This project, funded by NASA through the University of Arizona Space Engineering Research Center, is an extension of earlier work, and is aimed at developing the base technology for continuous profiling geophysical systems that will be able to determine not only where anomalous features lie, but also what they look like and, ultimately, what has caused them. A hybrid approach was used that employed object oriented and procedural programming, neural networks, fuzzy systems theory, genetic algorithms, and symbolic processing initially within a distributed computing architecture, and later on an 80486 PC platform. Neural networks were used to map synthetic GPR patterns to geometric models. Object oriented programming was combined with fuzzy theory to map these geometric models to a database of real world objects. GPR objects were then combined to build extended objects and systems. Genetic algorithms were used to fine tune the system. Testing was done solely with synthetic data, with future intent of progressing to laboratory and field geophysical patterns. The field context assigned to the vision system for this research corresponds to a buried prehistoric archaeological site comprising occupation and utility/storage rooms of various sizes. This context was chosen to take advantage of the rich suite of GPR patterns already collected, and the GPR modeling underway to characterize archaeological signatures on GPR. A room system was selected as the GPR target because it incorporated most of the basic characteristics expected for GPR systems in general. The interpretation system was able to handle, (1) Multiple components; (2) Offset components; (3) Non-continuous components; (4) Nonmonotonic states; (5) Fuzziness.

This thesis describes a programme of work which has been undertaken with the objective of obtaining data relating to the performance of on-line mass flow rate meters as applied to pulverised coal injection systems. Such injection systems are utilised widely in power generation, cement and steel manufacture. A technology review was carried out, incorporating an extensive literature survey. This review precipitated the conclusion that a number of techniques have been proposed, which may be applicable to the measurement under investigation. However, very little experimental verification of sensing systems based on these techniques had been undertaken. A test facility, suitable for such verification was therefore developed and an extensive programme of tests were carried out, of a sensing system based on an electrostatic technique. The development of a mathematical model of the sensor operation has also been undertaken, in an attempt to explain some of the more unusual aspects of the experimental results. The overall conclusion is that some aspects of the measurement can be achieved without major difficulties, whilst problems have yet to be resolved in respect of other aspects of the measurement system. The principle of the measurement system is such that the independent measurement of average particle velocity and suspension density are required in order to measure mass flow rate. The measurement of average particle velocity was shown to be achievable by either of two techniques, whilst the measurement of suspension density proved more problematic. Recommendations for further work, aimed at addressing these remaining aspects are detailed.

In this thesis aluminium alloys containing small additions of both tin (~ 0.1 wt %) and gallium (~ 0.05 wt %) dissolve anodically at high rates in brine media; at room temperature, current densities > 0.2 A cm-2 can be obtained at potentials close to the open circuit potential, ~ -1.5 V vs SCE. Alloys without both tin and gallium do not dissolve at such a negative potential. The tin exists in the alloys as a second phase, typically as ~ 1 μm inclusions throughout the aluminium structure. Anodic dissolution leads to rounded pits around the tin inclusions. The pits are different in structure from the crystallographic pits observed with Al and other alloys. Clearly, the AlMgSnGa alloys dissolve by a different mechanism. Although the distribution of the gallium in the alloy could not be established, it is essential to the formation of these pits and maintaining dissolution. In addition to the composition, mechanical working and heat treatment influence both the stability of the alloys to open circuit corrosion and the overpotential for high rate dissolution, factors critical to battery performance. The correlation between performance and alloy microstructure has been investigated. Imaging with a high speed camera with a resolution of 10 – 20 μm was used to observe the dissolution of AlMgSnGa alloys. Using microelectrodes with only a few Sn inclusions in their surface, allows confirmation that hydrogen evolution occurs only from the Sn inclusions and also showed that the evolution of H2 is not continuous. Therate of H2 evolution correlates with shifts in potential between - 1.5 V and much less negative potentials. The performance of a laboratory Al-air battery with 2 M NaCl electrolyte was limited by both the performance of the O2 cathode and the extent of dissolution of the alloy. Using a cell with a low electrolyte volume/surface area ratio, dissolution of the anode stopped after the passage of 1000 C cm-2 due to a high impedance, thick film of crystals clinging to the surface. Removal of this film allowed the dissolution to recommence. The charge limitation depends on cell design but a high charge density would be difficult to achieve with a low volume battery.

