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By Steven W. Hunt

Appropriate seals, portal ground improvement, and compatible shaft construction techniques are vital elements for launching and receiving tunnels effectively in urban areas where adjacent property requires protection from excess ground movements. This paper focuses on seals and ground improvement along with shaft wall types, required to launch or receive tunnel boring machines within wet, permeable ground at the portal zone. The paper also discusses probing to verify suitability before the tunnel eye is cut. Methods addressed include: rubber gasket seals; soft eyes; double walls; top hats for reception; and, portal zone ground improvement (permeation grouting, jet grouting, un-reinforced slurry diaphragm wall panels, ground freezing, deep soil mixing, dewatering, and over-excavation and backfilling). This paper focuses on challenges with launch and reception of pressurized-face TBMs with precast concrete segment linings. Challenges related to pipe jacking are discussed in a separate paper titled ?Mitigating Microtunnel Launch and Reception Challenges? (Hunt and Finney 2008).

Jan 1, 2008

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

The price of copper has gone into the tank. So has gold. Environmental regulations are more restrictive. Global warming has world leaders and environmental groups seeking international regulations to keep the planet from heating up - mostly by restricting the use of fossil fuels. And the US Secretary of the Interior wants to make it more costly -prohibitively so for smaller companies - to mine hard rock metals in the United States. By rights, miners should be carrying around a pessimistic attitude about their industry. But miners are an optimistic lot, always believing that things will improve. That optimism was in evidence in Tucson, AZ in early December, when about 620 miners met at the Double- tree Hotel for the Annual Meeting of the Arizona Conference, put on by SME. Attendees listened as a United States congressman commented on the recent tax cut bill, mining regulations and the continuing need for the mining industry to improve its image in the eyes of the general public. Session speakers discussed how improved technology has made their processing operations at Sierrita and Morenci more efficient and cost-effective.

Jan 1, 1998

By A. W. Dickerson

Following on from many years of research aimed at improving the effectiveness of truck haulage operations in mines operated by BHP Minerals, BHP Research developed a concept for an Innovative Large Mining Truck, (ILMT) which has the potential to significantly improve the cost effectiveness of rear dump mining trucks. The ILMT concept reduces the empty vehicle weight dramatically, greatly reduces unequal rear tyre loading and improves ride and handling characteristics. The concept has been taken to the "proof of concept" prototype truck stage with the cooperative efforts of BHP Coal, BHP Research, Liebherr Mining Truck, Inc., Liebherr-Australia and Birrana Engineering. Testing of the prototype truck commenced at a coal mine in Queensland, Australia during May 1996. Preliminary results from the testing program are very encouraging. Expectations are being met and in some cases exceeded.

Jan 1, 1997

Continued market pressure on the US coal industry was the overriding factor affecting developments in underground mining in 1986. An oversupply of coal in the spot market kept prices low throughout the year and caused a number of operations to close their doors. Operators stepped up their efforts to improve productivity at existing operations. They made technology advances and improved their relations with employees. A continuing market-related development during 1986 was the divesting of coal properties and operations by major oil companies, which were faced with economic pressures in both the oil and coal industries. Further increases in contract mining production resulted as some larger operators were unable to compete in a tough economic environment. Longwall mining is still seen by many as the technology that will provide the necessary productivity to remain cost-effective. But the number of active faces in the US declined in 1986, as reserves were depleted and economics forced some closures. At the first Longwall USA meeting in June, much attention was placed on improved technology, as electro-hydraulic controls for roof supports gained acceptance. Other recent developments include shearer initiation of roof supports, automatic horizon control for shearer drums, and collection and storage of machine data for predicting maintenance requirements. The government and academic communities continued their research on dust control at longwall faces. Jankowski, Kissel, and Daniel, (October 1986, Mining Engineering), gave an overview of progress in longwall dust control. And Mukherjee, Singh and Jayarman (November 1986, Mining Engineering), recommended design guidelines for improving water spray systems for dust control. Surface subsidence Increasing attention is being given to surface subsidence. This is primarily because of longwall mining and the Surface Mining Control and Reclamation Act. Improved methods of prediction of surface subsidence, especially computerized methods, are being continually developed. Mining engineering faculty at major universities such as Virginia are helping develop public policy and regulations concerning subsidence. As part of this effort, Unrug and Johnson identified major subsidence areas of Western Kentucky. Peng and Chen (February 1986, Mining Engineering), gave an overview of history and research of surface subsidence. And Elifrits and Aughenbaugh, (February 1986, Mining Engineering), discussed effects of moisture variations and overburden on subsidence. This research culminated in a Symposium on Surface Subsi¬dence at the SME 1986 Fall Meeting in St. Louis and the 2nd Workshop on Surface Subsidence at West Virginia University. Ground control in coal mining continued to be an item of major research interest. Some 30 papers were presented at the 5th International Conference on Ground Control in Mining at West Virginia University. And six sessions were related to coal mining at the 27th US Symposium on Rock Mechanics at the University of Alabama. At the 4th Annual Workshop, Generic Mineral Technology Center, Mine Systems Design and Ground Control emphasized efforts of the participating universities to improve ground control. Peng and Chiang summarized results of studying support capacity and roof behavior with longwall shield supports. And Unrug, Johnson, and Nandy analyzed the process of deterioration of shale roof in a case study of a room-and-pillar coal mine. The importance of geologic conditions in determining mining productivity is receiving increased attention in coal mine design in the US. Mullenex related, through case studies, the benefits to be derived through analyzing the depositional system of coalbeds as an integral part of mine design. Improved technology in this area was related by Lloyd, Semborski, and Stolarczyk. They discussed a case study of using radio imaging to indicate coal-seam discontinuities in advance of mining. Improved coal mining technology in general is being researched more heavily, to help improve US coal competitiveness. However, much of this research and development process has yet to be widely implemented. Equipment manufacturers are devoting more resources to development of continuous-haulage systems, mobile roof-supports, mine-monitoring systems, and predictive-maintenance systems using computers to extract machine data.

