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By D. C. Torre

The need for a successful, efficient and reliable continuous face- haulage .system for use with continuous mining machines has been apparent since the first continuous miners were introduced some twenty-five years ago. Some thought and effort were given to the development of continuous haulage over the last twenty years or so. Some initial success was experienced in this area by The Long Company with a system involving bridge conveyors, as far back as the late 1950's. However, extensive success with continuous face haulage for use behind modern, high product¬ion, continuous miners escaped the industry until the early 1970's. It is true that continuous face haulage was successfully introduced into low seam mining, generally in seams ranging under 1.07 m (42") in height, in the 1960's, for use with relatively low production, low seam, auger type continuous miners. However, those available systems which have achieved success in the lower seams, where relatively low capacities are adequate, are not directly applicable for use with today's medium and high seam miners with their standard production capacity of 9.1 - 10.9 mtpm (10 - 12 tpm). Since the late 1960's and early 1970's, several machinery manufacturers, and at least two major coal companies, have devoted considerable expense, time and effort to developing truly successful continuous face haulage for use in coal seams ranging upward from 1.2 m (4') in height. Continuous face haulage equipment has been developed in the last five years employing a variety of transportation media and design concepts, including some which have received wide publicity such as those employing hydraulics, and pleated belt. The truth of the matter is, however, that the only universally applicable and widely successful continuous face haulage equipment introduced to date has been that employing a combination of bridge conveyors and mobile, self-propelled, bridge carriers, connected at the inby end to the tail of the high production continuous miner, and at the outby end attached directly to the panel conveyor (Fig. 1 & Fig. 2) or, on occasion, to a short, self-contained conveyor which, in turn, empties directly onto the panel conveyor. While these bridge type continuous haulage systems are available with both belt and chain conveyor components, the most widely applied and successful system in seams above 1.07 m (42") in height is that offered by The Long-Airdox Company. The standard unit for use with 9.1 - 10.9 mtpm (10 - 12 tpm) continuous miners is normally equipped with belt. However, they have built, and successfully applied, versions of this system employing chain conveyors, (Fig. 3), mainly for operators having extremely difficult mining conditions, including excessive amounts of water

Jan 1, 1977

By John W. Critchfield

This paper presents an overview of some of the basic issues related to tunnel construction in the presence of flammable and toxic strata gases. Gas properties and possible sources are outlined for the various gases that are commonly encountered underground. Assessment of potential gas hazards prior to construction is discussed. Measures for mitigating the problem during construction are summarized. This RETC Session on Gassy Ground has been organized by the Underground Technology Research Council (UTRC), Technical Committee on Gassy Tunnels.

Jan 1, 1985

By Victor Rudenno

Cut-off grade is one of the most critical parameters affecting project cash flow. Its sensitivity is due to the number of other parameters that are correlated with any change in its value. Changes in cut-off grade, average grade and ore tonnage vary and they in turn can affect such parameters as capital and replacement costs, recovery, life of the project and operating costs. Perhaps one of the best definitions of cut-off grade is that of Taylor (1), "... any grade that, for any specific reason, is used to separate two courses of action, e.g. to mine or to leave, to mill or to dump ... . Obviously the most likely specific reason is one governed by economics, involving the return of investment and sufficient profit to motivate development and mining of the deposit. In this paper the cut-off grade is defined as that mining limit which will maximise the economic return for a projected mining venture. The following brief literature survey indicates that when computing the optimum cut-off grade there is a need to be able to directly compute the Discounted Cash Flow Rate of Return (DCFRR) or Net Present Value (NPV), as economically as possible, while allowing for parameter dependencies and variation in project structure.

Jan 1, 1979

By C. V. Deutsch, J. B. Boisvert, M. A. Cuba

The amount of information available for characterizing a deposit increases over time due to the continuous acquisition of data during mining. This additional information is collected from different sources, including geologic mapping, production data and infill drilling. Throughout the lifetime of a mining project, the block model and the mining sequence are periodically updated to account for this new data. In general, the acquisition of additional data increases the accuracy of the block model, reduces uncertainty in ore/waste limits and clarifies the optimal mining sequence. There has been extensive research on mine planning, but current techniques do not consider the decrease in uncertainty as additional information becomes available. Conventional paradigms assume either 1) the kriged model is correct and uncertainty due to multiple realizations does not change the mining sequence, or 2) the mining sequence is unrealistically adapted to each realization. A new paradigm is proposed for evaluating minable reserves of surface mining projects, which accounts for the acquisition of additional information in the design of the long term mine plan. Multiple scenarios characterizing the dynamic nature of mining and data collection are created. In the proposed methodology, the performance of the long-term mine plan depends on both mining and data acquisition strategies. Each scenario considers the same extracted volume for the first period, resulting in a set of scenarios that diverge from a common initial period, accounting for how the mine may develop over time as new data are acquired and provide a more realistic evaluation of reserves with an appropriate level of uncertainty. A synthetic example is presented to illustrate the implementation of the methodology and the benefits over conventional paradigms.

