Search Documents

By D. J. Charlton

"IntroductionMaintenance is a business, which to be successful, requires good management, systems and reporting. The prime objective of the maintenance management group, be they large or small, must be to anticipate and prevent interruptions in operations by keeping equipment in good mechanical condition. This objective should be carried out at minimum cost consistent with maximum productiveness.The objective of this chapter is to give an insight into the various aspects of maintenance management that must be considered to effectively and efficiently operate a mill complex. The degree to which the maintenance sub-systems are developed in an operating mill will be determined by the size of the mill and the needs of the operation.The criterion of the management system used is that the system serve the operation and not vice versa. The systems presented should be considered as tools and, as with all tools, they must be sharpened and replaced as the need arises or as more effective tools become available.To understand what is involved in maintenance management, it is worthwhile to consider a systems approach to analyzing management problems. This approach was developed by J.A.B. Rae while reviewing maintenance management systems for Cominco Ltd.A very simple system involving managing results and objectives is shown diagrammatically in Figure 1.The systems approach to organizational development involves four basic elements: an objective, a result, an activity and feedback. In the analysis, the activity element is broken down into individual actions that people could be held responsible for. If we introduce the action of operating into the diagram of Figure l, we arrive diagrammatically in Figure 2."

Jan 1, 1989

By I. C. Brown, J. F. Henderson

"IntroductionThe Yellowknife greenstone belt lies along the west side of Yellowknife bay on the north shore of Great Slave lake, some 600 miles north of Edmonton, Alberta. The producing gold mines along the belt include the Con-Rycon and Negus which came into production in 1938 and 1939, and the Giant Yellowknife, which followed in 1948. In addition to these, the Akaitcho and Crestaurum mines are potential producers and there are several promising prospects.Early geological work along the belt was done by A. W. Jolliffe who first recognized a number of great faults, the largest of which is the West Bay fault with a horizontal movement of more than 3 miles. In 1943, A. S. Dadson, following an examination of the Giant-Yellowknife property, advanced the hypothesis that Baker Creek valley was underlain by a series of major gold-bearing shear zones. Subsequent diamond drilling in 1944 bore out the correctness of this view and outlined the great ore-bearing shear zones that are now being developed and mined by Giant Yellowknife Gold Mines. Near the south boundary of the Giant property, the shear zones are cut off by the West Bay fault. This prompted Neil Campbell, District Geologist for the Consolidated Mining and Smelting Company, to make a detailed study of the geology along the West Bay fault in the hope of finding the faulted extension of the Giant shear-zone system on the west side of this fault. In this he was entirely successful. By careful geological mapping he matched several faulted diabase dykes on both sides of the fault and, knowing their dip, determined the horizontal and vertical components of movement along the fault. Subsequent •diamond drilling based on Campbell's work located the presumed correlative of the Giant shear-zone system on the Con-Rycon and Negus properties, where it has been named the Campbell zone or system. At the present time, all production at the Negus Mines property is coming from orebodies along the Campbell zone."

Jan 1, 1950

By Yutaro Fukase

Various types of service robots have recently been developed for guarding facilities, caring for the elderly, carrying objects, and cleaning buildings. As barrier-free facilities improve and their use expands, these robots have more space within which to move inside buildings. Yet robots that move autonomously rely on position-detection systems. Though improving rapidly, these systems are far from perfect in determining positions in certain situations, especially when robots navigate large areas or cross various locations. Our group is working to solve this problem by developing a position-detection system using random-dot patterns on a floor. First, we construct a floor with a random-dot pattern and register the positions of all of the dots into a database. As the robot moves across the floor, a camera on the robot captures an image of the floor beneath it and crops the dot pattern in the image. The cropped dot pattern is matched to the dot patterns in the database to determine the position of the robot and the direction in which the robot is facing or moving. In this paper we propose a self-localization system and matching algorithms derived from a space technology and present the results of several experiments.