Thesis (MTech (Chemical Engineering))--Cape Technikon, 2000. / Internationally, there is an increase in the need for safer environmental processes that can be applied to mining operations, especially on a small scale, where mercury amalgamation is the main process used for the recovery of free gold. An alternative, more environmentally acceptable, process called the Coal Gold Agglomeration (CGA) process has been investigated at the Cape Technikon. This paper explains the application of flotation as a means of separation for the CGA process. The CGA process is based on the recovery of hydrophobic gold particles from ore slurries into agglomerates formed from coal and oil. The agglomerates are separated from the slurry through scraping, screening, flotation or a combination of the aforementioned. They are then ashed to release the gold particles, after which it is smelted to form gold bullion. All components were contacted for fifty minutes after which a frother was added and after three minutes of conditioning, air, at a rate of one I/min per cell volume was introduced into the system. The addition of a collector (Potassium Amyl Xanthate) at the start of each run significantly improved gold recoveries. Preliminary experiments indicated that the use of baffles decreased the gold recoveries, which was concluded to be due to agglomerate breakage. The system was also found to be frother-selective and hence only DOW-200 was used in subsequent experiments. A significant increase or decrease in the air addition rate both had a negative effect on the recoveries; therefore, the air addition rate was not altered during further tests. The use of tap water as opposed to distilled water decreased the attainable recoveries by less than five per cent. This was a very encouraging result, in terms of the practical implementation of the CGA process.

Structural geology, groundwater, shear strength and blasting control pitwall stability at Equity Silver Mines, Houston, British Columbia. A geotechnical investigation of, these parameters was carried out in the Main Zone pit during the summer of 1984. The objective of the study was to develop a pitwall design based on geologic and groundwater conditions observed in each design sector. This thesis presents the results of the investigation; methods of improving stability by drainage and control blasting are also discussed. Information on structural geology was obtained by line mapping of existing berms. The discodat package of computer programs was used to process the structural data and to identify trends in orientation of discontinuities. Based on this information, the Main Zone pit was divided into ten design sectors, each sector having a consistent pattern of discontinuity orientations, rock type, groundwater conditions and pit wall orientation. Kinematically possible failure modes were identified in each design sector. Failure modes that were expected to present stability problems were analyzed to calculate factor of safety. Pit wall and berm face angles were then selected such that only a small number of potential failure modes will daylight. The stability evaluation has shown that it should be possible to increase pitwall angles by 5〫 in the west half of the pit. However, the data base in this area of the pit is presently limited because only a small number of berms are exposed. Therefore, additional line mapping will be required before the west wall design can be finalized. Groundwater will reduce pitwall stability, especially in the east half of the Main Zone pit. Multi-berm failures are very sensitive to groundwater conditions. A dewatering system should be installed in the Main Zone pit to minimize the possibility of such failures occuring. Wet blastholes dictate that expensive water resistant slurry explosives be used in many areas of the Main Zone pit. The dewatering system should also draw down the water table so blastholes will become dryer and less expensive ANFO can be utilized. The magnitude of shear strength on failure surfaces is required in order to evaluate stability of potential failures. Slip tests, point load tests and back analyses of existing failures were used to determine the shear strength parameters. Further studies should be carried out to better define the parameters at higher stress levels that will develop in a multi-berm failure. Further potential for pit steepening exists if the berm face in the volcanics can be maintained at a slightly steeper angle, e.g. 70 instead of the present 66°. It may be possible to achieve this goal if trim blasting procedures are modified to reduce blast damage to the final wall. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

