Many of the attempts by the U.S. Geological Survey and other groups to assess the mineral resource potential of selected areas have produced qualitative results, i.e. one area is more favorable or has a higher potential for mineralization. A relatively small subset of assessments has produced quantitative estimates; many of these were based on subjective quantitative estimation of number of deposits Very few assessments, especially quantitative assessments, have seriously addressed the potential of industrial minerals. Quantitative assessment of industrial minerals by the U.S. Geological Survey is hindered by a relative lack of expertise in industrial minerals, lack of data for industrial minerals, and lack of confidence in subjective quantitative assessment methodologies. This study developed two potential methodologies, a statistical approach and a process-based approach, to quantitatively assess borate in playas and minimize these concerns. Selection of a Quaternary surficial deposit type where many of the criteria could be measured from existing geologic maps or inferred from current conditions and processes was one of the steps taken to minimize concerns about the techniques. Qualitative and quantitative data were collected on 22 playa-lacustrine basins containing one or more borate deposits and 21 basins in the same areas that have no known borate deposit(s). Statistical techniques were successfully employed using dominantly lithologic data to differentiate mineralized vs. non-mineralized basins (stepwise discriminant analysis) and to estimate boron endowment of mineralized basins (stepwise regression analysis). Boron estimation for the 22 mineralized basins was also attempted from a simple process-based model. Precipitation/evaporation estimates and the amount of Quaternary volcanics in each basin were used as a basis for estimating total boron concentrations in the playas. Selection of a Quaternary deposit type was made in part to minimize unrecognized processes and maximize the ability to measure variables. However, results using this methodology were highly variable and reflect the uncertainties of geologic process, climate, and time estimations, especially factors related to loss of boron from the mineralizing system. The methodologies developed here offer two different perspectives for quantitatively estimating B endowment that can be used to establish whether a basin is likely to contain boron mineralization, calculate a minimal endowment level and the probability of that level of endowment, and determine a maximum level of endowment given no boron losses to the mineralizing system. These results can be used in isolation or to constrain a subjective assessment.

Wheel loaders are widely used in mines, construction projects, and waste processing fields due to their merits of high mobility, remarkable operational flexibility, and relative low capital cost. Automatic control of the loading process will achieve high productivity, solve the problem of shortage of experienced operators, release human workers from hazardous working environments, and reduce maintenance cost associated with machine abuse. Existing research on wheel loader control only automate the manipulator mechanism while leave the locomotion system to human operators. The research in this dissertation focuses on the development of a digging controller that can simultaneously control bucket motion and vehicle advancement, and can adapt its parameters in different digging conditions. In this controller, a digging task is decomposed into three sequentially implemented operations: attacking, crowding, and scooping; each of them can be carried out with different strategies. An ideal trajectory is pre-generated based on the physical property of the wheel loader and rock pile, and is generally followed during the digging process. Human operators' practice in regulating vehicle speed and coordinating bucket motion and vehicle advancement is intensively investigated, refined into control rules, and implemented with intelligent and conventional control methods. Machine features are analyzed in depth and incorporated into control algorithm design. The investigation on the non-trivial time-delay characteristic of the manipulator hydraulic system leads to the building of dynamic models and the application of predictive control principle in digging decision-making. The feature of small working space of wheel loader was considered in bucket trajectory generation and instant bucket motion planning. The research on wheel slip occurrence leads to a detection algorithm being developed and a slip restrain strategy being presented. Self-adaptation mechanism is constructed in which trajectory tracking-quality is applied for evaluating digging control performance, statistical analysis is applied for improving the accuracy on bucket penetration depth prediction, and machine-learning technique is applied for revising the membership function of fuzzy consequent variables. Simulation experiments show that the controller works effectively in rock piles with different conditions, from fine sand and soil to big fragmented rock pieces.

The laboratory shear tests on Apache Leap tuff have been conducted to investigate the joint dilatant behavior and the influence of surface roughness, sample size, water and shear velocity on joint shear behavior, and to compare the fit between Coulomb's linear and Archard's non-linear model. Experimental results indicate that the dilation of rock joint is influenced by joint surface roughness and normal stress. Surface roughness also determines joint shear strength. Sample scale influences the following joint properties, e.g. peak shear strength, peak dilation angle, peak shear displacement and mode of shear failure. This effect depends on normal stress. The shear strength of rock joint also varies with the presence of water and shear velocity. Archard's power law generally gives a better fit on the experimental data than does Coulomb's linear law.

