Search Documents

By G. T. Krempasky

In an attempt to develop a suitable precast concrete support for underground use, two different models (1955 and 1958) of a five-piece concrete set were designed, fabricated, and tested under adverse loading conditions. Model 1955 was designed to withstand an ultimate, uniformly distributed, vertical load equivalent to what a three-piece, 12- by 12-inch wood set of intermediate-grade Douglas fir would withstand. A design figure of 138,000 pounds for the vertical load was used on both the 1955 and 1958 models. In addition, the 1958 model was designed to withstand a uniform horizontal load of 7,000 pounds per foot and additional concentrated-point loading. The step- by-step design of each model is presented in the appendixes. A series of five destruction tests was conducted underground on the 1955 model, and results of the tests showed that the type and method of blocking were of major significance.

Jan 1, 1963

By Mauricio Terceros, Martin Achmus, Freddy Lopez

The massive use of deep foundations had a remarkable influence in the building industry in the 20th century. Piles and micropiles made possible to erect thousands of civil structures around the world, changing quintessentially the urban and rural landscapes. Especially in urban areas, the ongoing development requires not only new infrastructure, but also to increase the capacity and/or to extend the serviceability of existing structures (buildings, bridges, etc.). Factors such as the change of use of existing facilities or the requirement to comply with updated building regulations confront Civil Engineers with the question, whether to tear down and build new structures, or to reinforce the existing structures from their foundations. Micropiling has enabled designers to come up with technical feasible solutions to retrofit the existing deep foundations, making the structural reinforcement a real option, even under considerable changes in the loading conditions. The following article presents an overview of an intervention project, where micropiles were designed to reinforce the original pile foundation of an existing building, enabling it to be reused with a different structural function. This paper will focus mainly on the analysis of the interaction between the existing piles and the reinforcing micropiles, especially in terms of settlements’ compatibility. Finally, the adopted solution, with its correspondent design considerations and execution process will be presented.

Jan 1, 2018

By Derek J. Penrice

The Caltrain Downtown Extension (DTX) project will extend commuter and future statewide high-speed rail service into the Transbay Transit Center, which will be located in the business district in downtown San Francisco. The DTX project includes 1.5 miles of underground construction, comprising complex sections of mined and cut-and-cover tunnel. As part of the DTX preliminary engineering process, development of appropriate contracting practices, including contract packaging, procurement methods and contract terms for the underground construction, has been initiated. This paper provides a summary of the evaluations undertaken, preliminary conclusions reached, and proposed next steps to promote industry interest and maximize bid competition.

By D. L. Soreck

The hazards to the public posed by abandoned mine shafts are well documented. As private development encroaches on previously mined areas, the potential for fatalities and serious injuries from abandoned mine shafts increases. The U.S. Bureau of Mines has conducted research into cellular concrete as a material for sealing these openings. The current work involves testing the characteristics of cellular concrete before and after it had been pumped or dropped from different heights into a simulated mine shaft. Cellular concrete was pumped vertically up to and subsequently dropped from heights of 18 and 37 m into concrete forms. Wet density measurements were made at multiple sampling points in the test circuit. Air content determinations and uniaxial compressive strength testing were conducted. Research results showed significant loss in air content and changes in the characteristics of cellular concrete during pumping or dropping from various heights. Recommendations on effective use of cellular concrete for sealing abandoned mine shafts are made.

Jan 1, 2010

By Rafael Utsch Braga

Neste trabalho foi analisada a influência da microestrutura de diferentes composições químicas de aço de alta resistência (HSS, do inglês High Strength Steel) na resistência à corrosão sob tensão assistida por sulfetos (SSC, do inglês Sulfide Stress Corrosion). Quatro aços ao boro com quantidades variáveis de V e Ti foram tratados termicamente para atingir propriedades mecânicas de aços de alta resistência. A resistência à corrosão do material foi avaliada de acordo com a norma NACE-TM0177 Método D, utilizando corpos de prova do tipo DCB. A microestrutura dos aços foi caracterizada utilizando microscopia eletrônica de varredura (MEV) através da análise de réplicas de carbono, por meio das quais foram determinados o tamanho e a distribuição dos precipitados, cuja composição química foi avaliada através de espectroscopia por dispersão de energia (EDS). Foi observada uma influência do teor de V, sendo o acréscimo de V favorável ao aumento da resistência à corrosão. O aumento do tamanho médio de precipitados de CrMo através do coalescimento dos mesmos também mostrou-se eficaz para melhorar a resistência a corrosão sob tensão em meio contendo H2S. As propriedades mecânicas e o tamanho de grão foram também avaliados, no entanto sem encontrar correlação com a resistência a corrosão sob tensão.

