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By T. T. Chen

Gold in the Twin Creeks ore is primarily associated with arsenian pyrite. During pressure oxidation, the sulphides are solubilized, but part of the dissolved iron reprecipitates as jarosite and as an iron sulphate-arsenate-phosphate phase. The pressure oxidation products are subjected to cyanide leaching. The cyanide leach residues consist of quartz, gypsum, bassanite, anhydrite, small amounts of jarosite, an iron-sulphate-arsenate-phosphate phase, as well as trace amounts of orthoclase, rutile, pyrite, hematite and monazite; all these particles are dispersed in a fine grained matrix of illite-muscovite. The autoclave leach residues contain a small amount of carbonaceous matter. Many gold grains are detected on the surfaces of the carbon particles, and these gold particles are not leached during cyanidation. The gold particles are typically 0.1-0.2/Lm in size and commonly are embedded in the carbon surface or are coated with a K-AI-Si-S-O phase on the surface of the carbon. The gold grains are consistently associated with elevated CI contents (50-300 ppm Cl). The poor gold cyanide leach recoveries, which initially occurred in the Twin Creek developmental circuit under certain operating conditions, are attributed to the presence of chloride in the feed. This results in the formation of soluble gold chlorocomplexes in the autolcave and the subsequent sequestering of the gold on the surfaces of the carbon particles.

Jan 1, 2000

By Richter, E. Charikinya

"Mineral processing unit models require information on particulate properties such as particle size, solids flowrate and mineralogical composition to model their operations. Process models that describe the separation process can be classified based on the level of information required from the ore, i.e. the feed stream to the separating unit. The most comprehensive level of mineral processing models is the particle-based modelling approach. Particle based modelling describes a modelling approach where mineral composition, mineral liberation and textural information of particles making up the process streams is used in modelling. The advantage of this approach is that all model streams carry particle level information (size, liberation, shape). This information is obtained by applying automated mineralogy techniques such as Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) analysis which provide accurate and detailed information on process stream particle properties. Currently the use of liberation information in modelling and simulation is rare, due to the limited number of separation models that liberation data as input. The objective of this study is to develop a particle based model for a dry magnetic separator, where mineralogical information is used directly to simulate a dry magnetic separator operation. Magnetic separation tests were carried out on high, medium and low grade magnetite ores using a laboratory magnetic separator. Streams from the separator were sampled and sized for chemical and liberation analyses. A sized mass and elemental balance around the magnetic separator was carried out. The elemental assays of each stream were converted to mineral quantities and a sized mineral balance was done. QEMSCAN measured liberation data was reconciled to the mineral balance based on mineral quantities obtained from chemical assays. This was followed by the development of a particle based model that calculates the trajectory of a single particle based on its mineral composition and textural properties. The model was tested on experimental data and was able to predict the effect of variation in process feed stream mineralogical attributes (liberation, grade, particle size) on magnetic separation performance. Results of this study highlight the benefits of the particle based modelling approach. INTRODUCTION The extraction of mineral values from ore requires liberation of the value minerals from the gangue followed by their separation. Liberation is achieved by size reduction operations (Desmond, 2008; Fuerstenau and Abouzeid, 2002). Separation of gangue material from value mineral takes place in various mineral upgrading stages such as classification, magnetic separation and flotation. In these concentration stages value minerals are separated from gangue minerals based on the physical properties of the ore particles making up the feed such as size, liberation, volume of magnetic material and density. The success of separation is related to the liberation of the feed particles, the performance of the separation technology applied, as well as the inherent characteristics of the feed material (Leißner et al., 2013)."

Jan 1, 2018

By Muhammad I. Kabir

A new minitest of in situ uranium leaching processes at reservoir conditions is proposed. The test which consists of a single observation/ production well and two observation wells is designed to permit the evaluation of both restoration and leaching parameters. It is shown that by using a straight forward history matching procedure, sometimes called a type curve analysis, both the rate of leaching and the ultimate uranium recovery can be evaluated based on the results of the test. Type curves are presented for the case in which the reaction rate is kinetically controlled and there are no other minerals competing for oxidant. Other situations can be approached using the same techniques as those presented here.

