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By George Anagnostou

Time-dependent ground behavior may have important implications for the construction process or the life of a tunnel. The paper gives a concise overview of the influence of time on the deformations and the stability of underground openings, including topics such as face stability in soft ground or the time-development of pressure or deformations in squeezing or swelling rock. While keeping in mind practical questions of tunnel engineering, emphasis is placed on understanding the observed time-dependency, on the underlying mechanisms (such as pore water pressure dissipation or chemical processes) as well as on the respective inherent prediction-uncertainties and design-uncertainties.

Jan 1, 2007

By Leons Kovisars

Introduction Labor is the major cost element for most mining operations. Labor costs are continually increasing, both in nominal and constant terms. This is true in developed as well as less developed countries. There are two ways to control unit labor costs - labor costs per ton of ore mined. Replace labor with capital (increased mechanization) or improve productivity (reduce the labor force). Every miner is aware of specific inefficiencies at his or her particular operation. But the miner has no comparative measurement standards. So it is difficult to know whether these inefficiencies are major or minor. The miner may also be unaware of large-scale inefficiencies because ongoing labor practices may have caused management complacency. Met Research studied mining labor productivity. The firm collected pilot data by sending direct-mail questionnaires to 320 nonferrous mining operations around the world. The response rate was 27%, of which 78 operations provided full data on production and employment.

Jan 11, 1983

Multilevel-multiseam hardcoal mines on the European continent usually consist of a huge network of underground openings, sometimes more than 200 km long in total, with some longwalls operating down to a depth of 1,500 m. While operating several longwalls simultaneously, these mines are making use of a number of stationary and mobile measurement- and analysis units in their main ventilation passes combined with atmospheric measurements on the surface. This paper provides an overview over the systems and technology used and describes the typical set-up of a measuring net. To detect and monitor underground fires through fire gases measurement and -analysis, a mobile underground testing laboratory collects data locally in the area of the fire. These laboratories have proven to be extremely useful not only during the actual fire fighting but also for the long-term gas measurements in critical mine areas. They have repeatedly detected starting fires and have thus given the mine the opportunity to react early and to avoid larger damage. Therefore several mobile laboratory units have now been installed for long-term testing in a number of German mines and similar units are being used in the Czech Republic and Poland.

Jan 1, 2012

By B. R. Stewart, L. W. Zelazny

The exclusion of coal fly ash from regulation as a hazardous waste has led to increased interest in returning ash to the coalfields for co-disposal. A multi-year column study used coal refuse with high potential acidity (4% total-S), and two alkaline ashes in various bulk-blends. The unamended refuse acidified rapidly, producing acidic (pH 1.7) leachates, high in dissolved metals. Treatments blended with sufficiently high amounts (20 to 33%) of alkaline ash produced alkaline (pH >8.4) leachates with low metal levels, while lower ash blending rates acidified over time to produce metalliferous leachates. Examination of solid materials indicated that pyrite oxidation was occurring to some extent in all treatments. A regression equation (r2 = 0.95) was developed to estimate time to net acid release for mixtures of these materials. Ash alkalinity and refuse potential acidity must be balanced to insure water quality for co-disposal environments, or the ash materials should be isolated away from acidic drainage waters.

Feb 24, 1997

By Gerald G. Griswold, Allan G. Provost

INTRODUCTION The Norad Expansion Project was located 10 miles southwest of Colorado Springs, Colorado, within Cheyenne Mountain. The expansion areas to be excavated would be adjacent to the existing underground Norad complex, which would remain in operation during the work on the expansion. The original complex had been constructed approximately eight years earlier and had been in full operation for approximately five years. Phase I, Excavation was awarded the Tiro Construction Corporation, a subsidiary of Harrison Western Corporation, Denver, Colorado, in the fall of 1970. Notice to Proceed was given to Tiro on 28 December 1970. The project owner was the U. S. Air Force, design was performed by the U. S. Corps of Engineers, Omaha District, who would also serve as the construction agency. [ ]

