Showing papers in "Mineral Resources Engineering in 1999"

Automated interpretation of geophysical borehole logs for orebody delineation and grade estimation

Abstract: An automatic interpretation tool, LogTrans, for geophysical borehole logs was developed during a recent CMTE/AMIRA Project, The Application of Geophysics to Mine Planning and Operations. LogTrans performs rapid analysis of multi-parameter logs and expedites presentation of interpreted results in a form meaningful to mining engineers and geologists. The algorithm exploits the contrasts in petrophysical signatures between different "classes" of rock. The classes may be distinguished by lithology, grade, mechanical properties, or any combination of characteristics. The LogTrans procedure entails two stages: • statistical characterisation, involving determination of the centroids (means or medians) and ranges (standard deviations or spreads) of the distributions of each petrophysical parameter for each class, based on a representative control data set; • discrimination, in which data points are assigned to the "nearest" control class in multi-parameter space. The LogTrans discrimination algorithm is simple, intuitive, fast and flexible. However, it is not a Black Box. Its performance relies fundamentally on the integrity of the control information: the geological, geochemical, and/or geomechanical data from the control holes, as well as the geophysical logs. In particular, drilling depths must be carefully reconciled with borehole logging depths. Interpretational performance is enhanced when parameter distributions are uni-modal and compact, and when high petrophysical contrasts exist between classes. Critical assessment of the control information can prompt introduction of new classes (by sub-division of existing classes or otherwise) and derivation of new parameters (by mathematical combination of original parameters) to better achieve the interpretational objective. LogTrans has been applied successfully to logging data sets collected from a number of Australian and overseas mines. Prediction accuracy in excess of 90% has been achieved in several cases. Its application for orebody delineation at Century and for grade range interpretation at Rosebery is illustrated in this paper.

Issues in autonomous navigation of underground vehicles

Abstract: This paper describes current research at the Australian Centre for Field Robotics (ACFR) in collaboration with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) within the Cooperative Research Centre (CRC) for Mining Technology and Equipment (CMTE) towards achieving autonomous navigation of underground vehicles, like a Load-Haul-Dump (LHD) truck. This work is being sponsored by the mining industry through the Australian Mineral Industries Research Association Limited (AMIRA). Robust and reliable autonomous navigation can only be realised by achieving high level tasks such as path-planning and obstacle avoidance. This requires determining the pose (position and orientation) of the vehicle at all times. A minimal infrastructure localisation algorithm that has been developed for this purpose is outlined and the corresponding results are presented. Further research issues that are under investigation are also outlined briefly.

How to address the crisis of mining engineering education in the western world

Abstract: The difficulties experienced by many mining engineering departments in the western world are addressed and the most common causes of the problem discussed. It is shown that the poor public image of the mining industry and the financial difficulties experienced by the mining industry and many governments are the main reasons behind low student numbers and sub-critical mining engineering departments. Possible solutions to the problem of sub-critical student numbers and mining engineering departments are put forward. It is shown that the merger of mining engineering departments with other engineering department and the establishment of broader based study courses are no long term solutions to the problem of low numbers of mining engineering students and graduates. Industrial sponsorship, particularly research sponsorship, is vitally important for the continued existence of strong mining engineering departments. The establishment of networks between different mining engineering departments is seen as the most promising way of addressing the problem. Different concepts of establishing networks are discussed and examples of successful networks given. The possibilities offered by modern communication technologies have not been fully exploited by universities and should be pursued.

Analysis of flexible mining systems

Abstract: Flexible mining systems possess the ability to adapt to internal or external changes in operating conditions and maintain production expectations. This paper reviews the nature of the various types of mining flexibility and their controlling factors. Methods for assigning a value or figure of merit to flexibility are presented. Examples focus on the use of these methods at the mine level. Option pricing was found to be a useful approach for valuation of flexibility in a strategic, long-term context such as in mine design or major modification of mine operations. Computer simulation was found to be useful for tactical evaluation of flexible opportunities in mine production control.

