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By Dean Brox

Tunnel boring machines (TBMs) have been used for the construction of various tunnels for mining projects for the purpose of access, conveyance of ore and waste, drainage, exploration, water supply and water diversion. Several mining projects have seen the successful and economic beneficial use of TBMs, and there is an increasing awareness of the benefits of TBMs for mining projects. Key technical considerations for the use of TBMs for the construction of tunnels for mining projects include geological issues (rock type, rock alteration, rock strength, rock abrasivity, durability, ground water in flows), depth of cover and the potential for overstressing/rockbursts, site access and terrain, portal locations, TBM constraints, minimum tunnel size, tunnel support requirements, contractor and labor experience, and project schedule demands. TBMs offer key project schedule benefits with high rates of progress, which is a unique economic advantage recognized for mining projects where timing is of the essence in order to advance mining development and achieve early startup for operations. A thorough evaluation of the anticipated ground conditions should be performed as part of the decision to adopt a TBM for a mining project. Minimum specifications for TBMs are necessary in order to prevent the incorrect type of TBM from being used. Appropriate geotechnical investigations are necessary in order to provide key information on the anticipated subsurface conditions for careful planning and design of the proposed tunnel alignment. The overall site and geological conditions associated with some projects may suggest that it is not appropriate to use TBMs for some mining projects due to a perceived higher risk. Key words: TBM, Tunnel boring machines, Tunneling in mining

Feb 1, 2014

By Dean Brox

Tunnel boring machines (TBMs) have been used for the construction of various tunnels for mining projects for the purpose of access, conveyance of ore and waste, drainage, exploration, water supply and water diversion. Several mining projects have seen the successful and economic beneficial use of TBMs, and there is an increasing awareness of the benefits of TBMs for mining projects. Key technical considerations for the use of TBMs for the construction of tunnels for mining projects include geological issues (rock type, rock alteration, rock strength, rock abrasivity, durability, ground water inflows), depth of cover and the potential for overstressing/rockbursts, site access and terrain, portal locations, TBM constraints, minimum tunnel size, tunnel support requirements, contractor and labor experience, and project schedule demands. TBMs offer key project schedule benefits with high rates of progress, which is a unique economic advantage recognized for mining projects where timing is of the essence in order to advance mining development and achieve early startup for operations. A thorough evaluation of the anticipated ground conditions should be performed as part of the decision to adopt a TBM for a mining project. Minimum specifications for TBMs are necessary in order to prevent the incorrect type of TBM from being used. Appropriate geotechnical investigations are necessary in order to provide key information on the anticipated subsurface conditions for careful planning and design of the proposed tunnel alignment. The overall site and geological conditions associated with some projects may suggest that it is not appropriate to use TBMs for some mining projects due to a perceived higher risk.

Jan 1, 2013

By O. Konovalov, M. Zhuravkov

In report the results of performance of research works on building up of the connected geoecological and geomechanical monitoring system for modelling and study of a state of mining massif in a region with large-scale underground mining works are discussed. The connected geoecological monitoring requires radical change of methodology of carried out works. To carry out modelling and researches it is impossible without construction of the integrated connected information model of region. Basis of construction of information systems and databases for all sections of Earth Sciences is the set of the approaches, among which, for example, methods of remote sounding, GIS- and GPS-technology etc. Computer technologies are basis on the "supercomputer" technology. The results of performance of some researches for regions of excavation of deposits of potash salts in Russia and Belarus are presented.

