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By Erich U. Petersen

Recognition of mineralogical and chemical zoning patterns associated with mineralization is an integral part of mineral exploration. Even though the origin of zoning may not always be known, zoning patterns as expressed by the systematic distribution of ore and gangue minerals, alteration or elemental assays (soil and rock geochemistry) have received much attention and are extremely useful in guiding exploration efforts toward locating economic mineralization. By contrast, the potential of using zoning information recorded in solid-solution minerals to address practical geological-engineering problems has received less attention. Solid-solution minerals can provide critical information for common problems faced in exploration, mine development and valuation. Mineral zoning information from solid-solution minerals can now be easily obtained because advances in electron microprobe instrumentation have made these instruments a most efficient, accurate, economical and practical tool for analysis of large numbers of samples. Now entire mines and districts can be studied in a timely and cost-effective manner as required by modern mineral exploration and mining practice. This article shows how knowledge of the composition of fahlore minerals can be used in addressing important problems in exploration, development and valuation. Situations are described in which drilling intersected "low grade zones" (Case one: Orcopampa, Peru, precious metal system) and where there was a need to determine the "lateral correlation of multiple ore intercepts" (Case two: Sheep Creek, Montana, sediment-hosted sulfide deposit).

Jan 1, 1992

By Michael Lenz

Predictive maintenance technologies including vibration analysis, tribology, infrared thermography, ultrasonic detection, and electrical measurements have been applied to large electric mining shovels. The predictive program was initiated on the P&H Model 2300 and 4100 electric shovels. The utilization of these technologies has shown the potential for improving electric mining shovel availability and minimizing maintenance costs. Predictive technologies provide the tools to assess machinery condition. Availability is enhanced by the condition based planning of component replacement. Maintenance costs are minimized by focusing resources through condition based prioritization.

Feb 24, 1997

By G. A. Gamble

Fans used to ventilate subway, passenger rail and vehicular tunnels are similar to the fans used to ventilate underground mines. However, tunnel ventilation fan systems are typically designed to meet NFPA 130 or 502 standards, while mine ventilation fan systems must comply with the appropriate federal mine safety regulations. As a result, fan operation requirements and performance criteria, as well as typical fan and duct configurations differ significantly for tunnel and mine ventilation applications. Variations in environmental conditions in tunnels as compared to mines also result in differences in fan performance and material specifications. The need to enclose tunnel fans within building structures creates space restrictions impacting fan size selection that are not commonly encountered in mine fan installations, resulting in different approaches to selecting fans for the two types of tunnels. This paper discusses the various similarities and differences in design considerations for tunnel and mine ventilation fans.

Jan 1, 2009

By Helmut Westermayr, Michael Tergl

DESCRIPTION OF PROJECT Geographic Setting The Kops II plant is a pumped storage scheme of the hydroelectric power producer ‘Vorarlberger Illwerke AG’ which is currently under construction in the Austrian Province of Vorarlberg. The plant is located at the end of the Montafon valley and will be fed with water coming from the Silvretta mountain range (Figure 1) Description of Plant The Kops II plant shall be operated as a pumped storage plant with three highly flexible and quickly controllable power generating units. Each unit shall have a capacity of 150 MW and shall be equipped for both turbine operation and pump operation. The Kops II plant uses the existing Kops Lake as upper storage reservoir and the existing Rifa balancing reservoir as lower storage reservoir. All major plant components of the Kops II scheme are located below ground. Total investment costs areapprox. 360 million Euro. Construction Lots The construction works for the Kops II plant, which were subdivided into three lots, were launched in September 2004. It is planned that the first power generating unit shall go on line in the year 2007. The completion of the overall project and the operation start-up of the second and third unit are envisaged for the year 2008. Lot 1—Pressure Tunnel. The 5.5-km-long pressure tunnel forms the connection between the Kops Lake and the beginning of the pressure shaft. The tunnel was excavated by the use of a double-shield TBM. Lot 2—Pressure Shaft and Surge Chamber. The approx. 1.1-km-long pressure shaft was excavated by TBM, advancing from bottom to top. Featuring an inclination of80%, the pressure shaft overcomes a difference in height of approx. 700 m. Lot 3—Power House Cavern and Tailrace Structure. The power house cavern, which is being built approx. 150 m inside the mountain, forms the core of this plant. The power house is designed to accommodate three power generating units, and the transformer cavern is forseen to accommodate three transformer units. The tailrace structure serves the purpose of conveying the water to the lower storage reservoir during turbine operation and as water intake during pump operation (Figure 2).

