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By S. Barkhoudarian, R. R. Gupta, R. F. Steinberg

A study of the feasibility of using acoustic signals to detect discontinuities ahead of excavation has shown that reflecting interfaces in a homogeneous rock can be easily identified. Moreover, discontinuity interfaces in a very complex field site (where the rock face was weathered, was full of jointed rocks, and had a destressed zone running along the mine walls) could be identified with a reasonable level of confidence, using a cross-correlation technique for signal processing. The results of this study go a long way toward proving the feasibility of the technique. However, further development work is needed to optimize an operating system in a hard rock environment where boring machines are used for excavation.

Jan 1, 1997

By Terry A. Ring

Sand bed filters are used to remove large and small particles from liquid streams. The large particles are removed by the straining action of the filter bed and the small particles are removed by particle deposition on the surface of the bed particles. Particle deposition, while being essential for the filtering action of colloidal particles, is not the only process that occurs in the filter bed. Other processes that occur are (1) the substrate becomes filled with particles limiting further deposition, and (2) some deposited particles are resuspended. The sum total of all these processes determine the performance of a filter bed.

Jan 1, 1982

By W. E. Cobb

Mining companies, as developers of natural resources, are being forced to deal with the potential long-term liabilities of past, present, and future mining operations. As discussed in a previous paper (Cobb, et al., 1987), these liabilities can include solid waste disposal corrective action programs (state or federal actions), Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), (Superfund) (state or federal actions), or natural resource damage claims (typically filed by state agencies and provisions specified in CERCLA). These potential liabilities are very real, and should dramatically impact the way a company views its exploration and development programs, and operating mines.

Jan 1, 1988

By G. J. Joy, J. P. Rider

Technical advances in longwall mining over the last several years have resulted in much larger and faster shearers that have the capability of mining at speeds over 30 m/min (100 fpm). This has resulted in a substantial increase in the amount of dust that is generated at the shearer and during shield advances. Meanwhile, increased underground coal production has put a greater demand on longwall dust control systems as some operators have had difficulty maintaining consistent compliance with federal dust standards. To address this need, the U.S. National Institute for Occupational Safety and Health (NIOSH) is investigating the effectiveness of a water spray manifold mounted on the tailgate end of the shearer body. The sprays are oriented parallel to the tailgate ranging arm, and these sprays create a water curtain confining the dust plume near the face, preventing the dust from drifting into the walkway. This redirection of dust provides a clean air envelope for the tailgate shearer operator and jacksetters working near the tailgate drum. Three different tailgate spray manifold designs were tested and evaluated at the Office of Mine Safety and Health Research (OMSHR) Pittsburgh Longwall Test Facility. Manifolds were equipped with hollow cone or flat fan water spray nozzles and evaluated at three face air velocities — 152, 213 and 274 m/min (500, 700 and 900 fpm)— and at water pressures of 689, 1,034 and 1,379 kPa (100, 150 and 200 psi). Reductions in dust concentrations were observed at six face sampling locations for all the tailgate manifold systems at each of the tested spray pressures and face velocities. Average reduction efficiencies of at least 90 percent were seen at the three sampling locations closest to the shearer for all three manifold systems at nozzle spray pressures greater than 689 kPa (100 psi). Based on results from the laboratory tests showing reductions in dust concentrations at sampling locations downwind of the shearer, a spray manifold was fabricated and evaluated at an underground operation.

Jan 1, 2016

By L. Buckingham

Barrick Goldstrike Mines Inc. has embarked on a continuous improvement effort to ensure that Barrick Gold Corporation will retain its lead in the gold industry in years to come. The continuous improvement initiative is based on careful mapping of the key levers associated with each activity of business. The individual levers are then evaluated to determine their potential to affect the profitability and safety of the operation. The most promising are diagnosed for root causes. These root causes are then addressed to enhance benefits. Through a structured approach of mapping, brainstorming, evaluating and instigating change with follow up measurement and reporting; Barrick Goldstrike is anticipating an increase in throughput at the autoclave facility of 10% with little or no capital expenditure. The resultant approach to Continuous Improvement will be utilized throughout the Goldstrike facility and then throughout Barrick's world-wide operations.

Jan 1, 2002

By R. C. Klimpel

Size reduction of material in aqueous pulps by the use of tumbling media overflow discharge mills is an important and common unit operation in industry. There also has been extensive attention given in recent decades on developing a more fundamental understanding of the breakage processes involved, especially in ball mills. These studies have mostly emphasized the use of size-mass balance or population balance approaches for quantifying the analysis and design of size reduction circuits, ego Austin, et al (1984).