Aug 7, 2018

By M Cooper

Since its enactment in 1991, the Resource Management Act (RMA) has generated both praise and criticism. The major criticism is in relation to the costs the Act poses to industry and the time it takes to work through the process. In response to such criticisms the Minister for the Environment has initiated a review of the implementation of the RMA. The Minister's proposals for reform have not yet been released and the discussion that follows is based upon the report by the Minister's Review Group which was released in September.

Jan 1, 1998

By Forrest T. Moyer

The overall injury experience, excluding officeworkers, at metal mines and mills during the period 1961-63, reported by operators, was 174 fatal and 11,357 nonfatal disabling work injuries during an aggregate worktime of 451 million man-hours. These injuries occurred at a frequency rate of 25.55 per million man-hours, comprising 0.39 for the fatal and 25.17 for the nonfatal injuries. The combined severity rate of the disabilities was 3,779 days lost or charged per million man- hours, consisting of 2,314 for the fatal and 1,465 for the nonfatal injuries. The average severity of all disabilities during 1961-63, was 148 days per injury. The number of days lost and/or charged, ex- cluding officeworkers, at metal mines and mills during the period 1961-63, was 1,440,000 days charged to fatal injuries and 661,290 days lost from nonfatal injuries. An average of 70,966 men were at work daily. The outstanding cause for fatal injuries was the fall of rock or ore from the back, while most of the nonfatal injuries were caused by handling materials, slips or falls of persons, machinery, falls of rock or ore from back and side, and haulage. Injury experience at primary nonferrous smelters, refineries, and reduction plants during 1961-63, excluding officeworkers, was 23 fatal and 3,214 nonfatal disabling injuries during a total work- time of 277 million man-hours. The injuries occurred at frequency rates of 0.08 per million man-hours for the fatalities and 11.61 for the nonfatal disabilities. The severity rate for all injuries of 1,085 days lost or charged per million man-hours comprised 498 for fatal and 587 for nonfatal injuries. The number of days lost, excluding officeworkers, at primary nonferrous smelters, refineries, and reduction plants during 1961-63 was 138,000 from fatal injuries and 162,385 from nonfatal injuries, An average of 34,938 men were at work daily an active plant days during the three year period. The injury experience for officeworkers at metal mines and mills during the period 1961-63 was 20 nonfatal disabling work injuries, (there were no fatal injuries reported), during an aggregate work-time of 28,694,244 man-hours. These injuries occurred at a frequency rate of 0.70 per million man-hours. There were no fatal injuries reported for officeworkers at non-ferrous smelters, refineries, and reduction plants during 1961-63, but seven nonfatal injuries were reported during an aggregate work-time of 30,814,772 man-hours. The frequency rate for these injuries was 0.23 per million man-hours for this period.