Geotechnical investigation at lignite mines

Abstract: Open pit lignite mining provides the energy resources for about 80% of the electrical energy annually consumed in Greece. Optimum open pit slope stability design is related to the minable reserves as well as the cost of mining. This paper presents a geotechnical investigation for the "Tomeas 6" lignite mine at the Ptolemais-Amydeon basin (in northern Greece), including sample testing, interpretation of inclinometer and geodetic data, and slope stability analysis performed in order to determine the potential of mine slope failure. This investigation was initiated after slope cracks and floor heaving were observed following mining operations. Results indicate that cracking on the slope as well as floor heaving may be attributed to stress relief due to mining.

An application of logit model to injury experience data

Abstract: The influence of various casual factors on the severity of injury was examined using the 4-year injury data from a group of underground coal mines. Although there are many factors that could affect the injury severity: miners' age, experience, occupation, injury-location, shift-time and specific-mine were chosen as the affecting variables. The logit model was applied for this analysis. The bivariate analysis was conducted to separately study the effect of each of the factors on the severity of injury and to estimate the odds of severe injuries. For the case study mines, it was concluded that the injury severity varies by age, occupation, injury-location, shift-time and specific-mine. However, experience in general does not have any significant effect on it.

Petri nets as a tool for mine simulation

Abstract: Lately high-level Petri nets have found broadening applications to simulate compound systems in decision-making, informatics, and manufacturing. A process is reflected as a movement of tokens across logical transitions with time delays in places of net. The properties and computer interpretation of Petri nets are described. A complete mining system can be formed from standard components that are presented as Petri nets. Petri nets for a longwalling, driving, mine-wide conveyor net, conveyor-locomotive transport, and robotics-based mining had been constructed. They have been used to solve a number of practical problems, such as coordination of a cutting and supporting, designing and dispatching of compound transport systems, choice of loading strategy for LHD's, interaction between robots and mining machines, and design of mining robots.

Economic significance of sub-cutoff grades in open pits operating with concentrator bottleneck

Abstract: Mathematical models are built and a nonlinear algorithm is coded to determine solutions to cutoff grade, sub-cutoff grade and sub-grade stockpile sizes which optimise the open pit mining from an economic point of view. The purpose is to study the theory that it is more reasonable economically for an open pit mine to stockpile its low grade ores and treat them later, especially if the mine has a bottleneck condition at the concentrator.

Simulation of a large open pit mine operation in australia

Abstract: The open pit gold mining operation by Kalgoorlie Consolidated Gold Mines Pty Ltd (KCGM) is the largest in Australia. The final pit will result in combining a few existing pits and underground operations. That is why the current operation is also known as the "Super Pit". The scale of the operation demands efficient planning and the company has a very strong strategic planning department to support the mine planning and design activities. The author was supported by the KCGM in undertaking a study of the production system for the open pit mine operation and to develop a computer simulation of the existing system. A graduate student started working on this project as his Master's Thesis (Sappington, 1997) under the supervision of the author. This paper presents the initial study, formulation, and coding of the simulation and animation model developed for the above-mentioned operation. The model developed was also validated against existing performance measures and produced satisfactory results. Advantage of having such a model are emphasised and its role in strategic planning are addressed. The model developed was used later to test a few dispatch algorithm and for proposing a dispatch algorithm. However, the detailed sensitivity analysis and discussion of the dispatch algorithm are beyond the current scope of this paper.

Evaluation of the effectiveness of wetland treatment at rustler's roost gold mine in the northern territory

Abstract: The rationale for this paper was to examine the beneficial or detrimental effects of treating and disposing of process water from the production plant and wastewater from Rustler's Roost Gold Mine through a modified natural wetland system. Rustler's Roost is located in the wet/dry tropics, 90 km southeast of Darwin at the northern end of the Pine Creek Geosyncline in an area distant from the main centres of historic gold production. At the time of the trial, data on water quality indicated that elevated level's of Cu, Al, and NaCN (Total and WAD) Cr, Se and Zn were present in Rustler's Roost plant water. Wetland treatment was being examined as an alternative to traditional wastewater treatment options. With an increase in production wastewater expected for 1996/1997 wet season, disposal of wastewater would be essential to insure integrity of the hydraulic circuit. Release of waste was dependent on meeting release criteria set by the Controller of Water Resources in a site-specific discharge licence. A 3-month dry season trial was conducted by modifying a section of a relict creek system. Wastewater was introduced by pumping waste directly from retention ponds. Results of the trial indicated dramatic removal in metals from solution, in particular, Cu and cyanide species.

