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By P. Tolvanen, A. Jalili

"When hard times strike in the mining cycle, sites tighten their belts and focus on lowering their unit costs. Lower unit costs can be achieved by reducing expenditure, increasing production, or by a combination of both. Faced with these requirements, site personnel must turn to areas where they can focus their effort for maximum return. For many sites, both in Canada and overseas, focusing on improving flotation cell maintenance is one of the areas where gains can be made for minimum outlay. Due to resource limitations and/or lack of equipment understanding, maintenance on many sites is only conducted on a reactive basis, once equipment fails. This paper will promote the idea that mineral processors should become more familiar with their equipment so they can ensure that the plant’s ability to produce is not compromised. By better understanding the flotation equipment and ensuring the critical components are maintained, it should be possible to unlock value in an operation. Flotation equipment inspections will be discussed in detail, including key items to look for during these inspections. Potential approaches for predicting wear and change-out time for flotation equipment components will be also demonstrated. An example of one approach used at a South African nickel site will be given.INTRODUCTIONWith metal prices decreasing and operating costs rising, concentrator operators are looking for ways to improve their bottom line. Lower unit costs can be achieved by reducing expenditure, increasing production, or by a combination of both. To meet the expectation of shareholders, mineral processors must turn to areas where they can get the best return for their efforts. One area where there is a large opportunity for improvement is in the maintenance of flotation equipment.On many mine sites, both domestically and around the world, it is quite common to see the philosophy applied of repairing equipment only once it has failed. Though some sites have advanced enterprise management systems and monitoring programs, in the authors’ experience, the decision on flotation equipment maintenance is rarely made on a proactive basis. Two common trends that are evident in the mining industry are that operations are under pressure to keep the plant producing, and maintenance managers generally have very strict budget targets to meet. In addition to these factors, few sites have a good understanding of the financial implications of running with worn or broken flotation equipment. Knights, Jullian and Jofre (2006) summarize this situation well, stating that the lack of correlation between some commonly used maintenance performance measures and key business drivers can lead to maintenance being seen only as a cost center (that needs to be reduced) rather than a tool for productivity improvement."

Jan 1, 2015

By Christopher M. St. John, Tony F. Zahrah

Empirical and numerical methods are the two extremes of the tools available for the seismic design of subsurface excavations and underground structures. Both have their limitations: when relying on purely empirical methods directly relevant experience may be scant; site data may be insufficient to justify a comprehensive dynamic analysis. The primary purpose of this paper is to review the analytical tools available to the design engineer of subsurface excavations and underground structures. Particular attention is devoted to simplifed models that appear to be applicable in many practical cases.

Jan 1, 1985

By Larry Schneider

Are you one of the thousands of hunters, fisherman, or hikers who purchased handheld GPS systems over the past several years and then been disappointed in their accuracy and performance. Or maybe you are one of the hundreds of blasters who have attempted to use GPS as a method for locating the exact position of their blast and measure distances from the blast to nearby structures. If so, you may have found that the accuracy of the handheld GPS systems left much to be desired. It may be time to get the units back out of storage and give them another try. As of midnight, May 1, 2000, the federal government has turned off the “error” built into the system known as “selective availability.” Here is a brief explanation of what that means in a question and answer format.

Jan 1, 2001

By Peter Amelunxen, Craig Lockhart

Significant effort was made in 2003 and 2004 to upgrade the existing instrumentation and process control infrastructure at the Phelps Dodge Bagdad copper concentrator. Specifically, • cameras were installed on the feed belt for online image analysis data, • ultrasonic level sensors were installed for froth height and sump level control, • a trial froth image system was installed on one of the rougher rows, and • a new expert system to tie everything together was integrated and tuned in-house. Control philosophy, observations, opinions, and general tips and tricks are discussed with the hope of assisting other plant personnel and expert system integrators.

Jan 1, 2005

By G Veillette, B Parker, S Hart

This paper provides a history of the challenges that were experienced while treating both the clayey oxide gold ores and the supergene copper-gold ores at the Boddington Gold Mine during the period 1989 to 2001. However the bigger challenge was to find a process flow sheet that would allow the economic treatment of the large low-grade competent gold-copper resource that underlies the oxide and supergene gold resource. Metallurgical test work and engineering studies on this resource started in the mid 1990s and culminated in the approval in 2006 of the 35 Mtpa Boddington Expansion Project to treat this material. The process flow sheet provides the basis of an energy efficient comminution circuit that includes high pressure grinding rolls and a treatment circuit with gravity separation, flash and conventional flotation to produce a precious metal low-grade copper concentrate followed by cyanide leaching of the rougher-scavenger and cleaner tailings streams. The treatment circuit allows maximum removal of copper minerals prior to cyanide leaching and so provides an environmentally responsible tailings disposal circuit.

