987

By W. L. Dam

Grand Junction, Colorado’s legacy with uranium mining and milling serves as a model attracting international interest. Access to water and central location to carnotite ore containing uranium and vanadium resulted in the World War II military creating a site in Grand Junction for developing extraction techniques; subsequently, several commercial mill sites were built in the area. Uranium mills produced ore into the 1970’s as well as tonnes of radioactive waste tailings. Tailings contain radium that emits radon gas. Despite the radiation hazard, sandy tailings were added to concrete and became incorporated into roads, schools, businesses and homes. Clean up of sites containing tailings and mill sites began in the 1970’s involving city, state, and federal officials. The Climax mill site had become an auto junk yard mixed with mill tailings. A new disposal site was built out of town and away from the river in the 1990’s. After Climax mill tailings were removed to the disposal site, the land sat vacant for two decades until citizens and city officials developed a masterplan for the riverfront property. The Las Colonias river park is being built in stages including an amphitheater, gardens, businesses and parks. One of the biggest obstacles to site remediation and reuse was overcoming public outrage, fear, and lack of trust which made funding sources scarce.

Jan 1, 2020

By R. D. Lama

This paper presents the results of a study of the mechanics of methane gas flow in coal. Desorption tests carried out on cylindrical coal specimens showed that an analytical formulation can be made to model the process of gas flow in coal based on an integration of Darcy's law, Fick's law and Langmuir's relation. The diffusivity term in the flow equation varies directly with local gas content. Permeability tests carried out on the same coal result in permeability constants with values higher than equivalent permeabilities obtained from desorption tests by many orders of magnitude. The study also revealed that permeability is highly dependent on the applied gas pressure and the rock stress.

Jan 1, 1987

By Richard C. Smith, Steven H. Brown

Commercial scale in-situ leach uranium facilities (i.e., solution mining) have operated since late 1975, and have begun to appear in increasing numbers in the last few years. Solution mining involves the pumping of ground water, fortified with oxidizing and complexing agents, into an ore body, leaching and solubilizing the uranium in-situ, and then pumping the solutions to the surface where they are fed to a mill. Milling is by conventional means, involving ion exchange, precipitation, calcining and packaging processes. This paper presents an overview of the solution mining process, and discusses an empirical method that has been used to determine the radon gas release rate in Bq (curies) per year for the overall operation of the facility including wellfields, milling processes and waste storage reservoirs. In addition to radon generation on the surface from radium decay, it has been determined that the major component of radon release is associated with the dynamic generation of radon from solutions returning from underground. Process parameters impacting this evaluation and the mathematical expressions developed are discussed. The preliminary data accrued is presented.

Jan 1, 1981

By B. Erdem

This article introduces a computer model, which emphasizes panel design for draglines deployed in direct side-casting mode. The study covers flat and inclined coal-seam conditions with the dragline operating along the strike-line. Two casting methods are embedded in the model: material is placed in the open set adjacent to the one on which the dragline is located (the DNS method) and material is placed in the open set adjacent to the one the dragline excavates (the DND method). While in the first method the unproductive walking time is reduced as the set is enlarged, in the second method the cycle time is lessened as the dragline swings along an acute angle. The side-casting model is shaped so as to provide several panel configurations instead of a single one to conform to the characteristics for an opencast mine. This is achieved by assigning the pit width an interval of values ranging from a minimum to a maximum. The model includes solutions to other critical design parameters such as: set length, swing angles at key cut and main cut positions, and required dragline reach at key cut and main cut positions. The model outcomes reveal the following: the stripping operation is largely affected when the coal-seam is inclined. The downhill spoiling mode should be applied wherever possible. The DNS pattern allows wider pit width intervals as well as longer sets and longer reaches.

