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By Takuji Yamamoto

High-speed TBM excavation requires rapid ground assessment ahead of excavation, particularly in complex grounds. The Tunnel Reflector Tracing technology (TRT) developed by authors, uses seismic reflections to produce volumetric images of ground anomalies. To further minimize interruption in the TBM excavation the authors modified surveying technique switching from cable (wired) to radio (wireless) data acquisition system. This paper presents the outline of the Wireless TRT system, and compares the results for the wired and the wireless surveys. The comparison shows that the wireless system offers high precision data, is more efficient and economical and significantly less intrusive in tunneling operations.

By R. J. Gochin, G. D. Schena, R. Spencer

The impact of a mineral project in a developing country is evaluated in the broad context of its economy using input-output models. Minimum economic theory is used to develop simple numerical models. Sets of technical coefficients are exploited in the development of linear models of the productive element of an economy. The analysis allows assessment of the overall economic consequences of a mineral development in which issues broader in scope than financial objectives need to be incorporated in the evaluation. In part 1, the framework for the development of the input-output model is presented. The model is refined to incorporate country-specific behaviour. The increased flexibility of the enhanced semi-input-output model permits a more confident investigation of the economy-wide effects associated with a new project in the mineral sector of a developing country. The relevance of the models is illustrated using an example from Namibia

Sep 1, 1991

By Peter Zhang, I. BERK TULU, Morgan M. Sears, Mark Van Dyke, Heather Dougherty, Ted Klemetti, Gabriel S. Esterhuizen

Ground falls in longwall gateroad entries remain a concern in modern longwall operations. The gateroads are subject to changing horizontal and vertical ground stress induced by longwall extraction. These stress changes can result in failure of the strata around an entry leading to large deformations of the entry roof, floor, and ribs. The gateroad support systems are required to control the failed strata while maintaining safe access to the longwall face and unimpeded ventilation. This paper presents research that was conducted to better understand the stability issues in gateroad excavations and to develop procedures for evaluating support and layout alternatives for longwall gateroads. Using the results of a field-monitoring program and numerical model analysis of case histories, a conceptual model of gateroad support needs was developed. The conceptual model formed the basis for developing a set of equations that can be used to estimate likely roof sag and support loading for given roof geology and longwall-induced loading conditions. The developed equations were used to compare predicted gateroad stability to field study results, showing satisfactory agreement. The calculation procedures are used to demonstrate their application in assessing support alternatives at a case study mine. It is concluded that the developed analysis procedures provide realistic assessments of likely ground stability and can be used to evaluate alternative gateroad support systems at operating longwall mines.

May 13, 2021

By Peter Zhang, I. BERK TULU, Morgan M. Sears, Heather Dougherty, Ted Klemetti, DYKE MARK VAN, Gabriel S. Esterhuizen

Ground falls in longwall gateroad entries remain a concern in modern longwall operations. The gateroads are subject to changing horizontal and vertical ground stress induced by longwall extraction. These stress changes can result in failure of the strata around an entry leading to large deformations of the entry roof, floor and ribs. The gateroad support systems are required to control the failed strata while maintaining safe access to the longwall face and unimpeded ventilation. This paper presents research conducted to better understand the stability issues in gateroad excavations and to develop procedures for evaluating support and layout alternatives for longwall gateroads. Using the results of a field-monitoring program and numerical model analysis of case histories, a conceptual model of gateroad support needs was developed. The conceptual model formed the basis for developing a set of equations that can be used to estimate likely roof sag and support loading for given roof geology and longwall-induced loading conditions. The developed equations were used to compare predicted gateroad stability to field study results, showing satisfactory agreement. The calculation procedures are used to demonstrate their application in assessing support alternatives at a case study mine. It is concluded that the developed analysis procedures provide realistic assessments of likely ground stability and can be used to evaluate alternative gateroad support systems at operating longwall mines.

