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By Pratoomkhuan N. Lertsgoon

A large underground cavern with dimensions of 25m × 175m × 49m (W×L×H) was excavated in sandstone and siltstone to house 4 units of hydropower generator and was completed in 2000. In feasibility study stage, the property of the siltstone which governs the ceiling of the cavern was questionable due to slaking phenomenon. Parameters on rock properties for design were back calculated from actual ground response measured from a trial excavation. For safety of construction, comparison between prediction and actual ground responses during excavation had proceeded. The prediction was provided by means of PHASES and PHASE2 software and the actual rock response was detected by the provided monitoring system.

Jan 1, 2003

By K. Park

Coupled influence of sulphidizers and xanthates on the electrokinetic property and flotation behavior of malachite was systematically examined via electrophoretic mobility measurements and microflotation tests. The electrophoretic mobility results for the malachite before and after surface modification with different types (Na2S and (NH4)2S) and amounts (1×10-7?1×10-4 moles/g) of sulphidizers, showed that the isoelectric points (IEP) of malachite differed at the low dosage level depending on the type of the sulphidizer, which ranged between 5 and 9.5. However, the IEP values were observed to be shifted from high to low pH values with increasing amount of sulphidizers and finally ranged between 3 and 4, indicating that the sulphidizers played a different role on changing the surface property of malachite. In order to further understand the effect of sulphidizers on the electrokinetic property and flotation behavior of malachite in a sulphidizer+xanthate system, flotation tests were carried out with malachite sulphidized with Na2S and (NH4)2S (adsorptive amount=8×10-5 moles/g) at different bulk xanthate concentrations. The results showed that the flotability of (NH4)2S-treated malachite was greater than Na2S-treated one over the entire xanthate concentration investigated, indicating that the type of sulphidizers played important role in malachite flotation; however, no obvious correlation between electrokinetic property and flotability of malachite was observed.

Feb 27, 2013

By B. K. Belle

The use of diesel engine locomotives in South African mines can be traced to Van Dyk Consolidated Mines Ltd on the Witwatersrand gold mines in 1928 as a replacement for battery locomotives. The advantages and disadvantages were recognized in those days, and surprisingly, there are no significant additions to this list, but only refinements. In the absence of any Occupational Exposure Limit (OEL) for Diesel Particulate Matter (DPM) in SA, the Mine Safety and Health Administration (USA) rule is currently being used as a benchmark for the ventilation engineering designs. This paper discusses the ongoing SA journey of measurement and limitations of exposure data for ventilation planning and regulatory purposes. The currently accepted DPM limits are based upon the belief that they are economically and technically feasible for the mines to reach and are not necessarily health based. For SA underground platinum mines, a median TC/EC ratio of 1.8 with a range of 1.2 to 5.8 was observed. For SA coal mines, a median TC/EC ratio of 1.44 with a range of 1.25 to 2.13 was observed. While it is common practice in the USA to use the ratio of TC/EC for metal mines to be 1.3, the ratio found in local platinum mines is 2.2 and for coal mines, the ratio was 1.53 which is lower than Australian studies, i.e., 1.96. It has been shown that a need for critical analysis of TC/EC ratios exists, and possible reasons for variance must be understood before stringent adoption of overseas recommended limits for DPM. It is hoped that the findings from this paper would provide input to scientific approaches in developing appropriate conversion factors, limits for DPM and also in ensuring appropriate error factors (currently 1.14 for TC and 1.2 for EC) for compliance determination.

Jan 1, 2009

By J. Chilton

The fact that methane ignitions continue to occur at the mining face indicates that monitoring with machine-mounted methanometers does not always indicate the presence of high methane concentrations. Methane concentrations at the face change quickly due to changes in airflow. By measuring these changes in airflow, it may be possible to predict changes in face methane levels more quickly. Currently there are no techniques or instruments to accurately measure airflow inby the mouth of the ventilation curtain or tubing. Tests conducted in the NIOSH ventilation test gallery compare the data provided by one-, two-, and three-axis ultrasonic anemometers. The effects of changes in airflow direction and turbulence on instrument readings are discussed, and guidelines are given for selecting the type of instruments to be used for monitoring airflow near the mining face.

Jan 1, 2007

By S. G. Gendler

The choice of ventilation schemes in the Northern Mujsky railway tunnel and definition of the nec-essary quantities of air ensuring regulated radiation conditions in the tunnel system has been accomplished. The influence of natural draught on the stability of tunnel ventilation has been estimated. The design of a portal venti-lation gate allowing minimal influence from natural factors is described. The dependence of pressure loss in the sliding ventilation gates on their spanning value of the vehicle tunnel section has been determined. The selection of parameters for an atmospheric air heating system in winter has been carried out. The operation regimes of air heaters, dependent on the temperature of atmospheric air, have been established.