Aug 1, 2013

By B. Chareyre, H. Pourpak, L. Scholtès, E. Papachristos

"Numerical methods used to study hydraulic fracturing in low permeability rock masses need to take into account the interaction between the progressive failure mechanism of the intact rock matrix and the pre-existing natural fractures. A fully coupled hydro-mechanical 3D discrete elements model dealing with such interaction is presented here. The ultimate objective is to grasp the role of the rock-matrix failure on the propagation of the main fluid driven fracture under different stress fields and pre-existing fracture orientations. The proposed method provides the spatiotemporal distribution of the induced crack events which can be tracked during the simulations, making possible the identification of the local mechanisms leading to macro-failure in the rock matrix or reactivation of the discontinuity planes. Fluid flow inside a fracture, pressurized crack and hydro-fracking experimental tests were simulated as part of the validation process of the model and, are presented in this paper.INTRODUCTIONWith the expansion of shale gas and geothermal reservoirs exploitation, the technique of Hydraulic Fracturing (HF) has been widely used over the past years (McClure, 2012; Britt, 2012). Despite recent advances in micro-seismicity analysis or numerical modeling (Nagel et al., 2013), the way progressive failure of rocks affects the fluid flow depending on the in situ stress conditions or the rock heterogeneities is not fully controlled yet (Zoback, 2010).In this work we focused on setting up a three-dimensional discrete elements model to study fluid driven fractures propagation. The intact rock is modeled by a discrete element method (DEM) able to reproduce fracture initiation and propagation (Scholtès and Donzé, 2013, Garcia et al., 2013). The pre-existing fractures are explicitly modeled and can be individually defined or be part of a discrete fracture network (DFN) (Harthong et al., 2012). Their mechanical response is fully coupled with the fluid within a HM-DEM framework. The fluid flow and it’s interaction with the intact matrix and the pre-existing discontinuities is modeled through a Pore-scale Finite Volume (PFV) scheme specially enhanced for fractured rock modeling (Chareyre et al., 2012, Catalano et al., 2014) ."

Jan 1, 2015

By N. Schreithofer

The deposition of octadecylamine (ODA) at the KCI crystal/NaCI-KCI brine interface was investigated using atomic force microscopy (AFM). The AFM images of freshly cleaved KCI specimens immersed in KCI-NaCI saturated brine at room temperature reveal disappearance with time of the atomic steps and formation of cubic NaC1 crystals. These crystals were found to form when the specimen was withdrawn from the saturated solution. Depending on the way of contacting the specimens with the octadecylamine dispersion, the AFM images show huge differences in the deposition patterns of ODA on KCI crystals. Adequate dispersion was found to help the formation of quite even ODA coverage. The coverage was several monolayers thicker when air/brine/solid contact took place, suggesting that in the potash flotation the collector is likely to be carried to the solid surfaces by air bubbles. The presence of methyl-isobutyl carbinol (M IBC) enhanced the dispersion of ODA in brine, thus helping the spreading of the surfactant on the KCI crystal surface.

Jan 1, 2006

By E. De Souza

Energy associated with ventilating an underground operation comprises a significant portion of a mine operation's base energy demand and is consequently responsible for a large percentage of the total operating costs. Ventilation systems may account from 25?40% of the total energy costs and 40?50% of the energy consumption of a mine operation. Fans are the most important mechanical devices used to ventilate underground mines and the total fan power installed in a single mine operation can easily exceed 10,000 kW. Investigations of a number of mine main fan installations have determined their assemblage to be, in general, very energy inefficient. The author has found that 40?80% of the energy consumed by a main fan is used to overcome the resistance of fan assemblage components. This paper presents how engineering design principles can be applied to improve the performance and efficiency of fan installations, resulting in substantial reductions in power consumption, operating cost and greenhouse gas emissions. A detailed case study is presented to demonstrate that, by designing fan assemblages using proper engineering concepts of fluid physics and industrial ventilation design, main fan systems will operate at efficiencies well above 80?90% (compared to common operating efficiencies of between 20 and 65%), resulting in a drastic reduction in a mine's overall costs and base electrical and energy loads.