Jan 1, 2013

By J. Patrick Powers

In tunneling through water-bearing formations, the expense of controlling the water can have a major impact on overall project cost. The author has seen the cost of an eight-foot, finished sewer tunnel rise from under $500 per foot to over $1,000 when a water problem, anticipated as modest, became severe. There is need for greater professionalism in the approach to groundwater control. The days of the forked stick should be behind us. The basic technology exists. Its application is not yet widespread. This paper discusses predrainage; that is, the lowering of water in advance of tunnel excavation. Both free air and compressed air tunnels are considered. Examples from recent tunnel projects are described. SPECIAL NATURE OF TUNNEL DEWATERING Tunneling is unlike other excavations below the water table in a number of significant ways. The tunnel excavation is always on the critical path; if production slows or stops, there is no other work for the heading crews, no other work to carry the cost of service crews and job overhead. The dewatering commitment must be made well in advance. Construction of wells, and pumping down take time. After the heading reaches a trouble area, time is not available

Jan 1, 1997

By Bruce K. Cantrell, Stephen W. Stein, Kenneth L. Williams, David Hassel, Harvey Patashnick

In June 1992, the Mine Safety and Health Administration (MSHA) published the 'Report of the Coal Mine Respirable Dust Task Group; Review of the Program to Control Respirable Coal Mine Dust in the United States." As one of its recommendations, the report called for the accelerated development of two mine dust monitors: (1) a fixed-site monitor capable of providing continuous information on dust levels to the miner, mine operator, and to MSHA, if necessary, and (2) a personal sampling device capable of providing both a short-term personal exposure measurement as well as a full-shift measurement. In response to this recommendation, the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Center, initiated the development of a fixed-site machine-mounted continuous respirable dust monitor. The technology chosen for monitor development is the Rupprecht and Patashnick Co., Inc. tapered element oscillating microbalance. Laboratory and in- mine tests have indicated that, with modification, this sensor can meet the humidity and vibration requirements for underground coal mine use. NIOSH is continuing that effort by developing prototypes of a continuous dust monitor based on this technology. These prototypes are being evaluated in underground coal mines as they become available. This effort, conducted as a joint venture with MSHA, is nearing completion with every promise of success. The immediate benefit of this effort will be to researchers, regulatory personnel, and mine personnel, by permitting evaluation of specific mining practices to see which expose mine workers to excessive dust levels. Using this information, mine personnel can optimize mining procedures to reduce dust exposure. MSHA and the operators will also be able to use the dust concentration data to judge whether dust plan parameters are adequate to continuously maintaining environmental dust levels below the applicable standard. The second development recommended by the Dust Task Group was a person-wearable version of the continuous dust monitor. It will be a monitoring system designed to provide a measurement of worker exposure to respirable dust, both during and at the end of the shift.

Jan 1, 1997

By Amri Priambodo, Ian Leslie, Valérie Laflèche, Agustina Ratnaningrum, Robin Paine, Andrianus Sinaga, Willem de Beer

Freeport Indonesia consists of surface, civil and underground mining areas exposed to numerous geotechnical risks and hazards. PTFI uses various monitoring systems (Micro-Seismic, Firefly Light System, Mira Geoscience machine learning, etc.) to effectively manage these risks. The significant volumes of data from these sensors must be integrated into actionable information to provide the expected risk management. This occurs at the GeoEngineering Integrated Monitoring Centre (GIMC), a centralized department within the GeoEngineering Division, tasked with the responsibility to manage all geotechnical monitoring systems. The main hazard the GIMC is responsible for managing in real time is mine seismicity within the underground mining areas and the potential impacts on safe operations. Seismic system engineers achieve this objective through 24 hours a day and seven days a week operations of the GIMC, providing a centralized point of communication, alerts, evacuations and control during seismic events and emergencies. This paper will describe how the GIMC achieves its goal using reliable procedures and strategies based on detailed Triggered Action Response Plan (TARP), concise communications, novel technologies (FireFly Lighting System), and proven seismic re-entry programs to manage risk within the underground mining operations. The integration of geotechnical monitoring and reporting into a centralized group has improved the effectiveness and management of seismic risks and hazards at PT Freeport Indonesia (PTFI) mining operations.

