Developments in Petrology

Patnayak S., Tannant D.D.

A shovel performance monitoring study at an oil sands mine used current and voltage data from hoist, crowd and swing motors of P&H 4100 series electric cable shovels. The goal was to identify key shovel performance indicators using only data from the motors. It was found that hoist and crowd motor responses can be used to identify different shovel activities, especially the dig cycle. Some key shovel performance indicators examined are the dig cycle time, digging energy and digging power. By averaging the hoist power over a number of dig cycles, the average hoist power is less sensitive to digging trajectory and could be a useful parameter for assessing ground diggability characteristics. Analysis of performance indicators showed that the shovel performance can be significantly influenced by the operator. The study revealed that freezing temperatures can have a minor and localized influence on shovel performance.

Frimpong S., Li Y.

Hydraulic shovels are large-capacity equipment for excavating and loading dump trucks in constrained surface mining environments. Kinematics simulation of such equipment allows mine planning engineers to plan, design and control their spatial environments to achieve operating safety and efficiency. In this study, a hydraulic shovel was modelled as a mechanical manipulator with five degrees of freedom comprising the crawler, upper, boom, stick, bucket and bucket door components. The model was captured in a schematic diagram consisting of a six-bar linkage using the symbolic notation of Denavit and Hartenberg (Ho and Sriwattanathmma 1989). Homogeneous transformation matrices were used to capture the spatial configuration between adjacent links. The forward kinematics method was used to formulate the kinematics equations by attaching Cartesian coordinates to the schematic shovel diagram. Based on the kinematics model, a 3D virtual prototype of the hydraulic shovel was built in the Automatic Dynamic Analysis ...

Chugh Y.P., De I., Powell E.

This paper describes a model study of the flow phenomena in a pneumatic backfilling technique that involves application of short-duration high-pressure impulses. The study involved using fluidized bed combustion (FBC) fly ash as the backfilling material. The goal of this research was to develop a backfilling technique for abandoned mines that will be capable of filling underground voids to a distance of 300 ft from the injection point. The studies were conducted using a glass-top physical model of cross-section 13 in. × 4 in. and length 30 ft. The material was conveyed by formation of meandering conduits. Plugs were formed in the conduits during backfilling. Air impulses knocked the plugs and cleaned the conduits for material flow. The results indicate: (1) short-duration air impulses enhance the rate and range of the fill; (2) two successive impulses are more effective than a single impulse; (3) a seven-minute interval between impulse(s) give the best results.

Huang Y., Espley S.

In this paper, the philosophy, methodology, objectives, mining process logic, program structure and its state-of-the-art for our recently developed mine simulation model (a decision-making tool for mine design and production) are discussed. This simulation model is a detailed 3D model that can be used for many different mine sites without the need for programming but requiring only different input data that characterize the mine being simulated. The simulation model generates development, production and performance data throughout mine lifetime. The model also provides economics analyses such as operating cost, revenue, cash flow, rate of return on investment, net present value, ore tons mined and mine lifetime based on simulation results. Further, it studies the sensitivity and risk for the variation of parameters such as ore grade, dilution rate, market price and pre-production investment. The model thus provides all-important information for decision-making in mine design and production. This decision-...

Apel D.B., Dezelic V.

This paper presents how high frequency Ground Penetrating Radar (GPR) can be effectively used for mapping the subsurface characterization of dolomite and limestone strata for determination if the rock is suitable for ripping. The results of the experiments conducted in the course of this project illustrated that water saturation helps in increasing the contrast between the dielectric constants of the separations, due to water escaping into cracks and clay layers. Running the survey on a dry rock will give a larger penetration depth; but during the interpretation of the results, one can omit small voids or clay layers.

Asad M.W.

Lane's theory of cutoff grade optimization maximizes the Net Present Value (NPV) of an open pit mining operation with a declining effect as the deposit moves toward exhaustion. This declining effect of NPV defines dynamic cutoff grades, i.e. higher cutoff grades in the early years of mine life and lower cutoff grades in the later years. This phenomenon allows the creation of stockpiles with material between the lowest (breakeven) and optimum cutoff grades for processing during later years, when it becomes economical. As an extension to Lane's original theory of cutoff grades in deposits of two economic minerals, the management, i.e. supplies of material from the mine to the stockpile and from the stockpile to the processing plant, is addressed through the development of a cutoff grade optimization algorithm with option to stockpile. The benefits of the methodology are elaborated in a hypothetical case study.