Jan 5, 1987

By Joachim H. Schubert, David G. Hulbert, Ian K. Craig, Roger G. D. Henning

This paper presents a stabilizing controller for flotation plants which uses a quasi-multivariable technique. The controller monitors all the levels in the plant, and by anticipating interactions between various parts of the plant, is able to stabilize the plant far more successfully than the normal plant control. Once stabilizing control has been achieved, optimization of the process becomes easier and more sustainable. An estimate of the improvement in metallurgical performance is made and a singular value analysis was conducted to verify that the multivariable algorithm will theoretically control better than a collection of individual PID loops. Metallurgical results are presented to show that the improvements are attainable in practice. Control by the Mintek algorithm was alternated with normal plant control, to show that the improvements are statistically significant.

Jan 1, 1995

By G. Deschênes

Following a successful investigation on the Central Zone sample, a cyanidation study was conducted on an ore sample from the AD-MW Zone of Clarence Stream Property, owned by Freewest Resources Canada, to develop a leaching strategy to extract gold. At a grade of 6.48 g/t, gold is present in the forms of aurostibite, free gold and electrum. The ore contains 4.3% berthierite/gudmundite, 1.3% pyrrhotite, 0.7% pyrite, 0.07% stibnite and 0.9% arsenopyrite. Similar to the Central Zone, the extraction of gold from the AD-MW Zone can be performed at atmospheric pressure, pH 10.5 and with a low concentration of cyanide. The grind size had no effect on gold extraction between a P80 of 28 to 71 µm. The oxygen and cyanide requirement significantly increased with a ?ner grind. Consequently, a very close control of cyanide addition is required to minimize passivation of gold. Lead nitrate, added in the pretreatment, increased the extraction of gold by 2.3%. Leaching at pH < 10 improved gold extraction but increased the cyanide consumption by 5%. Passivation of gold occurred when the pretreatment was longer than 2 hours. A longer pretreatment reduced the cyanide consumption by 5%. Mineralogical characterization of the leach residue with no gravity pretreatment prior to leaching indicated the presence of unleached gold grains and passivated gold grains. Removal of coarse gold by gravity increased the extraction by 2.8% (leach residue at 0.74 g/t Au). Increasing the DO to 16 ppm or the lead nitrate from 500 to 1,000 g/t increased the overall gold extraction to 90.4% (leach residue at 0.62 g/t), which is the maximum gold extraction obtained. The leaching parameters were 800 ppm NaCN, DO 16 ppm and pH 10.5 for a duration of 120 hours. The associated cyanide consumption was 4.0 kg/t. Gold leaching was not sensitive to cyanide concentration. Reducing the cyanide concentration to 250 ppm resulted in a gold extraction of 89.5% with a cyanide consumption of 2.6 kg/t.