Jan 1, 1967

By Gene Mattila, Ron Boyd

Introduction Rock bolting is a general term that encompasses pinning, roof bolting, rib bolting, and cable bolting. Rock bolting contributes the highest nonproductive cost and is the most significant safety risk in mining today. Total installed bolt costs are now more than $20 per bolt. Rebolting or repair work doubles this. And bolting accidents account for about 30% of all fatal and nonfatal lost time accidents. It is only logical, then, for the mine operator to install the highest quality anchors possible. Every bolt on the market - tensioned, untensioned, full contact, or point anchor - has designed capabilities in axial, shear, and fluctuating ground conditions. Bolts will provide a designed support if material specifications and installation procedures fall within the manufacturer's recommendations. This also assumes that there are no unexpected geological or operational changes. Proper material specifications and installation procedures should guarantee the mine operator a quality anchor. To help assure this, the Mine Safety and Health Administration (MSHA), the US Bureau of Mines (USBM), and the AMC Manufacturers group developed stringent ASTM materials standards. These govern mechanical point anchor bolts and bolts using threaded and nonthreaded rebar. There are also minimum standards that suppliers must comply with in the manufacture of frictional bolts. However, most frictional bolt standards are based on the manufacturer's own specifications. It would be impossible to set uniform regulations on frictional bolts. Each bolt provides support in a slightly different manner and thereby requires different material needs. Quality Control In any case, material quality can generally be assured through tight order specifications and periodic quality control checks. The problem with installing quality anchors does not solely lie with the material. It includes all the events that occur from the time a bolt leaves a manufacturer to the time it is installed. The anchoring ability of any major type bolt can be affected by transportation, storage, mechanical performance of installation equipment, installation demands of the operator, proper drilling accessories, and local geology. Table 1 and Fig. 1 document the negative events that can affect each bolt and the degree to which it can be affected. Drilling a hole of oversized diameter, for example, is an operator controlled factor. It will adversely affect most bolts. An over-sized diameter reduces, or even eliminates, the anchorage capability of a mechanical shell. It will reduce the support capacity of a split set to nearly nothing. And it will cause a partial or incomplete grouting around the resin bolt. Frequently, due to bit wear, holes are drilled undersized in diameter and may not be properly cleaned out. In this case, it will be difficult for the operator to push the mechanical shell into the hole, thereby causing him to drill another hole. In cases where the bolt is obviously not providing anchorage, operators will probably drill another hole and place another bolt. Rock Bolt Regulations It is the situations where a bolt is improperly installed in the hole, but gives the appearance of a good bolt, that are frightening. In fact, some safety officials and engineers believe that only 50% to 60% of installed bolts are working. These bolts cause irregular ground load transfers in other bolts and overload them. This causes hazardous situations and overstressing. It is these bolts that fail prematurely 200 to 255 mm (8 to 10 in.) behind the face and possibly contribute to the high accident rate. The government and several manufacturers recognized the need to check the integrity of rock bolts. These programs are in different stages today. Tight torque regulations have been established for mechanical

Jan 4, 1985

By Richard H. Mote, W. C. Schroeder

The endlessly changing pattern of mineral supply and demand offers opportunity to the alert and can bring disaster to the unwary. The discovery of ore bodies, the invention of extractive processes, the provision of new transport facilities, the political stabilization of underdeveloped areas, and many other changes can increase supply dramatically. Such new outpourings of mineral wealth from ore bodies bring fortunes to their developers, and consumers frequently find their competitive positions decidedly improved by new and cheap sources of supply. On the other hand, operators of marginal properties can find competition from newly opened high-grade mines intolerable. Consumers that have depended on the products of nearby, high-cost mines may find new, remote, low-cost supplies advantageous only to their competitors. The invention of new prospecting methods can have spectacular effects. Shortly after World War I the discovery rate of petroleum pools began to decline. The leading prospecting technique of that day, the projection downward of surface reflections of geologic structure, was proving less rewarding. Prophets foretold an oil shortage in the near future. But at that very moment scientists were perfecting the application of seismic waves to reveal underground oil-bearing geologic structures. As these geophysical methods were put into commercial use the whole outlook changed-the problem of the 1930's became how to cope with the surplus from discovery, not how to meet the ever rising demand. Many lead mines were being abandoned as unprofitable about this same time because the penalties charged by smelters for the zinc in the ores and concentrates more than counterbalanced the payments for lead and silver. Then selective flotation (at the time called differential flotation) appeared,

Jan 1, 1959

By Greg J. Hasenfus, Allison M. Haines, Joshua M. Silvis

The floodable volume of longwall gob can be of great importance in developing accurate coal mine operation plans, particularly for mine water management and environmental control strategies. Given the inaccessibility and difficulty in direct measurement of gob characteristics following gob recompression, hydrologic, geomechanical, and spatial data and principles were used to solve for the porosity and height of the residual gob using a mathematical model framework and bulking-based techniques. Based on this approach, gob porosity of Appalachian longwalls appears to be tighter than previously reported, ranging between 4.99 and 14.31%. Residual gob height, as normalized with respect to mine extraction height, ranges between 1.90 and 2.45. A novel, bedding-based bulking approach is ampliative with respect to existing roof caving and bulking fundamentals, as it has greater explanatory value compared with the traditional, lithologic-based bulking application. The efficacy of using the residual gob characteristics determined by the mathematical model and bedding-based bulking is examined using a causal comparative method, whereby time series prediction of historical groundwater rebound is compared with observed mine pool elevation data. Prediction accuracy is significantly improved using a prototype model to calculate void volume of longwall gob, specifically, the dependence of porosity of the gob material upon the longwall width to overburden depth ratio for movement basins of subcritical and critical panel widths. The potential implication of these findings toward hydrologic, geomechanical, and ventilation studies of longwall gob could be significant.