Jan 1, 1989

By Tracy E. Barnes

The process of computerized reserve estimation consists of assuming a model of the spatial continuity of a deposit and then, working within the assumed model, estimating the grade and tonnage of the deposit. The basis for geostatistical analysis is a statistical definition of this continuity or the variogram. The true variogram is essentially impossible to define. So an experimental variogram is defined from the sample data and kriging proceeds assuming that this experimental variogram is a good approximation of the true variogram. Therefore the closer the experimental variogram is to the true variogram the better the estimate will be. Realizing that the variogram is nothing more than the definition of the spatial continuity of the deposit, taking the known geologic continuity of the deposit into account will give a superior variogram. The use of known geology is a widely recognized necessity for good structural analysis of a deposit, but is rarely fully incorporated into the structural analysis.

Jan 1, 1982

On longwall coal faces in some Japanese coal mines more than half of the air coming from the intake gate road flows into the caved goaf and the air heated by the hot waste rocks in the goaf comes out through the latter half of the face. This still constitutes a major heat problem in spite of the introduction of gate and face air coolers. Therefore, in order to establish effective measures to improve the environ- mental conditions, it is essential to obtain information pertaining to the air flow pattern on the face as affected by the goaf conditions and the air flow regulating measures taken at the intake side of the face. Experiments for this purpose were carried out using a coal face model. The model was reduced to a scale of 1110th of the real face measuring 100 m long and 2.2 m high, equipped with self-advancing supports. The model design was also conceived to accomodate eventual modifications of the space of the caved goaf as imposed by the actual conditions.

Jan 1, 1980

By C. Williard

Computer based mine monitoring and control systems represent a relatively new technology to be applied in the U.S. mining industry. While computer assisted engineering, design, and planning have been accepted as tools for specific technical and engineering jobs within the industry, integrating mine-wide monitoring and control systems into mining operations has been slow. This paper reviews the state of the art of mine monitoring and control systems and provides insights into future trends and developments.

Jan 1, 1988

By H. H. Kleizen

The operation range and efficiency of dewatering apparatus are important factors in the selection of an apparatus for a given purpose. In this paper theories are presented allowing to predict these basic characteristics for different dewatering apparatus and compared with experimental and practical data obtained on coal and ore slurries.

Jan 1, 1989

By Roy J. Leonard

Two small diameter sewer tunnel projects being hand dug under major highways in the Greater Kansas City area encountered problems which were unforeseen from the geotechnical engineering information supplied with the contract documents. Both tunnels were being excavated by experienced crews using steel liner plates. One required the use of compressed air for completion, while the other required poling boards. Both contractors overran their budgets and filed changed condition claims, and this promoted further geotechnical engineering investigations. Fissured clays beneath a water table were encountered at both sites, but the character of these clays differed; however, both were inadequately described in the original geotechnical engineering reports.

Jan 1, 1987

By L. Xiao

Using K-oleate as a collector and alizarin red S (ARS) as a modifying agent, selective depression of dolomite from francolite was achieved in alkaline medium (pH> 9.0). Interestingly. ARS was also found to depress igneous apatite in alkaline medium in oleate flotation of apatite and calcite. Adsorption of ARS alone on dolomite was found to be higher than that on francolite. Complimentary adsorption experiments of ARS and K-oleate showed that oleate adsorption was increased in the presence of ARS on francolite but not on dolomite. K-oleate adsorbs on both francolite and dolomite and causes precipitation of calcium and magnesium oleate. Such precipitates can be pre-vented when ARS is present. The results are explained in terms of competitive adsorption for the active sites on francolite and dolomite by oleate and ARS, and their interactions with dis-solved mineral species in solution.

Jan 1, 1988

By Karl Kuhnhenn

One substantial element of the NATM is to take into consideration the geotechnical rock behavior in the design of excavation and support methods. Even if this opinion is being shared increasingly, the stress analysis is not the sole criterion for a successful tunnel drive. By the beginning, the inventors of the NATM have clearly defined a number of principles which have kept their validity until now. The evaluation of different failure cases demonstrate how necessary the observance of these principles and their strict following during execution are besides the stress analysis. The great number of successfully excavated NATM tunnels are an impressive evidence for these principles.

Jan 1, 1995

By D. Lauriski, E. D. Thimons, A. C. Smith, D. C. Fredley

The National Institute for Occupational Safety and Health (NIOSH) and Northwest Barricade LLC (NWB) conducted a study to evaluate the effectiveness of a novel fire blocking gel for use in underground coal mines to extinguish or retard the growth of a coal fire. The gel agent was subjected to controlled laboratory testing to assess its ability to delay coal ignition. It was then evaluated to determine if manual fire hose application could be used to apply the agent to mine roofs and ribs to provide a safe egress for mine rescue teams from a fire area. The gel agent was also evaluated in a water sprinkler system to determine its potential for use in conveyor belt fire suppression systems. The agent was then tested in live-fire exercises to examine its effectiveness in retarding and extinguishing a deep-seated coal fire and wood fire. Lastly, the ability of a mine rescue team to quickly and safely apply the gel agent to a mine entry during a simulated mine fire exercise was determined.