Zipf R.K., Mark C.

Highwall mining is an important coal mining method in the USA and may account for approximately 4% of total USA coal production. Highwall stability is the major ground-control-related safety concern in highwall mining. Engineering away the safety risk by decreasing the highwall slope angle may be the best solution to the hazard posed by vertical joints in highwalls. The Mine Safety and Health Administration (MSHA) requires a ground control plan that usually specifies the hole width, maximum hole depth, maximum overburden depth, seam thickness, web pillar width, barrier pillar width and number of holes between barriers. Design charts for these parameters are given. Web pillars containing pre-existing auger holes are analysed and a design chart for estimating their minimum width is also presented. Close-proximity multiple-split highwall mining, which caused several serious highwall failures, is analysed and recommendations are made. Finally, this study examined records from 5289 highwall miner hole...

Lind G.H.

Analysis of Pillar Extraction Potential (A-PEP) is an intelligent tool that could be used as a preliminary output indicator when considering the secondary extraction of regional support pillars in the Witbank and Highveld coalfields of South Africa. Pillar extraction practices in South Africa have consumed a significant proportion of safety and fatality statistics in relation to its relative output (less than 5% of total South African coal production) and as a result research was undertaken in local pillar extraction operations and extended to similar operations in New South Wales, Australia to assess a way forward for pillar extraction in South Africa. The A-PEP tool is based on certain physical, risk and economic factors that combine to be indicative of operational success in terms of economic, health and safety attributes. In this paper it is successfully tested against two existing pillar extraction operations.

Ta C.H., Kresta J.V., Forbes J.F., Marquez H.J.

In the mining industry, truck assignment is an important and complex process and an optimal truck allocation can result in significant savings. In this paper, a truck allocation model is formulated using a chance-constrained, stochastic optimization approach that can accommodate uncertain parameters such as truckload and cycle time. A real-time hauling framework, which consists of the chance-constrained optimization model and a model updater, is developed to compensate for changes in the uncertain key operating parameters. The use of the model updater helps the truck allocation system to adapt to random operational changes. The effectiveness of the chance-constrained approach in dealing with uncertain process parameters, when coupled with model updating, is shown to be a viable implementation framework in the dispatching operation.

Frostad S., Klein B., Lawrence R.

Prediction of the relative rates of acid generation and neutralization is required to determine if and when acidic drainage will occur for mining waste. Results of laboratory kinetic tests are routinely used to predict the long-term weathering rates of a waste dump. More specifically, an estimate of the ‘time to acidity’ (lag time) is needed to predict if exposed waste rock will become acidic before underwater disposal. A meaningful prediction requires consideration of the differences between the conditions in the laboratory and an actual waste dump. Field tests, which are less commonly conducted, provide site-specific weathering conditions but return results that are difficult to interpret. The results from field tests were compared to those obtained from laboratory kinetic tests. The field rates of weathering were determined to be an order of magnitude greater than the adjusted laboratory results, which were corrected for both surface area and temperature. The difference between the field and laboratory...

Aldas G.

Vibration frequency depends strongly on the propagating media and blast delay intervals. Frequency analysis is therefore important in selecting optimum blast delay intervals. The application of Fourier frequency analysis to determine the dominant frequency in ground motion is quite common. The Fourier spectra provide a complete description of the amplitudes of waveforms versus frequency, but these do not contain information regarding the time duration of these waveforms. Moreover, it is well known that damage to structures is dependent on the time duration of blasts as well as on the amplitudes and frequency of waves. Therefore, in addition to the dominant frequency of the waveform, the time duration of the waveform at that frequency must also be known. The Stockwell transform (S-transform) overcomes this difficulty in such a way that the S-transform of particle velocity records offers a means of representing the variation of spectral components with time. This paper examines the use of the S-transform fo...