Jan 1, 2009

By Michael Gilbert

In the world of tunneling the glamour is in the large diameter, long tunnels, but perhaps the number of projects for small diameter and short length tunnels are greater and generally have higher risk factors. Reasons for these higher risks include both the ?boiler plate? contract provisions used on these types of contracts, the technical specifications related to the tunnel work (versus the pipeline construction), the bid practices including measurement and payment and the construction. This paper reviews and comments on some of the key issues the authors have observed in recent major pipe-line projects that involve a small percentage of tunneling footage of the total contract.

Cripple Creek and Victor Gold Mine is an epithermal gold deposit located in the Rocky Mountains of Colorado. Surface operations are continuing along with an expansion for an onsite mill to take place in the next couple of years. The surface pit is currently progressing downward from an oxidized zone into a transitional, more sulfide/ telluride-rich zone. Gold mineralization includes native gold, electrum, and tellurides. Cyanide heap leaching is the recovery process for the oxidized ore with the sulfide/telluride-rich ore to be processed at the new onsite mill. Ore characterization prior to mining is vital when there are two possible recovery processes. This characterization is dependent on geometallurgy. To identify the causes of the variability, multiple parameters are analyzed and assayed. These parameters are measured by a variety of analytical testwork. The analytical testwork provides measurements for the desired parameters. Geometallurgical models are developed for the parameters per recovery process, so estimations can be inserted into the resource model to optimize operations and recoveries.

Feb 27, 2013

By W. D. Bachman

A study has been made of wet, autogenous grinding of disseminated copper ores, including testing of a large number of samples from Kennecott Copper Corporation's Chino mine. The efficiency with which the various samples could be ground was found to vary over an extremely wide range, even among samples taken from different locations within the same ore body. These variations in grindability can be qualitatively correlated with the composition of the rock and the fracturing and alteration that had occurred. Because of the large-scale non-homogeneity of disseminated copper ore bodies, extensive and careful testing of autogenous grinding is needed. An accurate correlation of the grinding data from various samples with the geology of the ore body and with mining plans will indicate if variations in grinding mill throughput can be avoided in practice by mixing or blending of mill feed and if, therefore, autogenous grinding can be applied successfully.

Jan 1, 1970

One of the most important parameters in mine ventilation planning is the friction factor (K). Accurate values of friction factors are critical especially when carrying out mine ventilation simulations. No computer simulation of a mine ventilation network is meaningful if the airway resistances are not accurately estimated (when planning a new mine) or measured (for an existing mine). However, in the first case not many reliable values of friction factors exist in the international literature. This paper presents the results of a research project carried out in the province of Quebec where ventilation friction factors were measured in all underground metal mines. These friction factors are statistically analyzed and tabulated. A friction factor database was created that also includes the friction factors measured in the past by other people. This database can help the mine engineer to accurately estimate ventilation friction factors according to the specific conditions. This database offers several values of friction factors typical for hard rock mine conditions typical of modern underground metal mines.

Jan 1, 2009

By Alan Weakly

The Powder River Basin (PRB) of northeastern Wyoming and south-central Montana is the largest strippable reserve of compliant coal (0.6 or less lb of sulfur per million Btu) in the United States. In mining parlance, it is the Mother Lode! Wyoming’s portion of the Basin provides one fifth of the coal produced in the United States annually, and the state has been the nation’s top coal producer for the past six years. Based on 1993 production statistics and estimated strippable compliance coal reserves, Wyoming may remain the nation’s top producer for the next 76 plus years. Past articles on the PRB have focused mainly on production. After living and working in the Basin for the past five years, I have developed an appreciation for the area and its major industry that transcends size and production data. In the fall of 1993, MINING ENGINEERING’s publisher and I decided to present a series of articles that would cover many other aspects of the Basin. Ten topics were outlined, and specific individuals, selected for their knowledge and experience, were asked to contribute articles about their specialties. Although Montana has four large mines producing coal from the PRB, this series of articles will concentrate on the Wyoming portion of the Basin.