Aug 1, 2013

By K. Himbeault, D. Campbell, N. C. Garisto, D. A. Orava, A. Rosaasen

"The level of scientific knowledge about the effects of contaminants is increasing and changes in environmental monitoring are likely to allow for the assessment of environment effects particularly to the aquatic environment. This paper provides an overview of recent developments in this area which include the environmental effects monitoring program for pulp and paper operations, the assessment of the Aquatic Effects of Mining (AQUAMIN) program, the Aquatic Effects Technology Evaluation (AETE) program, and the review of the federal Metal Mining Liquid Effluent Regulations (MMLER). The paper also provides a look forward at the direction of environmental monitoring of mine projects in Canada. IntroductionEnvironmental monitoring programs provide a wide range of data to environmental management systems, regulatory authorities, and stakeholders. The data obtained are used to demonstrate that operations are in compliance with regulatory environmental protection requirements, and provide the scientific basis for assessing the effectiveness of environmental protection measures. Environmental monitoring requirements for mine projects are established based on the type of operation, site specific issues and concerns, and the requirements of regulators and mine proponents.The level of scientific knowledge regarding the potential effects of contaminants on the receiving environment is increasing, and in particular with regards to the receiving aquatic environment. Regulatory controls regarding the protection of fish, fish habitat, and fishery resources are being reviewed with regards to their adequacy, and the environmental effects monitoring program on the pulp and paper industry is expected to provide useful data relevant to those types of operations. These developments are of interest to mine proponents as it is presently expected that an environment effects monitoring program will be developed specifically for the metal mining industry under a regulated environmental effects monitoring program as part of the Fisheries Act. This paper reviews recent developments in this area, and provides a look forward on the future directions of environmental monitoring programs."

Jan 1, 2000

By R. Heikkilä

A large research and development program called RYM PRE (Process Re-Engineering) has been active in Finland since 2010. As a part of the program, a work packet Infra FINBIM is focused on the development of new national process model, specifications and requirements for the whole Finnish Infra Industry. In the Infra FINBIM, total 15 companies and main owners and 3 research organisations are included. The work is further continuing. The main achieved results up today have been the first specifications and requirements of the BIM based total process for infra sector, about 30 different pilot projects for testing of the new design and construction process models producing a lot of results and observations, a new open information transfer format Inframodel3 based on LandXML standard, the achieved acceptance of the Building SMART organization for support of international development, utilization and extension of the format within the whole infra industry, processes, software and other technical equipment. An evaluation of the results and this work will be drawn.

Aug 1, 2013

By J. Fellowes, Z. Liang, J. Robson, M. Kenyon

"Dispersoids play a significant role in the recrystallization and texture development for wrought Al-Mg-Si (6xxx series) alloys by inhibiting grain boundary motion. It is therefore important to understand the precipitation kinetics of such particles. It is the additions of Mn and Cr in Al-Mg-Si based systems that can lead to dispersoid phases being formed. These phases are currently thought to nucleate on ß’-Mg2Si via an intermediate semi-coherent precipitate. Scanning transmission electron microscopy (STEM) has been conducted to study the precipitation of a-Al(CrFe)Si and a’-AlCrSi dispersoids. Corresponding electron dispersive spectroscopy (EDS) has been used to distinguish the dispersoids. The volume fraction and size distribution of dispersoids has been measured as a function of distance across a grain. Electron probe microanalysis (EPMA) has been conducted to study the inhomogeneity of elements in the cast structure and the effect on dispersoid precipitation. Dispersoid free regions have been observed in the microstructure correlating to regions depleted in the dispersoid forming elements.INTRODUCTION Al-Mg-Si (6xxx series) based alloys are increasingly being used in the automotive industry. The primary reason is to reduce the weight of vehicles, resulting in a reduction of CO2 emissions and increased fuel efficiency. The demand for 6xxx series is predicted to increase over the coming decade. Due to the high cost and CO2 emissions produced by raw extraction of aluminium, close loop recycling of these alloys becomes a more important process. However recycling of automotive alloys can be difficult due to pick up of impurity elements such as Mn, Cr and Fe. The addition of these elements can form dispersoid particles during early heat treatment processes. Although a controlled population of dispersoids is necessary to control the grain structure during thermo-mechanical processing, a significant change to the dispersoid population due to a composition change could profoundly influence the final microstructure, affecting the final properties of the material. More research is required on the precipitation and effect of additional minor alloying elements; in order to increase the 6xxx series alloys recyclability."