Jan 1, 2007

By M. D. Khattar

Problems discussed concern encountering of high temperatures [up to 66°C] and heavy flow of water [150 L.P.S] during the construction of the 10.15 MØH.R.T. for the 2500 MW Nathpa Jhakri Hydro Power Project in the Himalayas(India). Over a length of 2500 M progress of work got seriously affected resulting in excessive time for completion - two years [max. monthly progress achieved was 178 M [Heading]. Many innovative and simple steps were taken to complete the work in these inhospitable environs affecting working of both men and machines. Also it meant a review of the design of concrete lining. Other geological conditions affecting the progress are also described.

Jan 1, 1999

By B. Caro Vargas

The Toulon South Tunnel in France is the second part of a project started 20 years ago. After the problems and delays suffered during the construction of the North Tunnel, due to a complex geologic context of highly fractured and soft rocks under a highly urbanized environment, a very dense automatic monitoring system was implemented to control the settlements of surface (more than 1000 points), the structures adjacent to the tunnel alignment and the underground galleries being constructed. The latest automatic instrumentation systems were installed, using for example AMTS capabilities in terms of ?automatic prismless settlement monitoring?. All the data (geotechnical, structural and geological) was gathered in a global automatic data acquisition system and continuously available on a web based interface. Three different threshold levels (notification, anomaly, alert) were set up, each one with a differential and an absolute value for settlements. Depending on the actual geological site conditions and the actual monitored settlements, different supporting systems and excavation techniques were used. Furthermore, the monitoring data was also used to predict and anticipate the future settlement, by comparing it continuously with the theoretical Peck settlement curves. This method allowed a better risk management by limiting the settlement on existing structures and helped to secure the Works progress schedule, for a project that lasts from July 2007 to March 2011. The implementation of this observational method application is presented in this paper.

Jan 1, 2012

By Steve Kral

In a lagging economy where profits are tight, businesses cut costs. No revelation there. The mining industry, though, has always looked for ways to reduce production costs — no matter the state of the economy or commodity prices. The fact is, when planning a new mine or the expansion of an existing one, mining companies gamble that commodity prices will be reasonably high when a project comes onstream. It takes millions of dollars and several years to bring a mine into operation. And a lot can happen economically between the time management gives the go-ahead for a new project and its completion.

Jan 1, 2002

By H. S. Rathor

NTPC (National Thermal Power Corporation), a multi-unit organization, is generating 26% of India’s total power. This power is produced from its 14 coal based stations and 7 gas based stations. NTPC is entering into the business of power-distribution, power-trading, setting up of coal mines and diversification in non-conventional energy sector as well. For achieving the goal of the country “Power for All” NTPC has taken a giant stride by entering into Hydro Power generation which is also the cheapest and the cleanest renewable source of energy. In its pursuit for excellence, 800 MW Koldam Hydro Power Project is NTPC’s first venture in hydro sector. In Koldam, hydropower potential will be harnessed by constructing a 163m high earth and rock fill dam in a narrow gorge at upstream end of Bhakra reservoir. The river diversion is envisaged through two parallel, 14m finished diameter ‘horseshoe’ tunnels of length 901m and 934m at village Kian on the right bank, where the river forms a 180° loop. The diversion tunnels are designed to accommodate a flood of 6500m3/sec, taking into account the maximum probable discharge of 200 years return period. The tunnels pass through dolomite and limestone rock formations. The excavation of tunnels was done with drill and blast method. The excavation was attempted from both inlet and outlet faces. During geological investigation a rock fault was located at the outlet area. The location of the fault was such that it was passing through the edge of the Tunnel-1portal and around 30m away from the face of the Tunnel-2 portal. The quality of the rock at Inlet was also poor. To save the portals from slips, excavation of the tunnels was planned to start after the completion of the open excavation and its support system both at inlet and outlet. The tunnel excavation at inlet was envisaged by approaching the tunnels’ portal by constructing a road through 540EL bench and meeting the inlet portals on the upstream end, which would have been ready by mid2003, only after completion of the open excavation and its support system. To save time and cost, it was felt necessary to modify the planning by starting the tunnel excavation simultaneously along with open works both at inlet and outlet. The excavation at the inlet face of the tunnels started in December 2002 after rerouting the approach road to inlet portals through haulage road on the downstream and similarly Tunnel-1 at the outlet was started in the low cover area before completion of open area works. Thus the tunnel—heading excavation was started nearly 06 months early with the change of methodology.

Jan 1, 2005

By N. Dhawan

With ever-increasing demand, low-grade complex ores and strict environmental regulations, metallurgical processing options have become limited. Heap leach technology provides several benefits to combat these issues including low cost, flexibility and diversified process conditions. This paper provides an overview of heap leaching technology with specific emphasis on chemical aspects. Hence, influencing factors, advantages and disadvantages, testing approaches and some fundamentals will be discussed. Finally, heap leach technology for different ore types (copper, nickel, uranium and gold) will be briefly compared.

