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By Thomas M. Barczak

Wood cribs are used extensively to stabilize openings in underground coal mines. This U.S. Bureau of Mines report describes the results of full-scale testing of several multitimbered wood crib configurations. Multitimbered configurations are wood cribs that are constructed with two or more timbers per layer. Nine different crib configurations were evaluated. Configuration parameters under study included the aspect ratio (height-to-width relationship) and the percentage of solid rr:aterial used in crib construction. Test results and generalized wood crib behavior are discussed and recommendations are made concerning crib constructions to maximize strength and stability. Crib performance is enhanced by reducing buckling effects by decreasing the aspect ratio and geometry considerations that increase the moment of inertia. A cost benefit analysis of multitimbered wood crib configurations is made. Generally, increasing the percentage of solid provides more resistance at less unit construction cost. A comparison of laboratory results and underground observations of several wood pack wall supports suggest in situ load capacity is less than that measured in laboratory testing. Reasons for the apparent decrease of in situ load-bearing capability include load rate effects, stiffness of reaction surfaces, and varying boundary conditions that alter the load transfer mechanics of the crib structure.

Jan 1, 1991

By B. Samanta

LHD (load haul dumper) is now used as a loading machine for intermediate mechanization in underground coal mining. For survival in the intense competition in the global business environment in recent years it is essential that LHD machine should be reliable and maintained effectively and efficiently. This paper seeks to study the reliability, availability and maintainability (RAM)of an LHD machine with failure and repair data by Markov modelling. The constraints and reasons for machine unavailability are outlined. The reliability and maintainability of an LHD and its subsystems are evaluated. Possible modification or design alternatives are highlighted. Reliability and maintainability of an LHD system are disappointing. There is room to take decisions on optimal maintenance planning and machine improvement from this analysis. Keywords: reliability, availability, maintainability, Markov model, LHD

Jan 1, 2004

By Jacob Masliyah, Zhiang Zhou, Tshitende Kasongo, Jianjun Liu, Zhenghe Xu, Jeawon Choung

"Slime coating is a recognized challenge in fine particle flotation, not only in decreasing recovery, but also in reducing the selectivity and hence froth quality. In this presentation, a novel method based on electrophoretic mobility distribution measurement to study slime coatings is described. By measuring electrophoretic mobility distribution of individual minerals and their mixtures, the interactions between these minerals can be evaluated.For illustrative purposes, a model system of fine coals, or oil sands with two different types of fine clays was studied. Flotation tests showed a significant decrease in coal (bitumen) flotation recovery with montmorillonite but not with kaolinite clay addition. When electrophoretic mobility distribution of a fine coal/montmorillonite clay mixture was measured, a single modal zeta potential distribution was obtained, in contrast to a bimodal distribution for fine coalkaolinite clay mixture. This finding suggests a stronger adhesion of montmorillonite than kaolinite clays on fine coal surfaces. In the case of bitumen, the bimodal zeta potential distribution was measured for the mixture of bitumen emulsion and kaolinite or montmorillonite, indicating a weak attraction of the clays by bitumen. In the presence of calcium, however, a single modal zeta potential distribution was obtained in the mixture of bitumen emulsion with montmorillonite but not kaolinite clays. These findings are in excellent agreement with bitumen flotation results, demonstrating that the electrophoretic distribution measurement is a powerful tool to study slime coating phenomenon in a complex fine particle flotation system."

Jan 1, 2002

By Robert Martin, Brian W. Stump, David P. Anderson

2We use field measurements to quantify physical processes that accompany different types of mining explosions. The data sets collected include three-component ground motion, acoustic, video and high speed film, three dimensional topography, geological and geophysical properties, design blast pattern and timing, and velocity of detonation in the explosive for individual borehole detonation times. The explosions include simple single-fired contained explosions, ones designed to bulk and fracture material and those that cast material. Our goal is a physical understanding of these sources for the purposes of optimizing blasting practices.