Jan 1, 2018

By Mark Sherman, M. Dennis, Raj Rajamani

"The two Alumbrera 36ft (10.97m)dia. SAG mills were sized, using the FDW ""Grindpower 'I program, to treat an average of 1852 tph each. This paper describes how modelling of the shell lifter design, using the Millsoft program, identified milling inefficiencies caused by poor charge motion. This explained the ""as built"" circuit's inability to achieve the throughput rates predcted by the circuit's designer. Use of the Millsoft program to design a new, dramatically different lifter configuration, in conjunction with a different approach to variable speed drive utilization, has resulted in an improved charge motion and a 30% increase in hard ore milling rates. The new lifter design has allowed the designer's predicted average throughput rates to be achieved.IntroductionThe Alumbrera project grinding circuit consists of two 36ft dia. X 17ft EGL, 13 500 kW, variable speed, gearless drive SAG mills coupled to four 20ft dia. X 30ft EGL, 6 000 kW fixed speed, gear driven, ball mills. The circuit is configured as two identical grinding aisles, each consisting of one SAG mill and two ball mills. No pebble crushing circuit was installed due to the expected absence of a critical size fraction in the first years of production. However, the grinding circuit layout does incorporate space for a pebble crushing retrofit. At present, only about 5% - 10% of the new mill feed reports as trommel oversize and is recycled back to each SAG mill using a water cannon.The circuit was designed to be ball mill limited and to treat the four major Alumbrera ore types at rates varying between 68 000 tpd, and 89 750 tpd, depending on ore hardness. Average throughput rate, and hence nominal design rate, for the grinding circuit was 80 000 tpd (1 852tph per line at 90% availability)."

Jan 1, 1999

By C. Stapel, P. D. Roberts, D. G. Jones, W. G. Macdonald, R. J. De Meijer

"Measurement of natural radioactivity has been used in both a qualitative and a quantitative way in mineral exploration, particularly in the search for uranium. In the last ?ve years, the Kernfysisch Versneller Instituut (KVI) and British Geological Survey (BGS) have designed, built and tested a new detector system that greatly improves quantitative applications in mineral exploration, especially on the sea?oor and in the nearshore zone. The new system is an enhancement of an earlier BGS design. The major improvements comprise the use of a highly sensitive ?-ray detector, together with new data processing, from which concentrations of natural radio nuclides may be deduced in real time. After laboratory analysis of samples, these concentrations can be converted into mineral percentages. Once the mineralogy of an area has been characterized, this conversion can also be done in real time.Thus far the system has mainly been used to map heavy-mineral concentrations in coastal subtidal and intertidal sediments. For such work the multi-sensor detector probe is towed on the sea?oor and various parameters are recorded continuously. The probe contains, in addition to the gamma-ray detector, a water-pressure sensor (giving water depth) and an acoustic device to measure bottom roughness. The system, when used together with high-precision positioning systems such as D-GPS,enables the production of detailed maps of bathymetry, bottom roughness, and sea?oor radioactivity or mineral distribution. These maps allow mineral concentrations to be readily correlated with sea-bed topography and sediment type. In the same way, ?-ray detectors could be used advantageously during dredging operations to provide on-line assessment of the mineral content of the dredged sediment as well as to guide the direction of dredging. Additionally, the same technique could be used to monitor the subsequent fate of a dredge spoil after dumping on the sea?oor.Natural radioactivity arising from potassium and the thorium and uranium decay series has potential use for the fast and reliable assessment of siliciclastic and phosphatic impurities in limestones. Detection of such impurities may preclude the use of the limestone for chemical or cement production.Apart from its use in exploration, the technique has signi?cant potential in mineral processing, particularly of heavy minerals. It can be applied as on-line quality control in dry and wet separation processes and for process control, by using decisions based on the results to control valves and other instrumentation. In addition, it can also be used in environmental monitoring of waste arising from mineral extraction and processing. In conclusion, the technique described has a diversity of applications in exploration, mining and mineral processing."