Jan 1, 2007

By Qingxiang Huang

Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems. One of them is subsurface dewatering. In this paper, the physical simulating model was performed to study overburden movement and aquiclude stability in the shallow seam mining of Yushuwan coal field, China. According to the characteristic of clay aquiclude in the overburden, the proper simulation materials and proportions of mixture for simulating the plastic clay aquiclude layers and brittle bedrock layers were determined by the stress-strain tests. The physical simulating model was carried out to simulate the failure and caving process of the roof and overburden. Based on the simulating tests, it was found that the movement of clay aquiclude follows the movement of the underlying bedrock layers. The basic caving mechanism of the overburden roof strata was also presented. The tests also showed that the best way to control the stability of aquiclude is to reduce the subsiding gradient Ts. This research provides a foundation for further study on mining dewatering and water conservation.

Jan 1, 2006

By Philip J. Daynes

As part of the regeneration of the centre of Dublin, a multi-functional development is being constructed on the site of the historic Smithfield Fruit Market. The site is being developed in three phases, and includes one of the deepest basements (10m) constructed in Ireland to date. Until the recent improved economic climate, there has been little requirement for deep basements in Dublin, and this is the first to be constructed entirely within fluvio-glacial gravels and boulders. The difficult ground conditions led to the adoption of a diaphragm wall solution to ensure a watertight construction. Tie-back anchorages are utilised in the temporary case, and the wall is propped by floor slabs in the permanent case. Where required by high bedrock levels, the diaphragm wall is dowelled into limestone bedrock to ensure toe stability. The recorded lateral movement of the wall is significantly below that calculated by numerical analysis. Temporary bentonite cut-off walls were installed to divide the site into discrete sections. The basement was constructed as a tanked structure, and is subject to uplift water pressure. Passive tension minipiles provides an innovative alternative to the standard stressed anchorage solution. This paper describes:- design and construction aspects of the diaphragm wall, tie-back anchorages, and anti-flotation minipiles, together with recorded lateral wall movements,

Jan 1, 2003

By Yates C, Gillie E. W, Finucane K. J

During the year 1940 a complete investigation was made of the whole of the stoping operations throughout the Great Boulder Mine and, as a result, it was decided to convert some of the existing shrinkage stopes into cut-and-fill stopes, and also to mine many of the more recently developed ore blocks by the latter method. The necessity for filling was due primarily to the structure of the ore blocks, the character of the walls and possible excessive dilution, but was influenced also by the grade of the ore-block and by the fact that cleaner mining can be carried out by cut-and-fill stoping.The comparatively few cut-and-fill stopes in operation prior to 1940 had been filled mainly with waste rock from development work, but as the amount of this material available, or likely to become available, would have been wholly inadequate for future operations, it was proposed to construct a system of passes to supply filling material from the surface.Owing to the distribution of the stopes, no central pass or system of passes could be devised which would service all the stopes satisfactorily.However, work was commenced on two passes, one designed to service the cut-and-fill stopes in the Eastern Section of the mine, and another to service those in the Western Section. It was realised that these passes could serve only a small proportion of the total number of Stopes (Figs. 1 and 2). During the progress of this work experiments were undertaken to test the possibility of using filtered tailings underground as an adjunct to the above scheme, but for various reasons these were only partially completed.Early in 1942 it was suggested by the Mill Superintendent that an attempt be made to fill with wet classified flotation tailings as practised at Mt. Lyell in Tasmania and at the Triton Mine at Reedy, West Australia. For the purpose of testing this, an experimental stope was prepared on the 309-ft. level, "X" Lode. This was 100 feet long and averaged 4 feet in width. Water-tight rearings were built at each end of the stope and waste rock fill was spread to a height of 6 to 8 feet above the timber. Used filter cloths were laid on top of the fill and brought a few feet, up the walls of the stope. A two-inch victaulic drainage line was then placed in position, the end passing through a hole in one of the bearings and thence to a sump. In the central portion of the stope two vertical pipes were brought up from this line. These were bored with one-inch holes staggered on opposite sides of the pipe, the vertical interval between each hole being one inch. The holes were then stopped with...