"Liberation is a key requirement for efficient separation in mineral processing. As a consequence of this an understanding of the inherent textural features of an ore is no longer possible since during the process of liberation, texture is destroyed. Knowledge of key textural features, such as mineral grain size and distribution, prior to breakage processes provides the opportunity to understand the textural drivers for ore hardness. Modern characterisation methods, including automated SEM-based techniques, provide the possibility of measuring mineral characteristics at a range of scales. This paper discusses how textural features of two different ore types in a porphyry copper deposit can be measured and interpreted at a number of scales. Standard breakage tests conducted on the ores indicate that one of the ores can be characterised as hard and the other as soft. The impact of mineral grain size and the presence and scale of vein type structures in the two ores have been used to determine the extent to which these features influence ore hardness.INTRODUCTIONIn order to effectively convert ore into metal, knowledge of both the processing stages and the characteristics of the ore are essential. Prior to the advent of technologies that enabled the fundamental understanding of the sub-process at each stage of processing and the measurement of appropriate ore properties the most effective way to understand how an ore would respond to a process was to put it through that process, for example the way to determine how an ore would break was to first break it. Existing comminution models seek to predict the size distribution of rock fragments as the result of applied energy based on knowledge of the rock strength. It is common for these models to consider the rock as homogeneous and despite providing important data for the design and optimisation of industrial comminution circuits these models are only applicable within a narrow range of operation. In order for reliable predictive models to be developed that account for the inherent ore characteristics, a step change is required in the type of measurements that are carried out to characterise an ore and the type of data that is extracted and used as model inputs."

Jan 1, 2016

Ventilation challenges are often encountered when an underground mine expands to new zones and it often is the case to make a thorough review of the existing system and assess immediate and future airflow needs at the desired quantity and quality. An unexpected mine plan change that calls for increased development and production from new areas can impose a strain on the existing ventilation system. Budgetary constraints can also demand creativity in design on the mine ventilation engineerÆs part. Since the addition of several mining horizons it had become obvious at the Meikle mine that something had to be done to increase airflow quantity and quality in the old main zones because most of the ventilation resources had been channelled for development in the new mining horizons. An airflow assessment of the existing system had to be performed and it was determined that the airflow quantity had to be increased by at least 30 per cent and the quality of the air had to be improved by reducing nuisance and respirable dust and at the same time reducing the airflow temperature before it was used in a few mining zones. At the conclusion of the airflow assessment it was determined that a third centrifugal fan would be installed on a new 3.05 m diameter borehole from surface to underground. By a careful study of temperature conditions over time it was determined that an evaporative cooling spray chamber would be sufficient to cool the airflow down from the high dry bulb temperatures observed down to saturation at the wet bulb temperature. At the same time excessive nuisance dust generated as a result of the airflow travelling a long way in a haulage drift will be knocked down in the spray chamber resulting in cool, clean air in the mining districts. Expansion of the existing surface ammonia refrigeration plant was out of the question for several reasons. The fact that the airflow was hot and dry meant that evaporative cooling spray chambers could achieve lower working temperatures at a very low cost compared to the expansion of the chilled water plant. The expansion of the ventilation system at Meikle mine and the use of evaporative cooling spray chambers were demonstrated to be very successful and the information presented in this paper can be of benefit to other mines experiencing the same ventilation problems as was the case at the Meikle mine.

Jan 1, 2005

By P A. Dowd

This paper describes an integrated approach to the evaluation of ore loss and ore dilution via geostatistical simulation of in situ geology and grade characteristics, simulation of blasting mechanisms and simulation of loading from a blast muck pile. The approach is demonstrated on a case study. The sequential Gaussian method is used to simulate in situ bench grades on the scale of the smallest selectable volume within a blast muck pile. The simulated grades of these component volumes are interpreted as the reality that would be available with exhaustive sampling. The simulated bench is subjected to a blast simulator, based on the SCRAMBLE model, which effectively moves each of the component model volumes to its final resting place in the blast muck pile. Ore/waste delineation and selective loading processes are applied to the simulated muck pile to determine the degree of selectivity that can be achieved by various sizes of loader and types of loading and to quantify ore dilution and ore loss. An in situ model representing the reality of knowing only the data and information that are available from specific grade control drilling and sampling grids is obtained by sampling the geostatistically simulated model on a specified grid. The volumes comprising the in situ model are then populated by estimates based only on the data and from the specified grade control drilling and sampling grids. Different drilling and sampling grids are used to generate different models, each reflecting the levels of data and information available. Selectivity is assessed as a function of the drilling and sampling grids as well as the size and type of loader. Performance is assessed against the ideal selectivity that could be achieved on the perfect knowledge model comprising the simulated values of each component volume. Costs, prices and financial criteria enable an optimal selection of the grade control drilling grid, size of loader, type of loading and blast design.