Jan 1, 1997

"Here, we statistically proved that giant earthquakes occur at lunar phases specific to each subduction zone. Enough attention during the lunar period, especially when seismicity is occurring, will significantly reduce damage from giant earthquakes. Two case studies in which giant earthquakes occurred after seismicity in dangerous lunar phases were discussed, and the mechanisms underlying why giant earthquakes occur around neap tide at some subduction zones were explained by prohibition of giant earthquake occurrences due to high strain rates at spring tides at N–S subduction zones. The prohibition was statistically proven for uniaxial creep tests on Inada granite with slight stress disturbances. INTRODUCTIONIn previous studies, we showed that from 1900 to present, giant earthquakes (MW ??8) have occurred at lunar phases specific to each subduction zone (Fujii & Ozaki, 2012; Ozaki & Fujii, 2012). Although we later proposed a possible reason for these occurrences, the study lacked statistical analyses (Fujii et al., 2013). Therefore, this paper shows the results of such statistical testing and presents case studies for the Tohoku 2011 and Chile 2014 events, thereby providing updated data on giant earthquakes through July 2014."

Jan 1, 2015

By C. Tasker

Introduction In the Early part of 1930 the Ontario Research Foundation was asked by the Minister of Mines, the Hon. Charles McCrea, K.C., M.P.P., to undertake a technical and economic investigation of the Northern Ontario lignite deposit. This investigation has been under way since June, 1930, and has necessitated considerable work at the deposit, in the laboratories of the Foundation, and at test plants in Europe. All the work has been carried out in active co-operation with the Provincial Department of Mines, the Deputy Minister, Mr. T. F. Sutherland, and several of his technical colleagues being associated with members of the staff of the Foundation on the Advisory Committee, which has met at frequent intervals to co-ordinate and direct the various lines of research. An interim report was made to the Minister of Mines by the Director of the Foundation, Dr. H. B. Speakman, at the end of December, 1932, and is at present under consideration by the Minister. This report deals with the extent and character of the deposit, the methods and costs of mining, and the methods and costs of processing raw lignite, the characteristics of certain lignite products, and the technology and economics of present fuel utilization by railways, industry, and domestic users in northern Ontario. It is not the purpose of the author to discuss in this paper either the geology of the deposit or the economics of the mining, processing, and utilization of lignite, but rather to deal briefly with some of the technical problems investigated by the Foundation during the study of the characteristics and methods of utilization of Northern Ontario lignite. Some mention, however, of the work carried out to define the extent of the deposit is a prerequisite to any discussion of the nature of the lignite.

Jan 1, 1933

By C. Stapel, P. D. Roberts, D. G. Jones, W. G. Macdonald, R. J. De Meijer

"Abstract-Measurement of natural radioactivity has been used in both a qualitative and a quantitative way in mineral exploration, particularly in the search for uranium. In the last five years, the Kernfysisch Versneller Instituut (KVI) and British Geological Survey (BGS) have designed, built and tested a new detector system that greatly improves quantitative applications in mineral exploration, especially on the seafloor and in the nearshore zone. The new system is an enhancement of an earlier BGS design. The major improvements comprise the use of a highly sensitive ?-ray detector, together with new data processing, from which concentrations of natural radionuclides may be deduced in real time. After laboratory analysis of samples, these concentrations can be converted into mineral percentages. Once the mineralogy of an area has been characterized, this conversion can also be done in real time.Thus far the system has mainly been used to map heavy-mineral concentrations in coastal subtidaland intertidal sediments. For such work the multi-sensor detector probe is towed on the seafloor and various parameters are recorded continuously. The probe contains, in addition to the gamma-ray detector, a water-pressure sensor (giving water depth) and an acoustic device to measure bottom roughness. The system, when used together with high-precision positioning systems such as D-GPS, enables the production of detailed maps of bathymetry, bottom roughness, and seafloor radioactivity or mineral distribution. These maps allow mineral concentrations to be readily correlated with seabed topography and sediment type. In the same way, ?-ray detectors could be used advantageously during dredging operations to provide on-line assessment of the mineral content of the dredged sediment as well as to guide the direction of dredging. Additionally, the same technique could be used to monitor the subsequent fate of a dredge spoil after dumping on the seafloor.Natural radioactivity arising from potassium and the thorium and uranium decay series has potential use for the fast and reliable assessment of siliciclastic and phosphatic impurities in limestones. Detection of such impurities may preclude the use of the limestone for chemical or cement production.Apart from its use in exploration, the technique has significant potential in mineral processing, particularly of heavy minerals. It can be applied as on-line quality control in dry and wet separation processes and for process control, by using decisions based on the results to control valves and other instrumentation. In addition, it can also be used in environmental monitoring of waste arising from mineral extraction and processing. In conclusion, the technique described has a diversity of applications in exploration, mining and mineral processing."