Jan 1, 2005

By M. A. Trevits, G. L. Finfinger

Various methods have been developed through US Bureau of Mines research to remove gas in advance of, during, and subsequent to mining. These include drilling horizontal or cross-measure boreholes from a mine opening, and vertical boreholes stimulated for drainage in advance of mining or for gob gas drainage. Techniques and equipment now exist that allow drilling a borehole at any angle to the vertical, and even along an arc. Stimulation treatments have also been developed that provide for increased gas production capability. This paper describes the long-term production history of five select gas drainage installations. The Bureau of Mines conducted or participated in four studies. The remaining study was conducted by the Equitable Gas Co. Principles of storage, release, and migration of coal bed gases The amount of gas contained within any given area of a coalbed depends on the coal's inherent storage capacity and the physical conditions of the coalbed. The gas storage capacity of coal is primarily a function of rank. As such, it cannot be affected by the presence of drainage holes (Kim, 1977). Certain physical conditions of the coalbed can, however, be changed that will affect the release and migration of gas. By pumping water out of the coalbed through the vertical boreholes, two important changes occur - pressure is reduced and water saturation is lowered. Reducing reservoir pressure releases gas as the coalbed adjusts and equilibrates gas to the change. Increasingly large amounts of gas are released for each incremental decrease in pressure. Lowering the water saturation level raises the permeability of the coalbed to gas and allows the gas to more readily migrate to the wellbore (Kisse and Edwards, 1975). For horizontal boreholes completed near mine openings, the coalbed has already undergone a pressure or water saturation reduction phase. This condition thus allows such boreholes to be highly productive with minimal water production. Case studies of coalbed gas production Pittsburgh Coalbed - Marianna mine 58 A methane drainage study was begun in July 1978 at Bethlehem Mines Corp.'s Marianna mine 58, Marianna, PA (Fig. 1). The work was conducted in a section of the mine that was advanced 1.5 km

Jan 8, 1986

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

By Keith A. Heasley, Lee W. Saperstein

This paper investigates the use of backfill zones and yielding pillars for subsidence control. The investigation begins by choosing an appropriate subsidence predictive technique to simulate the proposed subsidence-control schemes. Two case studies are performed in order to delineate the accuracy and utlility of the chosen predictive technique and then the results of these case studies are used to establish appropriate sets of regional site parameters. Next, a detailed analysis of the major variables affecting the outcome of the subsidence-control simulations is conducted and graphical displays of the exact sensitivity of the surface subsidence to these variables are given. Finally, alterations to the surface subsidence that are expected from using two major subsidence-control techniques are presented. The first technique to be assessed is a backfilled pillar centered longitudinally in a panel. With this arrangement, a minimal amount of backfill material can produce substantial decreases in vertical displacements. The second technique to be assessed is the use of yielding gate pillars to reduce the sinuosity of the transverse subsidence over adjacent panels. With proper design, this technique can greatly curtail surface strains and help minimize remedial drainage control.

Jan 1, 1986

By A. B. Cecala

Enclosed cabs have been used for many years to isolate workers on mobile equipment in the mining industry for health and safety reasons. These enclosed cabs create a microenvironment for workers where they can be either more protected or more vulnerable to contaminants. Over the past decade, the National Institute for Occupational Safety and Health (NIOSH) has performed substantial research efforts to improve the air quality inside enclosed cabs of both underground and surface mobile mining equipment. In these efforts, NIOSH has partnered with mining companies, original equipment manufacturers (OEMs), and manufacturers of filtrations and pressurizations systems in a synergistic effort to reduce respirable dust and improve the air quality inside these enclosed cabs. Various field studies over this time have shown an array of results ranging from very minor to very significant reductions (protection factor: 3 ? 89) in respirable dust levels inside these enclosed cabs. In addition to and concurrent to the field work, NIOSH also performed a comprehensive laboratory study to evaluate all the factors involved in cab filtration and pressurization systems and identified those factors that were most significant for an effective system. From this comprehensive research effort, the key components for an effective filtration and pressurization system have been identified in an effort to provide the best air quality, thus minimizing the respirable dust exposure, to equipment operators inside of enclosed cabs of mobile mining equipment.

Feb 27, 2013

By V. McLemore, A. Fakhimi, K. Donahue, D. Sweeney, V. Viterbo

In order to evaluate the relationships between weathering and durability and strength of rock samples from the Goathill North rock pile at the Molycorp Questa mine, NM, we conducted slake durability and point load tests. Slake durability index (ID2) values ranged from 84 to 98%. Point load strength index (Is50) averaged for all rock units ranged from 1.1 to 5.7 MPa. Results show a slight positive trend between ID2 and paste pH. Two populations of data are distinguishable when ID2 is plotted versus the percentages of chlorite, illite and internal friction angle. In general, Is50 values increase toward the interior of the rock pile. Preliminary conclusions indicate that the durability and strength of the rock pile material generally increase toward the interior of the rock pile. Pre-rock pile alteration and post-rock pile weathering history have affected the durability of the GHN rock pile samples.