Statistical quality control: a multivariate approach

Abstract: Many quality control operations in mining deal in controlling more than one variable for meeting the quality specifications. In such cases, an application of the Shewhart's univariate control chart for each of the variables is unsatisfactory as it fails to consider the problem in a multivariate situation ignoring correlation structures amongst the variables. In this paper, an application of the Hotelling's multivariate control chart is demonstrated in an iron ore mine through a case study. The study revealed that the sensitivity of detecting an out-of-control condition is increased using a multivariate control chart. It is suggested that once an out-of-control is detected in multivariate chart, the corresponding univariate control charts should be investigated to identify which variable(s) causes the out-of-control condition. While investigating multivariate and univariate control charts for the case study mine, two possible out of control conditions were encountered: one due to the out-of-control condition of the individual variables and the other relates to the correlation structure of the variables. For the case study mine, it was also revealed that even if the application of control charts will improve the quality of ore, it is difficult to meet all the quality specifications, especially Fe% and Al2O3% on a regular basis. To overcome this problem, it is suggested that the system may require a fundamental change in the mining process or the specification limits may be reviewed. The fundamental change may be the review of cut-off grade, changing of blending ratio of material from different faces and further blending of material.

A design criteria for a management system for the control and treatment of acid rock drainage from mining operations in the northern territory

Abstract: Acid mine drainage is an intensifying problem facing mining companies in the Northern Territory. Increasingly, more and more mining practitioners and researchers are studying ways to control the potential environmental impact of acid rock drainage. To date, conventional engineering methods are failing against the extremes of the Top End wet/dry climate. Because of this defalcation, a method of abatement will be required for the long-term protection of aquatic ecosystems. The purpose of this paper was to identify a "whole mine" method of abatement, which could remain at the waste site, generally, maintenance free and provide a significant buffering affect for receiving water bodies. Although wetland treatment has been proven in the treatment of heavy metals, little evidence exists on their viability once subjected to extended periods of low pH water. This paper proposes a design incorporating both control and abatement features. The key to the design is the sequence in which the effluent is received, as we...

Evaluation of in situ leaching processes: dual-porosity model

Abstract: A dual-porosity model is developed to study processes of in situ leaching. The model involves two overlaying continua at the macroscopic level: a permeable fracture system that determines the flow field of leach solution and a relatively impermeable matrix system that determines the leaching kinetics. The most obvious advantage of the model is that parameters it requires are minimal and easily available in practice. These parameters include the in situ hydraulic conductivity, longitudinal and transverse dispersivities, the lumped rate constant, and an empirical rock mass classification index, RQD (Rock Quality Designation). The simulation of in situ leaching processes is linked to RQD through the effective porosity of fractured media. The incorporation of RQD enables the simulation of in situ leaching processes to be carried out for a whole spectrum of ore deposits. When RQD approaches 0, it represents that the ore deposit may be a porous medium with a high effective porosity. This may reduce the double-porosity model to a single porosity model. When RQD approaches 100, it represents that the ore deposit may be considered as impermeable and unleachable. These values bound the possible ranges in behavior of the system. Based on the double-porosity model, the relation between particle size and leachability is developed, and the effects of double porosities on the concentration of a dissolved mineral are investigated. It is demonstrated through model results that the recovery rate of a valuable mineral is mainly determined by the effective porosity of the fracture pore system, the porosity of the rock matrix system, and their ratios in addition to the concentration of reagent and the ore grade.

A new method of truck number calculation for shovel-truck system

Abstract: A brand new method of truck number selection with division onto operating trucks and reserve has been considered. All major technical and stochastic properties of the equipment involved and random properties of the exploitation process were taken into account. Some new stochastic phenomena occurring in this process were found and their effects were included.

Dragline swing automation

Abstract: Draglines are used extensively for overburden stripping in Australian open cut coal mines. This paper outlines the design of a computer control system to implement an automated swing cycle on a production dragline. Subsystems and sensors have been developed to satisfy the constraints imposed by the task, the harsh operating environment and the mine's production requirements.