Jan 1, 2004

In the late 1970's and early 1980's a considerable number of large scale open pit mines were developed in N.S.W. and Queensland. At the time these mines were planned, the industry was characterised by rising coal prices, rising fuel prices, and a host of other labour and government constraints different to the situation today. Yet some mines have clearly been able to cope with this change much better than others. While one mine may now be expanding and profitable, its neighbour may still be labouring under painful adjustment processes. This paper examines the major reasons for this difference. It suggests more robust criteria for assessment of future projects to reduce their sensitivity to changes outside management control.

Jan 1, 1990

By M. B. Fonseca

Risk quantification in grade-tonnage curves is critical for capital investment in mining projects and can be obtained through geostatistical simulations of orebodies. A practical difficulty may arise in multi-element deposits, as the joint modelling of the related attributes using the traditional co-simulation approaches is computationally intensive and may be impractical for use in the industrial environment. This paper presents the construction of risk-integrating grade-tonnage curves for a complex copper deposit in northern Brazil, by jointly simulating its key geochemical attributes of interest: Cu, Fe and K. The joint conditional simulation of these elements is based on Minimum/Maximum Autocorrelation Factors (MAF). MAF is an approach, based on principal components, that spatially decorrelates the variables involved to non-correlated factors. MAF’sspatial decorrelation at any lag distance is the main and critical difference of this approach from the principal component approach attempted in the past. In the MAF approach, the independent factors are individually simulated and back-transformed to the conditional simulations of the correlated deposit attributes that reproduce the cross-correlations of the original variables. Keywords: Joint simulation; mini/max autocorrelation factors; grade-tonnage curves.

Jan 1, 2003

By Gregory M. Rumbaugh, Christopher Mark

"The proliferation of unconventional gas well development in the Northern Appalachian coalfields has raised a number of mine safety concerns. Unconventional wells, which extract gas from deep shale formations, are characterized by gas volumes and pressures that are significantly higher than those observed at many conventional wells. The gas is composed largely of methane as well as other hydrocarbons. Hundreds of planned and actively producing wells penetrate protective coal pillars or barriers within active mine boundaries, including chain pillars located between longwall panels. Gas released from a well damaged by mining-induced ground movements could pose a risk to miners by flowing into the mine atmosphere. The mining-induced ground movements that may cause well damage include conventional subsidence, non-conventional subsidence (e.g., bedding plane slip), pillar failure, and floor instability. This paper describes the known risk factors for each of the four failure mechanisms. It includes a framework that can guide the risk assessment process when mining takes place near gas or oil wells.INTRODUCTIONSouthwestern Pennsylvania has served for centuries as a producer of coal, oil, and natural gas. Coal mines were first developed in the Pittsburgh Coal Seam in the 1760s, with the first recorded mine in 1761 being the Fort Pitt Mine (Edmunds, 2002). Natural gas was introduced to the region when the Haymaker Well in Murrysville, Pennsylvania experienced a blowout on November 3, 1878. Although it was originally drilled prospecting for oil, it produced an estimated 30 million cubic feet per day of natural gas. Without well controls or pipeline infrastructure in place, it burst into flames and lit the night sky for over a year. Soon after, the Penn Fuel Company continued development of the Murrysville gas field and is credited with making Pittsburgh, Pennsylvania the first major city in the U.S. to have natural gas supplied for home and industrial uses. “Natural gas is king in Pittsburgh,” proclaimed an October 18, 1885, article in the New York Times headlined “Value of Natural Gas, Its Use Clarifies the Atmosphere at Pittsburgh” (AOGHS, 2018). By the early 1900s, coal, oil, and natural gas production had reached the southern extents of Pennsylvania in Greene County. The county had first produced oil in 1886, and shortly after began producing natural gas in 1890. By 1906, over 1,300 wells had been drilled (Stone and Clapp, 1906)."