Jan 1, 1981

By Yotamu Stephen Rainford Hara

"The aim of our work is to investigate a low energy and clean route for the recovery of copper and cobalt from complex sulphide mineral concentrates. The mineral concentrates were roasted in air, in the presence of CaO (MS + CaO + 202 =MO+ CaS04) at temperatures below 973K. The roasted products containing CuO, CoO and Fe203 were carbothermically reduced at 1073K within an hour to preferentially reduce copper and cobalt. The kinetics of reactions were studied using the thermogravimetric technique and by characterisation ofreaction products using the XRDSEM-EDX techniques. The effects of MS:CaO ratio, roasting temperatures and physical nature of the mineral concentrates were analysed. The method for capturing S02 by forming CaS04 was analysed for reuse in the process. The energy balance for the above process is compared with that of conventional continuous smelting/converting process.1.0 IntroductionCopper sulphide mineral concentrates from Zambia contains substantial amouot of cobalt. The cobalt metal content in the concentrates ranges between 0.7 and 2 % weight, which corresponds to 3 and 9 % weight copper, based on the spot price of copper ($7 386/tone) and cobalt ($31 000/tone). Although the traditional approach using a combination of roasting-leaching-electrowining steps can be applied to recover copper and cobalt from sulphide mineral concentrates [1-4], there are two major draw backs of the traditional process: (i) the S02 emitted during roasting is too lean for economical conversion for sulphuric acid manufacture, which causes serious environmental pollution. (ii) silver and gold which are normally present in the sulphide concentrates are lost out [5] because they are not leachable by H2S04 or HCl which are the common leachants. The above two problems have been overcome by adopting flash smelting in which a rich S02 gas above 20% is produced [1, 5] and successfully converted into sulphuric acid. The precious metals tend to partition to blister copper and recovered during refming. However, nearly all cobalt is lost into the slag phase uoder oxidising condition which prevails during flash smelting. It is important to note that the cobalt content in the slag can be up to 2.6 % weight [6]. The recovery of cobalt from the slag is a process which requires huge amouot of energy since the slag is smelted above 1873K [6]. With a view of minimising the amouot of energy and S02 emission during metal recovery, our investigation involves roasting the sulphide concentrates in the presence of lime and reducing the roasted samples with carbon."

Jan 1, 2013

By William R. Opie

Considerable effort by extractive metallurgical research organizations has been devoted recently to developing pollution-free processes for treating copper sulfide concentrates. A number of hydrometallurgical processes are in various stages of development and have been subjected to economic evaluation. Although the hydrometallurgical approaches eliminate SO2 emission problems, they create objectionable effluents and residues, make precious metals recovery complex, and are not very efficient for treating chalcopyrite. Furthermore, they are consumers of considerably more energy than pyrometallurgical processes which produce blister copper that can be electrorefined to commercial grade cathodes. This paper discusses a pyrometallurgical process under development by AMAX Base Metals Research & Development, Inc. (1) The original objectives set for the process development were: 1. Sulfur control of at least 95% with elimination of fugitive emissions. 2. Copper and precious metal recoveries as good as or better than conventional processes. 3. Low capital cost. 4. Competitive operating costs 5. Use of known proven technology where applicable.

Jan 1, 1976

By W. G. Jewitt

YELLOWKNIFE, the most northerly Canadian gold mining district, is once more in the throes of a boom. Touched off by spectacular and well-publicized diamond-drilling results on the property of Giant Yellowknife Gold Mines, Ltd., mining companies and the general public are competing for mining claims and for the shares of companies owning mining claims in the area, with little regard for values. Such a stock-market boom has various unfortunate consequences but undoubtedly one beneficial result is that considerable amounts of money are made available for serious development. The Yellowknife mining area lies on the north shore of Great Slave Lake, in the Northwest Territories, at a latitude of approximately 62°30' north. The topography is a low-relief phase of that usual in the Canadian Laurentian shield. Roughly, one third of the surface is lake-covered, one third muskeg or overburden, and one third is bare

Jan 1, 1944

By Carlo Sampaio, Moacir Veras, Aaron Young, Carlo Petter

"Three major challenges for the mining industry are the minimization of energy use, water consumption and environmental impact. Therefore, any technique that reduces milling waste, decreases water usage and shrinks impact during mine life must be considered a major innovation in mining.To these ends, one of the most impactful developments in mining within the last 10 years has been the expanded use of high technology sensors to create preconcentrations of mine ore (Jönsson, 2014). The most common sensors used are charge-coupled device (CCD) cameras, that allow through a red, green and blue (RGB) coloring system, the separation of minerals with different colors, tones and, in many cases, with differences in brightness.More recently, the development and use of dual energy X-ray transmission (DE-XRT) to enable the separation by atomic density of the constituent minerals within a given rock has become a reality. Within this work, a rapid bibliographical review of the CCD and DE-XRT methods and examples of their usage within mining and the industrial minerals sector are presented.Sensor-based sorting in miningAutomation within mining is one of the industry’s current goals. Sensors of various kinds have been used as steps toward automation in recent years, from improving the safety and productivity of haul trucks through the use of cameras and global positioning satellites (GPS), to the divination of slope failures. Just as with other mining areas, sorting has improved dramatically and made great steps toward automation in recent years (Wotruba et al., 2014).Sensor-based sorting (SBS) uses spectromatic sensors to identify intrinsic characteristics of particles and separates them by either mechanical or pneumatic means into different product streams (Wotruba et al., 2014). SBS can be used with great effectiveness to improve gravimetric beneficiation through the selective separation or preconcentration of run of mine ores (ROM)."