Apr 26, 2022

Small-scale flotation tests have been conducted to examine the effect of froth stability on the column flotation of finely pulverized coal. The results of this study demonstrate that the upgrading of coal in a column flotation cell can be significantly improved when froth stability is properly controlled through the manipulation of appropriate operating variables. Several important correlations have been established from the test data. These relationships should prove useful for the design and ore ration of column flotation cells for fine coal processing.

Jan 1, 1991

By Robert L. Russell

Production at Freeport Indonesia's Ertsberg open pit copper-gold mine started in 1972 at a rate of 7.5 kt/d (8270 stpd). Mill throughput remained at that rate for several years until the discovery of the Ertsberg East (GBT) ore body. This discovery prompted three succes¬sive expansion stages from 1981 to 1988 that boosted production to 20 kt/d (22,000 stpd). In 1988, the discovery of the huge Grasberg porphyry copper deposit launched an era of much larger expansions. The first of these was the installation of a fourth primary mill in 1989 that increased throughput to 32 kt/d (35,270 stpd). That was followed by an expansion of the crushing and screening plant and in 1991 the addition of a new south concentrator to bring production to 57 kt/d (62,830 stpd). The addition of a primary ball mill and the changeout of the original Denver flotation cells in 1993 brought production to its current level of 66 kt/d (72,750 stpd).

Jan 1, 1994

By N. K. Davé

Water quality impacts of shallow water submersion of partially weathered and oxidized waste rock containing reactive sulphide minerals were investigated in laboratory column lysimeter studies. The waste rock investigated was highly reactive, contained oxidation reaction products from previous exposure and weathering, and had a low sulphur content of approximately 2 % S, mostly as pyrite. The submerged waste rock, though previously weathered, had high oxygen consumption, resulting in rapid depletion of dissolved oxygen in its pore water, within a shallow depth of ~2?5 cm from the surface. The surface and pore water qualities of the submerged waste rock were significantly impacted by the dissolution and release of previous-oxidation-reaction products, which contributed to their rapid acidification and having increased concentrations of dissolved SO4, Fe total and other metals: Al, Mn, Ca, Cu, Ni, Zn and Pb. Despite the high porosity and permeability of the waste rock, the diffusion controlled mass transfer from the submerged waste rock to the overlying water cover was relatively low for most ionic species. Additional surface oxidation of the sub-merged, partially weathered waste rock was on-going, but its impact on the overall surface water quality was low and masked by the dissolution and release of previous oxidation reaction products to both surface and pore water regimes.

Jan 1, 2006

By Ingo Ossenbühl, Wolfgang Dolsak, Vojtech Gall, Axel G. Nitschke

"Yielding support systems for application in underground construction have a long history, primarily in mining. Typical examples are tunnels subject to loading conditions that lead to overstressing of the newly installed support or existing tunnel structures in active fault zones. Recent applications for tunnel rehabilitation projects unveiled the capabilities and flexibility of combined yielding support systems presented in this paper. Frequently, the main requirements for tunnel rehabilitation applications are a fast, safe, and simple installation along with the need for flexibility with regards to existing tunnel geometries. A combined support system consisting of steel sets with yielding connections and special groutable hoses has proven to be an efficient support measure providing a multitude of advantages compared to conventional rehabilitation approaches. The presented yielding support system provides an immediate and active support, while it allows for controlled yielding upon experiencing loads beyond its support capacity. INTRODUCTION The excavation of underground spaces leads to redistribution in the existing stress regime. This load redistribution goes along with deformations in the surrounding rock mass. Magnitude and duration of these deformations depend on the tunnel’s depth and geological conditions, but also on the installed support system. Modern civil tunneling infrastructure has generally an envisioned service life of about 120 years. Conventional tunneling provides typically a dual support system, split into the initial (or primary) and final (or secondary) lining. A typical design principle in civil tunneling is to let the vast majority of deformations acting on the initial lining cease, before the final lining is installed. Based on this approach, the loading on the final lining is significantly reduced and signs of overstressing, such as cracking of the lining, are typically limited to the initial lining. However, special cases in swelling and squeezing ground require different approaches, including yielding support systems."