Jan 1, 2009

By John A. Herbst

In recent years, diminishing supplies of high grade ores and increasing consumption of mineral and metal products have demanded high efficiencies in extraction processes. The rising cost of energy has influenced plant operating policies. Rather than merely processing as much ore as possible, other process factors are being considered in process analysis, with energy consumed per ton of product produced taking on increased importance. Alternate processes and more efficient plant design may satisfy part of the demand placed on the mineral processing industries. However it is expected that the improvement of existing operatives will be responsible for most of the gains in efficiency in the short term. Even slight improvements in process efficiency lead to significant cost saving. Grinding, for example, is an inherently energy-intensive process. Grinding circuit capital and operating costs are high and it is essential that circuits run as efficiently as possible. In flotation plants, low-grade ores demand optimum recovery of valuables to maintain overall metallurgical efficiency. The use of modern data, treatment methods and systems analysis provide the means to achieve many goals, previously beyond reach. The design of more efficient plants and the evaluation and. improvement of existing plant operations constitute the general area of process analysis. Process analysis can be used to identify the capacity available in a process unit in some cases. In other cases, the goal may be to investigate alternative equipment configurations for an existing plant for possible improvement in efficiency. This goal is virtually impossible to achieve using plant data alone. A simulator of the process units involved can provide an excellent basis for performing the required process analysis.

Jan 1, 1979

By N. O. Lotter

The reliability of a set of flotation results is key to minimizing project risk, either at the commissioning of a concentrator or at the point of implementing an improvement to an existing concentrator operation. High-confidence flotation testing (HCFT) was developed for this purpose and is part of the list of technologies at various scales used by Xstrata Process Support (XPS) in addressing these projects. The methodology is based on two principles: one, to ensure that the ore sample is representative and has been well-blended and subsampled; two, to perform the flotation tests in sufficient numbers of replicates with appropriate quality controls, so as to improve the reproducibility of the test data. Across ten years of research on this methodology at Xstrata Process Support, Sudbury, several improvements to the HCFT method and complementary connections between sampling and quantitative mineralogy have been developed. Two case studies are reviewed. These show the capability of this system in both optimizing an existing concentrator operation and in serving a new mine scenario. Further work to improve the efficiency of this procedure has been identified. Key words: Flotation testing, Flotation

Jan 1, 2010

By J. W. Walkiewicz

The U.S. Bureau of Mines has conducted studies using microwave energy to stress-crack iron ores. In a microwave chamber which simulates a continuous throughput operation, the Bond grindability of a taconite sample was improved by 13 pct at a bulk temperature of 197? C. To further improve the economics of microwave fracturing, higher powers up to 16 kW were used to rapidly heat samples to relatively low temperatures in a continuous belt-fed applicator. A significant enhancement of grindability was obtained with a minus 1.9-cm taconite rod mill feed. At a sample temperature of 130? C, the grindability was improved a maximum of 26.1 pct over the non-microwaved sample.

Jan 1, 1993

By Gerald H. Luttrell, Roe-Hoan Yoon

Flotation columns are becoming increasingly popular due to their ability to improve selectivity and to reduce operating costs. Unfortunately, these advantages are not often realized because of poor operating practices and difficulties associated with design and maintenance. This article provides guidelines for the operation and design of columns. The discussion will focus on designing proper wash water systems for improved selectivity, maximizing throughput by increasing the bubble surface area rate, and minimizing operating and maintenance costs. It is suggested that the design of the air sparging system is the most critical element in column flotation.

Jan 1, 1993

By Jukka Pukkila, Pekka Särkkä

Intensive co-operation between mining industry and mining machine manufacturers during an eight year program Intelligent Mine™ led to a new concept for applying automation technology in mining to improve the productivity and safety of mines. &apos;The results of the program are now implemented in several mines in Finland and with similar ideas as well elsewhere in the world. The degree of optimal automation of an intelligent mine depends on several technical and economical factors. The basic precondition for the approach is a clear improvement in total economy of the mine.