Jan 1, 1997

By B. Surender Mohan

Mother Earth being a treasure of minerals, it is prime duty of the mankind to preserve this natural source to ensure steady growth of the nation. Utmost care is to be taken to see that these natural resources are explored and exploited scientifically in a sustained manner to ensure that the resource base improves and last longer. In this backdrop, the topic of ?Lignite - its resource and technology options to exploit deep seated deposits? is an apt subject to be deliberated upon in the present context, where the shallow deposits may slowly get dwindled. I shall deliberate upon the resource base of lignite, production profiles of the last five decades, consumption pattern, demand / supply projections, future available technology options to exploit the deep seated deposits, growth trends of the sector etc. in my paper. With the available resource base and future technology options, I can confidentially make a statement that ?lignite will remain as cocontributor along with coal to India?s energy generation and may well maintain its same status in the 21st century too, as it has been in the later part of the twentieth century?.

Aug 1, 2013

Operating and Social Considerations from a Contractor?s Perspective

May 1, 2013

By J. B. Heslop, D. S. Bubar

"The Gondor Zn-Ag-Pb-Cu deposit is a stratabound massive sulphide lens occurring within Archean volcaniclastic rocks of the Yellowknife Supergroup. The deposit is located in the west-central portion of the Slave Structural Province, approximately 350 km north of Yellowknife.Initial diamond drilling at Gondor has outlined a steeply dipping, L-shaped, folded, massive sulphide body, which may be traced over a strike length of approximately 800 m, and to a depth of 350 m. True widths of up to 40 m have been intersected in the thickest part of the deposit. Preliminary estimates suggest that the deposit contains a minimum of 7.5 million tonnes grading 6% Zn, 50 g/tonne Ag and less than I% combined Cu and Pb. In addition, significant gold, grading up to 2.8 g/tonne, occurs in some parts of the deposit. The mineralization is open both down-dip and along strike.The Gondor deposit lies conformably within a predominantly east-west striking, north-facing sequence of felsic to intermediate volcaniclastic rocks. Coarse fragmental rocks are abundant in the hanging wall, whereas ash and lapilli-tuffs predominate in the footwall. The main structural feature in the area is a large-scale, steeply northeast-plunging, Z-shaped fold. The sulphide mineralization lies within the synformal portion of this fold, with the thickest part of the deposit coinciding with its hinge zone. Several episodes of faulting have also affected the local stratigraphy.The wallrocks of the Gondor deposit were hydrothermally altered prior to the onset of medium-grade regional metamorphism. A halo of altered rocks surrounds the massive sulphide lens, with no apparent difference in the degree of alteration between the hanging wall and footwall strata. The alteration zone is characterized by the addition of MgO and K20 and by the depletion of Na20 and CaO. These changes are reflected in the mineralogy of the altered wallrocks by local enrichment in chlorite, biotite, muscovite and cordierite.The mineralized zone is medium- to coarse-grained, well-banded and is composed largely of pyrite, quartz, and sphalerite with subordinate galena and chalcopyrite. Preliminary studies of metal distribution indicate that a lateral zonation is present, with lead enrichment in the central part of the deposit, and copper enrichment toward both ends. Stringer-type copper mineralization has not yet been discovered in the footwall of the Gondor deposit."