In the South African gold mining industry, mining is being conducted at depths of over 3 000 m below the surface. Severe fracturing and deformation of the rock occurs making it unlikely that stress analysis which treats the rock as a homogeneous elastic material will yield useful results about the behaviour around the excavation. The excavation, or stope, considered in this study is tabular. The stope occurs in stratified rock with bedding planes at approximately 1 m intervals. The height of the stope is about 1 m to 1.5 m and the length increases to over 100 m as mining progresses. Shear fractures initiate ahead of the advancing stope, which together with the bedding planes separate the rock into distinct blocks of relatively intact material. The stratified nature of the material in the hangingwall (or roof) of the excavation, and the lack of cohesion in the bedding planes, suggests that separation occurs along the bedding planes, with each layer supporting its own weight. The lowest of these layers is referred to as the "hangingwall beam". Stope closure occurs at a distance of around 30 to 40 m behind the stope face. This study focuses on the mechanics of the hangingwall beam with particular emphasis on the conditions for stable closure. In order to do this the stope is first analysed using a finite element model which treats the rock as a homogeneous elastic medium. By treating the hangingwall beam as a separate layer, 1 m thick, its behaviour is compared to that observed in practice. We find that the hangingwall beam does separate from the overlying rock, but that the axial stresses in the beam are tensile, thus contradicting the observed behaviour. In practice, compressive stresses exist in the hangingwall and footwall. It has been suggested that slip along the shear fractures generates the compressive stresses. In constructing a mathematical model of the hangingwall beam we consider the beam to be made up of blocks 1 m deep and 1 m long. The blocks are treated as a homogeneous elastic material. The behaviour of such a beam is different from that of a fully homogeneous beam, because of the possibility of the formation of hinges. By considering a range of simplified models of a beam composed of blocks, various questions regarding its stability can be addressed. These models consider beams of fixed span in which the weight is increased from zero to the full value. The largest unsupported halfspan which can be stably equilibrated is of the order of 31 m. The maximum stable deflection is 0. 4 m, and therefore additional support is required to allow closure to occur statically. The nature of a single supporting spring that will let down the beam in a limiting, stable manner is identified. Once closure has taken place, the hangingwall beam is stable. In order to obtain a realistic picture of the steady state configuration of the hangingwall beam, an analysis is performed which simulates the advancing stope face. The results show that the distance between the face and the point of closure is around 34 m which is in accord with the behaviour observed in practice. The results have shown that the model which treats the hangingwall as a beam composed of blocks provides useful information about the mechanics of the hangingwall.

A research report submitted to the Faculty of Engineering and the Built Environment, School of Mechanical, Industrial and Aeronautical Engineering, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. / This study was based on the hypothesis that there are opportunities to maximize production outputs in many existing underground hard rock trackless mining systems using the same or less resources by improvement in decision making paradigms. This is very important in the current operating environments of uncertainties and continued drop in metal prices. The project main goal was thus to carry out a detailed investigation of trackless mining production systems and test how to maximize output by focusing on three objectives, namely: analyzing key technical factors that impact the production rates in terms of tons per hour, identifying major operational activities which impact effective equipment operating hours, and identifying decision support systems (DSS) to improve operational decision making. Regarding the first objective (production rates), through the analysis of trackless mining as a serial production system, it was shown that production rates could be increased by focusing at system level, process level and work station/equipment level decisions. System level decisions must minimize the total residence time of the material (ore) in transit or work in process(WIP). This will open capacity for generating more ore. Process level decisions must reduce the gross cycle times at the work stations to equal or be below the Takt times inorder to smoothen production flow. Takt time is an important factor in a production system which shows the maximum cycle time allowed to meet the daily demand. The third level focuses on the capability of the mining equipment itself through decisions that improves the reliability, maintainability and capacity. Decision tables based on reducing the equipment failure rates (λ), improving the repair rates (µ) and the cycle times were developed to aid in making the reliability, maintainability or capacity decisions. For the second objective (operational activities), the focus is to maximize effective operating times of the equipment through reduction of delays. The study shows this can be achieved through use of real-time decision support systems (DSS) for better control of the operations. The third objective was able to identify functional modern DSS that can be implemented in trackless mining. Effectively, the study was able to highlight opportunities of generating extra capacity for trackless mines at same or less resources by focusing on the above three objectives. / TL2019

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M.Sc. (Mining Engineering), Faculty of Engineering, University of the Witwatersrand, 1995

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