Jan 1, 1998

By Mark C. L. Patterson

Hydrothermal brines are extracted from significant depths below the surface of the earth and arrive at the surface at elevated pressure and temperature. The exact chemistry and conditions of these brines depends upon the rock formations through which the water travels, but many of the brines are rich in dissolved minerals especially silica which is often saturated in the brine. At pressure and temperature the minerals remain in solution but in order to extract heat from the brines, they need to be cooled and during which many of the minerals precipitate causing problems. Where precipitation is a problem in the downstream processing, the brines are maintained at a high enough temperature and pressure so as to avoid precipitation and injected back into the geothermal formation. This results in a significant loss in potential energy that could be recovered from the geothermal brines. If left to precipitate in an uncontrolled manner, many of the minerals will precipitate as gels, in a high surface area form which is difficult to extract from the liquor and which can causes problems. Precipitation in this manner often builds up on the inside of pipes, reducing the pipe cross-section available for fluid flow and reducing the overall efficiency of the plant. If the brines are seeded at the appropriate time or the precipitation conditions are changed, mineral particles can be grown and separated more easily from the brine. During this precipitation and growth phase the chemistry of the local environment can also be altered to grow more valuable particulates. Some of the specific chemistries will be discussed with reference to known geothermal brines and what needs to be done to precipitate value added products. A theoretical approach to the complete extraction of minerals from geothermal brines is also discussed with the goal of extracting more heat from the brine prior to reinjection into the well.

Jan 1, 2006

By Vojtech Gall

Pre-support measures for urban tunneling have seen a substantial development in the recent past. Ground improvement techniques, pipe-arch and spiling methods now allow for non-disruptive tunneling at very shallow depths under sensitive structures, rail tracks and roadways. The paper presents experience gained on national and international projects built over the past decade that represent case histories and therefore may be used as guidance for the development of similar solutions for future tunneling projects at shallow depths. Reference projects include tunnels for the Washington, DC Metro, London Underground, Dulles Inter-national Airport, Busway tunnels in Boston and the Ft. Canning Tunnel in Singapore.

Jan 1, 2008

By Larry A. Haas

Carbonyl sulfide (COS) was decomposed to sulfur and CO in a silent electrical discharge. A threshold of about 4 kv at 60 Hz was required to dissociate the gas in a laboratory ozonizer at 790 torr with electrode gaps between 1 and 5.5 mm. Above the threshold value, the reaction rate increased with increasing voltage with helium or nitrogen diluent. With the latter diluent, higher voltages had to be applied to obtain the same yield in the 4-to 12-kv range. The COS decomposition rate increased with COS concentration, but a saturation value was reached at about 10 pct COS. The reaction rate decreased at low linear gas velocities as obtained at lower gas flows, larger electrode gaps, or larger reactor volumes. Increasing gas temperature also decreased the decomposition rate. The presence of solid adsorbents such as quartz wool, bauxite, or charcoal had no significant effect on the reaction rate. The addition of S02 did not affect the COS decomposition rate, but small amounts of water decreased the reaction rate. Over 50 pct of the COS was decomposed at room temperature and atmospheric pressure in a l7-kv ozonizer using a gas containing 0.9 pct COS in helium flowing at a rate of 0.3 liter/min. The average current was less than 5 ma. This method has possible application in eliminating the toxic air pollutant, COS, which is generated in petroleum refineries and in processes involving reactions between sulfurous and carbonaceous materials. Carbon monoxide that is formed can be further oxidized to CO2 after the collection of elemental sulfur.