Jan 1, 1945

By A. Farnoud

Thousands of miners, construction workers, and truck drivers are exposed to diesel exhaust particles. Diesel Particulate Matter (DPM) is a probable human carcinogen and stringent occupational and environmental standards have been established or are planned worldwide. Modifications in fuels and diesel engine designs have reduced emissions, but may not be enough to comply with the tightest standards. Post-combustion aftertreatment devices are likely necessary for many engine operators. However, even the most common and well studied aftertreatment devices fail from time to time. The objective of this study was to design, construct, and test an electrostatic aftertreatment device to treat DPM. An electrostatic precipitator (ESP) was designed and constructed to capture DPM from diesel exhaust, and different configurations were tested to optimize its performance. DPM was produced by a 6 kW diesel-powered electric generator and directed to the ESP through a short section of galvanized steel pipe after the muffler. Number and mass removal efficiencies were measured with a condensation particle counter (CPC) and by sampling through a stainless steel cassette and collecting the DPM on Teflon filters. Particle size distributions were measured with and without control using a 6-stage cascade impactor. The experiments were performed with the engine running at idle and also at medium load. The results show that our first generation ESP provides 60 percent mass removal efficiency, and up to 80 percent number removal efficiency. Power consumption was generally low, about 20 to 30 watts, to achieve these levels of performance.

Jan 1, 2009

By A. V. Roschin, N. V. Malkov, V. N. Karnoukhov, V. E. Roschin

Reduction interactions in solid phases are widespread and occur in most complex metallurgical processes. Among these processes, reactions between oxides and carbon have a special importance. The authors conducted experiments for comparison of reduction by different reducing agents of impregnated chromite ores, in which grains of the reducible chromite spinel are isolated from direct contact with the reducing agent by layers of non-ore material. The results of the experiments have revealed that the beginning of reduction is preceded by thermal and impurity order-disorder transformation of the oxide lattice whilst the transformation of the oxide lattice into the metal lattice takes place as a result of removal of oxygen anions from the zone of metal germ nucleation. Since anions are charge carriers, increase of their mobility can be monitored by changes in electrical conductivity of oxides. Respective measurements of electrical resistance of ores of different metals and a number of pure refractory oxides under heating have indicated that the beginning of reduction coincides with the time of drastic (tens of thousands times) increase of conductivity of the oxides. Besides, the temperature of the beginning of carbon-thermal reduction is in line with the Tammann temperature, i.e. the temperature of transition from the predominantly surface diffusion to volume diffusion. Segregation of metals from the oxide lattice occurs as a result of merging of anion vacancies with defect electrons on defects of the oxide lattice. The transformation of the oxide lattice into the metal lattice requires a certain concentration of anion vacancies and inflow of electrons from the reducing agent to the site of metal segregation. Such inflow has no difficulties due to the mixed anion-electron nature of high-temperature conductivity of oxides. Thus, the reduction is not determined by oxygen diffusion, it is determined by oxygen vacancies diffusion whose speed exceeds the speed of oxygen diffusion by orders of magnitude. This determines that the kinetics of reduction considerably exceeds the kinetics of oxidation at similar temperatures since oxidation proceeds by means of mass transfer of oxygen through the layer of the generated oxide.

Jan 1, 2004

By Jim Frazier

Tradition has often dictated low design load stresses on piles. Such traditions often developed prior to modern static or dynamic pile testing methods and perhaps result from a few limiting situations. These low stress limits were then broadly applied, even in cases where the piles could carry substantially higher loads. With sufficient testing to prove the design, higher design loads may present significant overall savings to the project owner. The cost of the testing then becomes an insignificant cost compared to the potentially great benefit of increased pile loadings. To confirm higher load possibilities for driven piles, the pile is tested either statically or dynamically. Further savings and increased testing efficiency result from remote dynamic pile testing. This paper presents a project where design stresses were considerably increased as a result of additional testing and use of remote dynamic pile testing equipment.