Jan 1, 2007

By J. Olsson

Introduction Stainless steel has by tradition been a common construction material for hydrometallurgy processes and the most common grades can be found amongst the ASTM 300-series, i.e. austenitic grades of type 304L, 316L and 317L. However, there are a number of new grades available today, which imply more cost effective solutions for those designing plants where good resistance to acids, containing the desired metal ions, often contaminated with chlorides and other halides, is the key issue. There are austenitic-ferritic or duplex grades having the same or even better corrosion resistance than the austenitic grades and approximately twice the strength, which enables design in thinner gauges, which in turn implies less weight and less cost. They have also excellent engineering properties, enabling fabrication of process equipment, machinery and different types of tanks. On top of that, they contain less nickel and molybdenum than their austenitic counterparts, which implies not only lower cost for alloying elements, but also a more stable price when considering the price fluctuations for these alloying elements during the last years. This paper describes briefly the family of duplex stainless steel and it presents a number of relevant corrosion tests where duplex grades have been compared with austenitic grades. The results have in several cases been verified by in-plant exposures in zinc and copper production plants. It also describes applications and experience of duplex grades within a variety of hydrometallurgy plants. Installations of highly alloyed austenitic grades will be described as well. The corrosion tests and service experience reported cover hydrometallurgical processes based on sulphuric acid.

Jan 1, 2007

By Jafar Khademi Hamidi

The Zagros long tunnel is one of the main components of Sirvan water transfer project in western Iran. It is approximately 48 km in length and consisted of two lots. The second 26 km lot of this tunnel is under construction by a 6.73 m diameter double shield (DS) TBM. The tunnel passes through several formations with wide range rock mass qualities. During the tunnel alignment, changes in rock quality were highly frequent from poor to very good. The encountered geological conditions required TBM operation to change frequently from hard rock to soft, dry to flowing, sticky to nonsticky ground (and vice versa), more often than expected. In the course of tunneling, the machine has encountered nearly many adverse geologic conditions. The most important problems have been sudden high volume water inflow into the tunnel, sticky ground, and gas seepage, all of which resulted in reduced TBM advance rates. This study will high-light two difficult ground conditions including large water ingress and sticky ground and also the related problems encountered by the TBM along 8 km of excavated tunnel. In sticky grounds, cleaning of the clogged cutter head caused many delays and contributed to additional downtime. Application of some operational modifications, including decreased TBM thrust showed satisfactory results in such cases. While reduced thrust resulted in reduced penetration rate, but the overall TBM advance was greatly improved by the increase utilization rate and elimination of down time related to cleaning of the head. To cope with high water inflow, application of preventive measures such as pre-grouting has proved to be a more efficientsolution. The sealing of ground water inflow also decreased seepage of dangerous H2S gas and other chemicals such as hydrocarbons accompanying the groundwater.

By William R. Yernberg

The combined 76th Annual Minnesota Section of SME meeting and 64th Annual University of Minnesota Mining Symposium were held April 8and 9, 2003, in Duluth, MN. This year’s theme was “Stakeholders, Partners in Change.” The meeting included four keynote speakers, technical presentations and a tradeshow. Engineers, executives, mining managers and suppliers from throughout the United States and eastern Canada attended the meeting. Reflecting the theme of the meeting, all agreed that the mine owners, the government, the community and the employees are all “stakeholders.” They must be “partners in change” for the iron ore mining industry to survive in the region. Compared with past meetings, where improved technology was the primary focus, this year the focus was on the dramatic restructuring of the entire industry. As noted by several of the speakers, “This time, the change is not in technology.”

Jan 1, 2003

By Hiroshi Yamazaki

The paper describes prediction, control and validation of face pressures, and special TBM features for the bored tunnels of the New Metro Rail City Project, Perth, Australia. The selected EPB-TBM passed below a heritage bridge and the operational Perth Railway station in ground conditions consisting of fully saturated uniform sand combined with shallow overburden and a horizontal alignment radius of only 135m. Therefore, strict control of volume loss, TBM operations and ground movements was vital requiring continuous evaluation and adjustments to TBM operation parameters. The paper discusses the effectiveness of applied TBM face pressures and the used foam/polymer soil conditioning which was measured against achieved volume loss and the predicted range of ground settlements.