Jan 1, 2012

By Laszlo Toth

A feeder is used to control the gravity flow of bulk solids from storage areas, like a bin or a stockpile. For this type of application, it is important to select a proper drive that can fulfill all of the demands put on it. High starting torque capacity, variable speed and the ability to handle frequent starts and stops are some of the demands that the drive must be able to meet. The following is a comparison of the most common type of drives used today for feeder applications. When a feeder is started, the breakaway torque may reach as high as200% of the running torque. The accelerating torque usually is set to protect the carrying element of the feeder, like the belt for the belt feeder and the carrying chain of the apron feeder (Fig. 1).

Jan 1, 2003

By H. H. Murray

Recently developed clay deposits that will impact regional and world markets are described. These deposits, their location, geology, and physical properties are delineated. Kaolins from the State of Para in Brazil and from Ukraine; bentonites from Argentina and India; and palygorskite and sepiolite from China are world class deposits that when processed using modem technology will produce excellent products. Other deposits that may affect regional markets are kaolins from China, Australia and Indonesia; bentonites from Georgia (formerly USSR) and China; and palygorskite from India and Ukraine. New ball clay deposits that will affect regional markets are in China and Indonesia.

Jan 1, 1999

By C. Sun

The Leeville underground mine has been in operation since 2006 and currently produces 3,500 tons of ore per day with an average gold grade of 0.34 opt. The mine has a large horizontal extent of 2,500 feet by 500 feet and a vertical extent of 20 to 200 feet. Based on the characteristics of the ore bodies, a long-hole stope and cut-and-fill mining methods are used at the deposits which are divided into several mining zones. Cemented rock fill (CRF) is used as the backfill in the open stope. CRF design includes the aggregate design, the ratio of cement and fly ash design, and strengths for the long-hole stope and cut-and-fill. In the aggregate design, the particle size distribution is one of the most influential aggregate characteristics in determining how it will perform as a basic backfill material. Gradation helps determine durability, porosity, cement and water requirements, strength, and shrinkage. To cut the backfill cost, fly ash usually is added into the binder to replace some part of cement. However, adding fly ash can affect the strength of the backfill. The reasonable percentage of fly ash is also important for making a good and low cost backfill. Based on the different mining method, the different backfill with different strength is designed. A systematic quality control procedure for aggregate and backfill is followed. After four yeas application, CRF system in Leeville achieved very good results.

Jan 1, 2011

By Don C. White

The Vulture mine near Wickenburg, Arizona was a major gold producer from 1863 to 1942, having yielded about 11t(12.1 st) Au and 8t (8.8st) Ag. Gold occurs as coarse native metal and electrum in quartz veins and also finely dis¬seminated within a quartz monzonite sill and its silicified wall rock. The sill is semi-conformable within a Proterozoic volcaniclastic-dominated sequence, all dipping north about 35°. Early mining focused on the vein-hosted gold, particularly in the immediate hanging wall and footwall of the sill. Later efforts included some open-pit mining of the outcropping sill and adjacent altered and mineralized rock. Two sets of post-mineral faults have complicated the orebody geometry. The sill is a 350 m (1148 ft) long apophysis from a quartz mozonite stock to the west of the mine area. The stock has been dated at 85 my and contains abundant lesser gold occurrences in its core and about its margins. The Proterozoic rocks are notably lean in precious metals except where altered in proximity to the Creataceous stock and sill. Circumstances dictate an interpretation of epigenetic mineralization related to the Laramide intrusion.

Jan 1, 1990

By Dave Ragland

The SDSU tunnel and underground station are the first of these type facilities to be constructed by the Metropolitan Transit Development Board. Because there is no previous experience, and because tunneling activities are associated with some risk, he MTDB has undertaken a very proactive and wide reaching program to identify and control risks during construction. Finally, because the tunneling activity and underground station is on the San Diego State University, MTDB is working closely with their staff to identify construction impacts and mitigation’s, and thus ensure a quality project for both agencies.

Jan 1, 2001

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob.

By Franco Oboni, Iain G. Bruce

The design of tailings containment structures relies on well-understood engineering methods being applied consistently. Unfortunately, not all facilities are designed or managed to the same level of competency. To standardize procedures, the Mining Association of Canada (MAC, 1998) prepared a “Guide to Tailings Management.” It recommended review of designs and an assessment of the risks associated with tailings impoundments be implemented during all phases of amine life. This paper describes how the quantitative risk assessment (QRA) process can be used to define risks associated with the design, construction and operation of a tailings management facility. And it discusses how, once the risk tolerability curves (RTC) are defined for a project, they can assist the risk management (RM) process.