Jan 1, 2002

By A. J. Potgieter, C. Hill, A. Humpel, D. S. Magudulela, V. Scholtz, A. Coetzee

Keywords: Pyrometallurgy, long steel products, coke, sinter, blast furnace, steel plant Located in Northern KwaZulu Natal, Mittal Steel South Africa Newcastle works produces roughly 1.8 million tons per annum, supplying long steel products, locally and overseas. The great extent of local raw material availability and low conversion cost ensures that Mittal Steel South Africa is among the lowest cost, high quality producers of steel. MSSA Newcastle works can be subdivided into two main sections: The iron making side, comprising the coke ovens, sinter plant and blast furnace, and the steel making side, comprising the basic oxygen furnace, ladle furnace, continuous casters, and the medium, rod, and bar mills.

Jan 1, 2006

The paper outlines the development of a solvent extraction process for the recovery of scandium, yttrium, thorium, and heavy lanthanides from waste sulphate liquor at the Port Pirie uranium treatment plant. A summary is given of known solvents for these elements, including the recently developed alkyl-phosphoric acid esters which are applicable to sulphate solutions.A kerosene solution of di- (2'-ethylhexyl) phosphoric acid (EHPA) has been suggested by some workers as a suitable solvent for fractionation of the lanthanides. Experimental work with this solvent showed that it could be used for initial recovery of the above elements from low concentrations in the complex sulphate liquor. In particular, scandium could be recovered as a high grade product by extraction with 0·lM EHPA, followed by a purification strip with 9N sulphuric acid, and final stripping of scandium with sodium hydroxide solution.To enable alkaline stripping to be used successfully, the kerosene solution of the reagent was modified by the addition of a small proportion of nonanol. Experimental work included laboratory scale batch tests and small pilot scale continuous tests.A proposed extension of the process for the separate recovery of individual heavy lanthanides, yttrium, and thorium is described.INTRODUCTIONAt the Port Pirie uranium treatment plant of the South Australian Government, large volumes of "barren liquor", free from 'uranium, are at present run to waste. This "barren liquor" results from sulphuric acid leaching of Radium,Hill uranium concentrate, followed by separation of solid residues and removal of uranium from the clear solution by ion exchange. The mineral davidite, from which the uranium is derived, contains other potentially valuable components, notably vanadium, chromium, thorium, yttrium, scandium, and the lanthanides. These constituents are...

Jan 1, 1961

By N. I. Basuki, E. T. C. Spooner

"The Bongara area, northern Peru, contains Zn-Pb mineralization with characteristics typical of Mississippi Valley-type (MVT) systems. The northwest-southeast-trending late Triassic-Jurassic car¬bonate host rocks of the Pucará Group were locally replaced by early (D1) and late (D2) dolomite. Fluid inclusion microthermometric data from dolomite and sphalerite are typical of MVT ore fluids (78° to 187°C; ~15-23 wt.% CaCl2 equivalent), and do not show apparent covariation between temperature and salinity.Homogenization temperature data from D1 and D2 dolomite show a decrease from northern (mean Th = 138°C) to central (mean Th = 126°C) to southern areas (mean Th = 102°C), suggesting fluid flow from north to south. Assuming a geothermal gradient of ~30°C/km and an average surface temperature of ~20°C, the lower temperature limits might approximate the ambient host-rock temperatures, whereas the upper temperature limits may represent minimum temperatures of a deeper aquifer, probably at a maximum depth of ~6000 m. The lower temperature limits are also similar to the estimated temperatures if dolomitization and mineralization took place in the Late Cretaceous at ~2000-3000 m depth, probably during the formation of the Peruvian fold and thrust belt near the present day Peru-Ecuador border.Fluid inclusion data show that the fluids in each studied location had relatively uniform temperatures and salinities during dolomitization and mineralization. A significant salinity drop and a slight temperature decrease are observed during late calcite precipitation, suggesting mixing of brines with dilute, cooler fluids."