Jan 1, 2019

By L. Prosser, A. Iannacchione, G. Esterhuizen

The potential for roof falls in underground mines remains a clear and present danger for mine workers. An investigation of ground conditions in nearly 50% of the nation’s underground stone mines found that the state of roof stability is primarily determined in a limited and subjective manner. These large opening mines, with roof heights typically of 7 m or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information on roof stability, this practice is usually short-term and localized to address ground conditions in a particular section or part of the mine. A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method utilizes an observational technique to identify the risk of roof falls in three categories. Case study scenarios provide a realistic picture of model implementation. Providing the mine level decision maker with an accurate assessment tool to ascertain the level of risk related to ground conditions is expected to reduce mine worker injuries and fatalities. Moreover, the presences of danger can be overcome with a clear picture of quantified ground conditions.

Jan 1, 2006

By L. Prosser, A. Iannacchione, G. Esterhuizen

The potential for roof falls in underground mines remains a clear and present danger for mine workers. An investigation of ground conditions in nearly 50% of the nation’s underground stone mines found that the state of roof stability is primarily determined in a limited and subjective manner. These large opening mines, with roof heights typically of 7 m or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information on roof stability, this practice is usually short-term and localized to address ground conditions in a particular section or part of the mine. A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method utilizes an observational technique to identify the risk of roof falls in three categories. Case study scenarios provide a realistic picture of model implementation. Providing the mine level decision maker with an accurate assessment tool to ascertain the level of risk related to ground conditions is expected to reduce mine worker injuries and fatalities. Moreover, the presences of danger can be overcome with a clear picture of quantified ground conditions.

By H. Kinilakodi

In 2008, the authors developed a methodology for identifying underground coal mines at high risk for major-hazard events. It focused on major hazard-related violations of safety standards associated with high-risk conditions. Later, using a sample of 103 mines with 2008 and 2009 data, injury measures and U.S. Mine Safety and Health Administration (MSHA) citation data were combined into a safe performance index (SPI). The SPI was used to assess the relative safety-related risk of mines, including by mine-size category. In this paper, comparisons are made of SPI-associated, normalized safety performance measures across mine-size categories, with emphasis on small-mine safety performance as compared to large and medium-sized mines. Mining Engineering, 2011, Vol. 63, No. 10, pp. 73-77. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By H. Kinilakodi

In 2008, the authors developed a methodology for assessing underground coal mines for high risk for major-hazard events. It focused on major hazard-related violations of safety standards associated with high-risk conditions. Later using a sample of 103 mines with 2008 and 2009 data, injury measures and MSHA citation data were combined into a Safe Performance Index (SPI). The SPI was used to assess the relative safety-related risk of mines, including by mine-size category. In this paper, comparisons are made of SPI-associated, normalized safety performance measures across mine-size categories, with emphasis on small-mine safety performances as compared to large and medium-sized mines.

Jan 1, 2011

By A Litwinowicz, M Laxman, A Fourie, A L. Li

This paper presents a design approach and analytical methods that were used for assessing the potential of static liquefaction and developing the mitigation measures for a tailings dams. The rigour of the design and analysis approach represented leading practise in the industry to address static liquefaction, which contributed to a robust design with high confidence and certainty. The salient features of our approach to static liquefaction included geotechnical investigation and tailings characterisation, static liquefaction screening assessment, static liquefaction triggering analysis, limit equilibrium analyses and numerical modelling of static liquefaction using the NorSand model, which was amongst the first tailings dam projects involving numerical modelling of static liquefaction using these methods.