Jan 1, 2015

By George Wolff

To THE average person, the purport of the items and figures on the balance sheet of a mining company are hazy and the real financial condition of the company is cloaked in obscurity. It is also likely that the satisfaction of the stockholder in his investment, as well as the determination of the prospective investor, rests more on the reputation of the company, his confidence in the management, the stated earnings per share and the dividends paid, than on a comprehension of the information contained in the balance sheet. The balance sheet of any company at best can only closely approximate the true financial condition as of a given date. Any item of asset, except cash, can probably be altered if another's viewpoint is applied. It is difficult and expensive to drill and explore an orebody to determine the entire tonnage of ore therein. Those inherent difficulties render it practically impossible to prepare an absolutely correct balance sheet of a mining company. It is possible, however, to present the facts of a mining company more intelligently and comprehensively than is usually done. With this in mind, a balance sheet of an imaginary mining company is submitted, with supporting schedules. The same fundamental principles hold true whether we consider a large or a small company. Less complexity is involved in dealing with the affairs of a smaller company. Therefore, for this purpose, the assumed company operates but two mines and a smelting plant. It has been deemed advisable to introduce the features of the operation of a mine acquired prior to March 1, 1913 and one after that date. The presentation therefore is concerned in one mine with the appraisement as of March 1, 1913 and in the other with the appraisement by reason of discovery. A consequential factor pertains to dividends paid from depletion reserves and therefore free of surtax to the stockholders. While supporting schedules, when necessary, give details of certain items on the balance sheet, it seems desirable to give further explanations with respect to some of them. This seems to be important because some mining companies do not treat the items as indicated on the statements submitted.

Jan 1, 1928

I am honoured to be given the opportunity to share with you my thoughts on what will be the essential characteristics of æThe Mining Company for the 21st CenturyÆ. For me the 21st century is all about globalisation and the challenges and the opportunities that globalisation presents for the mining industry. To play on the global stage the successful mining companies must develop profiles that are global in: their operations diversity, their partnership relationships diversity, their customer relationships diversity, their workforce diversity, and their shareholder diversity. In my view æbigÆ will count in the 21st century, but big overlaid with quality: quality assets, quality people, quality partners, quality customer relationships, and quality image and reputation. Last year, Rio TintoÆs Leon Davis said when he addressed the Minerals Council of AustraliaÆs annual conference that Australian resource companies that wish to become global operators must develop an unequivocal international identity that will make that company a known and trusted quality wherever it seeks to do business. He went on to say that structuring and operating a business in a way that consistently manifests the qualities that inspire respect and evoke confidence is vital. I absolutely concur with what Leon said. Unfortunately, the fact is that, as we stand at the beginning of the 21st century, our industry and many of our companies are no better accepted by the world community than was the case five, ten, 15 or even 20 years ago. In fact, in some cases, the warmth of the acceptance may have subsided. To some extent the demonstrations that we saw recently in Seattle and Davos reflect a growing distrust, disquiet and cynicism in our communities. Here, however, I see an opportunity. While on the one hand the mood of disquiet presents many challenges, it also provides those of us who are willing to get out on the front foot in addressing the issues, and engaging in the dialogue, with a very significant opportunity to create a major competitive advantage. It provides the opportunity to earn respect and the opportunity to develop a reputation as a company that is sought as a joint venture partner and a company that is welcomed by governments and communities. Importantly, also, people will seek employment with such a company and will invest in such a company. The challenge is to change the way we behave and the way we are perceived by all the key stakeholders. Many of our industryÆs traditional skills are now commodities à many can be à and are out-sourced. The new critical skill for the 21st century à the real competitive advantage à will come from creating a real and genuine understanding of our role and what we stand for. Everything we do should demonstrate not only sound business principles, but also an understanding of the political, social, cultural and environmental impacts of our activities - at an international and a local level. This concept isnÆt new - but for large companies such as BHP, where we operate in more than 20 countries with diverse cultures, languages and religions - it requires enormous energy and dedication. It is complex. It is difficult. But I believe it is absolutely fundamental to our future.