By B. Burke, R. Colquhoun, K. Thomas, R. Walton, D. Fentie

The new Roasting Facility at Barrick’s Goldstrike Mine in Nevada, U.S.A. was developed to process 12,000 tons per day of refractory gold ore. The process consists of crushing, dry grinding, roasting, extensive gas purification, calcine quenching and leaching in the presence of activated carbon. The new plant is integrated into the existing Goldstrike facility, treating ore from both open pit and underground sources. The process design, procurement, construction and commissioning of the Roaster facility was performed successfully over a 3½ year period with peaks of 400 engineering personnel and 950 construction personnel supporting the project. The US$330,000,000 project was completed ahead of schedule and under budget. The commissioning was well planned and proceeded smoothly through a rapid start-up to achieve all primary goals within three months of the start of processing of ore.

Jan 1, 2001

By J. O. Marsden

Parts I and II in this series of papers presented the chemistry of medium-temperature pressure leaching of copper sulfide concentrates and reviewed the metallurgical development of a process to effectively recover copper using medium-temperature pressure leaching and direct electrowinning (DEW). Key features of the process were the use of superfine grinding of the concentrate (to a P98 of 12 to 15 µm and P80 of 6 to 7 µm), pressure leaching at 160ºC and 1,380 kPa (200 psi) oxygen overpressure, DEW to produce LME Grade A cathode, recycling of the lean electrolyte to the pressure leaching step and treatment of a lean electrolyte bleed by solution extraction (SX). Recycling of the lean electrolyte provided all of the acid required to effectively dissolve copper and convert approximately 65% to 70% of the sulfide sulfur to elemental sulfur, resulting in an ?acid-autogenous? process referred to as the ?MT-DEW-SX? process. This paper (Part III) discusses the steps taken to develop and complete a large-scale demonstration of the process at Bagdad, Arizona, in 2005.

Jan 1, 2007

By Charles W. Axten

Since the mid-1970s, samples of airborne and waterborne fibrous particulates have been collected in the area of the Northshore Taconite Ore Processing Facility by the Minnesota Department of Health (MDH), the Minnesota Pollution Control Agency (PCA), and the University of Minnesota. Indirect sample preparation has consistently been used although other aspects of the sampling methods and sites have varied and analytical procedures were altered over time as more accurate and precise microscopy methods were developed (i.e., phase contrast optical microscopy, transmission electron microscopy, transmission electron microscopy with energy dispersive spectroscopy). In the mid-1970s, levels of airborne fibrous particulate in the Silver Bay area averaged from 0.00030 to 0.03 f/ml. This level was significantly greater than levels of similar particulates in the St. Paul, MN area, although two of the Silver Bay sampling sites, considered individually, did not indicate levels of fibrous particulate markedly different than that seen in St. Paul. More recent sampling data (i.e., 1990?2001) indicate mean concentration of airborne fibrous particulates (amphibole-like fibrous particulates) of 0.0020 f/ml with a range of values from 0.0001 to 0.0140 f/ml. Such levels are not significantly different from those seen in other non-urban environments in the US and Europe. Concentrations of fibrous particulates in water samples were higher in the mid-1970 when iron ore tailings were being deposited in Lake Superior, but since the tailings have been deposited on land waterborne levels of fibrous particulate in the Beaver River have remained relatively constant averaging in the range of 7.5 MFL. This level is only slightly in excess of the current EPA drinking water standard for fibrous particulates. Review and consideration of this data is important in determining the potential health risks associated with airborne and waterborne fibrous particulates in the areas of the Northshore Taconite Ore Processing Facility. © 2007 Elsevier Inc. All rights reserved. Keywords: Taconite; Asbestos; Asbestiform fibers; Fibrous particulates; Cleavage fragments; Phase contrast optical microscopy; Transmission electron microscopy

Jan 1, 2007

By H. Sis, D. Dahlin, S. Chander, C. Summers

Bench-scale selective-flocculation tests were conducted on samples of Florida and Western phosphate process tailings. Physical, mineralogical, and surface characteristics were determined for both types of samples. The flocculation tests investigated dispersant and flocculant types and doses, pH, and slurry percent solids, while other parameters were held constant. Where selectivity was achieved, phosphate minerals remained dispersed, whereas silicate minerals flocculated and settled. In single-stage tests, flocculants having low to medium anionic character effectively upgraded products at moderately elevated pH. Multiple-stage tests, and tests in which flocculants of lower molecular weight were used as site-blockers, gave improved results.