Jul 1, 2021

By Breaux B. Castleman

The ultimate test of a business strategy is whether it achieves the owner's objectives. Most shareholders are interested in growth and profits, and share values on stock exchanges are very often closely correlated with profit growth and profitability measured as return on equity (ROE). Strategic management, then, involves managing investments or resource allocations to optimize long-term growth and real return on equity, within reasonable limits of risk. Figure 1 shows a plot of the five year, weighted average ROE of a number of communications companies against their stock market valuations in 1983, measured as a ratio of market value to book value. The principal explanation of the differences in the relative valuations of the individual stocks is historical ROE, weighted toward the most recent years. Further analysis demonstrates the added importance of growth in explaining the differences in stock market to book ratios. [ ] Research conducted by Booz Allen and others in recent years suggests that the relationships between ROE and market to book multiples hold true in industry after industry. Furthermore, we have found that in assessing business strategies for companies in these industries, the analyses should focus on whether proposed strategies are likely to lead to consistent long-term growth in real ROE, without excessive leverage. Our research also reveals, however, that these approaches to strategy assessment are not consistently applicable in the natural resource extractive industries. Figure 2 shows a similar comparison of market to book values against five year average ROE for a group of nine mining companies in 1983. Market value of the shares shows little correlation with ROE. [ ] Analysis of the data for other extractive industries indicates a similar pattern; that is, low correlation between share values and

Jan 1, 1985

By L Lorenzen

In this paper, we developed and implemented a fuzzy logic expert system capable of evaluating the degree of sustainability within the context of gold mining operations. The newly introduced approach of evaluating sustainability in the gold mining industry has the merit of sufficiently handling diverse, sustainable, development-related qualitative and quantitative data owing to fuzzy logic technology capabilities in dealing with linguistic syntax. The economic, environmental and social indicator inputs were independently evaluated and then combined with the aid of fuzzy logic to provide an overall sustainability index on a scale of zero to one. A total of 66 independent indicators were identified and applied in our model. The novelty of this work lies in providing a coherent numerical and automated approach in evaluating sustainability in the context of gold mining operations. In addition, the model can aid policy- and decision-makers in arriving at consistent decisions regarding the degree of sustainability on various aspects of gold mining operations. The functionality of this model will be illustrated through several examples.

Jan 1, 2007

By C. Guney Olgun, Fleur Loveridge, Tracy Brettmann, William Powrie

"Abstract Deep foundations are increasingly being used, not just to carry structural loads, but also to act as heat exchangers as part of a ground source heat pump system. Such foundations, often called energy piles, have the potential to make significant contributions towards meeting the heating and cooling demands of buildings, thus reducing the overall energy consumption and carbon dioxide emissions during their lifespan. To ensure that the available energy from these systems is maximized, it is important to determine the thermal conductivity of the surrounding soils, a key design input parameter. In situ thermal response tests are commonly used to carry out this task for small diameter borehole heat exchangers. However, there has been debate over the applicability of these tests to energy piles due to their larger diameter and the consequent increased influence of the pile thermal properties on the test outcome. This paper examines the results of three thermal response tests carried out on piles of different diameters and thermal properties installed at the same site in Texas. Transient analysis of the test results, combined with comparisons to laboratory testing of soil samples from the site, is used to given an indication of the applicability of the thermal response test over different timescales for the different piles. It is concluded that the test is most suited to smaller diameter piles constructed with lower thermal diffusivity materials. Recommendations are given for the conduction of pile thermal response tests and interpretation of test data.INTRODUCTIONAs issues of energy security and scarcity become more important, the use of ground source heat pumps to provide renewable and sustainable heating and cooling to buildings is set to increase. Traditionally such systems use special purpose ground heat exchangers to extract and/or inject heat from/into the ground. The heat exchangers comprise a series of plastic pipes cast into the ground and then connected to the heat pump via a series of header pipes. In the case of building space heating, the heat pump then steps up the temperature difference to deliver the extracted heat at a useable level. However, financial and carbon savings can result by utilizing the building foundations as heat exchangers as well as to carry the building structural loads.Piles, often termed “energy piles”, are the most common type of foundation heat exchanger, and their construction has been increasing in recent years (Amis et al, 2009). However, while energy piles have the potential to make significant contributions towards meeting building heating and cooling demands, there remains scope for improving their thermal efficiency through improved analysis approaches (e.g. Loveridge & Powrie, 2013). In fact the greater diameter of many energy piles means they have the potential to deliver increased short term thermal energy storage compared to more commonly installed borehole heat exchangers."