Jan 1, 1994

By R. A. Hodge

Over the past decade, there has been a significant increase in effort put to tracking progress toward sustainability. Many aspects of society are participating in this “movement” including mining. The drivers are diverse and include evolving ideas in business and public administration as well as concerns for human well-being, community robustness, environmental integrity, and overall social and ethical responsibility. The scale in question varies greatly from local to global. For the most part, there has been a pre-occupation with developing discrete measurable signals. This paper argues that the overwhelming focus on the quantitative is ill-advised and that a more effective approach is to bring together the best of both quantitative and qualitative. The mining industry in particular is well-placed to affect this shift and reap the associated benefits.

Jan 1, 2004

By T. Clarkin

This paper presents a hydrologic closure design concept to minimize the risk of water discharges from closed mine tailings facilities. It evaluates the applicability of U.S. Nuclear Regulatory Commission guidelines to develop acceptable designs for the closure of tailings facilities that have a calculated adequate surcharge capacity for environmental protection and an emergency spillway for dam safety. The guidelines provide a basis to estimate an acceptable surcharge capacity of a Probable Maximum Flood series for storage of surface runoff. To be conservative and for redundancy with respect to dam safety, an emergency spillway is provided to pass the Probable Maximum Flood. Depending on the annual water balance, the surcharge capacity may be used by surface runoff and minor amounts of sediment that accumulates in the impoundment from year to year. The emergency spillway crest is then set at this level or above the surcharge capacity, whichever is higher. An example is given of the active Red Dog Mine tailings facility in Alaska where this method was used for the preliminary design of the tailings main dam at its ultimate closure configuration.

Jan 1, 2012

By O?Connor. D. F.

The ever increasing energy costs associated with mining at depth has become an important issue that needs to be addressed for future sustainable production. Vale Inco Limited?s Creighton Mine being the deepest has the highest energy cost per ton due to the ventilation system requirements. A review of the ventilation systems was undertaken with respect to current practices and identification of opportunities to the practical application of technology that would facilitate energy savings. Energy conservation initiatives such as time of day controls have been implemented; however there still remained some opportunity for further reduction. Based on previous studies that identified opportunities due to actual time spent in the workplace, our mining method and ventilation design, it was determined that Ventilation on Demand (VOD) could provide further additional energy reductions with respect to our auxiliary fans. A pilot project has recently been initiated to apply a Ventilation on Demand concept to two 112 kW auxiliary fans and their related workings located on the 2340m level of Creighton Mine. The project objective is to determine the practical methodology and application of this technology in the field. This project involves the installation of variable frequency drive (VFD) starters on the auxiliary fans to allow variable volume (through speed control) based on demand. The required flow is determined based on equipment and/or personnel via identification tags. The Fans adjust to the flow requirements as measured by flow sensors. Since the fans are sized for the final requirements the required flows can be achieved regardless of system length. Energy savings are realized by supplying only the volumes (power) as required and only when required. This paper discusses the rational and program being tested at the VALE Inco Limited, Creighton Mine.

Jan 1, 2009

By R. J. F. Goodfellow

Many underground projects now include preparation of a Risk Register through planning and design as a tool for project and risk management. There is still significant discussion within the industry as to whether and how to best present the Risk Register through the bidding process and the construction phase of a project. While the ITIG Code of Practice for Risk Management of Tunnel Works recommends this approach of continuity in risk management procedures, it is silent on the specifics of how this should be achieved. This paper will explore the perceived benefits and disbenefit of including the project Risk Register with bid documents; format and content that should be transferred and lessons learned using the case history of bidding and early construction phase of the Bi-County Water Tunnel in Montgomery County, MD

By David R. Gossett

For the 22nd year, the chance to exchange knowledge, experience and business cards drew hundreds of mining and phosphate professionals for a two-day regional Phosphate Conference in Lakeland, Florida Nearly 400 people participated in the October conference, which focused on the phosphate industry?s future success. There were 41 exhibitors, 13 program advertisers and 23 sponsors among those supporting the conference. It was chaired by David Gossett, 2006-2007 SME Florida Section Chairman. In the opening panel session that he chaired, John Garlanger (SME) of Ardaman and Associates posed the questions; ?How successful has the industry been? How do we measure it and what factors contributed to the industry?s success? How long will the ethanol boom last? Can the industry obtain the permits it needs to mine for the next 30 years? Can the industry attract and retain the quality of workers it needs??

Jan 1, 2008

The efficiency of a coal mine ventilation circuit is usually measured by the ratio of the sum of the face quantities divided by the quantity supplied by the fans. Other types of systems use the power delivered to the power supplied to measure efficiency. This paper argues the case that the current measure may be inadequate and that by also looking at the power ratio, ventilation may be better managed. Problems associated with failing ventilation systems would be highlighted earlier so that crisis management could be avoided.