Jan 1, 2004

By R. Armstrong, C. Ware, P. Sudan, G. Whitmore

The northern KwaZulu-Natal (KZN) coastal dune cordon, South Africa, extends from north of Durban into Mozambique. The Quaternary dune cordon, which can be up to 2 km wide, comprises a series of stacked, unconsolidated dunes that in places attain a height of over 100 m. Mining of the dunes produces much of the world’s supply of ilmenite, rutile and zircon. This paper documents the age of zircon grains separated from dune units, identifies likely source rocks and presents an evolutionary history for the dune cordon. Between 30 and 60 detrital zircon grains from three distinct units from the northern KZN coastal dunes were analysed for U/Pb isotopic ages using the SHRIMP II at the Australian National University. The samples represent units from the base (ca. 250 ka; luminescence age1),middle (ca. 190 ka2) and upper (ca. 20 ka2) portions of the coastal dune cordon. Zircon grain ages identify three source populations: (1) a 1 000 to 1 200 Ma group correlated to the Natal Metamorphic Province, (2) a 500 to 650 Ma group representing a Pan-African belt, which may correlate to the Mozambique Belt and (3) a ca. 650 to 800 Ma group of unknown provenance. Surprisingly, the presently exposed basement, comprising the Kaapvaal Craton and Archaean volcano-sedimentary sequences, has not supplied a significant amount of zircon grains (< 5%).This suggests that unroofing of basement rocks in the region has only occurred during the last 20ka. In addition, the absence of zircon grains younger than 500 Ma indicates that the bulk of zirconis not reworked from the Karoo Supergroup cover succession, but may be sourced by reworking of the Natal Group sandstones.

Jan 1, 2003

By Daniel G. DiCanio

Investigation of the costs of industrial accidents dates back to the 1920s. The Bureau of Mines was one of the pioneers in accident cost investigation with numerous studies published between 1928 and 1933. The bulk of these early investigations dealt only with costs which appeared as payouts on company books; that is, the direct cost of insurance premiums and the costs of medical expenses which resulted from industrial accidents. These early investigations, especially the Bureau&apos;s study of accident costs in Pennsylvania and Indiana coal mines provided the first real evidence that promotion of industrial safety pays back in dollars as well as in human life and wellbeing. In the 30s and 40s, investigations began to accumulate evidence that industrial accidents impacted more than just the direct operating expenses of a company (i.e., higher insurance premiums). The work of Heinrich pioneered these investigations, and produced strong evidence that the un¬insured costs of accidents far outweighed those costs covered by insurance. Heinrich developed and published a ratio of insured to uninsured costs of 1.4. Despite his cautionary statements about blanket application of this ratio it is used even today to estimate total costs of accidents. Simonds, in the late 40s and early 50s, extended the definitions of uninsured or indirect accident costs and developed what is now regarded as the principal method for estimating the total economic impact of industrial accidents. Simonds&apos; method served as the basis for development of the logic of the Accident Cost Indicator Model (ACIM). However, several departures from Simonds&apos; method were made to satisfy certain requirements imposed by the Bureau of Mines, and because information gathered during the course of our investigation justified a departure. These departures are noted in the discussion which follows.

Jan 1, 1977

By P. Tsang, S. S. Peng

Mine floor failures, such as floor heave and floor buckling, occur frequently in underground coal mines where soft mine floor exists. The types of failure can usually be classified into two categories; shear punching failure and tensile failure. A model based on the Winkler&apos;s elastic foundation is proposed in this paper for floor stability analysis. The model considers material properties of floor strata, in-situ horizontal stress, pillar size, entry width, and configuration of multiple-entry system and predicts stress conditions in the mine floor based on given in-situ mining and geological conditions, as well as deformation of the mine floor. This information is used to predict possible failures of mine floor by comparing the strength of mine floor with its stress condition. The validity of the model is verified by in-situ data described in this paper.

Jan 1, 1992

By H. Do

In flotation, hydrophobic particles are selectively collected by air bubbles, and the bubble-particle aggregates enter the froth phase. However, less hydrophobic particles drop off from the froth phase, while more hydrophobic particles are recovered. Thus, the froth phase provides an important cleaning mechanism. In the present communication, the froth-phase recovery process has been modeled by considering particle retention times and the carrying capacities of bubbles. The model predictions are compared with the experimental data reported by Seaman et al. (2006). The results show that the froth-phase recovery varies with particle size, particle hydrophobicity, and bubble coarsening.