Jan 1, 2014

By Almer E. C. van der Stoel

"Abstract This paper deals with assessing the bearing capacity of existing wood pile foundations. With a wide range of restoration projects being performed in the Netherlands, on many locations deep excavations need to be constructed next to existing, many times listed buildings. The building are founded on piles that are often centuries old, so a close evaluation of the remaining bearing capacity, combined with and assessment of the influence of the excavation is in place.After giving an introduction on Dutch pile foundations, a methodology is described to assess the bearing capacity. Aspects as physical foundation investigation, determination of the current bearing capacity and a calculation of the bearing capacity in the new situation are discussed. The results of both analytical and Plaxis calculations are outlined, focussing on how to practically use this approach in renovation projects. Finally, cases studies of the successful application of this approach in major renovation projects in Amsterdam, such as the Conservatorium Hotel and the New Rijksmuseum are used to illustrate the successful application of this approach.A Short Dutch Pile Foundation History (based on Van der Stoel, 2001)The first houses built in Amsterdam, in the 12th century, were very light constructions of timber without foundations. Because of the soft peat layers found in Amsterdam, the houses there suffered from damage due to settlement. In the 13th century, castles and churches were increasingly built of bricks, which made it necessary to provide support for bigger loads. Under the wall of the construction a trench was dug, and this was filled on either side by alder fascines. Between the fascines small wood piles were driven (by hand) on which another series of fascines was put. On top of this construction, were placed oak slabs on which the bricks were then laid. From that moment on, a problem was caused by the decay of wood foundation elements in the humid soil. In 1503 a law was introduced forbidding building foundations on public streets without permission of the Building Inspection (to keep the fronts of the buildings in a straight line). In 1528 a law requiring permission from the local authorities for all building activities replaced this law. In this period developments started which led to the use of the type of foundation that can be considered the mother of the current “typical” Dutch pile foundation. The piles used in this period were shaft- bearing piles about 5 to 7 meters long. The mostly pine piles were driven between oak beams, which were placed on either sides of a trench, after which other oak beams were laid across at regular spaces: the so called “pile bent” pile foundation (Figure 1)."

Jan 1, 2014

By M. du Plessis, D. F. Malan

"Crush pillars are designed to be in a crushed state whilst being formed at the mining face. The residual stress state of these failed pillars provides a local support function in mining stopes and is used in the majority of the intermediate depth South African platinum mines. On mines utilising crush pillars, the pillar dimensions are selected to achieve a width to height ratio of approximately two. This is not achieved in most cases as a result of practical mining problems and poor pillar-cutting discipline. Furthermore, pillar dimensions are seldom adjusted to compensate for the various factors governing crush pillar behaviour. The pillars should, however, be in a crushed state whilst being formed or whilst still in close proximity to the mining face to prevent potential damaging seismicity.An underground investigation was conducted into the behaviour of the crush pillars in a trial site on the Merensky Reef at Lonmin Plc. The aim of this investigation was to examine the mechanism of pillar crushing and the related rock mass behaviour. The underground test results and pillar behaviour are compared to a limit equilibrium model to investigate if the model provides a useful approximation of the behaviour of the crush pillars. This paper details some of the preliminary findings.INTRODUCTIONOn most mining operations, the design of crush pillars is based on trial and error. As the pillar strength is unknown, the pillar sizes are adjusted to obtain the correct behaviour. Crush pillar dimensions are generally selected to give a width to height ratio (w:h) of approximately 2:1, (Ryder and Jager, 2002). Several factors affect the behaviour of the crush pillars and in many cases satisfactory pillar crushing is not achieved. This results in a seismic hazard in many of the mines using crush pillars. If pillar crushing is not initiated whilst the pillar is being formed at the mining face, as the mining face advances and the pillars move to the back area of a stope, some pillars may burst while oversized pillars may punch into the footwall. If pillars are designed in such a way that they are fractured during cutting by the face abutment stresses so that the pillars will already have yielded and reached their residual strength, further compression of the pillars will be associated with an increase in load and stability will be ensured, (Ozbay and Roberts, 1988). The stiffness of the strata must therefore be greater than the post-peak stiffness of the pillar (Figure 1) or violent pillar failure and hanging wall instability will occur. The pillar design should be aimed at determining pillar dimensions for which the post-peak curve of the pillar is as flat as possible."

Jan 1, 2015