Jan 1, 1979

By O. Schumacher

Guidelines for publication of information defining the amount and grade of resource material available in a deposit are well established in Australasia?s JORC Guidelines, Canada?s National Instrument 43-101 and similar documents in South Africa, Peru, Chile and elsewhere (Table 1). These guidelines provide standards to apply regarding the geologic and geostatistical basis for describing the level of confidence to be assumed for an estimate of the amount and grade of material. All of them provide for a strict distinction between material that has been demonstrated to be economically mineable and that which has not, and all of them provide terms such as ?resource? or ?exploration information? to be applied to data regarding material that has not been demonstrated to be economically mineable. It is not until an economic study has been completed that we are allowed to apply the powerful terms ?reserves? and ?ore? to our deposit material. Indeed, the application of these eye-catching labels immediately tells the reader that an economic study has been completed by a qualified person, and that the results of the study were positive. While extensive guidelines are established for describing the level of confidence in published geologic data, and the nature of the economic study that should be accomplished before using the terms ?reserves? or ?ore?, surprisingly little guidance is provided regarding the process to use, and the level of detail to attain, for estimating capital and operating costs for the study. The intent of this paper is to lay the groundwork for development of suitable guidelines for the cost estimating process. While the codes do not provide specific instructions for the cost estimate, they do provide numerous hints and clues to help determine the level of detail expected and the type of procedure to apply in preparing the estimate. This paper will first review the various codes to gain an insight into the thinking of the drafters of the codes regarding their unstated expectations for the cost estimating process. Based on this review, a series of guidelines are proposed for this purpose.

Feb 27, 2013

By David Smith

Construction of a new transportation link frequently requires crossing under an existing highway or railroad. Although traffic diversions may permit a cut and cover structure to be built, ‘zero impact’ tunnel solutions are becoming increasingly popular. The vertical clearance between the new tunnel structure and the existing highway or tracks may be very low; sometimes less than two meters. This leaves little room for error since any ground loss can rapidly translate into surface settlement. Problems can be avoided by maintaining the stability of the tunnel face and by minimizing ground movement around the tunnel lining. This paper examines construction methods that have been used to construct short tunnels with shallow cover, and highlights factors to be considered for future projects.

Jan 1, 2005

By O. D. Staman

The risk assessment project examines the likelihood of inorganic contaminants from copper dump-leaching operations to contaminate domestic water supplies. The project examines contaminant transport by modeling contaminant movement from the base of a leach pile through the unsaturated zone and into the saturated zone. The modeling effort is unique in that it models infiltration, contaminant transport in the unsaturated and saturated zone combined with geochemical modeling of the unsaturated zone. The project incorporates probability theory to reflect the uncertainty of hydrogeologic parameters.

Jan 1, 1994

By Jamal Rostami, Ebrahim Farrokh

Selection of tunneling method, specially the use of shielded machines for application in deep rock tunnels can be heavily impacted by presence of ground convergence and squeezing conditions. Tunnel convergence is a function of ground conditions (i.e., rock mass behavior, groundwater, in-situ stresses), size of the opening, and TBM operational parameters. The case study of Ghomroud water conveyance tunnel project in Central Iran, which is under construction using a double shield TBM, is used to examine the effect of rock parameters on tunnel convergence and hence on the need for over excavation and shield lubrication to avoid problems with the shield getting stuck. Although it is impractical to perform a continuous assessment of rock mass conditions within the shield or in the lined tunnel, results of field observations and subsequent studies show that the amount of the tunnel convergence has direct correlation with the percentage of fines and large rock fragments in the muck and TBM thrust/torque/ROP. These relationships have been examined and will be presented in this paper.

Jan 1, 2007

China’s vibrant economic growth is built on coal, the source of two thirds of the country’s electricity. Over 95 percent of China’s coal is mined underground with the average mining depth at 410 m and in-creasing at 10 m per year; today, the deepest Chinese coal mines have exceeded 1,000 m. With increasing mining depths, there are greater challenges including increased methane emissions and spontaneous combustion. According to the government, nearly half of China’s coal mines are classified as gassy (with specific gas content at least 10 m3/mt). Coalbed methane (CBM) is a clean energy source. However, only a small percentage of the methane is captured, and the rest is vented directly to the atmosphere. This paper describes China’s CBM resource, its production and utilization.

Jan 1, 2006

In order to ensure safe mining and reduce surface damage in shallow multiple-seam mining, the failure characteristics of interburden strata with different coal pillar offset distances between pillars in the upper and lower seams, the distribution characteristics of stress concentration in coal pillars, and the development characteristics of stratum cracks and subsidence were physically investigated and also using UDEC2D software. Meanwhile, the effect of different coal pillar offset distances on the stress concentration of coal pillars and development of stratum cracks were studied. Based on those results, a formula for safe mining and reducing surface damage was established, which provided a theoretical basis for safe and environmentally friendly mining in shallow multi-seams. According to the results of the study, the optimal coal pillar offset distance (the side-to-side horizontal distance of the upper and lower coal pillars) between the upper and lower coal seams was developed to reduce the stress concentration of coal pillars and surface damage. The results of this study have been applied in Ningtiaota coal mine and have achieved good results in safe and environmentally friendly mining.