Jan 1, 2008

By Sh. Karimidorabati

In the construction industry, project changes constitute a major cause of delay, disruption, cost increases, poor quality and unsatisfying performance. They are also known as a main factor of litigation between the owners and constructors. Construction projects are essentially process-based, and with the critical role of Information Technology (IT) in this industry, projects, especially mega projects, are being managed remotely. The volume of data and documents, such as Requests For Information (RFIs), different types of Change Requests (CRs) and Project Change Notices (PCNs), being transferred and exchanged amongst the stakeholders of a project is considerable. The circulation of these documents amongst project stakeholders still heavily relies on two methods or levels for management of change process; Conventional (fully paper-based, Faxes, Snail mails) and Electronic or semi-automated (Email, Internet, PDF files). These two methods are dependent on human discipline to follow specified processes which often break down because of human nature. This creates serious compliance problems. It is hypothesized here that fully that automated process-based management of change can lead to better compliance, more efficient management of change, and reduction of time and cost of data exchange. An approach of doing this is presented in this paper. Ultimately, its impact should improve project performance. Conclusions are presented on time savings and improved compliance.

Aug 1, 2013

By B. Govindarajan, L. S. Rao, T. C. Rao, B. R. Rao

Laboratory leaching experiments were conducted to extract potassium from glauconitic sandstone, and the effects of important variables were studied. The reduced time plot (RTP) for all of the variables obtained from the experimental data has been quantified by this simple equation: R = 100 (1 - exp (-0.693 *(T/T50)0.605) The time required for 50% extraction (T50) has been correlated by a regression equation to variables such as acid strength, temperature, fluorite: glauconite ratio and % solids. Both of these equations were used to predict the extraction percentage at different process-variable levels. In addition, several other experiments were conducted at arbitrary levels of the variables to verify the equations developed.

Jan 1, 1994

By R. Gerling

A computer program has been developed for finding a near-optimum schedule of the mining sequence for flat lying, tabular orebodies. The deposit is divided in blocks with equal areas and definite grades, thicknesses and ore contents. Mining is done by room and pillar method and trackless haulage to surface. Access from surface is by adits or ramps with additional vent raises. In total eight different general concepts for access and development can be realized. The optimum mining sequence is found by a heuristic method. Criterion is the maximization of the net present value over the lifetime of the mine. Specific stoping costs per t of ore are taken for con¬stant, whereas development and haulage costs for individual blocks and also sequences will be different. Correct ventilation and a technically sensible sequence are guaranteed. Beginning with a single block, neighbouring blocks are tested and an optimum stoping sequence is generated. The net present value of the total mining operation for the planning period is calculated, taking into account ore, which is mined during development. The program can also be used to investigate given mining sequences.

Jan 1, 1986

By Enrique Jelvez, Nelson Morales Varela, Christian Ihle, Joaquin Silva

All mineral beneficiation processes require water for its execution. Therefore, the availability and adequate management of water are key to the existence of any mine operation. However, many mines’ operations are affected by water scarcity and risk an increase of operational costs or even production in some cases. This paper proposes a model to minimize the losses of water due to evaporation and re-absorption by adjusting the active and inactive periods of the discharge in different points of the tailing. When applied, the model determines optimal or nearly optimal discharge operation in all the scenarios that were evaluated.

Jun 25, 2023

By R. W. Fedors, S. T. Green, F. T. Dodge, D. B. Walter

Spatial and temporal temperature variations in a high-level radioactive waste repository drift can give rise to moisture transport within the drift. Knowledge of this moisture transport may be important to assessing the potential for corrosion of all metallic components in the drift. The model presented here shows one approach to simulating evaporation, transport, and condensation of water in large underground openings using a framework based on computational fluid dynamics. Simulation results that explicitly model water and latent heat transport are presented.