Aug 13, 2021

By P M. Hetherington, F A. Pym, M P. Murphy, K E. Crook

Consultants in the mining industry have the opportunity to visit interesting deposits all over the world. Each deposit has its own set of challenges to face when it comes to defining and understanding the deposit geology and the economics to make it viable for extraction. Some of the challenges can include appropriate data capture, sampling techniques, structural characteristics, geochemistry, geophysics, lithology definition, and economic boundaries. It is essential that the practices used at each deposit (eg drilling, sampling, geological modelling, resource estimation etc) are documented and the results obtained are robust and defensible. The Competent Person is not always aware of instances where their resource estimation practices have not been substantiated. ‘You don’t know what you don’t know’ is a phrase frequently used during a mineral resource audit. Technical work to substantiate drilling, sampling, density, assaying, geological modelling and estimation processes is not always completed. Audited Competent Persons often comment: • ‘I was unaware that this was required.’ • ‘I have not had training in this area and do not know how to complete the checks required.’ • ‘This is how we’ve always done it.’ Examples of audits where it was found that geological practices were not substantiated are examined here. A discussion is included on why substantiation of these practices is important, and potential reasons as to why there are instances of unsubstantiated processes and practices are discussed.

Mar 22, 2022

By Steven Norris, William Moler, Michael Cole, Patrick Doig, Debi Lewis, Craig Pyle, Matthew Crow

The recently completed Lower Northwest Interceptor Program (LNWI) in Sacramento, California comprises, ten pairs of micro tunnels totaling 4,369 m (14,417 ft),three horizontal directionally drilled bores totaling 956 m (3,154 ft), and two large diameter tunnels under the Sacramento River totaling 1,198 m (3,953 ft). This paper briefly summarizes surface and subsurface conditions, and planning and design considerations. It then goes on to describe problems encounterd with each trenchless crossing, as well as lessons learned with respect to shaft construction, ground control at shafts during tunnel break-in and break-out, frac-out and heave, settlement, obstructions, coordination with permitting agencies, and application of geotechnical baseline reports.

Jan 1, 2007

By G. R. McMeekin

"THE TOPIC suggested for my contribution to this Symposium was ""Lead-Zinc Smelting - 40 Years of Pollution Control"". The history of the development of smelting industry at Trail and the control of sulphur dioxide could make quite an interesting historical study. However, in the field of environmental control, the public is not particularly interested in what you did yesterday, but rather what you are doing today and what you are planning to do tomorrow. I can't fault this approach, but because there are some subject lessons that history can demonstrate, I would like to tell enough of the story (under three headings) to bring a focus on matters of contemporary concern in regard to public relations and ecology. The three general headings suggested are: (1) time before the capture of by-product sulphur; (2) the capture of sulphur; and (3) the ecological and public relations conclusions from these."

Jan 1, 1972

By Mohammad R. Jafari

The Camp Dresser & McKee (CDM) has been retained by the Sacramento Regional County Sanitation District (SRCSD) to design the Mather Interceptor, a portion of the South Interceptor and Mather Interceptor program. The Mather Interceptor consists of 14,667 feet of 54 to 72 inch gravity interceptor. Approximately 90 percent of the alignment will be constructed via tunneling. Cobbles and boulders in a sand/gravel matrix dominate the ground conditions combined with seasonal perched groundwater table at some of the deeper reaches of the alignment, impacting design consideration. This paper will present the results of a comprehensive geotechnical investigation conducted for this project and in-depth technical evaluation of various trenchless techniques feasible for tunneling in the cobble and boulder laden formations of this project. This paper will also present the risks and issues of the design alternatives and selection criteria.