Jan 1, 2002

By Ronald O. Harma

Iron ore pellets made from concentrates produced from low grade iron ores are the primary iron bearing feedstock for iron making in North American blast furnaces. Steelmakers are demanding increasingly higher quality to provide for improved blast furnace productivity, efficiency, product quality and environmental compliance. Unfortunately, this higher quality iron ore product must be produced from the vast deposits of low grade iron ores that are becoming increasingly poorer in quality with regard to mineral liberation and ease of concentration. Since some of these low grade iron ores require grinding to as fine as 90% -500 mesh (25 microns) for liberation and since more of the silicious gangue and other minor undesirable constituents must be removed to provide the higher quality, we have come to depend on flotation to do the added work. Flotation technology and other preflotation unit operations must improve to meet these increasing demands. In many cases, flotation equipment, reagents and circuit operating performance have improved little during the last two to three decades. Mechanical flotation cells have grown from 14 cubic meters (500 cubic feet) to over 84 cubic meters (3000 cubic feet) to help reduce capital and operating costs; however, flotation metallurgical performance has not improved, Column flotation has only recently shown promise in improving metallurgical performance for iron ore rougher flotation. Previous column flotation success was mainly in scavenger and cleaner flotation steps for treating minerals other than iron ore. Although some new flotation chemicals have been developed for removal of silica and other minor constituents under widely varying mineralogical scenarios, recovery of iron mineral has not improved. The operation and control of flotation circuits have become more challenging because of the increasing workload on flotation. Better sensing, process control and operation of flotation circuits are essential as we go forward. Iron ore upgrading by flotation can be classified into either anionic or cationic methods. Anionic flotation of either iron oxide or silicious gangue is accomplished by collector type, pH control and selective chemical activation . Similarly, cationic flotation of silica or iron oxides is accomplished by collector type, activation and/or pH control. Removal of other minor constituents is achieved by using specialty chemicals under controlled conditions for preflotation, co-flotation or post flotation steps. Generally, anionic flotation is used for floating cleanly liberating crystalline oxidized iron ores such as hematite, specularite and martite. Earthy and hydrated oxides such as hematite and geothite can be upgraded with either anionic or cationic collectors after controlled dispersion of slimes or prior removal of slimes. Anionic flotation of silicious waste can be achieved by calcium activation of silica. For magnetic iron ores small amounts of locked silica particles (middlings) can be removed by cationic silica flotation, which is the only method in commercial use in North America today. Historically the efficiency of these iron ore flotation processes has been restricted by the loss of fine iron particles (minus 500 mesh) to the tailings product. New technology is required to overcome this loss and improve overall flotation performance. Development of technology for more selective separation of silica and other minor undesirable constituents from iron ore will provide both quality and cost benefits to the iron and steel producers. Development of future iron ore production in North America will face stiffer technical challenges. These new and undeveloped iron ore deposits are largely oxidized (non-magnetic) and by nature contain more slimes and other undesirable constituents. Unless other new technology evolves, flotation will be the major treatment process required to upgrade these difficult low grade iron ores.

Jan 1, 1993

By A. B. Holland-Batt

Following a relatively static period in the 1960s and 1970s when incremental development rather than innovation was the norm for gravity separation, the last 15 years has seen a number of new developments in this area. The paper briefly reviews the traditional gravity separation techniques and then examines the newer developments such as centrifugal separators. Particular emphasis has been placed on novel devices or improvements that offer either better control or improved performance.

Jan 1, 1998

By Roshan B. Bhappu

Although the economic importance of recovering copper by leaching of mine work dumps from open-pit operations has been realized for some time, serious attempts to understand and to improve such operations through scientific research has been made only in recent years. This progress report covers the results of chemical, physical, and biological studies pertaining to the dump leaching process and discusses salient features and parameters that may be helpful in improving such operations.

Jan 1, 1968

By A. W. Dickerson, G. Hollier, F. A. Bartley

Following on from many years of research aimed at improving the effectiveness of truck haulage operations in mines operated by BHP Minerals, BHP Research developed a concept for an Innovative Large Mining Truck, (ILMT) which has the potential to significantly improve the cost effectiveness of rear dump mining trucks. The ILMT concept reduces the empty vehicle weight dramatically, greatly reduces unequal rear tyre loading and improves ride and handling characteristics. The concept has been taken to the "proof of concept" prototype truck stage with the cooperative efforts of BHP Coal, BHP Research. Liebherr Mining Truck, Inc., Liebherr-Australia and Birrana Engineering. Testing of the prototype truck commenced at a coal mine in Queensland, Australia during May, 1996. Preliminary results from the testing program are very encouraging. Expectations are being met and in some cases exceeded.

Feb 24, 1997

By Robin P. Gardner

The mechanistic approach to comminution consisting of incorporating particulate breakage functions into a suitable population balance equation has been developed by a number of researchers over the past decade or so. (1) To date this approach has been developed and demonstrated primarily for batch-operated, laboratory or small-scale ball mills. However, since industrial mills are mostly quite large and operated in the continuous mode; suitable population balance models and methods for obtaining the necessary breakage and other model parameters must be developed. This paper describes and investigates a radioisotope tracer technique for this purpose, Population balance models previously developed(2,3) are adapted for this study.