The effects of shiftwork schedule practices and panel dimensions on injury experience in underground longwall coal mines

Abstract: Over the past two decades, there has been a tremendous growth in the amount of coal produced in the United States by the longwall-mining method. During the early-to-mid 1970s, approximately 120 longwall faces contributed less than 5% of the nations's underground coal output; currently, half as many faces contribute nearly 50% of the nation's underground coal output. All this has taken place during a time period when the total underground production grew less than 20%. In addition to the introduction of new technology, new management, operational, and engineering practices have contributed to this explosive growth. Specifically, changing out at the face, lengthened longwall faces, deeper panels, and longer shifts have increased system availability, thereby resulting in these remarkable production gains. However, longer faces and shifts create a concern for the health and safety of face personnel because of increased exposure to workplace hazards and fatigue. This paper examines the impact of increased face lengths, varying mining heights, and increased shift lengths on the accident and injury experience of U.S. longwall mines. Although no statistical significance was established between the three trends and the nonfatal days lost incidence rate, the no days lost incidence rate, and the severity measure — due to limited or nonexistent data, or widely varying incidence rates — a trend was established between the nonfatal days lost incidence rate and shift length. Specifically, for every hour of shift length above eight hours, the nonfatal days lost incident-rate ratio was 1.185, implying that a 18.5% increase in the number of nonfatal days lost incidents is predicted when a shift is extended one hour in the range from eight to nine, or nine to ten hours.

Effects of cutting head motion on the boom length of rock and coal cutting machines

Abstract: Cutting heads or cutting drums employing drag tools, perform the cutting action either in traversing or arcing motion. Laboratory rock cutting investigations on simulating roadheaders cutting head operating in traversing motion, showed that the pick forces were proportional to the cross-sectional areas swept by these picks. Theoretical analysis of these investigations indicated that under equivalent conditions, these areas were greater for arcing motion, and thus the pick forces became inversely proportional to the boom length. A number of in situ trials were also conducted with roadheaders of various types at OAL Mine in Turkey to evaluate the practical significance of the laboratory findings. Both the laboratory and the in situ trials indicated that within the size and the capacity of the current machines, a variation in the boom length does not significantly affect the cutting speed or the advance per revolution of the cutting head. It was however shown that if the effective boom length is around 2 m or less, together with the advance per revolution being in excess of 0.05 m, an axial type cutting head may perform better when in traversing mode. Furthermore, the concept suggesting that in arcing mode, smaller tilt angles are the case for corner cutting tools, was found to have no practical significance.

Impact of coal mass structure on fragmentation during mining and processing

Abstract: Coal fragmentation is a function of the material strength, lithotype bedding and banding, and fracture of a given seam and is induced through the application of energy during the mining and handling process. A large field and laboratory based project was designed to measure, model and understand this process so that tools can be developed to optimise fragmentation in the mining process. Field audits were conducted during which coal seams were characterised in situ and discrete parcels were mined blasted and free dug and then tracked through the handling and crushing stations. Samples of ROM, crusher product and breaker product and reject were sized and analysed for washability. The results show that the results of fragmentation can be linked to the inherent band size distribution of the coal. Band thickness distributions can also be used as an input to blast fragmentation models. The results also show that mining method does not significantly impact on the final size distribution of the ROM. However, it does impact significantly on downstream processing behaviour. Although size distributions of breaker product were similar for the blasted and free dug coals from the same block, the washability of the coarse and fine coal from each trial were significantly different.

Improving the value of wear debris analysis to the maintenance engineer

Abstract: This paper presents a number of developments that can be made to improve the value of wear debris analysis to the maintenance engineer. Although there have been many advances in the field of machine condition monitoring over the last few years, wear debris analysis has been left behind. This is an unfortunate situation because the technique can provide extensive and timely information on the condition of mechanical components lubricated by the oil. The lack of enthusiasm for this type of analysis can probably be attributed to the poor communication that exists between the various stages of the analysis. Typically, each stage is performed in isolation, by people who may be unaware of the conditions and techniques used in the other stages. This situation can be improved with education and training of maintenance workers but automation can provide a more lasting solution.