Jul 28, 2020

By J. D. Lowell, L. Quevedo

I will talk today about a porphyry copper exploration program now underway in the Amazon jungle in the southeastern part of Ecuador near the border with Peru. The project is unusual for two reasons: first the deposits are of Jurassic age, 153 m.y.o., which is unusually old for porphyry copper deposits and they may be the most significant pre-Tertiary age porphyry deposits known. Second, the district was found only six years ago which makes this the most recent discovery of a totally new porphyry copper district. The new porphyry district, known as the Zamora River Copper Belt, or the Corriente Copper Belt, is a north trending area 50 km long by 10-15 km wide, which is nearly aligned with the axis of the Jurassic age Zamora batholith and with the course of the Zamora river. Gencor in 1994 initiated a regional grassroots gold exploration program based on reconnaissance geologic mapping and geochem sampling which did not find a gold mine, but which identified the San Carlos porphyry copper system in April, 1995. In a later reorganization between Gencore and Billiton the Ecuador project was transferred to Billiton and between the Gencore work and Billiton’s a total of 10 porphyry copper systems were found over the next four years. In the period of 1997 - 1999 Billiton drilled a total of 11,000 meters of wide spaced core holes in the San Carlos, Panantza and Kutukus prospects. In October 1999 Billiton concluded a farm-out, joint venture agreement with Corriente Resources and Lowell Mineral Exploration for additional exploration of the Zamora property. This is funded by Corriente and managed by Lowell Mineral Exploration and a total of 28,000 m of core drilling was completed through August 2001. An immediate result of the Corriente Lowell project was the discovery of potentially commercial ore reserves in two new deposits at Mirador and Warintza. Additional closer spaced drilling was done in the Panantza deposit and additional drilling is planned at San Carlos, in targets related to Warintza, and elsewhere.

Jan 1, 2002

By Milka Madahana, John Ekoru

For efficient management of operations, mining companies are required to be able to predict potential scenarios for main market factors. Competitive advantage and value creation are established through managing the value chain well. The mining value chain is usually faced with challenges from various shifts in commodity markets as well as ongoing uncertainties. Therefore, there is a need for accurate analysis of data from the markets, for the prediction of commodities, for instance, Precious Group Metals (PGM). The main objective of this research work is to apply machine learning methodologies with the aim to identify patterns and trends in the Precious Group Metals, and thereafter analyze and predict the future trends of these markets. Numerous machine learning models are applied to a dataset consisting of 15 years of daily price for eight precious metals namely Platinum, Palladium, Rhodium, Ruthenium, Osmium, Indium, Silver, and Gold. The results reveal the patterns and trends within the data sets and that different machine learning methods could be suited for the prediction of market prices for each of the PGMs. The application of an amalgamation of various machine learning methods may result in more accurate predictions of the PGM markets. Accurate prediction of market prices for PGMs will possibly result in unlocking untapped sources of value in the mining industry.

Jun 25, 2023

By A. H. Shapiro

A decanter centrifuge of novel design was developed for the dewatering of fine-solids slurries having micron-range particles that form paste-like, flowable, hard-to-dewater cakes. The design combines a compound beach with a cake-flow control structure that allows expressed liquid from the cake in the dry beach region to be returned back to the liquid pool while maintaining high solids throughput. In order to provide optimal performance with various operating parameters (feed rate, centrifugal gravity, pool, differential speed, concentration of feed solids, and different slurry types), the cake-flow control is adjustable. The second part of the beach is preferably at zero angle. Tests showed that the new design allows increases in both solids dryness and solids throughput.

Jan 1, 2001

By D. J. Duck

INTRODUCTION Construction of the 3,600,000 kilowatt Third Powerplant at Grand Coulee Dam started in late summer 1967 approximately one year after authorization by Congress. The project was made possible by a treaty with Canada providing for cooperative development of the Columbia River which was signed in 1961 and ratified in 1964. Description of the Work The existing Grand Coulee power complex consisted of a dam and two powerplants with a switchyard serving each plant, one on each bank of the river. See Fig. 1. The switching facilities were connected to transformers at the powerplants by overhead 230-kilovolt and 115-kilovolt tie circuit conductors. [ ]