Jan 1, 1985

By A. J. Giroux

"The use of Ishikawa cause and effect diagrams in an analysis of requirements for improving safety and productivity at Falconbridge's Strathcona Mill is presented. The analysis lead to numerous small improvements being made with the cumulative effect being a significant improvement in both areas.INTRODUCTIONMill management in the 90's involves the major requirements to improve both safety and productivity in the workplace. These objectives, once seen as unrelated or even mutually exclusive, are now accepted as being complementary. Managers, trained either on the job (coming up through the ranks) or in an engineering discipline followed by first and second line supervisory experience are now turning to methods developed in consumer product manufacturing to ensure that all the components are in place to ensure the ore processing facilities are safe and efficient.This paper shows how management at Falconbridge' s Strathcona Mill used the Ishikawa ""fishbone"" diagram ( 1) , a method further developed by Deming(2), to put into place a comprehensive safety and productivity process. The Ishikawa/Deming concept is that no one element or program will itself continually improve a process or service. It is only by examining and then improving all the elements that are involved in the process or service that continuous improvement is obtained. The process was built on the Deming principle of worker ownership where management is the facilitator for putting into place the mechanisms whereby workers can themselves improve the operation. The process is illustrated mainly by examples of the changes made in the hope that these may be of direct help to other operations."

Jan 1, 1993

By J. Janzen

The cost to supply ventilation may exceed 40% of the total mine energy cost for underground mines and is often higher for deeper mines. The goal of Ventilation-on-Demand (VOD) is to ensure that the required quantity and quality of air is supplied to underground mining crews and diesel equipment at the least energy expenditure (minimum cost). A VOD system may include control of surface fans (Supply & Exhaust), underground booster fans, auxiliary fans and automated regulators/dampers to regulate the flow of air with more control elements providing more value. Strategically located Air monitoring stations measure air quantity and quality and provide feed-back enabling control. The modular design involving controls, intelligent instrument and intelligent motor control centres coupled with a communication network allows the quick installation, commissioning and expansion of the system as the mine develops. The result is a very robust, flexible system while reducing maintenance costs and spare parts. This paper discusses the impact of sensors, installation and commissioning on advanced controls and provides solutions for in-field applications.

Aug 1, 2013

By E. Heikkinen, J. Suikkanen, T. Siren, J. Valli, M. Hakala

Diametrically faced borehole breakout observations are a fairly good indication of magnitude of the secondary stresses acting perpendicular to the borehole. In cases of low in situ stresses, where borehole breakouts are not observed naturally, it is possible to increase the prevailing stress state around the borehole by increasing the rock temperature. When the temperature is increased sufficiently, thermally induced borehole breakouts will occur. By implementing the temperature increase in boreholes located at excavated tunnels, it is also possible to study the effect of the near-field stresses caused by the excavation. The near-field stress state changes as a function of borehole depth, thus increasing the information available from experiment. To study the feasibility of this proposed low cost method, a Borehole Thermal Spalling (BTS) experiment was executed in ONKALO Underground Rock Characterization Facility, in Western Finland in 2014. The first borehole pilot test with the method was conducted in ONKALO at the POSE niche in already at May 2010, with the second pilot test following in August 2010 at Äspö HRL. The major objective of the experiments was to define the trend of the maximum in situ stress component, while also providing knowledge of the in situ spalling strength of the ONKALO rock mass. The stress state in ONKALO is nearly isotropic in horizontal layer, causing problems for the use of more traditional stress measurement methods. With boreholes heated over long interval, the weakest rock parts are observed to fail, thus providing statistical confidence. For these reasons, continuous test sections have an advantage in ONKALO, compared to spatially limited stress measurement methods such as overcoring and hydraulic fracturing. The BTS experiment is conducted in 9 meter deep vertical boreholes located at the POSE niche, situated -345 m depth below the ground surface. The boreholes used within the BTS experiment are located in migmatitic granite, in an experiment area where the surrounding stress state and the rock strength are fairly well known. The prior knowledge of the stresses is favourable for the experiment, as it requires careful planning and iterations to determine the appropriate heating power domain. Too low heating power will not be sufficient to cause borehole breakout, while too high heating power causes breakout in all directions thus making determination of stress direction hard or impossible. The initial state of the borehole and induced borehole breakouts will be monitored using acoustic televiewer logging (ABI) and optical borehole logging (OBI) imaging techniques. Fracture mechanics modelling is used in planning of the experiment, also in back-analysis to link the observed breakout angle to stress state. Both the pilot test in 2010 and BTS test in 2014 resulted in similar borehole breakout direction. The results are in line with so called EDZ & VT1 stress interpretation, revealed the maximum horizontal component bearing the magnitude of 21.5 MPa, with the trend of 166°.

Jan 1, 2015