Jan 1, 2009

By Leonello Sciacca

Deepening of harbours has become a priority, necessary to the ongoing operation of the wharves in the face of deeper draft merchant vessels and cruise ships. It is now standard practice in many areas to provide for harbours to be dredged to significant depths below mean sea level, in the order of 12.00 m (39 ft) for existing berths and 15.00 m (49 ft) for new wharf construction. The Ravenna Port Authority initiated a project to deepen the harbour bottom at selected wharves to a depth of 12.00 m (39 ft). In preference to reconstruction of the wharves with longer and heavier sheet piling or other equally disruptive reconstruction, they identified the structural reinforcement of the existing wharves by means of deep underwater tie rods as a possible alternative cost-effective solution. Having defined the design concept, effort was concentrated on developing the required technology. A technique, already in use for the installation of tie rods by means of robotics, was identified as potentially suitable for underwater use. It was decided to carry out the fine tuning and the evolution of the technology for a marine environment of the robot unit and of the related remote control software that controls the installation of the tie rods. An experimental test site was set up to refine the drilling, installation, grouting, monitoring and testing of underwater tie rods. The purpose was to confirm the feasibility of the proposed solution and the reliability of these tie rods for use in the reinforcement and construction of wharves. The paper also discusses the theoretical and experimental study of underwater tie rods dealing with the theoretical analysis of the interaction between tie rod and soil, aimed at identifying the correlation between the forces of applied traction and the corresponding measured elongations. A series of tests were carried out with positive results, both at the operating load of 300 kN (67 kips) and at the nominal maximum load of 630 kN (142 kips). The tests were carried out on seven tie rods, of which three were installed at a depth of 5.00 m (16 ft), principally to test the reliability of the operating and remote control systems in the presence of a significant hydrostatic pressure, and four were placed at a depth of 8.00 m (26 ft) to check the load bearing capability of the tie rods positioned at the depth called for by the current project.

Jan 1, 2011

By Hessam Yazdani

In comparison to the conventional piled foundations, the piled-raft foundations provide a more economical solution to support high-rise buildings constructed on soft soils. In this type of foundations, the bearing capacity of the underlying soil is taken into account to support the superstructure loads and the piles are placed to control both the total and differential settlements of the superstructure. Currently, there is not a standard and worldwide acceptable approach to select the location of the piles and most of piled-raft foundations are designed based on the experience of designers. Therefore, particular attention should be given to the optimal design of this type of foundations in order to minimize the considerable construction costs involved. This paper examines the capability of the ant colony optimization (ACO) algorithm to optimize the piled-raft foundations subjected to static and seismic loadings. The soil-pile interaction is considered by modeling the side and tip resistance components of the piles using the nonlinear Winkler-based p-y and t-z curves in the OpenSees program. The soil-raft interaction is taken into consideration using the Winkler springs beneath the raft. The objective of the optimization problem is to minimize the construction cost of the foundation by taking the configuration and number of the piles as design variables. The side and tip forces of the piles as well as the total and differential settlements of the foundation under the serviceability limit state are considered as the constraints for the optimization problem. Results show that in addition to the type of analysis (linear/nonlinear), the regard or disregard of the soil-pile interaction in the analysis can significantly change the optimal solution. The optimal solutions obtained match the engineering expectations and indicate the effectiveness and capability of the ACO algorithm to minimize the construction cost.

Jan 1, 2013

By W. W. Adams

"The ninth yearly National Safety Competition covering the calendar year 1933, conducted by the United States Bureau of Mines, w participated in by 332 mines and quarries situated in 35 States. Enrollment represented as increase of 10 plants over 1932, and one addition was made to the number of States represented.The primary purpose of the United. States Bureau of Mines in conducting the contest is to promote safety in United States mineral industries. This purpose is accomplished directly through the efforts of the competing companies and their employees to win first place in the competition and thereupon receive recognition on a national scale for their achievement the purpose is accomplished indirectly through studies by the United States Bureau of Mines of the facts contained in the accident reports the competing companies furnish to enable the Bureau to compute the accident rates that are the basis for determining the winners of the contest.The statistics which constitute the basis for determining the winning companies and the relative standing of all companies are prepared uniformly without regard to the States in which the companies operate, or to differences in classes of accidents covered by State laws relating to compensation for injuries resulting, from industrial accidents.Bronze trophies, known as 'Sentinels of Safety', which were provided by The Explosives Engineer magazine to be awarded annually by the Bureau of Mines, were presented to five companies in the contest of 1933, each company having established the best accident-prevention record within one of the five classes into which all companies were divided, namely, anthracite-mining companies, bituminous-coal-mining companies, metal-mining companies, operators of nonmetallic-mineral mines other than coal mines, and quarries or opencut mines. The trophies are awarded for 1 year and are then transferred to the winners of the succeeding year's contest.The trophy for bituincus-coal mines was won by a company in Wyoming. A company in Tennessee won the trophy for metal mining. In the nonmetal-mine group the trophy was again won by a company in New York. A quarry in Michigan won the trophy for the quarry-and-opencut-mine group. The trophy for anthracite mines remains in Pennsylvania, as all anthracite mines in the contest are in that State."