Jan 1, 1972

By Douglas D. Campbell, Alan S. Imrie

INTRODUCTION Mica Dam is located on the Columbia River just downstream of the "big bend" of the Columbia, where it leaves the Rocky Mountain Trench and begins to flow southwards, approximately 85 miles north of Revelstoke, B.C. (Fig.l). The dam was built as one of three Columbia River Treaty dams in British Columbia which regulate the flow of the river and provide flood control downstream in Washington and Oregon. In addition, the three Canadian dams make possible greatly increased power generation at existing power plants in the United States and further development along the Columbia and its tributaries in British Columbia. History Mica Dam, constructed during the period 1967 to 1973, is a zoned earthfill embankment 650 feet high, which has 12,000,000 acre feet of live storage and an available head of 550 feet. Power intakes which would serve either a six-unit surface or underground plant were incorporated into the design and construction of the right abutment of the dam (Fig. 2). Prior to 1971 alternative 2500 MW capacity surface and underground powerplant arrangements were studied. Cost estimates for the two alternatives were the same within the limits of estimating procedures. However, it was believed there was a certain continuing risk in locating a surface plant at the toe of a steep canyon wall. Therefore, in 1971 a tentative decision was made to proceed with an underground plant, provided that additional exploration confirmed assumptions of

Jan 1, 1976

By Stephen C. Tadolini, Dennis R. Dolinar

The risk of injury caused by minor roof falls continues to increase in underground mining. Most ground control injuries result from small rock falls that occur in a supported area, but do not involve the failure of the support system. In the roof, these are the "skin failures" that occur between previously installed primary or secondary bolting systems. To minimize skin failures and the associated accidents, several devices were designed and tested in the laboratory to maximize stiffness, minimize material thickness and weight, and ease material storage and handling on roof bolting machines. The goal of this project was to design and evaluate devices that can be installed with traditional primary or secondary roof supports, and that are easy to handle/install under temporary or previously supported roof.

By Sam Bang Jr, Rodney Burke

As mining progresses in the West, the depth of material has increased, making highwall stability a major factor in safety and production. The Jim Bridger Coal Mine’has made highwall stability a priority, concentrating on safety as well as increasing and improving production. Overburden depths are increasing dramatically; the geological environment consists of medium to sot? material, faulting, water, and current pit alignment not favorable to joint planes. Angle drilling the presplit at 20 degrees became necessaryas vertical presplit drilling produced wall failures.

Jan 1, 1998

By W. J. Birch, D. Leckenby, R. Farnfield

The use of electronic detonators to improve fragmentation is becoming universally accepted. However their use in limiting peak particle vibrations levels is still in its infancy. Most of which is anecdotal, in that few actual scientific studies have been carried and published. This paper details the research work carried out at a limestone quarry in the County of North Yorkshire in Northern England. Here a series of blasts were carried out some used non-electric detonators whilst others used electronic detonators. The majority of blasts were carried out at the same burden, spacing and deck charge weight loadings. Initially, the key variable was the difference in detonator type and then leading on to using the electronic detonators at specific exact different detonator timing intervals. Later the study was extended to include double row as well as single row blasts.

Jan 1, 2007

The acoustic signals emitted from a laboratory-scale ball mill were used for the estimation of the comminution of two complex sulphide ores, viz. Merensky and UG2 ores from the Bushveld Igneous Complex in South Africa. The digital acoustic signals were transformed to power spectral densities that could be related to particle size distributions (-75 µm to 4000 µm) in the mill by use of continuum regression. This approach is more general than principal component regression methods or Kalman filtering used previously and resulted in significantly more accurate calibration in the case of the Merensky ore, where approximately 93.4% of the variance in the particle size distributions could be explained. With fewer data available, the variance in the particle size distributions in the UG2ore could be explained less accurately (82.4%), but still satisfactorily. In addition, smaller particle sizes (less than 300 µm) could be modelled more accurately in the case of the UG2 ore.