Jan 1, 2004

By Ruilin Yang

Blast vibration in the highwall from a cast blast in open pit mines or in the hanging walls from a stope blast in underground mines is a common concern. Vibration in such cases is a typical near-field situation where the distance from a blasthole to a point of interest varies significantly compared to the distance between the blast as a whole and the point of interest. Most existing blast vibration models are designed for far-field vibration using a single seed wave to represent all blastholes within a blast and do not simulate wave shape change over the distance. Using the site parameters from the analysis of signature hole vibrations, the present blast vibration model yields reasonable agreement with field measurements in terms of vibration amplitude and frequency. Case studies show that the model has been used successfully to assist field vibration control.

Jan 1, 2010

By D. Scott Scovira, Ruilin Yang

Blast vibration in the highwall from a cast blast in open pit mines or in the hanging walls from a stope blast in underground mines is a common concern. Vibration in such cases is a typical near-field situation where the distance from a blasthole to a point of interest varies significantly compared to the distance between the blast as a whole and the point of interest. Most existing blast vibration models are designed for far-field vibration using a single seed wave to represent all blastholes within a blast and do not simulate wave shape change over the distance.

Jan 1, 2010

By D S. Scovira

The effect of blast vibration on highwall stability is a common concern for many open pit mines. Vibration in such a case is a typical near-field blast vibration situation. Vibration modelling in the near-field of a blast requires consideration of both the amplitude and frequency attenuation of waveforms with distance. Most existing blast vibration models are designed for far-field vibration and do not simulate the frequency attenuation and its effect on waveform shape. With the advent of electronic detonators it is desirable to quantify the effects of blast delay on the amplitude as well as the frequency of blast vibrations. A suitable modelling tool is proposed here. At present, a blast vibration model with double attenuations(amplitude and frequency) has been developed at Orica. The present model simulates the amplitude and frequency attenuations separately using different transfer functions. The amplitude attenuation is modelled according to the non-linear relation between the peak particle velocity (PPV) and the charge weight scaled distance established from the signature hole vibration. The frequency attenuation is modelled with the signal broadening based on KjartanssonÆs transfer function û a linear model for attenuation of waves. The model is capable of taking multiple sets of signature waveforms as input to improve the modelling accuracy of the wave propagation in the geology at a site. The screening effect of the earlier firing holes in the path of a later firing hole is taken into account on not only the amplitude, but also frequency attenuation. The present blast vibration model is suitable for modelling both near-field and far-field blast vibrations. It yields reasonable agreement with measured field data for the near-field vibration examples discussed.

Jan 1, 2007

By Alan Rice

Abstract-The mechanism by which stratiform ore deposits of PGE (platinum-group elements) are laid down in ultramafic igneous complexes is not completely clear. Early studies by the author and coworkers on numerical analyses of the convective cooling of low-Rayleigh-number magma chambers examined the effect of suspended crystal load on fluid density, and raised the possibility that the growth of the suspended crystal load during cooling could split a magma chamber into several convecting layers. The lower layers would have a higher content of refractory phases than the upper layers, which would consist of more evolved melt. This paper considers numerical modelling, as well as theoretical and experimental work in other fields dealing with suspended loads in fluids. The calculations, which are based on the physics of convecting magmas, yield quantitative relationships consistent with the observation that economically interesting stratiform PGE deposits are restricted to large magma bodies, and also yield estimation of the depth in a magma chamber at which certain grades of mineralization may occur.

Jan 1, 1997

By Alan Rice

The mechanism by which stratiform ore deposits of PGE (platinum-group elements) are laid down in ultrama?c igneous complexes is not completely clear. Early studies by the author and coworkers on numerical analyses of the convective cooling of low-Rayleigh-number magma chambers examined the effect of suspended crystal load on ?uid density, and raised the possibility that the growth of the suspended crystal load during cooling could split a magma chamber into several convecting layers. The lower layers would have a higher content of refractory phases than the upper layers, which would consist of more evolved melt. This paper considers numerical modelling, as well as theoretical and experimental work in other ?elds dealing with suspended loads in ?uids. The calculations, which are based on the physics of convecting magmas, yield quantitative relationships consistent with the observation that economically interesting stratiform PGE deposits are restricted to large magma bodies, and also yield estimation of the depth in a magma chamber at which certain grades of mineralization may occur.

Jan 1, 1997