Jan 1, 2009

By Jimmy Thompson

The Santa Clara Valley Transportation Authority is designing the Silicon Valley Rapid Transit Project in San Jose, California. The project includes 6.9 km (4.3 miles) of twin-bored tunnels to be constructed through downtown San Jose using two earth pressure balance machines (EPBMs). This paper begins with a project description and update of the project status followed by a description of the relationship between anticipated ground conditions and EPBM requirements. Topics addressed include soil conditioning, abrasion resistance, annulus grouting, face pressure estimation, additional pressure control devices and control measures to limit over-excavation and settlement.

Jan 1, 2008

By R. Q. Honaker

Dense medium processes are used to clean over 50% of the coal that is fed into preparation plant facilities worldwide. The dense medium is formed using ultrafine magnetite which is recovered after the cleaning step using drain-and-rinse screens and magnetic separators. Despite the high efficiency of the recovery system, magnetite losses of around 0.5 to 1.0 kg/ton are common. Considering the recent escalation of magnetite to around $300/ton, an alternative source of magnetic material from coal combustion bottom ash has been investigated. A relatively low cost recovery system has been developed. Dense-medium tests using the bottom ash magnetics revealed a high level of efficiency as indicated by probable error values around 0.03 over the range of medium densities investigated. The results from both the recovery and coal cleaning efforts will be discussed in detail.

Jan 1, 2009

By Edward (Ted) Dowey

City Water Tunnel No. 3 is being built in order to provide a redundant system for delivering 4,542,500 m3 (1.2 billion gallons) of water per day throughout the five boroughs of New York City. The present tunnels, City Tunnel No. 1 and 2 (Figure 1), were put in service in 1917 and 1936 respectively, and both have been in continuous service. Tunnels No. 1 and 2 can-not be shut down for inspection or repair until City Tunnel No. 3 has been completed. City Tunnel No. 3 has two stages (Figure 1).Stage One is 20.1 km (12.5 mi) long and is presently delivering drinking water to the boroughs of the Bronx and Manhattan. Stage Two consists of the Brooklyn-Queens Tunnel 17.7 km (11 mi) and the Manhattan Tunnel 14 km (9 mi). The Brooklyn-Queens leg is complete and is set to be put in service soon. The Manhattan Tunnel is being constructed and is the subject of this paper. The Manhattan Tunnel (Figure 1) is comprised of three legs: the north, south and east legs. The con-tract includes the excavation of 8,976 m (29,500 ft) of tunnel and the lining of 14,561 m (47,773 ft) of tunnel. The south tunnel, 5,705 m (18,720 ft), was excavated but not lined, under a previous contract. The tunnel ranges from 181 m (600 ft) to 152 m (500 ft) in depth in the bedrock under Manhattan. The tunnel contract also includes the construction of nine new shafts, 161 m (530 ft) average depth, and the completion of a tenth shaft (the previously built construction shaft). The Manhattan Tunnel contract was awarded to the sole bidder Schiavone/Shea/Frontier Kemper Joint Venture (SSF) for $668,532,680.00, on January 31, 2005. The Manhattan Tunnel was designed ?in house? by the New York City Department of Environmental Protection (DEP) and the construction management was provided by a combined staff of the DEP and a joint venture of Jenny Engineering and URS.

Jan 1, 2008

By T. O. Dauda, L. O. Ojo

One of the results of the Earth summit (The United Nations Conference) on Environment and Development - UNDP is the statement of forest principles. Others include: the Rio Declaration which is that the human beings are entitled to a healthy and productive life in harmony with nature; Agenda 21-for achieving sustainable development in the 21st century; the convention on biological diversity and the frame work convention on climate change. In the preservation of the biological diversity, Government at various levels took series of steps such as legislation, establishment of forest reserves including strict nature reserves, Forest guards, afforestation projects and others. Omo Forest Reserves is one of the Forest reserves owned by the Ogun state Government of Nigeria. It houses the Omo Biosphere Reserve (that is Strict Nature Reserve of International standard). This biosphere reserve is surrounded by buffer zones, which are meant to serves as protection for the biosphere reserves against encroachments. This study showed that the richest plot in term of species composition (that is plot 15 with the species frequency of 123) is almost the least diverse (with Simpson diversity index of 0.9127 which is 0.0238 higher than the least). It could also be established from this study that the diameter size class of trees with the highest frequencies are the lower size classes (5cm-10cm and 10cm -20cm). These results revealed a magnanimous encroachment on the buffer zones, which is an indication of bad status for the Biosphere Reserves as well as against the spirit of the sustainable use of the natural resources.

Jan 1, 2005