Jan 1, 2016

By H. Braun, T. Kind, K. Gloe, D. B. Dreisinger, H. Stephan, O. Heitzsch, G. A. Kordosky

Municipal garbage incineration processes with coupled wet flue gas cleaning systems generate effluents containing toxic heavy metals such as mercury, zinc, cadmium and copper. The separation of these metal ions from the obtained scrubbing solutions is possible using liquid-liquid extraction. Extraction studies has been performed both with commercial extractants Aliquat 336, di(2-ethylhexyl) phosphoric acid and novel chelating agents as acyl thiourea and lipophilic oxathiaaza alkanes. Advantages and disadvantages of the investigated extraction systems are discussed. The paper reports on the basic research as well as on the testing in a laboratory scale.

Jan 1, 1993

By K. A. Natarajan, Namita Deo

The interaction of Bacillus polymyxa and minerals such as hematite, corundum and quartz resulted in significant surface chemical changes, both on the cell surfaces and on the interacted oxide minerals. After such treatment, quartz was rendered relatively more hydrophobic, while hematite and corundum were rendered more hydrophilic. Biopretreatment was observed to be beneficial in the separation of silica from hematite and alumina by both selective flocculation and flotation. The possible role of bacterial adhesion and metabilites in the biobeneficiation process is illustrated.

Jan 1, 1998

By David E. Thompson, Wesley E. Stimpson

The Massachusetts Bay Transportation Authority (MBTA) Red Line Extension Northwest is currently in the early stages of construction. The 3.1 mile extension of the Red Line from the existing Harvard Square Station in Cambridge, Massachusetts to Alewife Brook Parkway in Cambridge, Massachusetts will include a large, near surface hard rock, rapid transit station chamber at Porter Square in Cambridge (Figure 1). [ ]

Jan 1, 1979

By Brij M. Moudgil

Flotation was introduced in phosphate rock processing in the late twenties and since then it has been an important part of the concentration process. More than two thirds of the rock produced in Florida is upgraded by the flotation process. Since no crushing or milling steps are involved in the material preparation, the flotation plant feed is coarser than in most other mineral flotation systems. During hydraulic processing of the rock, particles in the size range of -14, +150 mesh constitute the flotation feed. This size fraction is further classified by hydraulic sizers, stationary screens and vibrating screens into a coarse (-14, +35 mesh) and a fine (-35, +150 mesh) flotation feed. The flotation techniques for concentrating the fine feed as practiced by the Florida Phosphate producers have been standardized over the years, however, methods for upgrading the coarse feed differ from plant to plant. In this paper an effort has been made to present relative merits of the techniques employed for concentrating the coarse phosphate rock..

Jan 1, 1977

By John Clarke Holman

Industrial growth and survival in today's competitive world means both economic efficiency and technological superiority. Superior technology includes not only exploiting the best methodologies and techniques presently available, but also a continuous search for and development of, better ones. In practical terms this translates into an investment of substantial sums of money. Of course, even a relatively small investment will not be justified if the fruits of the project cannot be secured to the investor and the inventor alike. There are at least three ways to protect new or improved technology. If the improvement reaches the height of an invention, "patenting" usually is the preferred mode of protection. If, however, the improvement is novel and valuable but does not satisfy the requirements of the patent laws, one may then consider "trade secret" agreements as a means of obtaining appropriate return for the investment made so long as the improvement is capable of being maintained in secret and cannot be "reverse engineered." If one develops a new and useful organism and seeks immediate protection from infringers, current thinking is that the copyright law may afford such protection simply by publishing the genetic code. Here is one instance where you may publish without perishing! This paper will endeavor to highlight the pros and cons of various legal mechanisms and their applicability to the frontiers of technology.

Jan 1, 1985

By R. W. Mossman, George E. Heim

Seismic exploration techniques offer the engineer and geologist a way of obtaining detailed information on the physical parameters and geometry of the rocks where extensive underground excavation or tunneling is proposed. Use of the seismic method can provide a greater amount of detailed information at relatively less cost than can be obtained by any other known subsurface exploration method. Boreholes are still required for calibration of the seismic data but at a much wider geographic spacing than otherwise would be needed for subsurface mapping. The seismic data can define with precision the actual location of zones of flexure or fracture of the rocks and reveal the configuration of the surface of the rock layers. ENGINEERING PROBLEMS One of the major requirements in the planning of subsurface installations is that of locating tunnels and other underground openings in favorable rock units. Such rock units should exhibit uniformity of composition, both vertically and horizontally, to minimize variation in excavation techniques. The depth and thickness of the unit must be known: a 30-foot diameter tunnel cannot be contained in a 25-foot thick limestone. The rock unit needs to be as free as possible from structural defects and should be suited to efficient excavation procedures. If liquid conduits are planned, the slope of the rock unit needs to be known so that maximum advantage can be taken of gravity flow with the tunnels wholly contained within the unit.