Jan 1, 1997

Queensland?s underground coal industry, as a whole, has arguably the best gas monitoring systems in the world. Each mine utilizes real time, tube bundle and onsite ultra fast gas chromatograph systems. Queensland?s mining legislation has specific requirements for mine gas monitoring but there is no requirement for all three techniques. Industry has however identified the need for all three and adopted this as a standard, resulting in over sixty thousand gas results collected each day. Automated monitoring systems are programmed to alarm for gas concentrations, gas ratios and explosibility. These alarms are then used to initiate predetermined actions to take control of the situation and prevent the compromise of safety to workers and the loss of resources. Dedicated software packages have been developed to assist in the interpretation of the large volume of results generated. The real time systems are used for real time warning, essential for incidents such as belt fires. Tube bundle systems suit long term trending used for identification of the onset of spontaneous combustion or for the determination of explosibility during the routine sealing of worked areas. Gas chromatograph analysis is used to provide a complete analysis and provides results for hydrogen and ethylene, key gases used in the assessment of spontaneous combustion. It is also crucial during significant spontaneous combustion events and coal fires to use gas chromatography to determine the explosibility status of the underground atmosphere otherwise the severity of the situation is likely to be under estimated. This paper outlines the need for all three techniques for assessing the underground status and outlines advantages and disadvantages of each.

Jan 1, 2009

By Narendra N. Khatri, Michael Deutscher, Jozef F. Zurawski

Five sewer connections were required to divert Combined Sewer Overflow (CSO)from existing outfalls to an old underutilized large diameter brick sewer (the Easterly Interceptor). The connections were part of an on-going CSO control program by the Northeast Ohio Regional Sewer District (NEORSD) in the City of Cleveland, Ohio. Each connection was made by pipejacking and hand-mining a fiberglass-reinforced polymer (FRP) pipe through soft glaciolacustrine clays and silts. Jet grouting was utilized to stabilize the soils and fill the voids surrounding the interceptor prior to making the underground connection. Reinforced concrete liners were constructed inside the aging brick sewer to provide structural stability during ground improvements and connection work. The project also involved micro tunneling two approximately400 foot lengths of FRP pipe through soft ground using a slurry pressure balanced machine.

Jan 1, 2005

By Dan Martz, Bill Moler, David Young, Wally Chen, Matthew Crow, Steve Norris, Tolga Togan

Two 610 m (2000 ft) long tunnels were driven through water bearing silts, sands and clays beneath the Sacramento River using a 4.59 m (15.1 ft) diameter Earth Pressure Balance Tunnel Boring Machine (EPBM). Four sheet pile shored shafts were sunk with and without dewatering. The pre-cast concrete segmentally lined and grouted tunnels were driven down at 6% grades beneath the river flood protection levees, buildings, roads, a railroad and adjacent to a Freeway Viaduct. Details of the schedule, cost, shaft construction, TBM, tunnel construction, and installation methodology for the twin1.676 m (66 in) steel force main pipes and environmental constraints are provided.

Jan 1, 2007

By Thomas E. Ban

During recent years fuel consuming industries of the United States have been caught between environmental restrictions and the uncertainty of obtaining an inexpensive fuel. With the advent of the National Energy Act of 1978 there has been added impetus to switch from gas and oil to coal. For industrial furnaces and boilers that were designed to bum coal, returning to an available compliance coal might be feasible. However, furnaces and boilers designed for gas or oil cannot reasonably be converted to coal unless the coal is initially gasified. All cases, nevertheless, depend upon the availability of an adequate structured coal of a compliance composition, a challenge to the coal mining industry. The foregoing problems have contributed to the current energy-coal crisis of today's economies. It therefore would be worthwhile to capitalize on previous experiences of the mineral processing industry.

Jan 1, 1979

By Matthew E. MacGregor, Hugh T. Kelly

I.H. 635 (LBJ Freeway) was constructed as a loop freeway around the city of Dallas in the late 1960s and early 1970s with a design capacity of 160,000 vehicles per day (vpd). Today’s facility is carrying over 270,000 vpd. To help mitigate community concerns with regard to right-of-way issues, noise, safety, and traffic disruption, the Texas Department of Transportation (TxDOT) is planning a number of significant improvements. The West Section improvements include the construction of managed HOV/Toll lanes. Within this 8-mile section, TxDOT is planning two mined tunnels(1.5 and 1.9 miles long) beneath the LBJ Freeway. The mined tunnels will connect to cut-and-cover box sections in both the east and west directions. This paper presents an overview of the project development from the design schematic, through the geotechnical investigations, into the current design stage. The project is being planned for implementation by use of a Comprehensive Development Agreement.

Jan 1, 2005