By K. Hanumantha Rao, A. Nayak, K. S. Narasimhan, S. N. Mahapatra

B.A. Hancock It is not at all surprising that causticized potato and potato derived amylopectin starch solutions performed much better than their parent starches. Some preparation is required to rupture the starch granules to effect the polymeric adsorption and interparticle bridging necessary for selective flocculation. In laboratory work comparing the deslime performance of causticized and autoclave cooked laboratory corn starch solution preparations, it was found that higher deslime weight rejections, with attendant proportionally greater iron unit losses, occurred with the causticized starch. These results may be specific to the ore involved but they do suggest that cooking and causticizing cause different starch granule rupture and/or starch breakdown, which have an effect on desliming response. I calculated from the data in the article that the slimes product grades were high - 24.3% and 20.3% Fe when 53.7% and 54.5% Fe concentrate products were obtained, respectively, in Table 4, and 21% Fe with a 62.6% Fe concentrate in Table 5 - using the natural tailings sample, which had a head of 34.3% Fe. It may be advisable for the authors to consider different starch preparations in future investigations. The combination of upgrading and selectivity results presented in Table 4 are not as good as the authors suggest. The authors' claim that a system has been developed to produce saleable concentrates from the Kudremukh tailings is quite disconcerting. There are many hurdles yet to be crossed before commercial application of selective flocculation becomes possible because differences between the very small-scale laboratory tests conducted and commercial application are rather large. Among the many differences are varying circuit feed grades that will occur from use of tailings, the apparent face that much lower tailings grades will be encountered in practice (it is much easier to achieve a high concentrate grade with reasonable recoveries using 34.3% Fe tailings as in the study rather than 25.3% Fe tailings grades that the plant apparently averages), the hydraulic nature of the thickeners used in operations compared to the static system used in laboratory tests, the different size distributions that will be obtained from a plant closed grinding-classification circuit, and differences in water used in a plant operation and the laboratory. The authors wrote that it was necessary to overgrind to be sure that the coarse gangue would not settle with the iron oxide floccules. This situation is likely to be exaggerated in commercial operations where it is assumed cyclones would be used for classification. Because cyclone classification is greatly influenced by particle densities, there will probably be an even greater difference in size between the iron and gangue particles in the plant, which would make the gangue slightly coarser still in relation to the iron. This would make the selective flocculation-desliming separations using the procedure employed by the authors even more difficult and, using the dispersant system the authors employed, greater overgrinding would be required. To grind finer to minimize the coarse gangue in the flocculated iron oxides is quite inefficient and appears not to broach the problem. The actual problem appears to be insufficient dispersion of the ground pulp. In this situation, addition of a dispersant would likely be required to attain a sufficiently high pulp dispersion level to efficiently effect a selective flocculation-desliming separation. Although the very coarse particles would still have a tendency to settle with the floccules, it probably would be found unnecessary to overgrind as much as indicated. Use of an optimum combination of dispersant and pH modifying reagents may also significantly improve the selectivity of desliming. Additionally, although it is possible that sufficient dispersion may be obtained by pH control alone in some situations, it is quite probable that added dispersity was obtained in the reported work from using distilled water. It is research experience that distilled water enhances dispersion. In commercial operations it may not be expected that sufficient dispersion will be obtained by pH control alone, unless the water used in the process is by nature quite dispersive. Overall, a change in the Kudremukh tailings dispersant scheme appears necessary where a dispersant is used in conjunction with a pH modifying reagent. With this change, different dispersion-flocculation responses will result that would have to be further evaluated. Therefore, it is still an open question whether an efficient and effective selective flocculation separation using Kudremukh tailings may be obtained that will produce saleable concentrates.

Jan 9, 1986

By J-P Franzidis

A study was undertaken to determine the effect of five industrial frothers on the relationship between entrainment recovery and water recovery. The experiments were conducted using a Batequip rectangular 60 liter steel cell which was run in parallel with the first cell in a copper/silver prefloat rougher circuit. The concentration of the frothers ranged from 2.5 g/ton to 8.4 g/ton. The experiments were repeated at three different froth depths. A power function was found to fit this relationship with no discontinuity in the relationship caused by the changes in frother type and concentration and froth depth.