Jan 1, 2002

The largest investment in mining equipment in Caterpillar?s history ? The F series mechanical and electrical drive trucks ? is rapidly advancing. Caterpillar showcased the 793F and 797F mechanical drive trucks and the 795F ac electric drive truck at MinExpo in 2008 and have continued testing since then. The 793F and the 797F have accumulated more than 75,000 hours of field testing and have proven their performance capabilities and their durability. The new Cat C175 engine that powers them has racked up 130,000 hours of field testing in mining trucks and more than 120,000 hours in power systems. Because of the success of these field-follow programs, the 793F is targeted to go into full production within a few months and the 797F late this year. Caterpillar engineers have been testing two 795F ac prototypes at the Tucson Proving Grounds in Arizona. The development program has provided input for the construction of a new 795F ac in Decatur, IL. The new truck recently shipped to a copper mine in North America where it will serve as the first field-follow 795F ac as it works at the mine. The 313-t- (345-st-) capacity 795F ac will enter a new size class for Caterpillar, and, as a result, the primary focus of the Caterpillar ac electric program has been on the 795F ac. The commercial launch date will be defined as the field-follow program progresses. ?It?s fitting that soon after producing the 50,000th Cat off-highway truck, we are now shipping our first ultra-class ac electric drive truck to a mine,? said Chris Curfman, president of Caterpillar Global Mining. ?Our new trucks further solidify our position as the one manufacturer to provide unparalleled options and unmatched customer support.?

Jan 1, 2009

The Functional Performance Equation for ball milling circuits provides plant staff with a new means to improve circuit performance. However, successful execution of a plant project, with verifiable circuit processing performance improvements, requires a significant number of accompanying steps beyond the equation alone. In order to identify and articulate all these steps, a study with plant staff from two milling operations and a grinding media supplier was undertaken. ?Task analysis? of improving plant grinding performance was carried out. This analysis called for the development of a number of system components, and ultimately yielded a ?Plant Grinding Circuit Processing Performance Management/Improvement System.?

Feb 23, 2014

In the dimension stone industry, workers in processing shops may be exposed to harmful levels of respirable silica dust when conducting the different tasks in stone preparation, which include cutting, grinding, polishing, and thermaling. To protect workers from this health hazard, operators sometimes ventilate processing shops using fan-powered dust collectors to capture and filter dust. To investigate this issue, NIOSH, Pittsburgh Research Laboratory, in cooperation with a dimension stone operation, upgraded an off-the-shelf dust collector the operator was utilizing in a polishing/cutting shop. Initial dust surveys showed that the unit was under-designed for the amount of dust being generated in the shop. The objective of the research was to cost-effectively increase the air cleaning volume and improve dust capture efficiency of the unit with a larger motor and blower. The unit?s original stock 0.56 kw motor and blower was replaced with a 2.24 kw motor and matching blower to increase airflow. The unit was evaluated both in the laboratory and the shop before and after the retrofit to determine the improvement of the upgrade. The study showed that the 2.24 kw upgrade improved the performance over the original 0.56 kw motor resulting in more dust being cleaned from the ambient air in the shop. The 2.24 kw unit cleaned 19% more air and captured 32% more respirable dust than the 0.56 kw unit.

Jan 1, 2009

By J. P. Rider

The number of extended cut mining systems has increased significantly in coal mines over the last decade, and there is a constant push to extend the face ventilation systems to even greater setback distances. The need to maintain airflow at setback distances of 12.2 m (40 ft) and beyond requires that methods for delivering intake air to the face be improved, or alternative ventilation techniques be implemented. The emphasis of this research effort was to examine various techniques to improve the distribution of available air at the mining face in order to reduce face methane levels. A study was conducted comparing the performance of a jet fan, used in conjunction with a machine mounted scrubber, with blowing curtain ventilation in a 27.5 m (90 ft) heading. In addition, a second study was performed on blowing curtain systems examining how scrubber flow, intake air velocity, and curtain setback influence face methane concentrations. Results showed that when the heading advances to a depth of 27.5 m (90 ft) blowing curtain systems were more efficient at diluting face methane levels when compared to a jet fan. Also, increases in scrubber flows and curtain velocity resulted in lower face methane concentrations for blowing curtain systems at 9.2 and 15.2 m (30 and 50 ft) setbacks.

Feb 24, 1997