<p> The mining and milling activities associated with extraction of metals directly generates waste in the form of mine tailings. This material is one of the largest sources of heavy metal contamination via water, air, flora, and fauna in the world. The re-use of this waste as an input to a construction material such as concrete could lead to a preventive method of reducing the environmental impact. This method of encapsulation of heavy metals has been applied to paste backfill; however, the compressive strength requirements are much lower compared to the ASTM standards for structural concrete. The objectives of this study were: (a) to examine the feasibility of maintaining the structural integrity of concrete, with compressive strength of 4,000 psi or greater with a slump of 3-4 inches, when using mine tailings as a fine aggregate, (b) investigate the ability of this material to encapsulate heavy metals, sulfates, and acid.</p><p> The waste material, collected from the Pride of the West mill in Silverton, CO, was first physically and chemically characterized. After performing batch leach extraction tests, the raw mine tailing leachate contained heavy metal concentrations above conservative regulatory limits. Then, the optimal tailing to fine aggregate ratio was investigated. It was found that the compressive strength was comparable to control samples made with aggregate and the concentration of heavy metals found in the leachate were consistently low when the ratio varied below 50%. Therefore, the ASTM standard for the minimum allowable fineness modulus was used to obtain in maximum amount of mine tailings allotted in the concrete mixture.</p><p> To examine whether metals could be leached from the concrete-tails mix, three extraction fluids varying in pH were used to accelerate the weathering process. The metals of concern were shown to have been thoroughly encapsulated in the concrete matrix, with a 2-4 log encapsulation capacity when compared to the metals leached from the raw tailings. Finally, a strength development experiment was conducted to observed changes over time. It was found that the specimens that contained mine tailings maintained comparable compressive strengths as the controls cylinders, above the minimum compressive strength requirements for structural concrete.</p>

In June 1996, a 2-D high-resolution seismic survey was conducted at an open pit porphyry copper mine in southwest New Mexico. The local geology consists of a Miocene conglomerate, overlying Precambrian to Eocene basement rock containing unaltered igneous rock and mineralogically altered rock that hosts the sulfide deposits. The survey employed reflection and refraction techniques to image the top of the ore body. A variety of filtering techniques was used to suppress strong coherent source generated noise, and high amplitude ambient noise from mine operations. The resulting seismic sections compare well with borehole data and photographs of the mine walls; showing lithology and structural features within the initial 300 m of the subsurface. Imaging differences in lithology, contrasts due to sulfide deposition, and structures has potential importance for mine operations for efficiency of extraction and for safety. Locating structural features, such as those controlling groundwater flow, also has environmental applications.

The hydrodynamics of the downwards concurrent flotation column (CDFC) of the Jameson design has been studied. The effect of operating variables on the gas holdup in two- and three-phase mixtures was measured. To measure gas holdup, the isolating technique, conductivity and pressure techniques were employed. Gas fractions between 10 and 65% were achieved. These high holdups are a consequence of bubbles being forced downwards against their buoyancy. The high gas fraction may account for the fast flotation claimed for this cell. / The conductivity technique using Maxwell's equation gave a maximum error of 6%, in both two- and three-phase systems (considering the water-solids mixture as one phase). / The drift flux model was applied to try to correlate the data. Both two- and three-phase systems showed consistent trends. The model was used to estimate bubble size. In the Richardson and Zaki equation the m factor was in the range 2.9 to 3.1. A dimensionless drift flux was defined assuming $m=3$ which fitted the data. For three-phase systems, however, the results predicted a trend in bubble size that seemed opposite to observation. (Abstract shortened by UMI.)

Paste backfill has recently emerged in the Canadian mining industry as a potential solution to some of the problems regarding the waste disposal of mine tailings. Surface disposal is costly and its potential harm to the environment is incalculable. / Besides waste disposal paste backfill also produces a stronger fill resulting in less dilution, less cement consumption and less clean up costs. These savings can only be realized with an accurate implementation of the new technology. / Presented is an overview of the current state of this emerging technology and the available equipment required for the preparation and transportation of paste backfill. It is hoped this work will provide the reader with a thorough grounding in paste backfill and enable him/her to understand that although large savings are possible the technology is still unproven within the context of the Canadian mining industry and further work is required before paste backfill becomes common practice. / Economic analyses are also presented regarding the different applications of paste at either existing or new mineral developments. Results from strength tests carried out as part of paste backfill feasibility projects are presented and show the increase in uniaxial compressive strength associated with an increase in slurry concentration. (Abstract shortened by UMI.)