Jan 1, 2002

Gary R. Steele is vice president, corporate marketing with Energy Fuels Resources. As such, he knows the global uranium market. The following are some of his thoughts on uranium?s place in the global energy picture. ME: What are Energy Fuels Resources? thoughts on the global nuclear power industry? Steele: The global nuclear power industry is a major contributor to the electrical needs of the world. Though generation by nuclear reactors has primarily attracted attention through the reactor accidents at Three Mile Island and Chernobyl, nuclear power continues to quietly and safely provide power to a growing and power-hungry world population. As of March 2008, 30 countries were operating 439 nuclear power reactors. Nuclear power plants provided about 15 percent of the world?s electricity production in 2007. France leads the world in nuclear utilization, with 77 percent of its power coming from nuclear plants. And Lithuania, Slovakia and Belgium each derive more than 50 percent of their power needs from nuclear plants. For much of the developed world, nuclear generation has already been contributing significantly to the supply of electricity. Additionally, 34 new nuclear plants are under construction in 14 countries. Leading the rush to build new nuclear generating plants are China, Russia and India. Each of these countries is building six new nuclear power plants. These 18 plants, totaling almost 12,000 MW of generation capacity, will require about 7.25 kt (16 million lbs) of U3O8 for their initial fuel load and will consume about 2.45 kt/a (5.4 million lbs/year) for the rest of their operating lives. The rest of the world, outside of the United States, has used nuclear power as a viable and economic generation alternative since the commercialization of utility nuclear reactors. And current activity supports the strong future of the nuclear alternative internationally.

Jan 1, 2008

By Erik Melchiorre, M. Katherine Crombie, Dante Lauretta, Chris Gholson

Rich Hill, also known as Weaver District No. 2, is among the most productive placer gold locations in Arizona. Located near Congress, AZ (Fig. 1), this district hosted major placer rushes in the 1860s and1930s. Those rushes were followed by an electronic metal detecting rush that started in the 1980s and continues today. Thousands of ounces of gold have been produced by these modern amateur and professional metal detectorists. Many of them see more gold in an afternoon than Nevada mine workers will ever see outside of the mill. Rich Hill discovery Inspired northeastward by Spanish legends, a party of 10 men left Yuma, AZ on April 1, 1863. Included in the group were Pauline Weaver (Fig. 2), Henry Wickenburg and Abraham Peeples. Wickenburg left the group near the Hassayampa River and discovered the Vulture deposit. The rest of the group arrived at the base of Rich Hill in late May. While drying antelope meat on the first day, a few of the men prospected a nearby creek bed and immediately found gold. In a couple of hours they picked up more than 2.8 kg (90 oz) of gold. The next day, four members of the party went searching for their horses and returned with news that a nearby hilltop was literally graveled with nuggets.

Jan 1, 2003

By R. P. Stahura

Conveyors are the lifeline of mining and processing operations. They continuously supply materials to and carry finished products and waste away from operations. When conveyors are running at less than maximum efficiency, the operation's productivity is in trouble. Inefficient conveyors suffer carryback, leading to the buildup of materials on idlers and other expensive components. They spill and leak material at loading zones and conveyor transfer points. This causes accumulations that can damage the belt, wear moving components and increase both clean-up labor and maintenance expenses. They wander or mistrack, spilling material and endangering personnel and conveyor components. And through these inefficiencies, they multiply the operation's hidden costs. These added expenses occur in lost production, increased downtime for service and maintenance and replacement costs for prematurely worn equip¬ment. In addition, the attitude that inefficiency is "good enough" is recognized elsewhere in the organization. As a result, other departments relax or operate at less than peak performance. Quality goes down along with employee morale. Costs of inefficient conveyors A key to efficiency is handling a product as few times as is necessary. That means conveyors should be loaded, track true to the unloading point and then be unloaded, all without material escape or waste motion. An inefficient conveyor is often signaled by accumulations of DURT - material that has escaped from the system and is now at large in the plant. This DURT adds costs to an operation that are uncounted and, perhaps, uncountable.

Jan 1, 1992

By M. Rice, M. Stanley, J. Marlow

Arizona construction aggregate industry remains in the crosshairs of public debate, caught between the need for aggregate-based building materials and alternative, high-value land-uses. To better manage lands and improve land-use decisions, the Arizona State Land Department has need for a system to assess potential aggregate resources on State Trust lands, and assign dollar values accordingly. Thereafter aggregate values can be compared to residential, commercial, agricultural, recreational, and habitat values -- in a determination of highest and best land-use.

Jan 1, 2002