Jan 1, 2000

By R. E. Krauss

The McLaughlin Mine is a world class epithermal gold deposit located in the coastal thrust fault of Northern California, U.S.A. Homestake adopted a proactive strategy in the permitting of the Mine. Extensive environmental base line studies were undertaken. Engineering and process alternatives were evaluated for environmental impact along with other factors. A unique pressure oxidation process was selected. Screening studies were conducted as a basis for the selection of waste rock and tailings disposal sites. Project engineering and permitting were fast tracked. Construction required eighteen months and the first gold bar was poured in Parch of 1985, six years after the initial discovery. Project facilities are designed and operated so as to minimize environmental impacts. A comprehensive monitering program demonstrates permit compliance. Reclamation of the site is ongoing throughout the Mine?s twenty year life. Non-mined lands are managed to maximize wildlife habitat value.

Jan 1, 1990

By J. R. Hoskins

This is the final report for Research Contract No. 00101300 (Min. 34) granted by the U.S. Bureau of Mines to the University of Idaho Mining Research Bureau. The research project is entitled "Development of Improved Ventilation Technology for Non-coal Mines and Other Underground Excavations.' The duration of the project was six calendar months, from 16 April to 16 October 1970. The budgeted cost was $34,867.00 of which $31,953.00 was to be furnished by the U.S. Bureau of Mines. The sequence of reporting that follows is to state the objectives as contracted, outline the program of investigation, highlight briefly the important technological factors peculiar to vein-type metal mine ventilation, and describe the normal methods of control. This is followed by the results achieved by the survey, and an itemization of the observed deficiencies in current technology. There follows a section dealing with the adopted Federal Regulations.

Jan 1, 1970

By Amanda Elioff

Success of the Gold Line Eastside Extension rail tunnels in Los Angeles has prompted Metro?s planning for two new rail lines to include underground alternatives. The Westside Extension Transit Corridor alternatives include up to 17 miles of subway to be constructed in soft ground. The routes will require construction in Los Angeles? ?Potential Methane Zone,? not considered for subway construction until recently. Slurry face TBMs will likely be specified. The Regional Connector, through the downtown area, includes one underground alternative with 1.7 miles of tunnel as well as three underground stations in soft ground and rock. Challenges will include tunnel and station construction under narrow streets. This paper will describe the alternatives, planning, geologic conditions and tunneling concepts for both planning studies.

By P. A. Hagerty

Biological treatment of metals-impacted water using sulfate reduction is a viable means of treatment that has been applied in pilot and full scale at numerous projects. One of the fundamental challenges with this type of treatment is the selection of an appropriate substrate to support the sulfate reduction process long-term. The substrate degradation products provide a carbon source and an electron donor for metabolism by sulfate-reducing bacteria and consequently organic characteristics are critical; however, the physical attributes of the substrate are equally critical to an efficient and optimized substrate mix. This paper explores the affect of particle size (a.k.a. grain size) of several substrate mixes on the treatment efficiency of sulfate reducing treatment systems. Substrate selection can be separated into two phases of evaluation, the primary selection phase and the secondary optimization phase. The primary selection phase considers such fundamental attributes as source availability, economics, bioavailability and longevity. These fundamental activities are conducted in order to identify potential candidate ingredients of the substrate mix which are regionally available, economically viable and consistent with the biogeochemical aspects of the project. Recent work has been conducted in the development of testing protocol for organic substrates to quantify bioavailability (Martinez Hernandez et al. 2010, Place et al. 2006) as part of the primary selection phase. Once the substrate ingredients have been selected based on the primary criteria, the mixture of these ingredients is then developed based on an optimization process, including consideration of the substrate ingredient?s particle size distribution.

Jan 1, 2011

By D. M. Milne, P. J. Lunder, R. C. Pakalnis

During the mining of an open stope, deformation of the hanging-wall and the potential for dilution generally increase with the size of the exposed hanging-wall. Excluding discrete structures that may delineate unstable blocks, the mechanisms that drive hanging-wall deformation and possible dilution comprise several factors which can include elastic, plastic and discontinuum deformation. These stages of deformation are not mutually exclusive and at any point during mining all three of these mechanisms may be acting on the hanging-wall rock mass. Computer modelling techniques are available to analyse the three stages of deformation, but the difficulty lies in trying to obtain realistic rock mass properties for input and in determining when each stage of deformation is acting. Instrumentation data can be used to predict the effect of continued mining. However, it is often difficult to calibrate numerical models against field data owing to the large number of input parameters required. An empirical approach is recommended that uses two new parameters, the radius factor and the effective radius factor. A method is proposed for predicting the effect of continued mining from existing deformation and dilution data for a given hanging-wall