Jan 1, 2011

By P. Asadollahi, M. Invernizzi

"This paper describes the innovative full-face conventional tunnel excavation technology, with its advantages in terms of savings and safety. The full-face approach has been developed throughout the experiences gained in tunnel construction. The innovative design approach is focused primarily on the deformation response of the ground acting first and foremost ahead of the face, which is analyzed, predicted and controlled by pre-confinement of the core. The advantage of this method is particularly evident in difficult grounds. This paper will present the outstanding benefits given by the adoption of the full-face approach in two projects, the “Sochi” and the “Visnove” tunnels. THEORY AND DESIGN ASPECTS OF THE FULL-FACE EXCAVATION The main challenges in tunnel and underground construction industry are gathering the design data from the ground that is being excavated and foreseeing the critical stage during construction, where the materials are in its most critical configuration. These challenges shall be addressed during excavation when the lining and the excavation disturbance have not yet reach the equilibrium. The in situ stresses in the ground are redistributed (forming an “arch-effect”) around the opening, with zones of increased stresses around the walls of the excavation (Figure 1). The distribution of the stresses can be close or far from the excavation profile, depending upon having a ground capable of withstanding the deviated stresses well or unable to withstand them, respectively. In the latter case, the ground will plasticize and deform in proportion to the volume of ground involved in the plasticization phenomenon. When the ground completely cannot withstand the stresses redistribution, it will cause the collapse of the excavation. While in the first case, the arch effect occurs naturally, in the second case, it does occur naturally only when the ground is stabilized properly. In the case of collapse, the arch-effect must be produced artificially operating on the ground prior excavation. The design should be based on the understanding of if and how the arch-effect can be mobilized during tunnel excavation and ensure that is formed by calibrating excavation and stabilization operations appropriately. The arch-effect is function of the medium that is being excavated, the action taken to excavate and the reaction expected following the excavation."

Jan 1, 2018

By Philip A. Mattson

INTRODUCTION Engineers involved with rock mechanics know the importance of discontinuities within a rock mass and their effect on its behavior when subjected to loads from structures or construction excavation activities. Various geophysical tools have been developed to provide comparative information on subsurface conditions, such as electrical resistivity, assorted seismic test methods, acoustic tests, etc. While these investigative means have proved invaluable in numerous situations, especially those where site alternatives are being evaluated, they shed little light on the difficult problem of quantifying the rock strength. For that purpose, a laboratory test program of samples obtained in the field is usually undertaken, often in conjunction with a variety of in-situ tests. While standard samples provide sufficient information on the rock properties, questions on the macro-structure of joints, faults, fissures, and their infillings often go unanswered. Presently, attempts are being made to incorporate into rock sampling technology new techniques which are directed towards providing better information on the incidense and orientation of discontinuities. One such device incorporates a scribe knife within the core barrel which scores the sample lengthwise as it is cored. The orientation of the scribe is known, thereby relating the bedding, planes, fractures, etc. to a spatial framework. A second approach, called the Integral Sampling Method, is the subject of this paper. Stated briefly, this method utilizes a grout injection to bond fractured rock to a steel reinforcing bar at the center of the coring. The bar is intended to act as a

Jan 1, 1979

By Lennart Mukka

This paper describes the experiences from construction of a new ventilation system in LKABs Kiruna Mine in Sweden as well as the choice of the method for air flow regulation with concern of life cycle cost and the description of the foundation design. The evaluation of the performance test will be presented.

Jan 1, 1997

By R. J. Snoby, P. Grotjohann

In processing heavy-mineral sands, the low feed concen¬tration and respective high value of the desired minerals require high-capacity production and sharp classification/ separation techniques to reduce the specific production costs. This paper describes the new allfux® separator, which can economically accomplish these criteria. The separator is a two-stage process that combines rising current and fluidized-bed technology. This allows for the treatment of ex¬tremely high mass flows in a single unit. This paper reports on test work performed on coal, iron ore and heavy minerals.

Jan 1, 2000

By J. R. Parga

Bacís mining is a young enterprise in Mexico that produces a pyrite concentrate rich in gold and silver. When gold and silver are associated to sulfide minerals, pre-treament such as: roasting, pressure oxidation and bioleching, is required to decompose the sulphides and thereby expose the gold and silver particles to the cyanide solution. A novel method demonstrates that the oxidation and dissolution of gold and silver in alka-line cyanide solution can be conducted simultaneously in the same autoclave in less than 90 minutes with a recovery that exceeds 96%. Factors affecting recovery efficiency such as pH, leaching time in the reactor, temperature, particle diameter, pressure, % of NaCN and pulp density were investigated.

Jan 1, 2007

By Priscilla P. Nelson, Steven D. Glaser, Thomas D. Rourke, O&apos

Construction records from six projects which employed full-face TBMs to drive 18 km of tunnel in sedimentary rock have been analyzed. More than twenty individual causes of delay could be identified. Delay causes are characterized on the basis of frequency and duration of incidents. Average utilization and downtime distributions are presented for each project, and frequency distributions of downtime per shift are discussed.

Jan 1, 1985