A new gold centrifugal concentrator, the Falcon SuperBowl, was tested both at plant and laboratory scales to assess its ability to recover gold from grinding circuits. / The performances of a 21-in SuperBowl (SB21) at Mineral Hill and New Britannia Mines showed that it could recover gravity recoverable gold (GRG) of all sizes, especially below 25 mum at Mineral Hill Mine. / Three types (to test the effect of gangue density and size distribution) of synthetic feeds were used to characterize a laboratory 4-in SuperBowl (SB4) as a function of feed rate and fluidization water flow rate. / A 20-in Knelson Concentrator and a shaking table were further tested in this program with the samples extracted from Casa Berardi and Mineral Hill Mine, respectively. The 30-in Knelson was tested at two different conditions to assess the impact of fluidization water flow rate and explore the importance of cycle time. (Abstract shortened by UMI.)

The separation of minerals by flotation depends on the effectiveness of the reagents used. The performance of depressants is paramount in rejecting the undesirable minerals while maintaining acceptable recoveries of the desired mineral. Iron-bearing minerals are the main contaminants in many ores: their removal is critical. Several different types of depressants have been used for this purpose, many of which are toxic. A shift has been made toward more environmentally friendly reagents including starch and dextrin. / The purpose of this thesis was to determine the depression mechanism of dextrin on pyrite. A number of techniques were applied to give insight into the mechanism, including adsorption studies, microflotation tests, and solution and surface analyses. It was revealed that dextrin only adsorbed on mineral surfaces that contained some metal ionic sites. The degree of adsorption depended on the nature of the metal species, with lead being more reactive than iron. Dextrin was able to depress pyrite, regardless of whether dextrin adsorbed or not; however, adsorbed dextrin was more effective. It appeared as if dextrin inhibited the formation of dixanthogen on the surface, which could lead to reduced floatability of pyrite. Finally, it was observed that over time, adsorbed dextrin underwent a conformational change on the surface of the mineral. This change permitted a greater amount of xanthate to adsorb on the mineral.

Overbreak and damage to rock walls is one of the most serious problems encountered in blasting operations. Several techniques have been developed to control the undesirable effects of rock blasting. These techniques are collectively known as wall-control blasting methods. / The stress distribution around pressurized holes has been numerically evaluated, in order to analyze the mechanism of wall-control blasting methods. The effect of blast geometry and the role of discontinuity on this stress field has also been studied in detail. The results obtained by numerical modelling have been verified by controlled blasting experiments, and further supported by analysis of existing roadcuts on a large scale. / It was found that the mechanism of wall-control blast can be explained by the collision and superposition of the stresses between the holes. A narrow fracture zone between the holes was produced by tensile stresses on the centreline. It is neither necessary nor realistic to assume onset of fractures at the midpoint between holes by reinforcement of the stresses from each hole. / The analysis shows that a burden can be defined as being infinite when the ratio of that to the spacing is greater than unity. For pre-split blasting (infinite burden) in an isotropic and homogeneous material the hole separation could range up to 15 borehole diameters. The decoupling ratio between the explosive charge and the borehole diameter should be smaller than 0.5. This ratio would generally be between 0.2 and 0.3 for pre-splitting (infinite burden), and between 0.3 and 0.4 in the presence of a free face. / A discontinuity parallel to the free face and located at the back of the holes causes high stress levels between the discontinuity and the boreholes, resulting is a shattered one in this region. The presence of a similar discontinuity at the front of the holes leads to considerable overbreak and development of an undamaged "hump" of rock between holes. The effect of a discontinuity oriented normal to the centreline at the midpoint between holes has minimal effect on the blast results. As the angle of the discontinuity with the free face decreases from 90$ sp circ,$ the damage zone between the holes and the discontinuity increases, and the shape of the final wall changes from a smooth face to a corrugated shape. A closed-discontinuity or an open discontinuity cemented with strong filling materials has little effect on the results of the blast. However, as the width of the discontinuity increases, the size of the damage zone also increases. An open discontinuity, 50 mm wide or more, plays a role similar to a free face. / In roadcut blast design, hole deviation is a key parameter in determining the quality of the face. However, consistent hole deviation in the same direction has minimal effect in the result of the blast. This type of deviation is usually associated with bedded rocks, with alternating bands of soft and hard rock on the face. The degree of deviation is dependent, amongst other factors, on orientation, thickness, frequency and the position of these bands.