Jan 1, 1997

By Karin Bäppler

"When considering large-scale infrastructure projects worldwide special attention has to be paid to the large diameter tunnel construction projects that were successfully completed in the Southern Hemisphere. The projects that are highlighted in this paper are large-scale infrastructure projects in the sector of transport. In focus are four road tunnel projects that were constructed in Australia and New Zealand using mechanized tunnelling technology. The tunnel boring machines (TBMs) that were reliably applied to these four major projects all exceed the bore diameter of 12 meters. These TBMs are therefore in the range of large to very large diameter TBMs. The technology used demonstrates state of the art technology with tailored tunnelling technology adapted to the specific project demands. Two Double Shielded Hard Rock TBMs (Ø 12.35 meters) were used for the construction of the Clem Jones Tunnel in Brisbane crossing beneath the Brisbane River and these two machines have been reused for the excavation of a 4.3km long two-lane highway tunnel for Legacy Way in Brisbane creating a new traffic artery towards the city centre. Two EPB Shields (Ø 12.48 meters) excavated and lined the twin-tube road tunnel for the Brisbane Airport Link. Excavation diameters in excess of 14 meters, such as the Earth Pressure Balance Shield (Ø 14.41 meters) involved in the Waterview Connection Project in New Zealand, are understood in the tunnelling industry as very large diameters. The machine is customized to the requirements and subsurface conditions of Auckland. The paper spotlights the large to very large diameter TBMs that were used and focuses on the comprehensive solutions developed by the machine manufacturer to provide a system with benefits for the contractor especially for the Waterview Project. INTRODUCTION Extensive large-scale road infrastructure projects like the ones implemented in Brisbane (Australia) and currently under construction in Auckland (New Zealand) show the tendency of today’s infrastructure construction projects. Functional infrastructures need to be put in place to cope with the demand of mobility and flexibility of people living in cities and metropolises. Impact during construction work to people or environment has to be kept as low as possible to ensure the quality of life is not disrupted."

Jan 1, 2016

By Gunnar Nord, Per-Anders Persson, Duri Prader

The paper gives a short resumé of the findings of the joint US - Swedish "Mechanical Boring (MB) or Drill and Blast Tunneling (DB) ? Workshop" in Stockholm December 1976. New developments and trends in both MB and DB techniques in Europe since 1976 are described, and information is given on some interesting new projects. Differences in contracting principles between the US and Europe lead to different practices for preinvestigations, design, excavation and arbitration and legal affairs. It is shown that this often leads to a higher cost in the US than in Europe for similar excavation jobs. A typical US tunnel job also has more men on the site than a similar job in Europe. This adds to the cost difference and is only partly balanced by a slightly higher rate of excavation in the US. A comparison is made between two quantitative methods of predicting MB penetration rates. These are in reasonable agreement. A probable future development in machine design is an increase in cutter load towards perhaps 25 tons per disc where the tunnel diameter is large enough to house the machine size dictated by the size of the very large electric motors required. Recent European developments in drill and blast technique include improved methods for cautious blasting, precision hydraulic drilling of small diameter holes, and non-electric interval blasting techniques. These developments still keep the drill and blast method ahead of mechanical boring costwise for tunnels in igneous rock whereas for most sedimentary materials mechanical boring has a lead, particularly for long tunnels.

Jan 1, 1979

The estimation of local recoveries, such as the local recovered tonnage of ore and its corresponding grade at a given cutoff grade, is an important problem in a selective mining operation. Multigaussian kriging provides a simple solution to this specific problem. The solution is also complete in the sense that local recoveries are estimated together with their estimation variances. It is thus possible to assess confidence limit intervals on the estimated recoveries. Multigaussian kriging has been applied to the Jerritt Canyon deposit in a most realistic situation. The various steps of the estimation procedure are presented in detail and the potential of the method is demonstrated in view of the results. The obtained results show that the estimated recoveries are in good agreement with the actual recoveries and the actual estimation errors are correctly predicted by the estimation variances. Multigaussian kriging thus appears as a useful and fully operationable tool for the mining industry.

Jan 1, 1986