Jan 1, 2000

By Prince Gelasio Caetani

PRESIDENT DWIGHT'S invitation to be a guest of the American Institute of Mining and Metal-lurgical Engineers was the first of the subsequently very numerous invitations to dinner I have received from my American friends. When I received his telegram I had not yet been even formally appointed Ambassador. I cannot tell you how deeply I appreciated it. It was a hearty welcome in returning to your country which has been for me a second home and it came from the American mining brotherhood which has been my second family.There are two distinct periods of learning in life. The first one are the years spent in school where we learn many things we after-wards forget; the second one are the years of prac-tical apprenticeship which engrave indelible signs in a man's character and shape his life. These latter years I spent in the United States and they have influenced the whole course of my life. I owe very much to my American friends who trained me. The earliest was Prof. Robert Peele, of Columbia University. At the Daly West mine, in Park City, Utah, he curbed my futuristic English spell-ing and had a hard time at it. Prof. James F. Kemp taught me that geology is a guess work just as unre-liable as the prediction of international events; he taught me also that a frank, honest and loyal character will lead a man equally straight through a mining report and through public life.

Jan 3, 1923

By A. V. Corlett

THE use of the diamond-drill hole as a means of breaking clown ore and waste is not new. Years ago, the method was adopted in mines in northern Ontario and in the western United States to reach out to bad pillars, or to remnants of ore left on walls, the winning of which by any other method might be dangerous or too expensive. The practice is still in vogue and has generally proved a success. Of the known mineral deposits in Canada and elsewhere, many are of very low grade. Some are marginal and not even worthy of being classed as 'ore' until some means is found and proved of exploiting them economically. Other conditions being favourable, if a mining method could be found that would give a large 'bulk break' with a sufficiently low cost of development and a low cast of mining per ton, mineral deposits of this latter type might be brought into the classification of ore. We know that any block-craving system whereby the ore may be undercut and allowed to crush and cave will give a very high breakage and low costs. In some cases, however, the physical characteristics of the ore do not lend themselves to this method. In such ore-bodies, the alternative system of 'bulk-breaking' might be aided by long diamond-drill blast holes. We could obtain this 'bulk breaking' by the use of long diamond-drill holes in conjunction with a sub-level system using extremely thick benches, or possibly by the adaption of modified open-pit methods to underground mining. ln fact, if conditions are favourable, the idea would be simply ta open up a slot or free face and break into it on a larger scale with longer holes. The use of deeper benches-that is, using each level as a sub-level and thereby eliminating much development footage, slashing, setting up, and mucking time-would naturally be expected to lead to cheaper mining.

Jan 1, 1940

By A. V. Corlett

MR. C. S. Gibson: Mr. Chairman, I listened with much interest to Mr. Corlett's paper. Those of us who are directly engaged in mine ventilation and dust control are impressed by the improved atmospheric conditions to be derived from the use of methods of mining such as those in operation at Aldermac, which Mr. Corlett has just described, and those employed at Noranda. It is a well known fact that drilling-dust is one of the most potent factors in the production of silicosis in mines handling ores containing quartz, so that from that angle the use of diamond drills, instead of percussion drills, to drill ore for blasts in stopes is an important development. A second point which I think merits mention is blasting. Blasting, we all know, creates the most dust in a mine and the fact that you can drill ore for a large blast with diamond drills and fire it, say, on Saturday night, and then have all the next day to ventilate the workings, is a great advance in dust control. 1 have wondered if Mr. Corlett, or possibly those at Noranda, can en-vision the use of the diamond drill as a means of advancing cross-cuts and drifts, preparing stopes, etc. I believe it is a matter which is receiving considerable attention at the moment in some parts of the world and J thought it would be interesting to have Mr. Corlett's reaction on that point. MR. A. V. CORLETT: I am not quite so hopeful of using diamond drills as a means of drilling holes in the ordinary drift. Maybe some of the diamond drill men can give us some further information on that point. MR. R. D. LoNGYEAR: The diamond drill manufacturers are working on that problem, but until further work is done we have nothing definite to offer. Drilling holes with a diamond drill to compete with rock drills for advancing drifts and cross-cuts is a desirable objective, because of the elimination of drilling dust and the ability to cut a smooth bore of uniform diameter. To reach this objective, higher rates of penetration are required, which can only be achieved by discovering the optimum bit rotating speed, by reducing vibration, and by further improving the bits and machines. We are optimistic, but the problem is still largely in the research stage.