Jul 1, 1934

By Enrique Castells

La extracción del mineral es el método más habitual para la explotación minera y se realiza a través de rampas, galerías, y túneles que permitan el acceso hasta la zona de minado. Sin embargo, cuando se da una excesiva profundizaciión del terreno, se emplea el método de pique vertical ya que logra el acceso de los operarios a las zonas más profundas de un modo más rentable y rápido a través de la extracción del mineral por izado de vagones o skip hasta el de nivel de superficie o intermedio. Por ello, es común que las minas replanteen la sustitución de su sistema de extracción habitual por el de izado por piques. En este sentido, el presente trabajo desarrolla la aplicación de los piques verticales en los sondeos de exploracion de la mina Hullera Vasco Leonesa. La primera parte del proyecto describe la ejecución de dos piques verticales (Aurelio y Emilio del Valle), y la segunda, en la ejecución de más de 17.000 m de galerías y obras de infraestructura de diversa índole.

Sep 13, 2001

B. P. Thomson (South Aust. Dept. of Mines): Dr. A. B. Edwards presents in the published discussion on the above paper, his interpretation of the dolerite dyke-lode relationship as a major objection to the syngenetic origin for Broken Hill ore bodies to which Mr. Condon subscribes.Dr. Edwards claims that the dyke-lode relationships indicate clearly that the Broken Hill orebody was formed after the folding and regional metamorphism of the Willyama Series. Field evidence compels m:e to join with H. F. King (1958), in finding this conclusion unacceptable-as follows:(1) Broken Hill type mineralization, as defined by King and Thomson (1953), is clearly confined by the regional sillimanite isograd and does not extend into the lower temperature almandine and biotite zones as does the Thackaringa type mineralization.(2) In the Corruga area the writer has mapped a dolerite dyke apparently cutting a conformable quartz gahnite lode of the Broken Hill type (see Edwards 1958, p. 12).(3) At the Champion mine a similar lode is cut by a fine grained granite dyke.An alternative history of the dolerite dykes to that given by Stillwell & Edwards (1956, p. 26) appears possible. It has been suggested by the writer in an unpublished thesis, (Thomson 1955, p. 30), that the pyroxenite and serpentine plugs and dolerite dykes are rheomorphic end-products of a complex regional metamorphic and metasomatic process involving the formation of amphibolite and pegmatite. The analogy in composition between the dolerite and normal amphibolite is close (see Edwards 1958, Fig. 1, p. 22).

Jan 1, 1959

By G. Caron, M. Boisclair

In 2005, CANMET-MMSL used its pool of expertise in ground control, open pit and underground mine engineering, mineral processing, information technology and applied mineralogy to launch a mine-to-mill research project. The objective of the project was to optimize the distribution of rock breakage energy among blasting, crushing and grinding activities, thereby maximizing the efficiency of energy utilization within comminution processes. Tests were designed to demonstrate that this approach could reduce the energy consumption, thus contributing to the reduction of Green House Gas (GHG) production in the Canadian mining industry. The project was accomplished in collaboration with DynoConsult and Dyno Nobel Canada Inc., a world leader in commercial explosives. Data analysis from 12 blasts (six with electronic and six with pyrotechnic detonators) in three different geological formations of a quarry (soft, medium and hard rock) shows that electronic blasting technology increases rock fragmentation by 15% (in hard rock) to 20% (in soft rock). A more uniform rock fragment size distribution is also obtained. The impact of the improved quality blast product on downstream processes of the quarry is a productivity increase of 5% in rock excavation and transportation, an energy reduction of 10% at the primary crusher and an increase of 15% of the primary crusher throughput. A soft-sensor prototype, based on primary crusher data (i.e. energy consumption, throughput, feed and product size distribution) and a simplified computerized process model, was developed for on-line measurement of the rock operating work index. Additionally, 385 rock samples and specimens were collected and prepared to determine the tensile and compressive strength of the rock material, to evaluate the aggregate crushing work index, and to examine the development of micro- and macro-fractures by means of binocular and SEM microscopy. Blast-induced rock damage was evaluated at the end of the laboratory testing program. Even though a reduction of rock hardness of around 30% was observed after blasting, the impact of the blasting method (i.e. use of electronic or pyrotechnic detonators) on the induced rock damage could not be observed. It is either absent or not perceptible with the accuracy of the measuring techniques and the number of samples analyzed.

Jan 1, 2007