Jan 1, 2000

Mineral Resource Throughput Management is based on the extraction of the maximum potential value from an ore reserve with the emphasis to generate maximum ROI and ROR (return on reserve). A steel producing company in India implemented MRTM to significantly improve their ROI and ROR. The value chain of this company consists of their own iron ore and coal mines, ore washing plants, sinter plants, steel plants, and sales and marketing division. The target for the mines was to produce at a stable and predictable rate and at specific quality requirements. These requirements were set to improve productivity and ROI of the steel plant. The implementation constituted the alignment of the reserve potential, total production chain, human resources and management culture at the mines with the requirements of the steel plant. Many typical mining practices were challenged and changed. Production targets regarding lump vs. fines ratio, consistent product tons, quality targets such as Fe, Al content and moist, and standard deviation on the quality targets were not achieved. A reverse distribution model with release mechanisms to satisfy the demand were developed and implemented at the mines. A stable and predictable flow of mine product with quality standards well within the required standard deviation targets were achieved. The contribution from the mines to significantly improve the Net Profit, ROI and ROR of the company were reached.

Jan 1, 2007

By K Cameron, S Strohmayr, J Wallace

In 2012, a single module heavy medium cyclone plant (HMP) was installed at the Glencore Zinc’s (then Xstrata Zinc) McArthur River lead zinc mine. The HMP formed the first part of the MRM Phase 3 Project to increase run of mine (ROM) capacity from 2.4 to 5.5 Mt/a.The purpose of the HMP is to remove liberated gangue from the crusher product at minimal loss of valuable mineral. The McArthur ores are very finely disseminated requiring a fine primary grind size prior to rougher flotation. Rejecting waste prior to grinding therefore offers significant power and grinding media savings. The plant was designed to treat only those ores with a reasonable upgrade ratio at the target zinc recovery across the HMP of 95%.On this basis, a 1.8 Mt/a single module plant was built based on 250 t/h feed rate and 82% availability. In contrast to existing base metal heavy medium plants in Australia, the MRM Flow sheet utilised the principles in modern coal heavy medium cyclone plant design. Since commissioning, the plant feed rate has been significantly increased and is now normally operated up to 540 t/h (dry basis).Although this throughput increase is partially due to debottlenecking work, it is also attributable to the conservative design parameters for base metal heavy medium cyclone circuits in comparison to those used in equivalent coal circuits.This paper discusses Flow sheet design and compares traditional base metal design parameters with those achieved at MRM and those of modern coal plants. It provides information on plant capital and operating costs and the net savings realised by its installation. In addition to power and grinding cost savings, the paper also highlights the savings in water through rejection of near dry waste and reduction of tailings pumped to the storage dam.CITATION:Wallace, J, Strohmayr, S and Cameron, K, 2015. McArthur River Mine heavy medium plant – the benefits of applying modern coal plant design principles to base metal heavy medium separation, in Proceedings MetPlant 2015, pp 311–323 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

The increased focus on best practice environmental management has led to mining and mineral processing companies developing a variety of procedures to ensure that the environmental impacts of their operations are minimised, and that company managements are fully aware of these impacts and the policies and procedures established to ensure this process. Parallel to this, international standards for the development and implementation of environmental management systems are being promoted as necessary for companies to demonstrate their due diligence. Good environmental management systems should be built upon the systems already established within companies, and should ensure that the process of continual improvement is integral to their operation. An outline of the basic components of environmental management systems is provided, along with examples of the way various mining companies have implemented such systems. The benefits of best practice environmental management to mining companies are also considered.

Jan 1, 1995

Flawed mining studies have been major contributors to poor investment decisions in mining for many years, contributing to the long period of poor industry profitability. Most of the major mining houses have now adopted quite formal processes and quality standards for mining studies to reduce the potential for poor investment decisions in the future. Other organisations such as the World Bank also have specific requirements for particular types of studies, such as bankable studies. This increasing requirement for rigour and discipline means a highly structured and phased sequence of studies is now required along with the development and adoption of industry-wide standards in mine ventilation studies. New terms in the study process such as ?independent peer review? and ?hold and review? are assisting in this process. More traditional terms such as ?feasibility study? and ?pre-feasibility study? now have much more precise technical definitions. Specific standards for the ventilation components of the various phases of a mining study are proposed in this paper.

Jan 1, 2009