Jan 1, 1940

By R. G. Votteler, A. C. Brent

"The business performance of mining corporations in South Africa is adversely affected by the constantly increasing electricity costs. The most commonly used power sources are the national utility supplier via a grid connection, and on-site diesel generators. Previous research has identified the renewable sources of solar photovoltaic (PV), onshore wind, and geothermal energy in hybrid versions with current sources as possible opportunities to counteract rising electricity costs. To provide a clear understanding of the new, developing market of renewable energy sources, this research is divided into two papers. This first paper investigates the internal business structure of mining corporations in order to evaluate electricity generating sources. The multi-criteria decision analysis (MCDA) method is selected as the most suitable approach for this. The paper identifies the criteria used by mining corporations to evaluate possible electricity generation sources for self-generation by means of the corporations’ own investment. Four mining corporations with several mining locations were interviewed. The interviews revealed both new and identical evaluation criteria when the findings were compared to earlier MCDA adaptations analysed in the literature review. The second paper (Part 2) combines current knowledge about the external macroeconomic environment with the findings about the internal environment described here. MCDA is adapted in Part 2 and implemented to analyse and compare current to hybrid renewable sources from the perspective of mines. IntroductionMining corporations in South Africa are currently adversely affected by increasing electricity prices. Electricity is supplied mainly by Eskom1 and, especially in remote locations, by on-site diesel generators (Boyse et al., 2014). Electricity price increases, emanating from diesel price hikes and Eskom, have escalated the total operational expenditure on electricity by the largest mining corporations from 8% to 20% of total operating costs in the past seven years (EIUG, 2015). The reliability of electricity supplied by Eskom has decreased drastically (Govender, 2008), and the prices will increase annually by at least 13% until 2018 (Numbi et al., 2014; Eskom, 2015b). In addition, the South African government plans to introduce a carbon tax on greenhouse gas emissions (Alton et al., 2014)."

Jan 1, 2017

By R. G. Votteler, A. C. Brent

"The first in this series of two papers, on the potential of renewable electricity sources for mining operations in South Africa, investigated the internal structure of mining corporations to evaluate feasible alternative electricity sources that were identified as through earlier research. The purpose of this paper is to combine current knowledge about the external macroeconomic and the internal environments to produce a clear picture of how renewable sources of electricity could perform from the perspective of mining corporations in South Africa. The multi-attribute value theory (MAVT) approach was adapted to structure the research and results. The model was fed with real-time data provided from five different energy companies and four mining corporations operating in South Africa. The results show that the performance of hybrid versions of the currently used electricity sources (diesel generators and Eskom grid connection) with solar PV and onshore wind is favourable compared with the current sources alone. The advantage of diesel generators is significantly greater than that of the Eskom grid connection. By combining the macroeconomic influences with the MAVT results, hybrid solar PV versions are identified as having the greatest potential. In second place are hybrid wind solutions, which have the shortcoming that good wind conditions occur only in coastal regions where there are fewer mining activities. Geothermal hybrid versions are the least favourable owing to the lack of service infrastructure and high initial investment costs.IntroductionRecent developments in the macroeconomic environment necessitate an investigation of the internal structure of mining corporations to evaluate possible alternative electricitygenerating sources (Roehrl and Riahi, 2000). To be able to combine current knowledge of macroeconomic factors and the internal structure of mining corporations, the research process is presented in two papers. The first paper (Votteler and Brent, 2016) investigated the internal structure and argued that a strategic tool should be used to evaluate electricity sources from the perspective of mining corporations. The multi-criteria decision analysis (MCDA) approach was selected as the most appropriate strategic tool. Based on a literature review of previous similar MCDA approaches in energy planning, it was concluded that no adaptation of MCDA methods could be found from a corporate, mining, or South African perspective. Finally, the paper investigated the internal evaluation structure in collaboration with mining corporations, by identifying the criteria they use to evaluate electricity sources."

Jan 1, 2017

By T. B. Szwilski

The paper gives an account of the development of a mine health and safety program in China from 1987 to 1996. The project was funded by the United Nations Development Program and managed by the International Labor Office (ILO). The objective was to strengthen the capability of the National Safety Training Center (NSTC), located near Beijing to train more than 2,000 engineers per year, and provide consulting and informational services to 39 safety training centers and coal mines. Presently China has the highest mortality rate in the world for coal mine operations, the greater incidence occurring at the many thousands of small, unlicensed underground mines.