Apr 1, 1996

The outlook for suppliers of energy to the expanding economies of the Pacific Basin region is essentially positive, but particularly for exporters of high quality steam coal. This paper argues that economic growth in the Pacific Basin region has exceeded world economic growth for some years and that this will continue to be the case for the next decade at least. It looks briefly at the link between economic growth and energy demand and at the relationship between energy demand and the demand for electricity. Changing preferences in fuel mix for electrical generation in the region are noted and tentative forecasts made about variations in this mix. The pros and cons of various forms of fuel used to generate electricity are considered from the point of view of the consumer. Having concluded that steaming coal in particular is likely to become even more important as a generator of base load electricity, the paper looks at the opportunities this presents for exporters such as Australia, and touches on some factors that could prevent development of those opportunities. This paper will concentrate on electrical energy. For the purposes of this paper, the Pacific Basin refers essentially to Australia, New Zealand and the Asian countries bordering the Western Pacific. As a supplier, Siberia is not included because, although it has great potential, it is thought that problems of climate, infrastructure and political restructuring will delay the realisation of that potential until the next century. Although it deals with the Pacific Basin region, where many countries are industrialising rapidly from a predominantly agricultural base, it looks at the experience of mature industrial DECD economies where their experiences seem relevant.

Jan 1, 1990

After the Loma Prieta Earthquake, which caused major damage to viaducts in the Bay Area, the California Department of Transportation set up a test programme for foundation piles. Funderingstechnieken Verstraeten B.V., beter known as Fundex, was approached, since one of the piling systems of Fundex, named Tubex, is extremely suitable in areas sensitive to earthquakes and we were very much interested to prove the capabilities of this piling system. Equipment For the installation of Tubex and Tubex grout-injection piles special piling equipment is required. Since our company is not only a contractor, but also a designer and manufacturer of piling equipment, all special equipment for our range of foundation techniques is designed and built by our own piling equipment department. For the installation of both Tubex piles and Tubex grout-injection piles for the Caltrans test programme, the following pieces of equipment were selected: a) Fundex F12 piling rig b) Drill table c) Hydraulic powerpack d) Grout mixing unit and high pressure pump

Jan 1, 1993

By Adrian Coombs, Paul Magowan, Derek Zoldy

Continued development and intensification are fuelling the urgent need for new trunk infrastructure within The Regional Municipality of York and throughout the Greater Toronto Area. Permitting of these projects is increasingly subject to public scrutiny to severely restrict dewatering through construction technologies and the requirement for a comprehensive and effective Environmental Management Plan. Three current projects: one on the York Durham Sewage System and two in the City of Toronto 1.Conventional Design, Tender, Award: 4,150m (13,600 ft.) 2.7m (9 ft.) finished interior diameter soft ground tunnel for York Region’s YDSS Interceptor Trunk Sewer 2.Negotiated Contract: 3,800m (12,500 ft.) 3.5m diameter (11.5 ft.) rock tunnels for Enwave’s environmentally sustainable and innovative chilled water system in downtown Toronto 3.Conventional Design, Tender, Award: 2,200m (7,200 ft.) 3.3m diameter (10.8 ft.) rock tunnel for reinforcement of Hydro One’s primary hydro feed in the downtown core of Toronto These projects exemplify issues such as: EPB tunnel and sealed shaft technologies Substantial permitting requirements associated with dewatering Mitigation of rock creep Congested downtown rights-of-way Deep shafts and confined working compounds Unique scheduling and cost benefits when Owner, Contractor and Consultant can work together cooperatively.

Jan 1, 2007