Jan 1, 1974

By Albert J. Shohet

The increasing scarcity of bentonite coupled with the potential of improved pellet strength have created a need for understanding the effects of thorough bentonite dispersion in taconite concentrate. It has been known for more than a decade that under certain conditions substantial savings of bentonite are realizable by using thorough mixing of bentonite as compared to poor mixing. Extensive work done by J. O. Zetterstrom l at the Univer¬sity of Minnesota indicated the effect of thorough bentonite mixing in a controlled laboratory testing. Commercial hardware was not available at the time Zetterstrom1 paper was published and not much work was done until R. L. Stone, J. M. Karpinsky2, did work with Muller mixing. Nabush 3 worked with the pugmill principle, and Hoogovens 4 and Robe River 5 used the fluidized bed principle. It was very hard to convince iron ore industries to improve the mixing of Bentonite and taconite for the following reasons: A. The initial capital investment for improved mixing equipment; B. The relatively low bentonite cost a few years back, which was not enough to justify new equip¬ment investment;

Jan 1, 1976

By S. Ersayin

In 1998, the Concentrator Modeling Center was established within the Coleraine Minerals Research Lab to develop models for simulation of iron ore processing plants, and to assist plant operators in improving performance of their aging plants. The short-term objective was to develop necessary models for reliable simulation using conventional techniques, while the long-term objective was set as liberation-based modeling and simulation of these plants. The short-term objective was achieved in 2002, after the development of models for magnetic separators, hydroseparators and fine screens. A project funded the US Department of Energy was carried out to demonstrate the capability in improving iron ore processing at the Mittal plant. As a result of this study, a 10% improvement in throughput at the plant was obtained, and simulation became a desired tool for plant operators. A significant step in the long-term objective was reached in 2005 with the development of a liberation model. This was followed by incorporation of models capable of processing liberation data into the software. By early 2007, the Center had the capability of performing liberation-based simulation of entire plants.

Jan 1, 2008

By L. Gutierrez, S. Gering, C. Calderon-Arteaga

"INTRODUCTION Drill and blast (DnB) represents the most important, and sometimes the most costly processes in a mine.. The cost of drilling and blasting operations greatly contributes to the “high cost trends of the overall mining operations” (Afum B. O. and Temeng V. A. 2015). The use of available information to improve the DnB processes can be the difference between a highly expensive process and an optimized one. Mining operations have access to several types of data sets and key information from a wide variety of different systems. This information is normally used to improve, evaluate and apply processes for drilling and blasting. This may include different types of data from the different stages of the process (before, during, and after the drilling and blasting operations), such as hole locations (planned and actual), penetration rates, drill operators, fragmentation (expected and resulting), explosive (design and usage), geology, vibration, and others. This information can be used on its own or combined for further analysis to reduce costs, improve safety, and evaluate results. Fortunately, due to advances in mining software, drill and blast engineers can exploit this data and create reports to evaluate results and improve the DnB process. However, as users start combining information from multiple datasets and establishing standard operating procedures for reporting this data across multiple sites, it becomes valuable to create auditable, automated, and sustainable processes for handling the information. In many cases the task of aggregating and standardizing the data formats has already been completed and is available to consumers via the Enterprise Data Warehouse (EDW). A data warehouse team extracts data from the source systems and transforms it so that it is meaningful for decision support (Barbara H. Wixom, Hugh J. Watson, 2007). Our initial implementation plan for the DnB solution included using data stored at the sites; however we learned early on in the process that much of the work for aggregating and supplying the required data was already completed. The goal for this case study is two-fold: to show how information can be used to make decisions and improve processes, highlighting the value of using an EDW for managing Drill&Blast information; and to discuss how technical challenges encountered during the implementations were resolved. This paper is targeted at users that want to better manage their DnB data or try to set up standardized workflows for using this information. This case study will discuss the process of implementing a DnB workflow at multiple sites within Freeport McMoRan Inc (FMI) using both data at the sites and information available using the EDW. The paper will begin with an overview of the project. The discussion will then describe how DnB processes were used to set up daily workflows in order to provide information for evaluating process and making decisions. The final section will discuss some of the technical challenges and how they were solved, as well as possible next steps for further improving the workflow."

Jan 1, 2017