Jan 1, 1998

By Terry R. Guilinger

A minitest of the new potassium chloride-potassium carbonate two-stage in situ uranium leach process has been carried out at the Intercontinental Energy Corporation (IEC) Zamzow project site in South Texas. Substantial quantities of high concentration uranium were produced indicating the viability of the leach solution. The test results yield information regarding the reservoir dispersivity, the average cation-exchange capacity of the formation, and the distribution coefficients describing carion-exchange reactions. The test a1 so indicates permeability anisotropy and the existence of disturbed flow fields. The research was partially funded by the U.S. Bureau of Mines.

Jan 1, 1984

By M. Gericke

The microbial leaching of metal sulfides is now an established biotechnological technology. Over the past 25 years, refinements in the engineering design of bioleaching processes have paralleled advances in our understanding of the diversity and role of the micro-organisms driving the process and the mechanisms by which micro-organisms enhance metal sulfide oxidation. Commercial success started with the treatment of refractory gold concentrates using mesophilic micro-organisms, followed by the development of tank bioleaching processes for the treatment of base metal concentrates. This was, initially, a mesophilic process with limited potential for recovery of copper from chalcopyrite concentrates due to slow rates and low copper extractions. The exploitation of thermophiles represents a major breakthrough in the development of bioleaching technology for the treatment of chalcopyrite-containing ores and concentrates. This development also opened the route to heap bioleaching of chalcopyrite ores, which is now a major focus of research programmes and piloting campaigns. This paper reviews the historical development of minerals bioleaching processes and gives an update on the current status of commercial tank and heap bioleach operations around the world.

Jan 1, 2009

By Kathleen M. Kowalski

In emergency management, the effects of stress on the performance of emergency personnel, typically have been ignored or regarded as too enigmatic to quantify. This paper discusses the concept of Critical Incident Stress in responders to emergencies. It presents the rationale for considering stress as a significant factor in the management of emergencies. It is proposed that Critical Incident Stress Debriefing in a disaster can improve the effectiveness of response teams on site, their turnaround time on site, and post-disaster time off the job. Critical Incident Stress intervention also can mitigate potential deleterious emotional effects associated with emergency work. This paper, prepared by a U.S. Bureau of Mines researcher, offers some ideas to the mining industry in general, to mine rescue team trainers, and to developers of program simulations on the specific issue of how people, time, materials and space may be factored into a plan for emergency management. The impact of stress on emergency workers is, presented as a missing component in present emergency management models.

This paper describes a mobile laboratory developed specifically for nickel prospecting, and which was designed to be operated by sub-professional staff in remote areas independently of established laboratories. An atomic absorption spectrophotometric procedure was used to determine nickel, cobalt, lead, zinc, and copper ID latentIc and sulphIde samples, with a detection limit better than 25 µg/g for all elements. The procedure was applicable to both soil and drill samples and the accuracy of the procedure, which was ±5 per cent relative at the 1,000 µg/g level was sufficient for the preliminary assessment of mineralized samples and the control of drilling operations. The analytical procedure and the means taken to ensure the necessary reproductibility and accuracy are described. One operator can carry out 400 elemental determinations per 8-hr day at an approximate cdst of 6 cents per elemental determination. The results are returned within a single day, a factor which can contribute materially to the efficiency of drilling operations.

Jan 1, 1970

By Gregory E. Korbin

The effectiveness of pre-reinforcement as an immediate stabilization measure as well as its contribution to the permanent stabilization of a tunnel were studied through the use of physical (Figure 1) and numerical models (1). Physical models were designed for the investigation of two pre-reinforcement systems: first, reinforcing far ahead of the main excavation (Figure 2); second, spiling reinforcement ahead of the face (Figure 3). In both cases, the use of reinforcement was responsible for permanently stabilizing an otherwise unstable opening. Data from the physical models were used to calibrate a numerical model from which additional information on long term behavior, methods to account for the capacity of a pre-reinforcement system, and the mechanisms involved were ascertained. These studies indicated that pre-reinforcement can stabilize a rock mass effectively as it reduces deformations and thereby deterioration due to strain softening, provides rock mass confinement leading to increased available strength, and maintains rock arch continuity allowing for increased tangential stress in the immediate vicinity of the opening. Field studies verified the capacity of spiling reinforcement to restrain initial deformations.

Jan 1, 1976